Unravelling environmental and economic criteria for resource recovery in centralised and decentralised wastewater treatment

TESE DE DOUTORAMENTO
UNRAVELLING ENVIRONMENTAL
AND ECONOMIC CRITERIA FOR
RESOURCE RECOVERY IN
CENTRALISED AND DECENTRALISED
WASTEWATER TREATMENT
And ea A ias Cis e na
ESCOLA DE DOUTORAMENTO INTERNACIONAL
PROGRAMA DE DOUTORAMENTO EN
ENXEÑERÍA QUÍMICA E AMBIENTAL
SANTIAGO DE COMPOSTELA
2021
DECLARACIÓN
DO AUTOR/A DA TESE
UNRAVELLING ENVIRONMENTAL AND ECONOMIC
CRITERIA FOR RESOURCE RECOVERY IN
CENTRALISED AND DECENTRALISED
WASTEWATER TREATMENT
Dña. And ea A ias Cis e na
P esen o a miña ese, seguindo o p ocedemen o axei ado ao
Regulamen o, e decla o que:
1) A ese aba ca os esul ados da elabo ación do meu aballo.
2) De selo caso, na ese aise e e encia ás colabo acións que i o es e
aballo.
3) A ese é a e sión de ini i a p esen ada pa a a súa de ensa e coincide
coa e sión en iada en o ma o elec ónico.
4) Con i mo que a ese non inco e en ningún ipo de plaxio dou os
au o es nin de aballos p esen ados po min pa a a ob ención dou os
í ulos.
En .........., ... de ..... de 20..
AUTORIZACIÓN DOS DIRECTORES DA TESE
UNRAVELLING ENVIRONMENTAL AND ECONOMIC
CRITERIA FOR RESOURCE RECOVERY IN
CENTRALISED AND DECENTRALISED
WASTEWATER TREATMENT
Dona Ma ía Te esa Mo ei a Vila , Ca ed á ica de Enxeñe ía Química y
Don Gume sindo Feijoo Cos a, Ca ed á ico de Enxeñe ía Química
INFORMAN:
Que a p esen e ese, co espóndese co aballo ealizado po D/Dna.
And ea A ias Cis e na, baixo a miña di ección, e au o izo a súa
p esen ación, conside ando que eúne os equisi os esixidos no
Regulamen o de Es udos de Dou o amen o da USC, e que como di ec o
des a non inco e nas causas de abs ención es ablecidas na Lei 40/2015.
De aco do co indicado no Regulamen o de Es udos de Dou o amen o,
decla a amén que a p esen e ese de dou o amen o é idónea pa a se
de endida en base á modalidade de Monog á ica con ep oducción de
publicaciones, nos que a pa icipación do/a dou o ando/a oi decisi a
pa a a súa elabo ación e as publicacións se axus an ao Plan de
In es igación.
En .........., ... de ..... de 20..

LISTS OF CONTENTS
Abb e ia ions .................................................................................................................. 13
Abs ac ………………………………………………………………………………………………….15
Resumo ............................................................................................................................... 19
CHAPTER 1. INTRODUCTION
1. Gene al in oduc ion ........................................................................................... 31
1.1. G owing en i onmen al conce n abou wa e as a ini e esou ce 31
1.2. Ci cula economy in he was ewa e ea men sec o ....................... 33
1.3. New was ewa e ea men s a egy o cen alised sys ems .......... 35
1.4. Decen alised app oach o was ewa e ea men ............................. 38
1.5. Li e cycle assessmen (LCA) me hodology and i s applica ion o
was ewa e ea men ............................................................................................. 42
1.6. Economic e alua ion ........................................................................................ 46
1.7. Thesis ou line: objec i es and s uc u e................................................... 48
1.8. Re e ences ............................................................................................................ 50
SECTION I: IMPROVING CENTRALISED WASTEWATER SYSTEMS
CHAPTER 2. Iden i ying en i onmen al and economic ba ie s associa ed
wi h he scale o ope a ion in he anae obic diges ion p ocess
2.1. In oduc ion ............................................................................................................. 69
2.2. Ma e ials and me hods ......................................................................................... 70
2.2.1. Goal and scope de ini ion ............................................................................ 70
2.2.2. Func ional uni ................................................................................................ 71
2.2.3. Sys em bounda ies ........................................................................................ 71
2.2.4. Li e cycle in en o y app oach ................................................................... 73
2.2.5. Li e cycle impac assessmen and in e p e a ion .............................. 76
2.2.6. Economic indica o s ..................................................................................... 77
2.3. Resul s and discussion ......................................................................................... 77
2.3.1. En i onmen al p o ile o he di e en sludge lines .......................... 77
2.3.2. Assessmen o he easibili y o he anae obic diges ion (AD) uni
.......................................................................................................................................... 80
2.3.3. Ene gy bene i in he di e en sludge lines ......................................... 82
2.3.4. Economic analysis o he di e en sludge lines.................................. 83
2.4. Conclusions ............................................................................................................... 85
2.5. Re e ences ................................................................................................................. 85
CHAPTER 3. Benchma king en i onmen al and economic indica o s o
sludge managemen al e na i es aimed a enhancing ene gy e iciency
eco e y
3.1. In oduc ion ............................................................................................................. 91
3.2. Ma e ials and me hods ......................................................................................... 92
3.2.1. Desc ip ion o he di e en sludge lines and scope o he s udy . 92
3.2.2. Li e cycle in en o y (LCI) o he di e en sludge p e- ea men s
.......................................................................................................................................... 94
3.2.3. En i onmen al and economic indica o s o he sludge p e-
ea men s .................................................................................................................... 99
3.3. Resul s and discussion ...................................................................................... 100
3.3.1. Main pa ame e s and li e cycle esul s o he di e en sludge
scena ios .................................................................................................................... 100
3.3.2. Economic e alua ion o he di e en sludge p e- ea men s .... 106
3.3.3. Sensi i i y analysis o he di e en p e- ea men p ocesses . 108
3.3.4. E alua ion o he e iciency o he di e en sludge p e- ea men s
....................................................................................................................................... 110
3.3.5. How o imp o e he e iciency o a WWTP ........................................ 110
3.4. Conclusions ............................................................................................................ 112
3.5. Re e ences .............................................................................................................. 112
CHAPTER 4. Pu sing ene gy sel -su icien in was ewa e ea men plan s:
en i onmen al and economic assessmen o inno a i e op ions
4.1. In oduc ion .......................................................................................................... 121
4.2. Ma e ials and me hods ...................................................................................... 123
4.2.1. Desc ip ion o he was ewa e schemes and scope o he s udy 123
4.2.2. In en o y da a acquisi ion o he new was ewa e con igu a ions
....................................................................................................................................... 128
4.2.3. Impac assessmen me hodology and economic e alua ion....... 132
4.3. En i onmen al and economic esul s .......................................................... 132
4.3.1. En i onmen al and economic app oach o he ou s udied
scena ios .................................................................................................................... 132
4.3.2. En i onmen al pe spec i e o each was ewa e ea men
con igu a ion ............................................................................................................ 136
4.4. Discussion .............................................................................................................. 140
4.4.1. Imp o ing was ewa e ea men e iciency in he WWTPs ....... 140
4.4.2. How con en ional and new echnologies in luence he e luen
quali y ..................................................................................................................... 1422
4.4.3. Economic aspec s ocused on ene gy eco e y ................................ 143
4.4.4. Sensi i i y analysis o he unc ional uni (FU) ................................ 144
4.5. Conclusions ............................................................................................................ 145
4.6. Re e ences .............................................................................................................. 145
CHAPTER 5. Mapping he en i onmen al and economic impac s o
inno a i e echnologies o enhancemen o biogas p oduc ion and sludge
managemen in was ewa e sys ems
5.1. In oduc ion .......................................................................................................... 155
5.2. Ma e ials and me hods ...................................................................................... 156
5.2.1. Me hodology on simula ion and en i onmen al assessmen ..... 156
5.2.2. Goal and scope o he wo was ewa e schemes conside ed ...... 159
5.2.3. Sys em bounda ies o he was ewa e ea men con igu a ions
....................................................................................................................................... 160
5.2.4. In en o y da a acquisi ion h ough he simula ion p ocess ...... 162
5.2.5. En i onmen al and economic indica o s selec ed o he case
s udies ......................................................................................................................... 168
5.3. Resul s ..................................................................................................................... 169
Subsequen ly, he was ewa e line was modi ied (Chap e s 4 and 5). A
s a egy based on o ganic ma e (OM) eco e y in p ima y ea men
and ni ogen emo al in seconda y ea men by pa ial ni i ica ion-
anammox was compa ed wi h a con en ional app oach. In Chap e 4, a
i ual plan designed o 100.000 popula ion equi alen s wi h di e en
schemes based on he abo e-men ioned s a egy was e alua ed. The
h ee inno a i e schemes a e: (i) up low anae obic sludge blanke
(UASB) ollowed by an in eg a ed ixed ac i a ed sludge (IFAS), (ii) high
a e ac i a ed sludge (HRAS) + IFAS, and, (iii) o a ing bel il e (RBF) +
chemically enhanced p ima y ea men (CEPT) + IFAS. These schemes
we e compa ed wi h a p ima y cla i ie (PC) ollowed by a con en ional
ac i a ed sludge (CAS) wi h ni ogen emo al. The main objec i es a e o
s udy ene gy p oduc ion, e luen quali y and sludge p oduc ion and how
hese ac o s can a ec he en i onmen al and economic p o ile o he
was ewa e line. Finally, in Chap e 5, he schemes we e i ually
modelled in wo eal plan s loca ed in Denma k and Spain. The exis ing
con igu a ion was eplaced by wo schemes: (i) HRAS + IFAS and (ii)
Enhanced Ro a ing Bel Fil e (ERBF) + IFAS. In his way, he main inpu s
and ou pu s o he di e en sys ems we e es ima ed o calcula e he
en i onmen al and economic p o ile. Finally, his sec ion will conclude
wi h he up-scale o a echnology o ni ogen emo al in he side s eam
(Chap e 6). The main objec i e is o es ablish he minimum scale o
eliably es ima e he en i onmen al and economic indica o s. In his way,
he s udy can help as a guideline o add ess he e alua ion o smalle uni s
such as hose o decen alized sys ems.
The second sec ion o his hesis “changing he pa adigm o was ewa e
ea men ” seeks o highligh he impo ance o decen alised sys ems o
esou ce eco e y ocusing on ene gy and wa e wi h he aim o
demons a ing en i onmen al and economic bene i s. This sec ion
consis s o wo chap e s (Chap e 7 and 8). The main objec i e o Chap e
7 is o e alua e he pe o mance o a memb ane plan o he eco e y o
i iga ion wa e in Tu key. The was ewa e plan is designed o 2,000
equi alen inhabi an s. In his Chap e , an indica o called AWARE
(a ailable emaining wa e me hod) was applied o measu e he wa e
sca ci y and he bene i s o wa e euse. Finally, Chap e 8 compa es he
app oaches o decen alised and cen alised sys ems om a ci izen

pe spec i e. The s udy aims o analyse he dec ease o inc ease in wa e
consump ion and ca bon oo p in o a ci izen li ing in a neighbou hood
ha inco po a es a decen alized o cen alized was ewa e ea men
sys em.
Keywo ds: ene gy p oduc ion, inno a i e echnologies, decen alised
was ewa e , economic indica o s, li e cycle assessmen (LCA), eclaimed
wa e
RESUMO
RESUMO
19
RESUMO
Du an e os úl imos anos, a poboación mundial expe imen ou un
c ecemen o subs ancial e p e ese que es a endencia con inúe. Is o
implica que se deban xe a máis alimen os, ene xía ou auga po able, en e
ou os bens pa a sa is ace ás necesidades de di a poboación. Non
obs an e, o consumo de máis ecu sos implica unha xe ación maio de
esiduos como, po exemplo, plás icos, augas esiduais, despe dicios
alimen a ios, e c. Es es esiduos deben se a ados co ec amen e pa a
e i a p oblemas elacionados coa con aminación do medio ambien e. No
a amen o de esiduos, as plan as de a amen o de augas esiduais son
ac o es cha e pa a ga an i a edución da desca ga de con aminan es ó
medio, xa que, se non son xes ionadas co ec amen e, poden causa
g a es p oblemas ambien ais e incluso a mo aldade das especies que
i en nel. Así mesmo, es as plan as de a amen o deben ace on e a
no os desa íos como a eliminación de con aminan es cada ez máis
complexos ales como á macos, ho monas ou ag ancias sendo cada ez
máis sus en ables dende o pun o de is a económico, ambien al e social.
Nes e con ex o, o e mo esiduo debe se subs i uído pola palab a
p odu o. Polo an o, as depu ado as deben aballa non pa a elimina
ecu sos senón pa a ecupe alos, é o que se coñece como pensamen o de
economía ci cula . De es a manei a, o que se consegue é ans o ma ás
xes o as de esiduos en bio e ine ías. O que se p e ende nes a ese é
abo da es e cambio a a és de di e sas con igu acións e dis in os
esquemas de a amen os. Pa a abo da es e cambio, a ese oi di idida
en dúas seccións, as cales anse explica a con inuación.
Capí ulo 1: In odución. Es e p imei o capí ulo p e ende se i como
ma co eó ico e explica o mo i o p incipal polo cal se decidiu ealiza
es a ese. O ma co eó ico engloba a p oblemá ica ac ual elacionada cos
p oblemas de con aminación de augas, cambio climá ico ou aumen o da
poboación, en e ou os. De iniuse o concep o de economía ci cula e
como engloba ás depu ado as den o des e e mo, así como as
es a exias que se poden le a a cabo pa a consegui es e p opósi o. Es es
sis emas poden es a o mados po dis in as ecnoloxías que eñen
dis in as uncións dependendo da súa aplicación.
RESUMO
20
Como un dos obxec i os des a ese é abo da a pa e ambien al e
económica de dis in os a amen os de auga, desc ibí onse en de alle as
dis in as e amen as e indicado es que se poden emp ega pa a es e in.
Ademais, es udouse o que le an ei o ou os au o es no ámbi o das augas
esiduais en combinación con c i e ios ambien ais e económicos. Di a
in o mación ecóllese nunha e isión bibliog á ica que se inclúe den o
des e capí ulo. Finalmen e, pa a concluí es e p imei o capí ulo,
esumí onse os obxec i os que pe segue cada capí ulo que o ma es a
ese.
A p imei a sección da ese i ulada “mello as pa a sis emas
cen alizados” ecolle un o al de 5 capí ulos. Es a pa e do aballo oi
inanciada po un p oxec o chamado Pionee _STP (polas súas siglas en
inglés The Po en ial o Inno a i e Tecnologies o Imp o e Sus ainabili y o
Sewage T ea men Plan s), o cal en como obxec i o p incipal, a alia os
desa íos elacionados co a amen o das augas esiduais dende un pun o
de is a holís ico que se cen a en concep os como a ecupe ación de
ene xía, a xes ión de lodos, a edución de cus os e a mello a da calidade
dos e luen es en sis emas cen alizados de auga. Pa a cump i con es es
p opósi os, p opuxé onse e analizá onse no os esquemas de a amen o
de augas. Di os esquemas o on a aliados dende un pun o de is a
económico e ambien al du an e es a ese (dende o capí ulo 2 a a o 6). A
in o mación con ida nes es capí ulos, así como os p incipais esul ados
explícanse a con inuación.
Capí ulo 2. A alia as ba ei as ambien ais e económicas asociadas
co escalado da dixes ión anae obia.
Es e capí ulo cen ouse na a aliación da dixes ión anae obia pa a
dis in os amaños de plan as eais de a amen o. Analizá onse ca o
liñas de lodos si uadas en dis in as localidades de España que an dende
os 25.000 habi an es equi alen es (a máis pequena) a a 1.000000
habi an es equi alen es. A p incipal di e enza é que a liña máis pequena
non en dixes ión anae obia men es que as ou as es con igu acións de
lodos si que dispoñen des a unidade. O p incipal obxec i o oi de ini a
escala de plan a de a amen o a pa i da cal con én con igu a a
ecnoloxía da dixes ión anae obia daco do con c i e ios ambien ais e
RESUMO
21
económicos, así como, iden i ica as ba ei as exis en es que impiden
unha implan ación xene alizada.
Os esul ados des e aballo indica on que es a ecnoloxía axuda a educi
os impac os ambien ais e cus os económicos debido á ecupe ación
ene xé ica a a és do biogás. A plan a de a amen o que non en
dixes ión anae obia p esen ou cus os de ope ación máis ele ados
elacionados co consumo ene xé ico e de químicos. Ademais, non se
ob i o ningún bene icio ambien al asociado á ecupe ación ene xé ica.
Cando a ecnoloxía se inco po ou nes a liña ob i é onse bene icios non
só ambien ais senón amén económicos. Se ben é ce o, ó inco po a a
unidade a complexidade ecnolóxica inc emen a. Así mesmo, es án as
limi acións elacionadas co seu endemen o. Unha opción pa a mello a
es e endemen o é a in odución de esiduos o gánicos ou ag ícolas no
p opio dixes o . Non obs an e, a dixes ión anae obia considé ase un
p oceso len o debido a hid ólise (p imei a e apa des e p oceso). Polo
an o, hoxe en día búscanse solucións ecnolóxicas pa a acele a es e
paso. Es as solucións así como da súa p oblemá ica es udá onse no
capí ulo 3.
Capí ulo 3. A aliación compa a i a dos indicado es ambien ais e
económicos das al e na i as de xes ión de lodos des inadas a
mello a a e iciencia ene xé ica e a ecupe ación de nu ien es.
Como se dixo an e io men e, o papel da xes ión de lodos xoga un papel
impo an e den o do esquema de a amen o. Polo an o, a inalidade
des e es udo oi analiza al e na i as pa a acele a a e apa de hid ólise,
mello a a deg adabilidade do lodo e inc emen a a p odución de ene xía.
Pa a es e p opósi o, es udá onse dous p e- a amen os de lodos: i) o
p imei o baseouse na adición de químicos e ou o ii) undamen ouse no
inc emen o de p esión e empe a u a (p oceso e mal) pa a xe a es as
mello as. As no as p opos as compa á onse cun sis ema con encional
(sen p e- a amen o de lodos). Tamén, se incluí on na análise dous ipos
de a amen os inais dos lodos: i) aplicación á ag icul u a e ii)
incine ación.
O sis ema con encional mos ou unha xe ación ene xé ica meno e unha
can idade de lodo maio en compa ación coas liñas de lodos que

RESUMO
22
inco po a on o a amen o químico e e mal. Polo an o, es as úl imas
ob i e on un pe il ambien al meno . En e mos de cus os, os p e-
a amen os asoma on cus os maio es elacionados coa ase de
cons ución pe o que poden se amo izados máis ápido debido á
p odución ene xé ica. A pesa de que no p oceso e mal hai máis
consumo ene xé ico que no químico, o lodo es á lib e de pa óxenos e pode
se aplicado á ag icul u a di ec amen e. Is o implica unha edución maio
en cus os de ope ación.
Con espec o ó a amen o inal dos lodos, a aplicación á ag icul u a
p esen ou mello es impac os, aínda que se debe p es a a ención á
concen ación de me ais pesados e mic ocon aminan es, xa que en
g andes can idades poden p esen a un p oblema de con aminación do
medio no que se aplican.
Unha ez es udada a liña de lodos dos sis emas cen alizados, o seguin e
paso oi p opo modi icacións en oda a plan a de a amen o (liña de
augas e lodos). As ecnoloxías usadas pa a es e in de iní onse nos
capí ulos 4 e 5.
Capí ulo 4: P ocu a da e iciencia ene xé ica nas plan as de augas de
a amen o: a aliación ambien al e económica de opcións
inno ado as
Os esquemas de a amen o es udados du an e es e capí ulo baseá onse
nunha no a es a exia de a amen o das augas que consis e na
ecupe ación de ma e ia o gánica no a amen o p ima io e a eliminación
do ni óxeno median e un p oceso de ni i icación pa cial-anammox. Un
o al de ca o con igu acións deseñá onse pa a unha plan a de 100.000
habi an es equi alen es. Os esquemas baseados na es a exia desc i a
an e io men e ( ecupe ación de ma e ia o gánica + p oceso de
ni i icación pa cial anammox) compa á onse cun on e a unha
es a exia con encional.
Os no os esquemas inco po a on as seguin es ecnoloxías: i) UASB (pola
súa ab e ia u a en inglés, up low anae obic sludge blanke ) seguido dun
p oceso de ni i icación pa cial-anammox denominado IFAS (pola súa
ab e ia u a en inglés, in eg a ed ixed ac i a ed sludge), ii) HRAS (pola
RESUMO
23
súa ab e ia u a en inglés, high a e ac i a ed sludge) unido a un IFAS, e
inalmen e, iii) RBF + CEPT (polas súas ab e ia u as en inglés, o a ing
bel il e ; chemical enhanced p ima y ea men ). O esquema
con encional oi un cla i icado p ima io acoplado a un sis ema
con encional de lodos (CAS polas súas siglas en inglés, con en ional
ac i a ed sludge) con eliminación de ni óxeno.
Os esquemas p opos os mos a on se máis e icien es en e mos de
ene xía ecupe ada a a és do biogás. Non obs an e, es e inc emen o
non xe ou unha diminución do pe il ambien al en odas as
con igu acións, xa que o baseado en RBF + CEPT + IFAS p esen ou
maio es impac os en compa ación cos ou os sis emas an o inno ado es
(UABS + IFAS e HRAS + IFAS) como co con encional (PC + CAS). Es e
inc emen o debeuse á adición de químicos que aínda que p oduza unha
mello a no pe il ene xé ico inc emen a os impac os ambien ais e
económicos. A mello con igu ación en e mos xe ais oi: UASB + IFAS
seguido do esquema HRAS + IFAS. O esquema UASB + IFAS p esen a a
an axe de que non p ecisa dunha liña de lodos moi complexa, xa que a
xe ación dos lodos é moi baixa nes a con igu ación. Is o pode axuda a
esol e a p oblemá ica elacionada coa can idade de lodos que xe an
es es sis emas, así como a súa xes ión e pos e io aplicación. Ou a
an axe dos sis emas inno ado es é que a edución ene xé ica en
ae ación cando se inco po a o p oceso IFAS pode chega a a un 13%.
Es e capí ulo se e pa a comp ende que non odos os esquemas
inno ado es implican mello es esul ados. Nes e sen ido, cando se
inco po a unha no a ecnoloxía, non só é necesa io unha alidación
ecnolóxica senón amén unha alidación dende o pun o de is a
económico e ambien al. Polo an o, a e amen a do análise do ciclo de
ida pe mi e axuda a alo a es as opcións, o cal pode axuda á ho a de
oma decisión ó deseña unha depu ado a.
Capí ulo 5: Consecuencias ambien ais e económicas ligadas á
ecupe ación de ene xía po medio de no os esquemas en plan as
de a amen o eais
Es e capí ulo es á ligado ó an e io debido a que se busca educi a
xe ación de lodo e aumen a a p odución ene xé ica. P opuxé onse
RESUMO
24
a ios esquemas de a amen o de augas esiduais pa a abo da os
desa íos nomeados an e io men e. As modi icacións an dende as e apas
de mode nización, onde se inclúen unidades no idosas en p ocesos
con encionais a a concepcións comple amen e no as, pasando po
modi icacións subs anciais do diag ama de luxo. As p incipais di e enzas
con espec o ó capí ulo an e io é que ago a os esquemas o on
implan ados en dúas plan as de a amen o eais si uadas en dis in os
países eu opeos (España e Dinama ca). Pa a es a a aliación é necesa io
usa e amen as pa a modela , op imiza e selecciona a mello
con igu ación de plan a dende un pun o de is a écnico, económico e
ambien al. En ambas plan as, usá onse da os eais de luxos de en ada
nas depu ado as. Os da os de ene xía, eliminación ou consumo de
químicos ob i é onse a pa i do modelado, que se ixo co so wa e
Ma lab, que é un dos máis comúns pa a modela plan as de a amen o
de augas. Es e aballo xu diu dunha colabo ación e es adía na
Uni e sidade Técnica de Dinama ca (DTU).
P imei o, modelouse a con igu ación eal de cada plan a de a amen o
que consis en en un cla i icado p ima io máis un sis ema de lodos
ac i os. Unha ez se modela on esas dúas plan as, o sis ema con encional
(cla i icado p ima io + sis ema de lodos ac i os) modi icouse po dúas
opcións al e na i as: (i) HRAS + IFAS e (ii) ERBF (pola súa ab e ia u a en
inglés, enhanced o a ing bel il e ) + IFAS. Os da os ob idos no modelado
usá onse pa a calcula os pe iles ambien ais e económicos de cada
con igu ación mencionada an e io men e. As no as con igu acións
demos a on se mello es en e mos de cus os e a o o ene xé ico, o que
p opiciou que o pe il ambien al e económico ose meno que nas
con igu acións con encionais ( PC + CAS).
Nes e capí ulo, o modelado demos ou se unha e amen a de cálculo
e icien e da cal se poden ob e da os álidos pa a calcula pe ís
ambien ais e económicos pa a ob e unha pe spec i a xe al da plan a.
Nes e caso, os no os esquemas axuda on a mello a o nexo auga-ene xía
e consegui que as plan as de a amen o sexan máis e icien es de
manei a in eg al acendo posible engloba es es sis emas de a amen o
den o da economía ci cula .
RESUMO
25
Capí ulo 6: Escalado dunha ecnoloxía inno ado a pa a a análise dos
impac os ambien ais e económicos
Es a p imei a sección ema a cun capí ulo que en como me a demos a
a escala na cal unha ecnoloxía inno ado a p opo ciona da os e alo es
iables pa a ealiza o análise de ciclo de ida e os cus os económicos,
asegu ando o a ance na di ección da eco-e iciencia. Así mesmo, a
impo ancia de medi a ince eza das e amen as de cálculo eside na
súa aplicación pa a sis emas descen alizados (cada ez máis pequenos).
Es e es udo a aliou os impac os ambien ais e económicos dunha
ecnoloxía de eliminación de ni óxeno au ó o o (ELAN® polas súas
siglas en español, eliminación au ó o a de ni óxeno) dende a
concepción de labo a o io (1,5 L) a a a escala eal (2 unidades de 115 m3)
pasando po dúas unidades a escala pilo o (200 L e 1,2 m3). As emisións
indi ec as elacionadas co consumo de ene xía o on a p incipal causa de
impac o en odas as ca ego ías excep o a eu o ización. Tamén se
obse ou que a medida que a escala inc emen a o impac o diminúe.
Á ho a de a alia a iabilidade dos da os, es e es udo p opo cionou que a
mínima á cal en sen ido aplica a análise de ciclo de ida é de 200 L,
men es que pa a os indicado es económicos ixouse en 1 m3 de olume
de eac o . Polo an o, se es as e amen as se aplican a escalas máis
pequenas a ince eza dos da os pode condiciona os esul ados.
A segunda pa e da ese dou o al consis iu en es uda os sis emas
descen alizados e es á o mada po dous capí ulos (Capí ulo 7 e 8)
esumidos a con inuación. Es a sección es á baseada nun p oxec o
eu opeo chamado Run4Li e (polas súas siglas en inglés, “Reco e y and
u iliza ion o nu ien s 4 low impac e ilize ”). Es e p oxec o adop a o
concep o de economía ci cula median e a ecupe ación ene xé ica, auga
ou bio e ilizan es. Con is o o p incipal obxec i o do p oxec o é in en a
cambia o obsole o concep o in de liña que se aplica pa a o a amen o
de augas esiduais. Pa a le a a cabo es e obxec i o o desen ol emen o
ecnolóxico combina ase con ac o es económicos e ambien ais, así como
unha a aliación de iscos non só pa a os compoñen es que poden se
pe igosos pa a a saúde das pe soas senón amén pa a o medio ambien e.
GENERAL INTRODUCTION
32
WWTPs p o ed o be e y e ec i e in emo ing ni ogen,
phospho us, and o ganic ma e . Howe e , in ecen yea s, eme ging
pollu an s called o ganic mic opollu an s (OMPs) ha e eme ged as one o
he p oblems in he WWTPs. OMPs a e de ined as an h opogenic o
na u al subs ances ha include pe sonal ca e p oduc s, pes icides, d ugs,
ho mones o pha maceu ical compounds, among o he s (Ba bosa e al.,
2016). OMPs can con amina e g oundwa e , soil o ege ables. WWTPs
a e no designed o emo e hese compounds and may p omo e hei
dispe sion and dis ibu ion in he en i onmen (Bell e -Domingo e al.,
2017).
Beyond he issue o mic opollu an emo al, WWTPs a e
cha ac e ised by high ene gy consump ion in he p ocess o emo ing
pollu an s and gene a e a signi ican sludge p oduc ion ha mus be
managed co ec ly (Gu e al., 2018). The e o e, hese p oblems can
inc ease he cos s o was ewa e ea men . In addi ion, hese sys ems
may be conside ed en i onmen ally and economically unsui able.
The e o e, i is necessa y o imp o e hese elemen s in o de o ha e
mo e sus ainable sys ems.
As pa o he e o o minimise en i onmen al p oblems and ensu e
access o sa e wa e and sani a ion sys ems, he Uni ed Na ions p omo ed
he adop ion o Agenda 2030 o Sus ainable De elopmen (Uni ed
Na ions, 2015). In his Agenda, 17 objec i es we e de eloped o he
p o ec ion o people and he plane . Wi h ega d o wa e p o ec ion, Goal
6 e e s o "clean wa e and sani a ion", which speci ies he imp o emen
o wa e quali y, was e minimisa ion, emo al o OMPs and he eco e y
o was ewa e p oduc s (Uni ed Na ions, 2015). So, WWTPs should be
adap ed o he new demands o he popula ion and mus be imp o ed.
Howe e , o achie e his pu pose, he bes way o de elop was ewa e
ea men plan s mus be sough om an en i onmen al, economic and
social poin o iew, as well as he bes ea men s a egy o ensu e
global sani a ion and p oduc eco e y.
The p e ious answe s will be de eloped in he ollowing sec ions o
Chap e 1 whe e he change o philosophy o was ewa e will be
explained h ough he concep o ci cula economy (Sec ion 1.2. Ci cula
economy in he was ewa e ea men sec o ). Then, wo s a egies o

CHAPTER 1: INTRODUCTION
33
imp o e he was ewa e ea men sec o will be de ined and explained
(1.3. New was ewa e ea men s a egy o cen alised sys ems and 1.4.
Decen alised app oach o he was ewa e ea men sec ions). Then,
he en i onmen al s a egy (1.5. Li e Cycle Assessmen me hodology and
i s applica ion o was ewa e ea men ) and economic s a egy (1.6.
Economic e alua ion) will be explained, and inally he main objec i es
and mo i a ions o his hesis will be summa ised.
1.2. Ci cula economy in he was ewa e ea men sec o
As men ioned be o e, in he pas , WWTPs ha e been conside ed end-
o -pipe sys ems wi h he main objec i e o ea ing a was e and
discha ging i in o he aqua ic en i onmen . This end-o -pipe model is
known as "linea " economy, which consis s o one-di ec ional model in
which esou ces a e used o p oduce goods ha a e pu chased and,
inally, he goods a e disposed o a e a single use (Figu e 1.1) (Esposi o
e al., 2017). De imen al ai en i onmen al quali y, long- e m economic
s abili y o unsus ainabili y a e he main p oblems o his ype o sys em
(Milla e al., 2019). Cu en ly, and in o de o y o sol e hese p oblems,
end-o -pipe sys ems a e being eplaced by he app oach o ci cula
economy based on a ci cula low model. The main objec i es a e o
p omo e esou ce eco e y, minimise en i onmen al impac and, a he
same ime, encou age g ow h (Figu e 1.2) (Ande sen, 2007).
GENERAL INTRODUCTION
34
Figu e 1.1. Linea economy philosophy
Figu e 1.2. Ci cula economy pe cep ion
In his amewo k, he ole played by he WWTPs (end-o -pipe
elemen s) should be modi ied and adap ed o his new "ci cula "
philosophy. Fo his objec i e, he esou ce eco e y can be a solu ion.
Nu ien s (ni ogen and phospho us) eclaimed wa e and ene gy
eco e y a e key ac o s in mee ing his objec i e. In addi ion, he
educ ion o sludge p oduc ion, as well as ene gy, ha e been unde he
ocus o imp o emen (Ley a-Díaz e al., 2020). These goals can be
CHAPTER 1: INTRODUCTION
35
achie ed h ough he modi ica ion o he was ewa e ea men s a egy
o cen alised sys ems (sec ion 1.3) o he implemen a ion o
decen alised was ewa e ea men schemes (sec ion 1.4). To be e
unde s and hese concep s, bo h a e explained in he ollowing sec ions.
1.3. New was ewa e ea men s a egy o cen alised sys ems
The con en ional app oach o was ewa e ea men is based on
la ge-scale sys ems in which was ewa e is collec ed h ough an
ex ensi e sewe ne wo k. In gene al, his implies high cons uc ion and
ope a ional cos s (Massoud e al., 2009). Mo eo e , he en i onmen al
impac s can inc ease in hese was ewa e schemes since hey a e
cha ac e ised by high ene gy consump ion and la ge sludge gene a ion
(Tang e al., 2020).
I is widely known ha one o he ho spo s in was ewa e ea men
is he ene gy consump ion in ae a ion o he biological p ocess (Gikas,
2017). Con en ional ni i ica ion-deni i ica ion is based on ae obic and
anoxic condi ions. In he i s s age (ni i ica ion p ocess), ammonium is
oxidised o ni a e o ni i e and hen bo h a e educed o dini ogen gas
(deni i ica ion p ocess). The e o e, in ni i ica ion, he e is an elec ici y
consump ion while in deni i ica ion, o ganic ma e is needed
(Iannacone e al., 2019). Ene gy consump ion can a y be ween 0.3
kWh/m3 o 0.6 kWh/m3 (Wan e al., 2016). Addi ionally, he C/N a io
should be highe han 5. An insu icien C/N a io implies he addi ion o
an ex e nal OM sou ce which can inc ease he ope a ional cos s and mo e
sludge p oduc ion (Jiang e al., 2019). Finally, he sludge has a lowe
me hanisa ion ac o because only 30-50% o ola ile solids a e
ans o med in o me hane (Cao and Pawłowski, 2013).
So a , much e o has been de o ed o explo ing new echnologies
and was ewa e al e na i es wi h he main objec i e o making sys ems
mo e sus ainable and ci cula (Gu e al., 2018). In his si ua ion, he
Anammox p ocess, in which ammonium is di ec ly con e ed oge he
wi h ni i e o dini ogen gas, was a e y signi ican ad ance in
was ewa e ea men . In his way, he ene gy in ae a ion can be educed
and an ex e nal sou ce o OM is no necessa y (Vázquez-Padín e al.,
2009). Se e al echnologies ha e been de eloped o use his pa hway o
GENERAL INTRODUCTION
36
emo e ni ogen. In eg a ed ixed ilm ac i a ed sludge (IFAS)
(Malo anyy e al., 2015a); au o ophic ni ogen emo al (ELAN,
eliminación au ó o a de ni ógeno, in Spanish) (Mo ales e al., 2015a) o
SHARON-Anammox (Van Dongen e al., 2001) a e some o hem.
Howe e , hese echnologies do no wo k p ope ly wi h a high
pe cen age o solids o a high C/N a io. Addi ionally, empe a u e and
pH can be limi ing ac o s (Xu e al., 2015).
The p oblems can be sol ed wi h he implemen a ion o a new
was ewa e s a egy ha has been main ained in ecen yea s. This
app oach consis s o eco e ing OM in p ima y ea men and emo ing
ni ogen wi h a pa ial ni i ica ion-Anammox uni . When OM is applied
in p ima y ea men , solids a e emo ed and no inco po a ed in o he
seconda y ea men . In addi ion, p ima y sludge is mo e biodeg adable
han seconda y sludge, so he me hanisa ion ac o is also highe . This
implies a g ea e p oduc ion o biogas ha can be ans o med in o
elec ici y and hea , making he WWTPs mo e sel -su icien in e ms o
ene gy (Pé ez-El i a and Fe nández-Polanco, 2012). New echnologies
such as o a ing bel il e s (RBFs), chemically enhanced p ima y
ea men (CEPT) o high a e ac i a ed sludge (HRAS) ha e been
included as p ima y ea men s (Gu e al., 2018; Rahman e al., 2019;
Ruiken e al., 2013) and o he s mo e widesp ead such as up low
anae obic sludge blanke (UASB) (Malo anyy e al., 2015b).
In addi ion o his echnology subs i u ion and change o s a egy in
he was ewa e line, he sludge line was also imp o ed. As men ioned
abo e, esea ch has been conduc ed in ecen yea s on how o maximise
ene gy p oduc ion in was ewa e ea men plan s o make sys ems
ca bon neu al. Today, he en i onmen al and economic ad an ages o
he anae obic diges ion (AD) uni ha e been p o en in g ea de ail
(Gianico e al., 2015). Howe e , no all was ewa e ea men plan s
include his ype o ea men . AD p ocess consis s o ou s eps:
hyd olysis, acidogenesis, ace ogenesis and me hanogenesis. The i s s ep
(hyd olysis) is a limi ing s ep due o polyme and ex acellula
memb ane p o ec ions (Dai e al., 2016). On he one hand, he main
eason o no implemen ed he AD a all le els is associa ed wi h sludge
p oduc ion. Tha is, in small was ewa e ea men plan s, he sludge
CHAPTER 1: INTRODUCTION
37
gene a ed is no su icien o gua an ee he use o biogas. To sol e his
p oblem, he co-diges ion p ocess can be applied in WWTPs. This me hod
is based on he addi ion o a solid was e ich in o ganic ma e (Gu e al.,
2020) and can imp o e he pe o mance o he AD p ocess o inc ease
biogas p oduc ion. Al e na i ely, he in eg a ion o a p e- ea men in he
sludge line may also a ou he p ocess as his ype o p e- ea men s aim
o accele a e he hyd olysis s ep, and o imp o e sludge dewa e ing.
Sludge p e- ea men s a e di ided in o ou main ypes: he mal,
chemical, physical and biological (Abellei a-Pe ei a e al., 2015; Neumann
e al., 2016). The mal p e- ea men consis s o he solubilisa ion o
complex o ganic ma e by inc easing empe a u e and p essu e
(Se ano e al., 2015). Op imal empe a u es can ange om 150 °C o
180 °C, while p essu e a ies om 600-2500 kPa (Elalami e al., 2019).
This uni is used o wo k in cycles o abou 30 o 60 min, and depending
on he cha ac e is ics o he p ocess, can achie e an ene gy inc ease o
abou 51% (Boug ie e al., 2008).
Biological p ocesses a e based on enzyma ic hyd olysis o he
addi ion o ungi/bio-su ac an s (Zhen e al., 2017). The addi ion o hese
compounds wo ks bes a he mophilic empe a u e because he
inc ease in his a iable p omo es he hyd olysis o he aw ma e ials (Ge
e al., 2010). The inc ease o me hane can luc ua e be ween 25% and
69% (Bolzonella e al., 2012). Rega ding chemical p e- ea men s, when
he e is a chemical addi ion, alkaline and acidic chemicals a e he mos
s udied (Khiewwiji e al., 2015a). Howe e , hese al e na i es can cause
p oblems o p ecipi a ion o inhibi ion, so hei addi ion mus be done
e y ca e ully. Fo his eason, o he me hods ha e been s udied such as
ee ammonia (Wei e al., 2018) o oxida ion wi h ozone o H2O2 (Chacana
e al., 2017; Yu e al., 2018). The main p oblems o his ype o p e-
ea men a e ha ammonia can inhibi he AD p ocess and oxida ion
equi es a lo o ene gy and a la ge consump ion o chemicals. Thus, hese
ac o s can penalize hese p e- ea men schemes when in oduced in o
he sludge line.
Finally, physical p e- ea men can be di ided in o high p essu e,
lysis, mic owa e and ul asound. High p essu e is simila o he mal p e-
ea men bu only by inc easing ope a ing p essu e. The e a e se e al

GENERAL INTRODUCTION
38
publica ions in which his p e- ea men can achie e a me hane
enhancemen o 60-80% (Engelha e al., 2000; Khiewwiji e al., 2015b).
Lysis is a simple p e- ea men ha causes pa ial cell des uc ion and
imp o es he biogas ield by abou 15-26% (Dohányos e al., 1997). As o
mic owa e and ul asound me hods, in addi ion o imp o ing biogas and
sludge dewa e ing, hey can also help elimina e pa hogens in he sludge.
Howe e , hese p ocesses can be ene gy-in ensi e, so biogas yield should
be highe han in he o he scena ios. Howe e , he de elopmen o hese
p e- ea men s is s ill in he labo a o y o pilo plan (Feng e al., 2009;
Neumann e al., 2016).
Al hough he e a e a wide ange o sludge p e- ea men s, hey all
ha e he same objec i es, namely, o imp o e biogas p oduc ion o mo e
independen ene gy sys ems and o imp o e sludge dewa e ing. In his
way, ope a ional cos s ela ed o sludge managemen can be signi ican ly
educed. The e o e, he new design o he WWTP can include all hese
concep s. Howe e , i is ue ha many o hese echnologies a e s ill
unde de elopmen and mo e esea ch is needed o ensu e ha hese
assump ions a e ul illed.
1.4. Decen alised app oach o was ewa e ea men
As men ioned abo e, was ewa e ea men is cons an ly changing
o seek di e en app oaches ha a e mo e sus ainable. Wi hin his
amewo k, he decen alised sys em o was ewa e ea men has
gained s eng h in ecen yea s (Hophmaye -Tokich, 2006). These
sys ems a e based on he sepa a ion o was ewa e gene a ed a di e en
poin s in a household. Black wa e (BW) is gene a ed in oile s, while g ey
wa e (GW) e e s o wa e om laund y, showe s, sinks o dishwashe s
(Ashok e al., 2018). Finally, ki chen was e (KW) is o ganic was e and can
be ea ed wi h he BW o sepa a ely.
The main ad an ages o hese sys ems compa ed o he cen alised
pe spec i e a e lexibili y and he elimina ion o long sewe sys ems
(Leigh and Lee, 2019). In addi ion, wa e euse and nu ien eco e y a e
inc eased due o sou ce sepa a ion. While BW and KW a e mo e
app op ia e o ene gy and nu ien eco e y, GW is used in i iga ion
because he concen a ion o pollu an s is e y low (Kobayashi e al.,
CHAPTER 1: INTRODUCTION
39
2020). These sys ems a e also mo e app op ia e o u al a eas and
de eloping coun ies because in es men and main enance cos s can be
economically mo e iable han con en ional sys ems (Machado e al.,
2017; Zeng e al., 2017).
Decen alised sys ems combine echnologies ha a e applied in
con en ional was ewa e ea men plan s and mo e inno a i e ones.
Rega ding GW, se e al echnologies ha e been s udied in ecen yea s
(Ashok e al., 2018; Boyjoo e al., 2013). The mos applicable a e
cons uc ed we lands (CW) due o he simplici y o ope a ion and low
ene gy consump ion ha implies lowe ope a ing cos s (Ga í e al., 2017;
Wu e al., 2015). In simple e ms, his echnology is conside ed as a
complex na u al bio eac o in which i e a ions occu be ween plan s, soil
and sedimen s (Co o o e al., 2019). The ype o ege a ion, subs a e,
mic oo ganism and physicochemical pa ame e s a e key ac o s o i s
applica ion (Co o o e al., 2019; Hijosa-Valse o e al., 2011). Howe e ,
hese sys ems equi e a la ge land a ea, which can be oublesome o
hei implemen a ion (A den and Ma, 2018).
In his con ex , memb ane bio eac o s (MBRs), mo ing bed bio ilm
bio eac o s (MBBRs) and sequencing ba ch eac o s (SBRs) ha e
eme ged as an al e na i e o ea ing GW. These sys ems a e mo e
compac , so he land use is lowe han in GW and p o ide a high-quali y
e luen . Howe e , hese echnologies a e mo e ope a ionally complex
and elec ici y consump ion is highe han in CWs (Ceccone e al., 2019;
Jab i e al., 2020). The ope a ion o hese uni s consis s o a combina ion
o ae a ion and non-ae a ion pe iods. The main di e ence is ha in MBR
and MBBR he e is a memb ane in eg a ed in he uni (Komesli and
Gökçay, 2014), while in SBR he emo al o OM o nu ien s is
accomplished (Vázquez-Padín e al., 2010a). The e luen can be used o
i iga ion o g een a eas, s ee washing o illing oile s (Chen and Wang,
2009) (Figu e 1.3).
GENERAL INTRODUCTION
40
Figu e 1.3. Mos commonly used echnologies o he ea men o
g eywa e . Abb e ia ions: GW: g ey wa e , CWs: cons uc ed we lands, SBR:
sequencing ba ch eac o s and MBR: memb ane bio eac o s.
BW and KW can be ea ed oge he o sepa a ely, bu he goal is he
same (nu ien s and ene gy eco e y). In e ms o BW, i is impo an o
dis inguish he ype o oile s ha can be implemen ed in a house.
Con en ional oile s a e he mos common and acuum oile s (new
sys ems). In con en ional oile s, wa e consump ion is high, be ween 6-
8 L pe lush, while in acuum oile s i is app oxima ely 1-2 L pe lush
(Gao e al., 2019). This implies ha in acuum oile s was ewa e is mo e
concen a ed and he p oduc ion o biogas will be highe han in
con en ional oile s. Howe e , acuum oile s en ail ene gy consump ion
and he noise gene a ed by each lush can be e y annoying (Bisschops e
al., 2019).
The main echnologies used o ea his ype o was ewa e a e
UASB (Kujawa-Roele eld e al., 2006) and anae obic memb ane
bio eac o s (anMBR) (P e el e al., 2016). Bo h a e cha ac e ised by he
ans o ma ion o OM in o biogas, which is alo ised in o elec ici y and
hea . In addi ion, high empe a u e anae obic diges ion (HTAD) has been
de eloped in ecen yea s o ea BW. The main di e ence wi h he o he
echnologies is ha his eac o wo ks a empe a u es o abou 70 °C.
This means ha he wa e is ee o pa hogens and can be applied di ec ly
CHAPTER 1: INTRODUCTION
41
o ag icul u al i iga ion (Zhang e al., 2020). AnMBRs and UASB can
wo k a ambien o mesophilic empe a u e (abou 35 °C). Howe e ,
when hese uni s wo k a ambien empe a u e, hey may ha e p oblems
wi h dissol ed me hane in he e luen , so his ac o should be aken in o
accoun when applying hem (Allegue e al., 2020).
In addi ion o ene gy, nu ien eco e y is ca ied ou in his ype o
was ewa e (BW and KW). Wi hin his amewo k, he s u i e uni is he
mos s udied me hod o phospho us eco e y and consis s o a physical-
chemical sepa a ion in which magnesium sal s a e added o acili a e
s u i e p ecipi a ion (Ishii and Boye , 2015). In his uni , he pH is a key
pa ame e and mus be con olled in a ange be ween 8-9 (Liu e al.,
2008). In addi ion, many di e en ypes o eac o s ha e been s udied by
di e en au ho s o achie e he bes phospho us eco e y (Le Co e e
al., 2009; Rahaman e al., 2014).
O he echnologies ocus on ni ogen eco e y, such as s ipping
me hods o bioelec ochemical sys ems (BES). S ipping me hods and
subsequen so p ion in sulphu ic o ni ous acid a e highly ene gy-
dependen (Bisschops e al., 2019). Bioelec ochemical p ocesses could
sepa a e di e en ypes o ions such as NO3-, NO2- o NH4+ (Kun ke e al.,
2018). The o al ammonia ni ogen is concen a ed by he in luence o an
elec ical cu en and anspo ed o he ca hode. Ni ogen is hen
eco e ed h ough s ipping. Howe e , in his me hod, he e is no
chemical addi ion (Bisschops e al., 2019). The main echnologies o
ea ing BW and KW a e summa ised in Figu e 1.4.
GENERAL INTRODUCTION
48
(2018) analysed e ia y echnologies and sludge managemen
al e na i es o di e en ni ogen emo al echnologies (Ja a inejad,
2017). Mo eo e , o he au ho s s udied he o al cos s o a gi en
echnology. P e el e al., (2016) es ima ed ha an anMBR uni can be
alues be ween 0.03 o 0.12 €/m3. In he case o MBR echnology, he e
a e mo e s udies ha es ima ed highe alues o 0.08 o 0.25 €/m3 (Gil e
al., 2010). Mo e ecen ly, o decen alised echnologies, Resende e al.
(2019) s udied we land cos s, be ween 1.55 $/m3 o 0.84 $/m3. Howe e ,
i is impo an o no e ha he economic indica o s can change
conside ably om coun y o coun y and o e he yea s. These changes
a e ela ed o changes in elec ici y, pe sonnel o chemicals, among
o he s. In his hesis, he cos s will be adap ed o he di e en
con igu a ions and coun ies and will be calcula ed aking in o accoun
he possible de ia ions.
1.7. Thesis ou line: objec i es and s uc u e
The main goal o his doc o al hesis was o analyse and compa e
di e en was ewa e ea men con igu a ions om an en i onmen al
and economic poin o iew o p o ide insigh s on he sus ainabili y o
exis ing and inno a i e schemes o was ewa e ea men . Wi h his in
mind, he hesis was s uc u ed in 2 sec ions: one o cen alised sys ems
and o he o decen alised schemes. Sec ion I is de eloped in 5 chap e s,
whe eas Sec ion II is composed by 2 chap e s. Finally, he main
conclusions o his hesis will be summa ised in Chap e 9.
Chap e 1 p esen s he s a e o he a in he was ewa e ea men
sec o . The main objec i e is o ha e a gene al idea abou he p oblems o
he was ewa e sec o , he impo ance o he ci cula economy and he
di e en schemes ha can be implemen ed o imp o e WWTPs.
Mo eo e , he me hodological ools used in his hesis will be explained
o be e unde s and i s applica ion.
Sec ion I: Imp o ing cen alised was ewa e sys ems. In his
sec ion di e en schemes and echnologies we e e alua ed o imp o e
he ene gy-wa e nexus om an en i onmen al and economic poin o
iew. Chap e s 2 and 3 a e ocused on echnologies o imp o ing he
sludge line a di e en sizes. In Chap e s 4 and 5, was ewa e ea men

CHAPTER 1: INTRODUCTION
49
schemes will be changed. New con igu a ions will be explo ed om an
en i onmen al and economic poin o iew o y o sea ch mo e e icien
con igu a ions. In Chap e 5, wo eal WWTPs in di e en coun ies will
be analysed and compa ed wi h he exis ing plan . The main objec i e o
his wo k is o achie e mo e e icien sys ems ha do no depend on he
elec ici y g id, as well as o imp o e he quali y o he e luen s. Finally,
he las chap e ha akes pa in his sec ion (Chap e 6) has as objec i e
o assess he scale-up o a echnology ocused on nu ien emo al. The
main eason o e alua ing his echnology is o e i y he eliabili y o
he LCA and economic indica o s in small scale as, o example, in
decen alised sys ems. In his way, hese esul s can se e o ha e a
e e ence when he decen alised sys ems (sec ion II) a e s udied.
Sec ion II: Changing he pa adigm o was ewa e ea men . This
sec ion is ocused on he e alua ion and implemen a ion o di e en
decen alised con igu a ions. In Chap e 7, a was ewa e ea men plan
based on a MBR is going o analyse o eco e ing eclaimed wa e in
Tu key which is a coun y wi h wa e de ici . Addi ionally, he
cons uc ion phase will be included in he analysis o know how a ec he
cons uc ion in he decen alised was ewa e schemes. In Chap e 8, wo
decen alised schemes a e s udied a neighbou hood le el and compa ed
wi h a cen alised sys em wi h he main objec i e o know i he ca bon
oo p in and wa e consump ion o a pe son who li es in a decen alised
a ea inc ease o dec ease in compa ison wi h a pe son ha decide o li e
in a cen alised zone. In his case, he chap e s co e he concep o
eco e y (ene gy and wa e ) bu also om he inhabi an pe spec i e.
Conclusions. The conclusions chap e aims o gi e a holis ic and
in eg a ed iew o he main indings and jus i ies he main con ibu ions
o he s udy. Fi s , a compa ison be ween di e en cen alized schemes
will be e alua ed o show which is he bes con igu a ion in e ms o
ene gy, e luen quali y and sludge p oduc ion. Finally, in he
decen alized schemes, he main indings and ad an ages o hese
sys ems in e ms o ene gy and wa e eco e y will be summa ized.
GENERAL INTRODUCTION
50
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2612. h ps://doi.o g/10.2166/ws .2013.537

IMPROVING CENTRALISED
WASTEWATER TREATMENT
SYSTEMS
And ea A ias*a, Gume sindo Feijooa, Ma ía Te esa Mo ei aa. “Wha is he bes scale o implemen ing he anae obic
diges ion acco ding o en i onmen al and economic indica o s?” Jou nal o Wa e P ocess and Enginee ing. 2020,
Vol. 32, 101235. h ps://doi.o g/10.1016/j.jwpe.2020.101235. aCRETUS ins i u e. Depa men o Chemical
Enginee ing. Uni e sidade de San iago de Compos ela, E-15782, San iago de Compos ela, Galicia, Spain
CHAPTER 2: Iden i ying en i onmen al and economic
ba ie s associa ed wi h he scale o ope a ion in he
anae obic diges ion p ocess
SUMMARY
WWTPs a e he mos widely used en i onmen al managemen
sys ems o ensu e ha wa e pollu ion is p ope ly managed. Since ene gy
cos s a e he la ges ac o in ope a ing cos s, new ins alla ions a e
designed unde ene gy op imisa ion pa ame e s. The AD uni allows he
alo isa ion o he o ganic load in o bioene gy. Howe e , no all WWTPs
inco po a e his echnology in he sludge line since a minimum scale
plan is equi ed o gua an ee s able and p o i able ope a ion o he uni .
Small ea men plan s imply a ce ain o e sizing o elec omechanical
equipmen , so ha he uni consump ion in such plan s is ela i ely high.
In la ge ea men plan s, he design and sizing a e op imized o achie e
g ea e con ol o e ene gy consump ion. Wi h he decen alized con ex
gaining momen um, i is impo an o assess he iabili y o AD in small
plan s.
In his chap e , ou di e en sludge lines wi h di e en plan sizes
we e e alua ed om an en i onmen al and economic poin o iew. The
sludge lines ange om 25,000 o 1,000,000 o equi alen inhabi an s,
al hough he small sludge line has no AD uni . A ga e- o-ga e app oach
was selec ed o pe o m he LCA. Acco ding o he esul s ob ained in
Chap e 2, he en i onmen al impac s o he AD echnology a e no
co ela ed wi h he size o he plan , so ha no only medium and la ge-
scale plan s epo en i onmen al and economic bene i s, bu also
smalle ones, p o ided ha he p emise o biogas low alo isa ion in o
bioene gy is me . Mo eo e , he AD echnology can be imp o ed wi h he
addi ion o ag owas e ha can enhance he o ganic load in anae obic
diges o and imp o e he yield o biogas p oduc ion and he eco-
e iciency. This al e na i e allows o imp o e he echnological, economic
and en i onmen al iabili y o he p ocess.
SECTION I: IMPROVING CENTRALISED WASTEWATER SYSTEMS
68
TABLE OF CONTENTS-CHAPTER 2
2.1. In oduc ion ............................................................................................... 69
2.2. Ma e ials and me hods ........................................................................... 70
2.2.1. Goal and scope de ini ion .............................................................. 70
2.2.2. Func ional uni .................................................................................. 71
2.2.3. Sys em bounda ies .......................................................................... 71
2.2.4. Li e cycle in en o y app oach ..................................................... 73
2.2.5. Li e cycle impac assessmen and in e p e a ion ................. 76
2.2.6. Economic indica o s ........................................................................ 77
2.3. Resul s and discussion ........................................................................... 77
2.3.1. En i onmen al p o ile o he di e en sludge lines ............ 77
2.3.2. Assessmen o he easibili y o he anae obic diges ion
(AD) uni .......................................................................................................... 80
2.3.3. Ene gy bene i in he di e en sludge lines ........................... 82
2.3.4. Economic analysis o he di e en sludge lines .................... 83
2.4. Conclusions ................................................................................................ 85
2.5. Re e ences .................................................................................................. 85
CHAPTER 2: IDENTIFYING ENVIRONMENTAL AND ECONOMIC BARRIERS ASSOCIATED
WITH THE SCALE OF OPERATION IN THE ANAEROBIC DIGESTION PROCESS
69
2.1. INTRODUCTION
As men ioned in Chap e 1, he WWTPs a e essen ial ac o s o he
ea men o was ewa e p io o i s discha ge in o he en i onmen (Pan
e al., 2015). In his con ex , he con igu a ion o new acili ies is
unde going a p ocess o dynamic change h ough he implemen a ion o
echnologies ha en ail lowe en i onmen al impac s and economic cos s
(Gude, 2015). In gene al, he high cos s ela ed o sludge managemen
and low ene gy p oduc ion a e wo key ac o s ha penalise he
ope a ion o WWTPs.
In e ms o ope a ional cos s, sludge p oduc ion can imply abou
50% o he o al cos s in a WWTP (Lo enzo-Toja e al., 2016b). Among he
di e en echnologies o sludge ea men , he mos widely implemen ed
al e na i e is cons i u ed by a hickening uni ollowed by
homogenisa ion and dewa e ing uni s (Rod iguez-Ga cia e al., 2011). In
his scheme, sludge is ea ed as a was e, so he e a e no en i onmen al
o economic bene i s. The mos widely used al e na i e in WWTPs o he
alo isa ion o biogas is he AD p ocess. Mo eo e , he solid ac ion can
be used as e ilise (Ka agiannidis and Pe koulidis, 2009). Howe e , no
all WWTPs in eg a e his sludge ea men scheme, which is a ibu ed o
he need o a minimum size o he ea men plan o ensu e s able and
cos -e ec i e ope a ion o he uni . In he con ex o popula ion g ow h,
in which new ea men plan s a e planned o ea he was ewa e o
newly buil dwellings wi h limi ed cen alised se ices, he e is an
undeniable in e es in assessing he iabili y o he AD echnology a
di e en sizes.
In his amewo k, i is in e es ing o combine an en i onmen al
app oach wi h he economic o cos s analysis associa ed wi h was ewa e
and sludge ea men s (Nelson e al., 2008). Bea ing in mind ha his uni
has signi ican bene i s, he ques ion a ises as o why i is no a uni e sal
and undeniable op ion o any ype o ea men plan . In addi ion, i is
impo an o compa e sludge lines lacking an AD uni wi h schemes ha
inco po a e his echnology in o de o alida e o ule ou i s
implemen a ion. Wi h his in mind, he main goal o Chap e 2 was o
e alua e he implemen a ion o he AD uni no only on a echnological
basis, bu also on he economic and en i onmen al ad an ages ha his

SECTION I: IMPROVING CENTRALISED WASTEWATER SYSTEMS
70
uni may ha e in di e en plan sizes. Consequen ly, i is impo an o
de ine he scale o he ea men plan om which i is con enien o se
up he AD echnology acco ding o en i onmen al and economic c i e ia
and o iden i y he exis ing ba ie s ha impede a gene alised
implemen a ion.
2.2. MATERIALS AND METHODS
2.2.1. Goal and scope de ini ion
En i onmen al and economic indica o s o he di e en sludge lines
o eal WWTPs, all o hem loca ed in Spain, we e e alua ed. Fou plan
sizes we e selec ed: i) one small (Scena io 0: 25,000 equi alen
inhabi an s); ii) wo medium (Scena ios 1 and 2: 200,000 and 400,000
equi alen inhabi an s, espec i ely) and, inally, iii) one la ge (Scena io
3: 1,000,000 equi alen inhabi an s). The plan s ha e di e en
was ewa e ea men lows, om 6,250 m3/d o S0 o 213,410 m3/d o
S3. The plan s a e mainly based on he ac i a ed sludge p ocess o
emo e OM. The small plan does no ha e a p ima y ea men , bu only
a p e- ea men o emo e g eases and solids, while he medium and
la ge plan s ha e a p ima y ea men o emo e solids and OM. Fo all
scena ios, a compos ing uni o he sludge was conside ed as a
managemen op ion as a bio e ilise . The main di e ences co espond
o he sludge line scheme.
The small plan (S0) consis s o a hickening uni , a homogenise and,
inally, a il a ion uni wi h a dewa e ing band il e . I is he e o e a basic
sludge line wi hou an AD uni . The o he plan s ha e an analogous
con igu a ion, excep o he ac ha hey include an AD uni o di e en
size, coupled o a cogene a ion hea powe (CHP) uni o ans o m biogas
in o elec ici y (Figu e 2.1).
CHAPTER 2: IDENTIFYING ENVIRONMENTAL AND ECONOMIC BARRIERS ASSOCIATED
WITH THE SCALE OF OPERATION IN THE ANAEROBIC DIGESTION PROCESS
71
Figu e 2.1. Di e en WWTP localisa ion conside ed in his s udy
2.2.2. Func ional uni
In his case, he s udy is ocused on biogas p oduc ion, bu i is no
possible o choose 1 kWh o ene gy p oduced because he small plan
does no ha e an AD uni , which would no allow he compa ison o
di e en ypes o plan . Fo his eason, 1 on o mixed sludge was
selec ed as FU, acco ding o o he publica ions ela ed o he opic o
sludge managemen (Dong e al., 2014).
2.2.3. Sys em bounda ies
To make he en i onmen al assessmen o he di e en sludge lines,
only he impac s associa ed o he ope a ional phase we e aken in o
accoun . The en i onmen al impac s ela ed o he cons uc ion and
decommissioning phases can be conside ed non-signi ican . This is
because he ope a ion o he acili y is conside ed mo e ele an o he
impac ca ego ies han he o he phases (Lassaux e al., 2007; Lundie e
al., 2004). All mass and ene gy lows o he di e en sludge lines we e
quan i ied. Figu e 2.2 shows he sys em bounda ies o he sludge lines.
SECTION I: IMPROVING CENTRALISED WASTEWATER SYSTEMS
72
Figu e 2.2. Sys em bounda ies o he di e en case s udies
CHAPTER 2: IDENTIFYING ENVIRONMENTAL AND ECONOMIC BARRIERS ASSOCIATED
WITH THE SCALE OF OPERATION IN THE ANAEROBIC DIGESTION PROCESS
73
2.2.4. Li e cycle in en o y app oach
In en o ies we e pe o med wi h p ima y ( eal da a coming om
he di e en sludge lines) and seconda y da a (es ima ed and
bibliog aphic da a). P ima y da a a e associa ed o he cha ac e is ics o
sludge such as ni ogen, phospho us o hea y me als, elec ici y
consump ion and biogas p oduc ion o he di e en plan s. Seconda y
da a comp ise ai emissions om he AD uni o sludge applied in
ag icul u e (De V ies e al., 2012). In addi ion, he da a we e comple ed
wi h he Ecoin en 3.5 da abase (Weidema e al., 2013). Se e al
simpli ica ions we e conside ed o make a mo e eliable LCI. All hese
da a a e p esen ed in Table 2.1 (main inpu s o he sludge lines) and
Table 2.2 (main ou pu s o he sys ems).
The Spanish elec ici y mix has been upda ed wi h he mos ecen
scena io acco ding o he annual epo o Red Eléc ica Española (REE,
2018). In addi ion, ansmission losses associa ed o he elec ici y we e
aken in o accoun . Eu o 4 ucks wi h a capaci y be ween 16 and 32
we e selec ed o he anspo o chemicals and sludge. An a e age o 25
km was selec ed as a medium dis ance (Hospido e al., 2004).
Biogas losses we e es ima ed a 1.5% o he o al biogas p oduc ion
(Lijó e al., 2017) and ai emissions associa ed wi h he applica ion o
sludge o he soil as e ilise and o he compos ing plan we e calcula ed
acco ding o he li e a u e (Bold in e al., 2009).
SECTION I: IMPROVING CENTRALISED WASTEWATER SYSTEMS
80
Figu e 2.3. Compa ison o he CC ou comes wi h and wi hou biogas
losses (FU: 1 on o mixed sludge). Symbols: S0 (□): small plan ; S1.1 and
S2.1(o): medium plan wi hou biogas losses; S1.2 and S2.2 (Δ): medium plan
wi h biogas; S3.1 (◊): la ge plan wi h biogas losses; S3.2(◊): la ge plan wi hou
biogas losses.
2.3.2. Assessmen o he easibili y o he anae obic diges ion (AD)
uni
Conside ing he in e es in implemen ing small-sized AD uni s, his
sec ion conside s wo main objec i es: (i) whe he o no he AD uni
imp o es he en i onmen al p o ile in S0, and (ii) o s udy he
impo ance o ene gy eco e y in sludge ea men .
The s udy was ca ied ou o he CC ca ego y because his ca ego y
is mo e sensi i e and is di ec ly ela ed o ene gy consump ion and
biogas losses. As in he p e ious scena ios, biogas losses a e es ima ed a
1.5% o he o al biogas p oduc ion. The esul s a e shown in Figu e 2.4.
The in eg a ion o he AD uni shows an imp o emen in he
en i onmen al p o ile o a ound 10%. This posi i e e ec is due o he
p oduc ion o biogas ha allows a pa ial au onomy o he use o ene gy
om he g id. This also means ha , om an en i onmen al poin o iew,
he AD echnology will be app op ia e o his plan size.
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0 200,000 400,000 600,000 800,000 1,000,000 1,200,000
CC [ kg CO2eq/ FU]
h-e
S0
S1.2
S1.1
S2.1
S2.2
S3.2
S3.1

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WITH THE SCALE OF OPERATION IN THE ANAEROBIC DIGESTION PROCESS
81
Figu e 2.4. Sensi i i y analysis o he small plan wi h and wi hou AD
echnology
Some au ho s e alua e he inco po a ion o echnologies such as
UASB o AnMBRs in small communi ies (less han 2,000 equi alen
inhabi an s) because hey can ha e bene i s such as biogas p oduc ion,
which can make hese small plan s sel -su icien in e ms o ene gy
(Kujawa-Roele eld e al., 2006; P e el e al., 2016). Howe e , o he
ea men o p ima y and seconda y sludge in his ype o plan , ex ensi e
in o ma ion on he ope a ional limi in e ms o size is no a ailable.
Pa an e al. (2007) s udied he e iciency o AD echnology wi h a
popula ion equi alen ange o 1,000 o 3,000 inhabi an s. Howe e , his
sludge was mixed wi h municipal solid was e. The e o e, o he AD
echnology o be app op ia e on a smalle scale, i would be necessa y o
ope a e wi h a highe o ganic load, such as mixing sewage sludge wi h
ag icul u al was e. The need o implemen a cogene a ion sys em
sui able o smalle diges e sizes should also be conside ed o ensu e
biogas alo isa ion.
This commen poin s ou a ecu en si ua ion in many WWTPs,
whe e biogas is p oduced and bu ned di ec ly in a o ch. In his sense, i
is impo an o highligh he ole o ene gy p oduc ion in achie ing he
wa e -ene gy nexus. The esul s o his analysis ( wo medium and one
la ge plan s) a e shown in Figu e 2.5. I biogas is no used in he WWTPs,
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
S0
CC [kg CO2eq/FU]
SECTION I: IMPROVING CENTRALISED WASTEWATER SYSTEMS
82
no only can he en i onmen ally impac s inc ease, bu also he ope a ing
cos s. In S1, en i onmen al impac s may inc ease by 10%; in he case o
he o he plan s, his inc ease in impac s is e en g ea e : abou 33% in S2
and 28% in S3. These esul s show he impo ance o biogas alo isa ion,
which is c ucial in he eco-e iciency p o ile o WWTPs.
Figu e 2.5. Sensi i i y analysis o he di e en plan sizes conside ing o
no he ene gy use. Symbols: (Δ) wi hou ene gy eco e y; (o) wi h ene gy
eco e y
2.3.3. Ene gy bene i in he di e en sludge lines
To e alua e he ene gy bene i o di e en sludge lines, an indica o
called Ene gy Re u n on In es men (EROI) was calcula ed. This indica o
is use ul o calcula e he ene gy p oduced in he sludge line in ela ion o
he ene gy consumed in he sludge line i sel . I he indica o is highe
han 1, he plan has a posi i e ene gy balance, which makes i ene gy
sel -su icien . Howe e , i he indica o is less han 1, he plan is no
ene gy e icien . EROI indica o is ep esen ed by Eq.1 (Bisinella de Fa ia
e al., 2015):
EROI= Elec ici y p oduced
Elec ici y consumed
[1]
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
S1 S2 S3
CC [kg CO2eq/FU]
CHAPTER 2: IDENTIFYING ENVIRONMENTAL AND ECONOMIC BARRIERS ASSOCIATED
WITH THE SCALE OF OPERATION IN THE ANAEROBIC DIGESTION PROCESS
83
The e o e, i he small plan has no AD uni , i s EROI alue is ze o
because he e is no elec ici y p oduc ion. Howe e , when he AD uni is
inco po a ed in o he sludge line, he EROI alue changes and is
app oxima ely 0.13, his means ha abou 13% o he elec ici y can be
supplied by he biogas ans o med in o elec ici y. As o he o he
plan s, he EROI alues o medium-sized plan s a e 0.39 (S1) and 1.41
(S2). Finally, he alue o he la ge plan is 1.19 (S3). Acco ding o hese
alues, o S2 and S3 i is no necessa y o consume ene gy om he g id
in he sludge line. In addi ion, he managemen o he plan is c ucial o
ha e a sa is ac o y sludge-ene gy nexus. The di e ence be ween S1 and
S2 a e e y signi ican when bo h plan s a e conside ed medium-sized
plan s. The e o e, o eco e biogas and ene gy he plan s mus be
p ope ly managed.
2.3.4. Economic analysis o he di e en sludge lines
F om he pe spec i e o economic analysis, ope a ional cos s a e
di e en om hose ob ained by conside ing he en i onmen al impac s
(Figu e 2.5). Consequen ly, he la ge plan (S3) p esen s he bes
economic esul s wi h an app oxima e alue o 50 €/ on o mixed sludge,
ollowed by he medium-sized plan s wi h app oxima e alues o 50-
71€/ on o mixed sludge. The use o biogas in he plan i sel can esul in
a bene i o be ween 11 and 9 €/ on o mixed sludge. These alues a e
e y impo an o educing he ope a ional cos s. In he small plan
lacking he AD uni , cos s a e highe (107 €/ on o mixed sludge). This
can esul in abou 30% mo e in o e all ope a ing cos s. In addi ion, in
he small plan , he e is a highe consump ion o polyelec oly e o
achie e adequa e sludge dewa e ing. Thus, i only he consump ion o
chemicals is compa ed, he ope a ing cos s inc ease by 98% compa ed o
he es o he plan s.
Finally, ope a ing cos s ela ed o sludge disposal a e highe in he
medium and la ge plan s. This makes sense because he amoun o sludge
ha needs o be managed, especially in he la ge plan . The end in small
plan s may change when he AD uni is inco po a ed in o he sludge
scheme. I he biogas is eco e ed and used in he plan , he o al
ope a ional cos s can be educed by 10%. This educ ion is no only due
o he biogas p oduc ion, bu i also o he educ ion o polyelec oly e
SECTION I: IMPROVING CENTRALISED WASTEWATER SYSTEMS
84
consump ion, which also educes he indi ec emissions associa ed wi h
he chemical consump ion. Thus, he AD echnology educes ope a ing
cos s, and he la ges plan p esen s he mos a ou able cos s.
Despi e he posi i e economic indica o s, Kalba e al., (2012) a gue
ha he AD echnology canno be implemen ed a all scales because he
amoun o sludge mus be su icien and gua an eed. In his sense, he e
a e o he esidues such as ag icul u al, li es ock o ood was e. I his
ype o was e is in oduced in he AD uni , he p oduc ion o biogas will
be highe , and he bene i s will inc ease be ween 0.05 and 0.20 €/kWh o
elec ici y gene a ed. The ange is e y di e en because, as al eady
men ioned, he ype o was e is e y impo an . Fo example, manu e
canno ha e an accep able e iciency in he AD uni due o he amoun o
wa e i con ains (Vasco-Co ea e al., 2018). In addi ion, hese economic
cos s ake in o accoun he bene i s o using sludge as bio e ilise .
Figu e 2.5. Compa ison o he economic esul s om he di e en plan sizes
(FU: 1 on o mixed sludge). Symbols: □ small plan , o medium plan (scena io
1), Δ medium plan (scena io 2), ◊ la ge plan
In o he wo ds, he sa ings om no ha ing o pu chase mine al
e ilise s, which can be a ound 50% o he o al cos s o e ilise s
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0 200 400 600 800 1,000 1,200
OPEX [€/FU]
1000 m h-e
S0
S1
S2
S3
CHAPTER 2: IDENTIFYING ENVIRONMENTAL AND ECONOMIC BARRIERS ASSOCIATED
WITH THE SCALE OF OPERATION IN THE ANAEROBIC DIGESTION PROCESS
85
(F ank, 1998). As men ioned abo e, a plan size o 25,000 equi alen
inhabi an s canno be conside ed as a small plan . I is ue ha , in his
case, he use o esou ces such as biogas o bio e ilise s ha e a high
a iabili y cos s and a e mo e limi ed. This is because i is di icul o
quan i y he bene i s o hese p oduc s because some imes he
echnology is no app op ia e and does no allow he ans o ma ion o
biogas in o ene gy o he use o bio e ilise s in ag icul u e (Bo ion e
al., 2012).
2.4. CONCLUSIONS
The AD echnology p o ed o be a iable al e na i e in sludge
ea men due o he gene a ion o a g een ene gy and a quali y diges a e
ha can be used in ag icul u e. Howe e , his echnology is no in eg a ed
in all plan sizes and is a ibu ed o he need o a minimum scale. This
s udy showed ha he AD uni is a sui able en i onmen al and economic
al e na i e o sludge ea men , ega dless o he plan size. Mo eo e ,
he use o biogas in he plan i sel can imp o e he eco-e iciency o he
WWTPs due o less dependence on he ene gy om he g id. This means
less CO2 emissions associa ed wi h non- enewable ene gy. In addi ion,
he echnological easibili y o he AD echnology can be gua an eed in
small plan s as sewage sludge managemen could be combined wi h
ag icul u al solid was e, which also implies a highe o ganic load in he
diges e and inc eased biogas p oduc ion.
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De V ies, J.W., G oenes ein, C.M., De Boe , I.J.M., 2012. En i onmen al
consequences o p ocessing manu e o p oduce mine al e ilize and bio-
ene gy. J. En i on. Manage. 102, 173–183. h ps://doi.o g/10.1016/
j.jen man.2012.02.032
Dong, J., Chi, Y., Tang, Y., Wang, F., Huang, Q., 2014. Combined li e cycle
en i onmen al and exe ge ic assessmen o ou ypical sewage sludge
ea men echniques in China. Ene gy and Fuels 28, 2114–2122.
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F ank, R., 1998. The use o biosolids om was ewa e ea men plan s in
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09566169810228926
Gude, V.G., 2015. Ene gy and wa e au a ky o was ewa e ea men and powe
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pe o mance o a municipal was ewa e ea men plan . In . J. Li e Cycle
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Huijb eg s, M.A.J., S einmann, Z.J.N., Elshou , P.M.F., S am, G., Ve ones, F., Viei a,
M.D.M., Hollande , A., Zijp, M., an Zelm, R., 2017. ReCiPe 2016 1.1.
Kalba , P.P., Ka maka , S., Asoleka , S.R., 2012. Technology assessmen o
was ewa e ea men using mul iple-a ibu e decision-making. Technol.
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Ka agiannidis, A., Pe koulidis, G., 2009. A mul i-c i e ia anking o di e en
echnologies o he anae obic diges ion o ene gy eco e y o he o ganic
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ea men o concen a ed black wa e and ki chen esidues wi hin DESAR
concep using wo ypes o anae obic diges e s. Wa e Sci. Technol. 53,
159–168. h ps://doi.o g/10.2166/ws .2006.265
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he pumping s a ion o he was ewa e ea men plan . In . J. Li e Cycle
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Lijó, L., Malamis, S., González-Ga cía, S., Mo ei a, M.T., Fa one, F., Ka sou, E., 2017.
Decen alised schemes o in eg a ed managemen o was ewa e and
domes ic o ganic was e: he case o a small communi y. J. En i on. Manage.
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Na a o, D., Mo ei a, M.T., Feijoo, G., 2016. Benchma king was ewa e
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Lundie, S., Pe e s, G.M., Bea is, P.C., 2004. Li e Cycle Assessmen o Sus ainable
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Nelson, K.L., Mu ay, A., Ho a , A., 2008. Hyb id Li e-Cycle En i onmen al and
Cos In en o y o Sewage Sludge T ea men and End-Use Scena ios : A Case
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Pan, S.-Y., Du, M.A., Huang, I.-T., Liu, I.-H., Chang, E.-E., Chiang, P.-C., 2015.
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Pa an, P., Bolzonella, D., Ba is oni, E., Cecchi, F., 2007. Anae obic co-diges ion o
sludge wi h o he o ganic was es in small was ewa e ea men plan s: An
economic conside a ions e alua ion. Wa e Sci. Technol. 56, 45–53.
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en i onmen al sus ainabili y o subme ged anae obic MBR-based
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Rod iguez-Ga cia, G., Molinos-Senan e, M., Hospido, A., He nández-Sancho, F.,
Mo ei a, M.T., Feijoo, G., 2011. En i onmen al and economic p o ile o six
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Supply Res. Tech. 62, 468–476. h ps://doi.o g/10.2166/ aqua.2013.110
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economic implica ions, and go e nmen policies. Bio esou . Technol. 247,
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ins i u e. Depa men o Chemical Enginee ing. Uni e sidade de San iago de Compos ela, E-15782, San iago de
Compos ela, Galicia, Spain
CHAPTER 3: Benchma king en i onmen al and
economic indica o s o sludge managemen
al e na i es aimed a enhancing ene gy e iciency
and nu ien eco e y
SUMMARY
The main objec i es o a WWTP a e o emo e he pollu an s p esen
in he was ewa e , educe he olume o sludge and imp o e he ene gy
e iciency. The sludge ea men has a ele an ole wi hin he o e all
managemen scheme and can imply he la ges sha e in ope a ional cos s.
Conside ing he sludge ea men as a key ac o o imp o e in a WWTP,
he main goal o his Chap e is o e alua e di e en al e na i es and
s a egies o sludge managemen and ea men om he pe spec i e o
LCA, wi h special emphasis on hose op ions ha educe he
en i onmen al impac s and economic cos s.
Two p e- ea men s (one chemical and ano he he mal) and wo
pos - ea men s (compos ing uni ollowed by land applica ion o
incine a ion) we e e alua ed o imp o e he e iciency o he AD uni in
e ms o ope a ion (biogas p oduc ion and diges ed sludge),
en i onmen al and economic indica o s. Acco ding o he esul s
ob ained, bo h sludge p e- ea men s al e na i es p o ed o be an
adequa e al e na i e o imp o e biogas p oduc ion wi hou nega i ely
a ec ing en i onmen al and economic impac s. I he inal disposal o he
diges a e is analysed, i s applica ion o he soil as a bio e ilise is
ecommended, since i p esen s a be e en i onmen al p o ile han
incine a ion. Ne e heless, soil applica ion mus be conduc ed unde
con olled condi ions, a oiding exceeding he soil o e sa u a ion, no
only due o he po en ial eu ophica ion p oblems, bu also o he
p esence o hea y me als ha can lead o oxici y p oblems.
SECTION I: IMPROVING CENTRALISED WASTEWATER SYSTEMS
96
Table 3.1. Main inpu s o he di e en sys ems (FU: 1 on o mixed sludge).
Scena io a) compos ing plan ; Scena io b) incine a ion plan
Scena io 0
Scena io 1
Scena io 2
Inpu s om he echnosphe e
Ma e ials and uel
In luen
TS (kg)
100
100
100
VS (kg)
70
70
70
COD (kg)
126
126
126
TN (kg)
3.70
3.70
3.70
TP (kg)
6.90
6.90
6.90
Elec ici y consump ion
Thickening (kWh)
21.67
21.67
21.67
TH (kWh)
−
−
12.5
Chemical p e- ea men (kWh)
−
0.97
−
AD (kWh)
15.85
10.39
10.39
Dewa e ing (kWh)
5.46
3.58
3.58
Compos ing (kWh)a
1.30
1.30
−
Incine a ion (kWh)b
16.80
16.80
16.80
Chemical consump ion
P e- ea men
KOH (kg)
−
9.63
−
Dewa e ing
Polyelec oly e (kg)
1.60
1.60
1.60
T anspo
Polyelec oly e (kg·km)
40
40
40
KOH (kg·km)
−
24.20
−
Sludge (kg·km)a
9.15
6.97
6.97
Ashes (kg∙km)b
1.45
1.45
1.45
Land ill
Amoun o ashes (kg)b
5.79∙10-2
5.79∙10-2
5.79∙10-2
Land applica ion
Ag icul u al machine y(kg)a
0.37
0.28
0.28

CHAPTER 3: BENCHMARKING ENVIRONMENTAL AND ECONOMIC INDICATORS OF SLUDGE
MANAGEMENT ALTERNATIVES
97
Table 3.2. Main inpu s o he di e en sys ems (FU: 1 on o mixed sludge).
Scena io a) compos ing plan ; Scena io b) incine a ion plan
Scena io 0
Scena io 1
Scena io 2
Ou pu s o he en i onmen
Emissions o ai
AD
CH4 (kg)
0.43
0.69
0.87
CO2 (kg)
0.84
1.35
1.70
H2S (kg)
0.01
0.02
0.03
Compos ing uni a
CH4 (kg)
0.53
0.53
−
CO2 (kg)
13.78
13.78
−
N2O (kg)
8.88∙10-3
0.01
−
NH3 (kg)
0.26
0.26
−
Land applica ion a
N2O (kg)
8.24
4.71
5.23
NH3 (kg)
4.93
3.88
4.31
Emissions o wa e
Land applica ion a
NO3- (kg)
5.50
3.14
3.49
PO43- (kg)
4.26
2.43
2.43
Emissions o soil
Land applica ion a
TN (kg)
2.00
2.00
2.00
TP (kg)
7.94
7.94
7.94
C (mg)
22.34
22.34
22.34
Fe (mg)
5676
5676
5676
Cu (mg)
603.49
603.49
603.49
Zn (mg)
754.49
754.49
754.49
As (mg)
9.21
9.21
9.21
Hg (mg)
0.95
0.95
0.95
Pb (mg)
51.07
51.07
51.07
Ou pu s o he echnosphe e
Cogene a ion
A oided elec ici y (kWh)
109
123.48
152.81
A oided hea (kWh)
98.83
105.04
137.53
SECTION I: IMPROVING CENTRALISED WASTEWATER SYSTEMS
98
3.2.3. En i onmen al and economic indica o s o he sludge p e-
ea men s
The di e en impac s we e e alua ed h ough wo me hods. EP was
calcula ed using he CML 2001 me hod (Guinée, 2002), while CC, OD, TA,
PMF, HT, TET, FET, MET, and FD we e calcula ed using he ReCiPe
Midpoin (H) me hod (Huijb eg s e al., 2017). As in p e ious chap e s,
he main eason o choosing wo me hodologies is based on how o
es ima e he impac o he COD con ibu ion.
Cos s can be di ided in o ope a ional and capi al cos s. The cos s o
cons uc ion, equipmen o main enance we e calcula ed based on
bibliog aphic da a (Tables 3.3 and 3.4). In addi ion, in he ope a ional
cos s, he disposal o sludge, elec ici y, chemical consump ion and s a
cos s we e included. Biogas ha is ans o med in o elec ici y and hea
was conside ed a bene i . In o he wo ds, he sha e o he o al elec ici y
om biogas will co e a ac ion o he o al equi emen s o he plan .
The alue o his elec ici y p oduc ion is shown in Table 3.2. Thus,
conside ing he p ice o elec ici y in Spain, his elec ici y p oduc ion
will be deduc ed om he o al cos o elec ici y (Mills e al., 2014).
Fu he mo e, in o de o sha e he same FU as in he LCA me hodology,
he o al cos s a e es ima ed pe 1 on o mixed sludge. The cos s a e
ep esen ed by he Ne P esen Value (NPV) de ined in Eq.1, whe e n is
he ime o use ul li e while i is he discoun a e adjus men o in la ion
equal o 5% (He melink and Ja ge , 2015).
NPV= CAPEX + ∑ 𝑂𝑃𝐸𝑋
(1+𝑖)𝑛
𝑛
[1]
In addi ion, in his s udy, i is impo an o calcula e he payback ime
acco ding o Eq.2, whe e Ms. ep esen s he mass o sludge p oduc ion in
a yea ( on/yea ); Cd is he alue ela ed o he cos s o he inal disposal
o he sludge in €/ on; ΔE is he di e ence in he elec ici y (p oduc ion
in he sludge line (kWh/yea ); Ce: cos s o elec ici y is associa ed wi h
he p ice o elec ici y and C ep esen s he o al capi al cos s.
CHAPTER 3: BENCHMARKING ENVIRONMENTAL AND ECONOMIC INDICATORS OF SLUDGE
MANAGEMENT ALTERNATIVES
99
Payback ime=𝑀𝑠 𝑥 𝐶𝑑+𝛥𝐸 𝑥 𝐶𝑒−𝐶
𝐼𝑛𝑣𝑒𝑠𝑡𝑚𝑒𝑛𝑡 𝑐𝑜𝑠𝑡
[2]
Table 3.3. In en o y da a o ope a ional cos s
Economic i em
Uni
Value
Sou ce
Specialized wo ke
€/yea
50,000
Longo e al., 2017
Uni cos o elec ic ene gy
€/kWh
0.12
Mo ales e al., 2015
Uni cos o polyelec oly e
€/kg
1.8
Longo e al., 2017
Uni cos o KOH
€/kg
0.65
Ca e e e al., 2012
Uni a y cos o sludge
compos ing and applica ion
€/ on
90
Longo e al., 2017
Uni a y cos o sludge
incine a ion
€/ on
354
Hong e al., 2009
Table 3.4. In en o y da a o he cons uc ion and main enance cos s
Economic i em
Uni
Value
Sou ce
Thickening uni
€
185,162
Mills e al., 2014
Anae obic diges ion uni
€
403,114
Mills e al., 2014
Cogene a ion uni
€
386,098
Mills e al., 2014
Dewa e ing + silo uni
€
265,903
Mills e al., 2014
Chemical p e- ea men uni
€
60,000
Diaman is e al., 2013
TH p e- ea men uni
€
410,850
Mills e al., 2014
Compos ing uni
€
385,500
Chen, 2016
Incine a ion uni
€
1,925,000
Panepin o e al., 2016
P ojec ime ame
y
20
Mills e al., 2014
In e es a e
%
5
Longo e al., 2017
Main enance cos s o ci il
wo ks
€
0.17
He nández e al.,
2006
Main enance cos s o
elec o-mechanic elemen s
€
1.24
He nández e al.,
2006
SECTION I: IMPROVING CENTRALISED WASTEWATER SYSTEMS
100
3.3. RESULTS AND DISCUSSION
3.3.1. Main pa ame e s and li e cycle esul s o he di e en sludge
scena ios
Table 3.5 p esen s he main a iables and pa ame e s associa ed
wi h he scena ios conside ed in e ms o ene gy consump ion, biogas
p oduc ion om he p ima y sludge o he cla i ying uni and om he
seconda y sludge o he ac i a ed sludge p ocess in e ms o me hane and
elec ici y, as well as he educ ion in he olume o sludge.
S2 (TH p e- ea men ) p esen s he bes esul s in e ms o biogas
p oduc ion, ollowed by S1 (chemical p e- ea men ). These p e-
ea men s can imp o e elec ici y p oduc ion be ween 6% and 11%
compa ed o he baseline scena io. In addi ion, he deg adabili y o
sludge imp o es by 30% when a p e- ea men is included in he sludge
line. Fo S0 (AD only) and S1 (chemical p e- ea men ), ene gy
consump ion is e y simila as i mus ake in o accoun ha he amoun
o elec ici y associa ed wi h he dosing and mixing o chemicals is mino .
The ene gy consump ion o he TH p e- ea men is app oxima ely 14%
highe han in he o he op ions. When he ene gy balance akes in o
accoun he inal managemen o he sludge (incine a ion o compos ing
ollowed by land applica ion), compos ing p esen s a be e ene gy
balance han he incine a ion uni , which ansla es in o di e ences o
a ound 25% o his pa ame e . Finally, hea is used en i ely o main ain
he empe a u e o he AD uni a 35°C.
CHAPTER 3: BENCHMARKING ENVIRONMENTAL AND ECONOMIC INDICATORS OF SLUDGE
MANAGEMENT ALTERNATIVES
101
Table 3.5. Va iables and ope a ional pa ame e s associa ed o he scena ios
conside ed including inal disposal o he sludge (FU: 1 on o mixed sludge).
Scena ios: a) compos ing and land applica ion; b) incine a ion.
Scena io 0
Scena io 1
Scena io 2
Ene gy consump ion a (kWh)
61.08
54.71
64.94
Ene gy consump ion b (kWh)
221.88
214.77
224.94
Biogas p oduc ion (m3)
54.04
57.44
75.21
Me hane yield (m3 CH4/kgVS eed)
P ima y sludge
0.30
0.33
0.38
Seconda y sludge
0.20
0.28
0.31
Elec ici y p oduc ion (kWh)
109
123.48
152.81
Ene gy balance (kWh) a
-47.92
-68.77
-87.87
Ene gy balance (kWh) b
112.88
91.23
72.31
Hea p oduc ion (kWh)
98.83
105.04
137.53
Sludge p oduc ion (kg/d)
22876
17435
17435
The en i onmen al p o ile is epo ed in e ms o a ious impac
ca ego ies (Table 3.6). The esul s show ha he en i onmen al impac s
a e e y di e en depending on he ca ego y conside ed. In he case o
chemical p e- ea men , g ea e en i onmen al impac s a e obse ed in
ca ego ies such as TA, PMF and TET due o he indi ec emissions
associa ed wi h chemical p oduc ion. Howe e , when he TH and
chemical p e- ea men a e implemen ed in he sludge line, he a oided
elec ici y may inc ease due o he g ea e amoun o biogas, p o ided
ha he alo isa ion o biogas en ails lowe dependence o g id
elec ici y. In addi ion, in S2a (TH p e- ea men ), he compos ing plan
is no necessa y because, acco ding o Di ec i e 86/278/CEE, he mally-
ea ed diges ed sludge can be applied di ec ly o ag icul u e. In addi ion,
impac s ela ed o a mosphe ic emissions associa ed wi h he
compos ing uni can be a oided (Table 3.2). Howe e , i is e y di icul
o know he o e all en i onmen al impac o hese p e- ea men s due o
he much la ge impac s o he pos - ea men s.
In ene gy-dependen ca ego ies such as CC, OD o FD, he
incine a ion uni has g ea e impac s han he compos ing uni ollowed

SECTION I: IMPROVING CENTRALISED WASTEWATER SYSTEMS
102
by land applica ion. This is due o he la ge amoun o elec ici y
consumed in his p ocess. Indi ec emissions a e ela ed o ossil CO2 and
N2O om he coal elec ici y p oduc ion. Con e sely, scena ios wi h
compos ing ollowed by land applica ion p esen wo se en i onmen al
p o ile han he incine a ion p ocess in oxici y- ela ed ca ego ies due o
he p esence o hea y me als in he sludge. In his case, only he hea y
me als in he sludge we e conside ed since he ou ine measu emen o
mic opollu an s is no ca ied ou due o he complexi y o he necessa y
equipmen , sample p epa a ion and cos s. I he pa hogens o
mic opollu an s we e included in his s udy, he oxici y ca ego ies would
p obably be he mos a ec ed, conside ing he applica ion o he sludge
o he soil. Howe e , al hough, o he oxici y impac ca ego ies, he
impac would be highe , he en i onmen al p o ile in o e all e ms will
no change as incine a ion con inues o be he main ac o wi h he
g ea es weigh in he ene gy-dependen ca ego ies. As a as oxici y is
conce ned, i is impo an o be awa e ha when he TH p e- ea men is
applied, he sludge can be conside ed s e ilised. In his sense, he
pa hogens p esen in he sludge would be emo ed and i s applica ion
would be sa e.
CHAPTER 3: BENCHMARKING ENVIRONMENTAL AND ECONOMIC INDICATORS OF SLUDGE
MANAGEMENT ALTERNATIVES
103
Table 3.6. Cha ac e isa ion esul s o he di e en scena ios e alua ed in his
s udy (including pos - ea men ) o 1 on o mixed sludge. a) compos ing plan ;
b) incine a ion plan
I.C
Scena io 0
Scena io 1
Scena io 2
A
B
A
B
A
B
CC
40.82
160.50
42.56
162.22
29.41
167.66
OD
8.3·10-5
9.1·10-6
9.6·10-5
9.2·10-5
1.1·10-5
9.3·10-5
TA
0.48
0.77
0.48
0.76
-0.08
0.73
EP
25.77
0.20
25.77
0.20
25.77
0.20
HT
115.62
4.17
115.60
4.15
115.32
3.88
PMF
0.03
0.29
0.03
0.29
-0.05
0.27
TET
43.80
173.75
43.76
173.71
31.58
162.20
FET
6260
3.24
6260
3.24
6260
3.24
MET
4877
4.30
4877
4.30
4877
4.30
FD
-3.10
31.43
-3.28
31.50
-5.29
29.34
SECTION I: IMPROVING CENTRALISED WASTEWATER SYSTEMS
104
In o de o disce n he con ibu ion o p e- ea men o he o e all
impac , wo analysis we e p oposed. The main en i onmen al ca ego ies
in WWTPs a e CC and EP (Rod iguez-Ga cia e al., 2011). Howe e , he EP
ca ego y is mo e a ec ed by he sludge disposal and, in his case, was no
aken in o accoun . Fo his eason, he CC ca ego y was e alua ed o he
di e en scena ios (con en ional, chemical p e- ea men and TH p e-
ea men ). In addi ion, he main sub-sys ems ha con ibu es o he
en i onmen al p o ile we e e alua ed in his ca ego y.
Fo he CC ca ego y (especially ele an in p ocesses depending on
ene gy p oduc ion and use), S1 p esen s he bes en i onmen al esul s
because chemical p e- ea men does no equi e much ene gy ollowed
by he TH p e- ea men . The wo s scena io is he con en ional one
(Figu e 3.2) because he biogas p oduc ion is lowe han in he o he
scena ios. Al hough he con en ional scena io has lowe ene gy
consump ion due o he lack o p e- ea men uni , biogas p oduc ion is
lowe han in he o he scena ios, which esul s in wo se en i onmen al
p o ile. Fu he mo e, conside ing he CC impac o he sub-sys ems, o
each scena io (Figu e 3.2), he AD uni has he wo s en i onmen al
impac s due o CH4, CO2 and H2S emissions (Table 3.2) while he impac
o chemical p e- ea men is conside ed negligible in his ca ego y.
Howe e , o S2 he impac o he ene gy consump ion o he TH p e-
ea men ep esen s 6% in his ca ego y.
CHAPTER 3: BENCHMARKING ENVIRONMENTAL AND ECONOMIC INDICATORS OF SLUDGE
MANAGEMENT ALTERNATIVES
105
Figu e 3.2. En i onmen al esul s o he clima e change (CC) ca ego y o he
di e en scena ios analysed. S0 (con en ional scena io); S1 (chemical p e-
ea men ) and S2 (TH p e- ea men )
SECTION I: IMPROVING CENTRALISED WASTEWATER SYSTEMS
112
3.4. CONCLUSIONS
The AD p ocess is nowadays he mos widesp ead p ocess o he
managemen o sewage sludge as i allows he p oduc ion o bioene gy
and he s abilisa ion o he sludge. E en hough i is a ma u e and widely
implemen ed echnology, i is necessa y o imp o e he p ocess
pe o mance by inc easing he biogas yield so his ene gy can be used in
he plan i sel . In his con ex , se e al p e- ea men s ha e p o en o
ha e bene icial e ec s on biogas p oduc ion: 12% ( o chemically
enhanced p ecipi a ion) and 30% ( o TH). Addi ionally, he
deg adabili y o sludge and li e cycle en i onmen al impac s a e
signi ican ly imp o ed. Al hough cons uc ion cos s inc ease when he
sludge p e- ea men is inco po a ed in o he sludge line, he payback
ime is educed compa ed o he con en ional con igu a ion. This implies
ha amo isa ion o hese sludge lines is mo e easible compa ed o he
con en ional case. Finally, he land applica ion o he sludge has a be e
en i onmen al and economic p o ile han he incine a ion uni . Howe e ,
he p esence o hea y me als mus be con olled and measu ed o a oid
oxici y impac s in his sludge disposal scheme.
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a CRETUS ins i u e. Depa men o Chemical Enginee ing. Uni e sidade de San iago de Compos ela,
E-15782, San iago de Compos ela, Galicia, Spain
CHAPTER 4: Pu sing ene gy sel -su icien in
was ewa e ea men plan s: en i onmen al and
economic assessmen o inno a i e op ions
SUMMARY
Nowadays, WWTPs should no longe be conside ed as end-o -pipe
sys ems bu should be app oached by in eg a ing s anda ds o
echnological pe o mance bu also en i onmen al, economic and social
indica o s. In his amewo k, i is necessa y o add ess he ene gy-wa e
nexus o he selec ion o he mos app op ia e echnology. Ta ge ing
inc eased biogas yields, he eco e y o OM in he p ima y ea men
eme ges as in e es ing al e na i e. Fo his pu pose, new echnologies
such as RBFs o HRAS and o he no so new as UASB has been
implemen ed as p ima y ea men in he wa e line.
Chap e 4 aims a iden i ying he li e-cycle en i onmen al impac s
and economic cos s associa ed o ou con igu a ions: h ee schemes
ocus on eco e ing OM in he p ima y ea men and one con en ional
using he LCA me hodology. Despi e he ac ha he echnological and
ope a ional complexi y is no ewo hy o OM-o ien ed p ocess, lowe
en i onmen al impac s we e es ima ed o echnologies such as UASB
and HRAS. Howe e , no all schemes based on OM eco e y ha e
en i onmen al bene i s and special a en ion should be paid o aspec s
associa ed wi h he chemical and ene gy consump ion, as well as land
occupa ion, which may be limi ing a iables o implemen hese
echnologies.
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120
TABLE OF CONTENTS-CHAPTER 4
4.1. In oduc ion ............................................................................................ 121
4.2. Ma e ials and me hods ........................................................................ 123
4.2.1. Desc ip ion o he was ewa e schemes and scope o he
s udy ................................................................................................................... 123
4.2.2. In en o y da a acquisi ion o he new was ewa e
con igu a ions ................................................................................................ 128
4.2.3. Impac assessmen me hodology and economic e alua ion
.............................................................................................................................. 132
4.3. En i onmen al and economic esul s ............................................ 132
4.3.1. En i onmen al and economic app oach o he ou s udied
scena ios ........................................................................................................... 132
4.3.2. En i onmen al pe spec i e o each was ewa e ea men
con igu a ion .................................................................................................. 136
4.4. Discussion ................................................................................................ 140
4.4.1. Imp o ing was ewa e ea men e iciency in he WWTPs
.............................................................................................................................. 140
4.4.2. How con en ional and new echnologies in luence he
e luen quali y ............................................................................................... 142
4.4.3. Economic aspec s ocused on ene gy eco e y....................... 143
4.4.4. Sensi i i y analysis o he unc ional uni (FU) ....................... 144
4.5. Conclusions ............................................................................................. 145
4.6. Re e ences ............................................................................................... 145
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4.1. INTRODUCTION
In gene al, cu en WWTPs mee en i onmen al equi emen s in
e ms o o ganic ma e , ni ogen and phospho us emo al. Howe e , i
is becoming inc easingly e iden ha was ewa e echnologies mus
add ess mo e complex challenges such as he sa e emo al o eme ging
con aminan s such as ecalci an compounds and pa hogens, as well as
e icien ope a ion wi h less esou ce consump ion (Ba bosa e al., 2016;
Gu e al., 2018).
As was men ioned in Chap e 1, one o he ho spo s in was ewa e
ea men is he ene gy consump ion in ae a ion o he biological
p ocess (Gikas, 2017). In his amewo k, he Anammox p ocess has
se e al ad an ages such as he educ ion o oxygen equi emen s,
he e o e, he ene gy equi emen o ae a ion can be educed. In
addi ion, he ex ao dina ily low biomass yield o 0.12 kg VSS/ kg N emo ed
means low sludge gene a ion (Mo ales e al., 2015b). The e a e se e al
schemes ha ha e been de eloped in ecen yea s, such as IFAS, SHARON
o CANON (Malo anyy e al., 2015a; Van Dongen e al., 2001; Vázquez-
Padín e al., 2010b). Al hough he s a egy is he same o di e en
echnologies, he main di e ence be ween echnologies is ha PN-
Anammox can be implemen ed in a single o wo s ages. Howe e , hese
echnologies encoun e limi a ions in he case o s eams wi h a la ge
pe cen age o solids o a high C/N a io (Xu e al., 2015).
In his con ex , i is necessa y o eco e OM in p ima y ea men . In
Chap e 1, hese echnologies such as HRAS, RBF, CEPT o UASB (Jimenez
e al., 2015; Lo i e al., 2015) we e explained. The choice o one o
ano he echnology and i s combina ion depend on se e al ac o s. Fo
example, he ene gy consump ion associa ed wi h UASB implies i s
implemen a ion in ho clima es (Bdou e al., 2009) o RBF can be
combined wi h echnologies such as HRAS and CEPT bu no wi h he
Anammox p ocess due o he high solid con en (Ruiken e al., 2012).
Sludge managemen is ano he decisi e elemen in he ope a ion o
WWTPs acco ding o he ci cula economy app oach. Al hough he mos
applied me hods a e incine a ion and land applica ion (Kelessidis and
S asinakis, 2012; Tomei e al., 2016), o he op ions such as gasi ica ion,
SECTION I: IMPROVING CENTRALISED WASTEWATER SYSTEMS
128
4.2.2. In en o y da a acquisi ion o he new was ewa e
con igu a ions
In his s udy, only he en i onmen al impac s associa ed wi h he
ope a ional phase we e e alua ed. Al hough sewe age impac s
con ibu e signi ican ly o nega i e e ec (Pe i -Boix e al., 2014), he
ope a ional phase is he main cause o he en i onmen al impac s. Sys em
bounda ies we e de ined as he ope a ion o he di e en scena ios ha
a e de ined in he p e ious sec ion (Figu e 4.1 o Figu e 4.4). The simples
FU selec ed could be 1 m3 o ea ed was ewa e . Howe e , bea ing in
mind ha he objec i e is o imp o e he e iciency o he WWTPs, 1 kWh
o ene gy p oduced was selec ed as FU.
LCI was ca ied ou wi h es ima ed da a ela ed wi h he di e en
echnologies conside ed in he scena ios such as sludge, was ewa e
cha ac e is ics o consump ion o chemicals, among o he s. In addi ion,
he es ima ed da a we e comple ed wi h bibliog aphic da a associa ed
wi h he ai emissions and hea y me als con ained in he solid diges a e
(Hijazi e al., 2016; Lo enzo-Toja e al., 2016b) and he Ecoin en 3.5
da abase (We ne e al., 2016). The da a used o build he in en o ies a e
p esen ed in Table 4.1 (main inpu s o he sys em) and Table 4.2 (main
ou pu s o he sys em). Mo eo e , se e al simpli ica ions ha e been
conside ed o comple e he in en o y in o ma ion. These simpli ica ions
a e p esen ed below:
T anspo : he dis ance o chemical and sludge dis ibu ion was
selec ed as 25 km (Hospido e al., 2004). Mo eo e , ucks Eu o 4 wi h a
capaci y be ween 16 o 32 we e selec ed as anspo ehicles (Lo enzo-
Toja e al., 2016b).
Consump ion o chemicals in he sludge line: he amoun o
polyelec oly e consumed in he dewa e ing uni was 5-8 kg polyme /
1000 kg o d y ma e (Tchobanoglous e al., 1998).
Ai emissions om he compos uni : hese emissions we e
calcula ed acco ding o he ype o compos ing plan selec ed. In his case,
he open wind ow ac i a e en ila ion p ocess was selec ed as a
compos ing p ocess (Bold in e al., 2009).

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Elec ici y: Ecoin en 3.5 da abase was upda ed o he 2018 Spanish
coun y mix (REE, 2018). Mo eo e , he ansmission losses associa ed
wi h elec ici y anspo we e aken in o accoun (Dones e al., 2007).
Table 4.1. Summa y o he in en o y da a o he ou scena ios conside ed. FU:
1 kWh o p oduced ene gy
S1
S2
S3
S4
Inpu s om echnosphe e
Ma e ials and uel
In luen
COD (g)
2632
2632
2941
8333
TN (g)
101.70
99.40
112.12
305.07
TP (g)
25.14
24.57
27.71
75.41
C (mg)
25.92
25.37
28.21
79.92
Mn (mg)
709.95
694.92
772.59
2189
Fe (mg)
14695.95
14384.92
15992.65
45312.50
Co (mg)
7.51
7.35
8.18
23.17
Ni (mg)
50.65
49.58
55.12
156.17
Cu (mg)
1997.27
1955
2173.50
6158.25
Zn (mg)
830.89
813.31
904.21
2591.92
As (mg)
28.16
25.57
30.65
86.83
Cd (mg)
2.00
1.96
2.18
6.17
Hg (mg)
1.35
1.32
1.47
4.17
Pb (mg)
46.68
45.69
50.79
143.92
Elec ici y consump ion
P e- ea men (kWh)
0.08
0.08
0.09
0.24
UASB (kWh)
0.05
-
-
-
RBF (kWh)
-
-
0.60
-
CEPT (kWh)
-
-
0.06
-
HRAS (kWh)
-
0.16
-
-
PC (kWh)
-
-
-
0.16
IFAS (kWh)
0.86
0.84
0.95
-
CAS (kWh)
-
-
-
3.40
Thickening (kWh)
3.46·10-2
0.03
0.04
0.10
AD (kWh)
-
0.25
0.17
0.75
Dewa e ing (kWh)
2.79·10-3
2.72·10-3
3.07·10-4
5.67·10-4
Compos ing (kWh)
5.29·10-2
5.71·10-2
5.83·10-2
1.59·10-1
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130
Table 4.1. (con .). Summa y o he in en o y da a o he ou scena ios
conside ed. FU: 1 kWh o p oduced ene gy
S1
S2
S3
S4
Chemical consump ion
CEPT
FeCl3 (kg)
-
-
0.59
-
Dewa e ing
Polyelec oly e (kg)
1.89·10-4
1.85·10-4
2.08·10-4
3.50·10-5
T anspo
Polyelec oly e (kg·km)
4.72·10-3
4.62·10-3
5.21·10-3
5.67·10-4
FeCl3 (kg)
-
-
14.89
-
Sludge (kg·km)
2.81
2.72
2.77
7.39
Land applica ion
Ag icul u al machine y (kg)
1.13·10-1
1.09·10-1
1.11·10-1
2.96·10-1
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Table 4.2. Summa y o he in en o y da a o he ou scena ios conside ed. FU:
1 kWh o p oduced ene gy
S1
S2
S3
S4
Ou pu s o he en i onmen
Emissions o ai
AD
CH4 (kg)
4.74·10-3
4.64·10-3
4.59·10-3
4.88·10-3
CO2 (kg)
9.37·10-3
9.17·10-3
8.84·10-3
9.63·10-3
H2S (kg)
1.65·10-4
1.62·10-4
1.56·10-4
1.70·10-4
Compos ing uni
CH4 (kg)
5.96·10-3
5.51·10-3
2.67·10-3
6.38·10-3
CO2 (kg)
1.27
1.71
5.69·10-1
1.36
N2O (kg)
9.42·10-5
8.71·10-5
4.55·10-5
1.01·10-4
NH3 (kg)
1.28·10-2
1.18·10-2
6.19·10-3
1.37·10-2
Land applica ion
N2O (kg)
3.05·10-4
5.35·10-5
1.48·10-4
3.27·10-4
NH3 (kg)
2.52·10-4
4.41·10-5
1.22·10-4
2.70·10-4
Emissions o wa e
NO3- (kg)
2.04·10-2
3.57·10-3
9.84·10-3
2.18·10-2
PO4-3 (kg)
2.56·10-3
4.47·10-4
1.19·10-3
2.56·10-3
Emissions o soil
COD (kg)
1.24
1.15
5.57·10-1
1.33
TN (kg)
1.30·10-2
1.20·10-2
6.26·10-3
1.39·10-2
TP (kg)
8.35·10-2
7.71·10-2
3.88·10-2
8.37·10-2
C (mg)
79.16
77.49
86.15
244.10
Fe (mg)
20118
19692
21894
62032
Cu (mg)
2138
2093
2327
6595
Zn (mg)
2674
2617
2910
8245
As (mg)
32.65
31.96
35.53
100.67
Hg (mg)
3.35
3.28
3.65
10.33
Pb (mg)
181
177.17
196.97
558.08
SECTION I: IMPROVING CENTRALISED WASTEWATER SYSTEMS
132
4.2.3. Impac assessmen me hodology and economic e alua ion
En i onmen al impac s and hei co esponding p ices we e
quan i ied h ough he SimaP o 9.0 so wa e. Two me hods we e selec ed
o measu e he mos ep esen a i e impac s o he di e en scena ios
conside ed. EP was calcula ed wi h he CML 2001 me hod (Guinée, 2002)
whe eas CC, PMF, HT, OD, FD, TA, TET, MET, FET and WC we e calcula ed
wi h he ReCiPE Midpoin (H) 1.1 (Huijb eg s e al., 2017). Mo eo e ,
hese impac ca ego ies we e ans o med in o hei en i onmen al
p ices. Howe e , no all ca ego ies ha e hei ans o ma ion in o cos s,
o his eason, WC and EP we e no included in his s udy (De B uyn e
al., 2018).
Ope a ing and cons uc ion cos s (OPEX + CAPEX) we e selec ed as
di ec economic indica o s, while en i onmen al p ices we e quan i ied
such as indi ec indica o s. Ope a ional cos s we e ela ed o sludge
managemen , elec ici y, s a and chemical consump ion. Rega ding
capi al cos s, cons uc ion, main enance and dep ecia ion cos s we e
included.
4.3. ENVIRONMENTAL AND ECONOMIC RESULTS
4.3.1. En i onmen al and economic app oach o he ou s udied
scena ios
The en i onmen al esul s a e p esen ed as a compa ison be ween
he di e en scena ios conside ed (Table 4.3). The bes scena ios a e
Scena io 1 (UASB + IFAS con igu a ion) ollowed by Scena io 2 (HRAS +
IFAS con igu a ion) because he e is mo e elec ici y p oduc ion han in
he o he s. In addi ion, he consump ion o chemicals in hese was ewa e
uni s (p ima y echnologies) is ze o. Howe e , Scena io 3 (RBF + CEPT +
IFAS scheme), which is a new scheme, has a high en i onmen al impac ,
e en highe han in he con en ional sys em in se e al ca ego ies. These
en i onmen al impac s a e due o he indi ec emissions associa ed wi h
he chemicals p oduc ion. Thus, he addi ion o chemicals o imp o e
biogas p oduc ion, i is no a good op ion om an en i onmen al poin o
iew. In eu ophica ion and oxici y ca ego ies (EP, FET and MET), which
depend on he quali y o e luen , Scena io 4 (con en ional sys em)
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p esen s he wo s esul s. The eu ophica ion impac is associa ed wi h
he discha ge o e luen in o he aqua ic en i onmen as i con ains N, P
and COD. In addi ion, he in eg a ion o he IFAS uni can dec ease by 13%
he elec ici y consump ion associa ed wi h ae a ion. This dec ease in
elec ici y imp o es he en i onmen al p o ile because i en ails lowe
ossil CO2 emissions (Table 4.3).
The en i onmen al impac s ob ained we e ans o med in o hei
co esponding en i onmen al cos s, which a e conside ed as indi ec
cos s addi ionally o cons uc ion and ope a ional cos s (Table 4.4).
Scena io 3 p esen s he wo s en i onmen al p ices wi h an inc ease
abou 52% in compa ison wi h Scena io 4 and 80% mo e han Scena ios
1 and 2. The main ca ego ies ha cause his nega i e e ec a e OD and
TET. These ca ego ies a e in luenced by indi ec chemical consump ion
emissions whe e Scena io 3 is wo se han he o he scena ios conside ed.
Conce ning he ope a ional cos s, Scena io 1 ollowed by Scena io 2
a e he mos ad isable due o elec ici y p oduc ion is highe han in he
o he was ewa e schemes conside ed. The e o e, in Scena io 1, whe e
he e is no AD uni in he sludge line, he inco po a ion o UASB shows
ha i is a good op ion o ea ing was ewa e and gene a ing elec ici y.
The wo s -scena io in e ms o ope a ing cos s is Scena io 3 due o he
consump ion o chemicals o imp o e he AD p ocess. In addi ion, in his
scena io, wo uni s a e included o elimina e OM, so elec ici y
consump ion is highe han in he o he cases. Ope a ing cos s inc ease
by 16% compa ed o he con en ional case and by 32% compa ed o he
o he inno a i e schemes.

SECTION I: IMPROVING CENTRALISED WASTEWATER SYSTEMS
134
Table 4.3. En i onmen al esul s o he di e en was ewa e ea men schemes
o he impac ca ego ies unde assessmen (FU: 1 kWh o ene gy p oduced)
Impac Ca ego ies
S1
S2
S3
S4
CC (kg CO2 eq)
0.75
0.86
3.63
2.06
OD (kg CFC-11 eq)
4.04·10-7
4.72·10-7
1.00·10-5
1.16·10-6
TA (kg SO2 eq)
0.03
0.03
0.02
0.04
EP (kg PO43- eq)
0.07
0.07
0.09
0.20
HT (kg 1,4-DCB eq)
0.01
0.02
0.11
0.06
PMF (kg PM10 eq)
4.06·10-3
4.08·10-3
5.67·10-3
7.27·10-3
TET (kg 1,4-DCB eq)
0.53
0.69
5.21
2.36
FET (kg 1,4-DCB eq)
0.05
0.07
0.12
0.21
MET (kg 1,4-DCB eq)
0.06
0.07
0.15
0.23
WC (m3)
3.20·10-3
4.20·10-3
0.03
0.01
In e ms o cons uc ion cos s, he mos un a ou able scena io is
Scena io 3 because he e is an ex a uni in compa ison wi h he o he
scena ios ollowed by Scena ios 1 and 2. Al hough ene gy p oduc ion is
highe in hese scena ios, he echnology is mo e complex han in he
con en ional scena ios. Fo his eason, also dep ecia ion cos s a e lowe
in he con en ional scena io. The in eg a ed analysis o en i onmen al,
ope a ional and cons uc ion cos s show ha Scena io 3 is he wo s -
case, abou 51% mo e han con en ional and when compa ed wi h
inno a i e schemes he di e ence inc eased up o 87% and 85% in
Scena ios 1 and 2, espec i ely.
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Table 4.4. Ope a ional and cons uc ion cos s o he di e en was ewa e
schemes conside ed (FU: 1 kWh o ene gy p oduced)
Cos s
S1
S2
S3
S4
Ope a ional cos s
Elec ici y
0.12
0.17
0.23
0.36
Chemical consump ion
3.31·10-4
3.31·10-4
0.35
6.30·10-4
Sludge managemen
9.87·10-3
9.77·10-3
9.84·10-3
1.64·10-2
S a
0.15
0.15
0.16
0.28
Lab. cos s
3.91·10-3
3.91·10-3
4.37·10-3
7.43·10-3
Main enance
0.09
0.09
0.10
0.18
O he cos s
0.03
0.03
0.04
0.06
TOTAL OPEX (€)
0.40
0.45
0.89
0.90
Cons uc ion cos s
P e- ea men
3.24·10-3
3.24·10-3
3.62·10-3
6.16·10-3
UASB
7.57·10-3
-
-
-
HRAS
-
2.51·10-3
-
-
CEPT
-
-
4.68·10-3
-
RBF
-
-
2.08·10-2
-
PC
-
-
-
1.70·10-2
Cogene a ion uni
1.33·10-3
1.33·10-3
1.48·10-3
2.52.10-3
IFAS
0.28
0.28
0.31
-
CAS
-
-
-
0.09
Thickening
1.16·10-3
1.16·10-3
1.30·10-3
2.21·10-3
AD uni
-
7.57·10-3
8.46·10-3
5.66·10-3
Dewa e ing
5.47·10-3
5.47·10-3
6.12·10-3
0.01
Compos ing uni
2.98·10-3
2.98·10-3
3.33·10-3
0.01
TOTAL CAPEX (€)
0.30
0.30
0.36
0.14
DEPRECIATION COSTS (€)
0.30
0.31
0.36
0.12
TOTAL INDIRECT COSTS (€)
5.45
6.95
47.81
22.63
TOTAL COSTS (€)
6.45
7.99
49.42
23.79
SECTION I: IMPROVING CENTRALISED WASTEWATER SYSTEMS
136
4.3.2. En i onmen al pe spec i e o each was ewa e ea men
con igu a ion
To be e unde s and he con ibu ion o he impac ha each uni
ha o med he was ewa e ea men scheme can c ea e, he
en i onmen al impac s a e s udied indi idually o each scena io. As in
he case be o e, he esul s a e calcula ed on he basis o he FU (1 kWh
o ene gy p oduced).
In Scena io 1 (UASB + IFAS), he main con ibu o o all impac
ca ego ies excep TA and PMF is he IFAS uni . This impac is ela ed o
he indi ec emissions associa ed wi h he elec ici y consump ion o he
CC, OF o FD ca ego ies. In ca ego ies such as EP, TET, FET and MET, he
impac is associa ed wi h he discha ge o he e luen in o he
en i onmen . The nega i e e ec is ela ed o he p esence o hea y
me als in he was ewa e . Thei bioaccumula ion po en ial can a ec
wildli e and ege a ion o e ime (Figu e 4.5a). In TA and PMF ca ego ies,
he main con ibu o o he impac is he compos ing uni . Ai emissions
associa ed wi h his uni a e he cause o he impac on his p ocess. The
alue o hese emissions is p esen ed in Table 4.3 (ma e ials and me hods
sec ion). In he CC ca ego y, he impac s a e mo e dis ibu ed: 40% IFAS
uni , 30% compos ing uni and 24% UASB uni . The impac o he UASB
uni is ela ed o he a mosphe ic emissions o CH4, H2S and CO2 (Table
4.3; ma e ial and me hods sec ion). Howe e , he UASB impac is e y
small and e en negligible in some ca ego ies such as FET, MET o TA.
Finally, he impac s o he o he uni s such as dewa e ing o cogene a ion
can be conside ed non-signi ican (Figu e 4.5a).
The esul s o Scena io 2 (HRAS + IFAS) a e shown in Figu e 4.5.b.
As in he p e ious scena io, he main con ibu o o he impac in all
ca ego ies excep TA and PMF is he IFAS uni . As explained abo e, he
impac is associa ed wi h he di ec emissions ela ed o he e luen
discha ge and he indi ec emissions associa ed o he elec ici y
consump ion in his uni . In his case, he AD uni ep esen s a nega i e
e ec be ween 3% in FET ca ego y and 30% in CC ca ego y, which is
mainly a ibu ed o biogas losses (Table 4.3; ma e ials and me hods
sec ion). The compos ing uni is he main con ibu o o he nega i e
e ec on TA and PMF (as in Scena io 1) and he e ec is caused by he ai
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emissions. As o HRAS, which is he new uni in his con igu a ion, he
impac anges om 11% in FD o 1% in he TA ca ego y. Finally, he e ec
o dewa e ing o hickening uni can be conside ed negligible (Figu e
4.5.b).
Figu e 4.5.c shows he con ibu ion pe subsys em in Scena io 3
(RBF + CEPT + IFAS). In his scena io, he esul s change (Table 4.3). The
CEPT uni is he main con ibu o o he impac in all ca ego ies excep
TA, CC and EP. This is due o he amoun o chemicals used o achie ed
g ea e OM eco e y. The impac s a e associa ed wi h indi ec emissions
ela ed o he p oduc ion o he chemical used in his p ocess (FeCl3). In
he TA ca ego y, ai emissions caused in he compos ing uni a e he main
ac o con ibu ing o he nega i e e ec (53%). In he EP ca ego y (as in
he p e ious scena ios), he discha ge o he e luen in o he aqua ic
en i onmen is de imen al o he en i onmen al sco e. In he RBF,
which is he new uni in his con igu a ion, he main impac anges om
13% in he OD ca ego y o 5% in he MET ca ego y. In CC, he AD uni
con ibu es a ound 46% o he o al impac , ollowed by he CEPT uni .
Finally, o he uni s such as dewa e ing, hickening o p e- ea men ha e
an impac ha can be conside ed non-signi ican .
Finally, Figu e 4.5.d p esen s he esul s o he con en ional
scena io (PC + CAS wi h ni ogen emo al). The ac i a ed sludge eac o
is he wo s uni in e ms o en i onmen al impac in all ca ego ies excep
TA and PMF. The nega i e e ec o his uni is associa ed wi h he high
elec ici y consump ion and he di ec emissions when he e luen is
discha ged in o he en i onmen . In he TA and PMF ca ego ies, he
compos ing uni is he main con ibu o o he impac . As in he p e ious
scena ios, he impac is ela ed o he ai emissions ha occu in his
p ocess when he compos is p oduced. The PC uni has a negligible
impac such as dewa e ing, cogene a ion o hickening uni s.
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144
4.4.4. Sensi i i y analysis o he unc ional uni (FU)
In LCA me hodology, a c ucial s ep is he de ini ion o he FU, since
his decision in luences he in en o y da a and he esul s. In his case,
maximising elec ici y p oduc ion is a key ac o in ou sys em. Howe e ,
he main unc ion o WWTPs is o ea was ewa e . In his sense, i is
impo an o e alua e he in luence o he selec ion o he FU on he
ou comes o he analysis. The e o e, wo FU we e s udied and compa ed
(1 kWh o ene gy p oduced and 1 m3 o ea ed was ewa e ). The
ca ego y s udied was he CC ca ego y, because his ca ego y is he mos
in luenced by possible changes in ene gy consump ion o p oduc ion
(Zouboulis and Tolkou, 2015).
Figu e 4.7 shows he esul s o he di e en scena ios o bo h FU.
These esul s a e e y simila and ange om 5% in Scena io 3 o 1% in
he o he scena ios; he e o e, he di e ence is no signi ican . Thus, he
choice o ano he FU does no change he esul s and Scena io 1 would be
he bes om an en i onmen al pe spec i e.
Figu e 4.7. Compa ison be ween wo di e en unc ional uni s (1 m3 o
ea ed was ewa e and 1 kWh o ene gy p oduced) o he clima e change
ca ego y. Symbols: o ep esen s 1 m3 o ea ed was ewa e ; Δ ep esen s 1
kWh o ene gy p oduced)

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4.5. CONCLUSIONS
In his s udy, a new ea men s a egy ocused on OM eco e y was
e alua ed om an en i onmen al and economic pe spec i e. Th ee
schemes based on his s a egy: (i) UASB + IFAS; (ii) HRAS + IFAS, and
(iii) RBF + CEPT + IFAS) we e compa ed wi h a con en ional ea men
scena io (PC + CAS). The UASB and HRAS ollowed by an IFAS uni had a
be e en i onmen al p o ile han he con en ional echnology.
Mo eo e , he ene gy consump ion in ae a ion can dec ease by 13%
when IFAS is in eg a ed. Howe e , no all schemes based on his s a egy
showed a be e en i onmen al and economic p o ile. Technologies ha
equi e chemical achie ed wo se esul s han he con en ional sys em in
he eco oxici y and human heal h ca ego ies. In addi ion, cos s can
inc ease by 51% compa ed o he con en ional plan . When a echnology
is implemen ed, alida ion is needed no only o m a echnology poin o
iew bu also om an en i onmen al and economic pe spec i e. In his
way, hese elemen s ha a e conside ed end-o -pipe sys ems o was e
ea men can be adap ed o he ci cula economy and become mo e
sus ainable.
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Bio esou . Technol. 239, 294–301.
h ps://doi.o g/10.1016/j.bio ech.2017.05.041
Zouboulis, A., Tolkou, A., 2015. E ec o Clima e Change in Was ewa e
T ea men Plan s: Re iewing he P oblems and Solu ions, in: Sh es ha, S.,
Anal, A.K., Salam, P.A., an de Valk, M. (Eds.), Managing Wa e Resou ces
unde Clima e Unce ain y: Examples om Asia, Eu ope, La in Ame ica,
and Aus alia. Sp inge In e na ional Publishing, Cham, pp. 197–220.
h ps://doi.o g/10.1007/978-3-319-10467-6_10
And ea A ias*a, Chi a Rajan Behe ab, Gume sindo Feijooa, Gü kan Sinb, Ma ía Te esa Mo ei aa. “Un a elling he
en i onmen al and economic impac s o inno a i e echnologies o he enhancemen o biogas p oduc ion and
sludge managemen in was ewa e sys ems”. Jou nal o En i onmen al Managemen . 2020, Vol. 227, 110965.
h ps://doi.o g/10.1016/j.jen man.2020.110965. aCRETUS ins i u e. Depa men o Chemical Enginee ing.
Uni e sidade de San iago de Compos ela, E-15782, San iago de Compos ela, Galicia, Spain. b P ocess and Sys ems
Enginee ing Cen e (PROSYS), Depa men o Chemical and Biochemical Enginee ing, Technical Uni e si y o
Denma k, Building 229, 2800 Kgs. Lyngby, Denma k
CHAPTER 5: Mapping he en i onmen al and
economic impac s o inno a i e echnologies o
enhancemen o biogas p oduc ion and sludge
managemen in was ewa e sys ems
SUMMARY
In ecen yea s, new was ewa e ea men plans ha e been
p oposed o ackle mo e complex challenges. To add ess hese new
con igu a ions, i is necessa y o use ools o model, op imise and selec
he mos app op ia e plan layou o each scena io. I is no possible o
emba k on he cons uc ion o new acili ies unless he p e ious
echnical, economic and en i onmen al easibili y s udies ha e been
igo ously conside ed.
I is well known ha he elemen s ha penalise he was ewa e
ea men a e: i) ene gy consump ion and ii) sludge managemen . Based
on hese p emises, he main objec i e o Chap e 5 is o e alua e which
ea men con igu a ion ensu es he e icien wa e -ene gy nexus and he
educ ion o he ope a ional cos s linked o he was ewa e scheme. Fo
his pu pose, he ea men con igu a ion o wo eal plan s o di e en
size was modi ied o include some no el concep s such as physical-
chemical and biological p ocesses o he eco e y o o ganic ma e OM
in he p ima y ea men , as well as he implemen a ion o a pa ial
ni i ica ion-anammox p ocess in he seconda y ea men . Acco ding o
he modelling esul s ha in eg a e he en i onmen al and economic
indica o s using he LCA me hodology, he schemes based on HRAS o
RBF + chemical addi ion ollowed a pa ial ni i ica ion-Anammox led o
he bes en i onmen al and economic esul s. These esul s a e
a ibu ed o inc eased biogas p oduc ion and educed elec ici y
demand om he g id. Fu he mo e, hese schemes p o ed o be cos -
e ec i e and en i onmen al- iendly o bo h plan sizes and
con igu a ions.
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Figu e 8.2. Decen alised neighbou hood scheme: a) gene al con igu a ion; b)
Sys em bounda ies o Scena io 3 (decen alised sys em wi h con en ional
oile s); c) Sys em bounda ies o Scena io 4 (decen alised sys em wi h
acuum oile s)
8.2.2. Li e cycle in en o y (LCI) o he di e en was ewa e
ea men con igu a ions
The in en o ies we e made wi h p ima y da a ( eal da a) and
seconda y da a (calcula ed o bibliog aphic da a), epo ed in Tables 8.1
and 8.2. The p ima y da a co espond wi h he eal da a which a e
associa ed wi h he cen alised case. The cha ac e is ics o he
was ewa e , he amoun o sludge gene a ed and he consump ion o
chemicals we e ob ained om an in e nal epo (PRTR, 2017).
Mo eo e , elec ici y consump ion and biogas p oduc ion (Scena io 2)
b)
c)

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we e ob ained using es ima ed da a. In he decen alised cases, he da a
a e ob ained h ough bibliog aphic in o ma ion and mass balances. BW,
GW, biogas ans o ma ion o ene gy consump ion a e bibliog aphical
da a (Komesli e al., 2007; Zang e al., 2015; Zeeman e al., 2008).
The e o e, he in en o ies we e comple ed wi h he Ecoin en 3.5
da abase (We ne e al., 2016). Finally, se e al simpli ica ions we e made
o backg ound da a.
Elec ici y: Spanish elec ici y coun y mix was upda ed o he
2018 yea wi h he da a o m he annual epo (REE, 2018). As ega ds
he consump ion o chemical p oduc s, polyelec oly e was implemen ed
as ca ionic esin aking in o accoun he Ecoin en 3.5 da abase (We ne
e al., 2016). Biogas composi ion was conside ed such as 75% CH4, 24%
CO2 and 1% H2S (Kujawa-Roele eld e al., 2006). Finally, he emissions o
compos ing o ai (CH4, CO2, N2O and NH3) we e es ima ed h ough
bibliog aphic da a (Bold in e al., 2009).
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Table 8.1. Main inpu s o he di e en scena ios conside ed in his s udy. FU: 1
esiden . S1: Scena io 1, S2: Scena io 2, S3: Scena io 3, and S4: Scena io 4
S1
S2
S3
S4
Inpu s om he echnosphe e
Ma e ials and uel
In luen
COD (g)
BW (g)
42.35
42.35
101.3
101.3
GW (g)
53.13
53.13
TN (g)
BW (g)
1.31
1.31
175
175
GW (g)
2.15
2.15
TP (g)
BW (g)
0.51
0.51
21.87
21.87
GW (g)
0.72
0.72
Elec ici y consump ion
P e- ea men (kWh)
1.57·10-3
1.57·10-3
-
-
Coagula ion- loccula ion
(kWh)
5.15·10-3
5.15·10-3
-
-
CAS (kWh)
4.03·10-2
4.03·10-2
-
-
Thickening +
homogeniza ion (kWh)
2.27·10-4
2.27·10-4
-
-
AD (kWh)
-
2.91·10-3
-
-
Dewa e ing (kWh)
2.27·10-3
2.27·10-3
-
-
Compos ing (kWh)
2.40·10-4
2.40·10-4
-
-
Toile s (kWh)
-
-
-
0.06
UASB (kWh)
-
-
3.76·10-3
0.01
MBR (kWh)
-
-
0.15
0.15
SBR (kWh)
-
-
0.10
0.10
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Table 8.1.(con .). Main inpu s o he di e en scena ios conside ed in his s udy.
FU: 1 esiden . S1: Scena io 1, S2: Scena io 2, S3: Scena io 3, and S4: Scena io 4
S1
S2
S3
S4
Inpu s om he echnosphe e
Chemical consump ion
-
Coagula ion- loccula ion
FeCl3 (kg)
1.93·10-3
1.93·10-3
-
-
Thickening + homogeniza ion
Polyelec oly e (kg)
4.51·10-2
4.51·10-2
-
-
T anspo
FeCl3 (kg·km)
0.05
0.05
-
-
Polyelec oly e (kg·km)
1.13
1.13
-
-
Sludge (kg·km)
0.96
0.96
-
-
Land applica ion
Ag icul u al machine y (kg)
0.04
0.04
-
-
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Table 8.2. Main ou pu s o he di e en scena ios conside ed in his s udy. FU:
1 esiden
S1
S2
S3
S4
Ou pu s o he en i onmen
Emissions o ai
AD uni
CH4 (kg)
-
4.67·10-4
1.06·10-2
1.26·10-2
CO2 (kg)
-
5.48·10-4
1.05·10-2
1.25·10-2
H2S (kg)
-
9.67·10-6
2.20·10-4
2.60·10-4
Compos ing uni
CH4 (mg)
4.68·10-4
4.68·10-4
-
-
CO2 (mg)
0.13
0.13
-
-
N2O (mg)
2.25·10-4
2.25·10-4
-
-
NH3 (mg)
1.87·10-2
1.87·10-2
-
-
Land applica ion
N2O (kg)
1.33·10-3
1.33·10-3
-
-
NH3 (kg)
1.09·10-3
1.09·10-3
-
-
Emissions o wa e
NO-3 (kg)
0.02
0.02
-
-
PO4-3 (kg)
1.72·10-3
1.72·10-3
-
-
Ou pu s o he echnosphe e
Cogene a ion uni
Elec ici y p oduc ion
(kWh)
-
0.01
0.28
0.33
Hea p oduc ion
(kWh)
-
0.01
0.25
0.29
Wa e o i iga ion
(m3)
-
-
0.01
0.01
8.2.3. Indica o s o e alua ing en i onmen al and economic p o ile
The in en o y da a we e implemen ed in he SimaP o 9.0 so wa e
o ob ain he mos ep esen a i e impac s o he di e en con igu a ions.
In his case, he mos ep esen a i e ca ego ies a e CC due o elec ici y
p oduc ion and consump ion ha can a ec he educ ion o inc ease o
he esiden ca bon oo p in . The o he ele an ca ego y in his s udy is
WC. As men ioned abo e, wa e is used o i iga ion. In he cen alised
case, his wa e comes om he ap wa e ne wo k, so his ap wa e has
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en i onmen al impac s, while in he decen alised case, he wa e comes
om he WWTP. The e o e, i is impo an o know how his change
a ec s he en i onmen al impac s associa ed wi h he esiden s li ing in
he neighbou hood. These wo impac ca ego ies we e calcula ed using
he ReCiPe Midpoin (H) me hod (Huijb eg s e al., 2017). In addi ion, o
he CC ca ego y, he en i onmen al impac s a e ans o med in o
en i onmen al p ices o ob ain how much i would cos o implemen
hese sys ems om an en i onmen al pe spec i e. The main eason o
calcula ing only he en i onmen al p ices in he CC ca ego y is because o
WC ca ego y does no ha e cha ac e isa ion ac o in his me hodology
(De B uyn e al., 2018).
Ope a ional and capi al cos s we e calcula ed as di ec economic
indica o s, whe eas en i onmen al p ices we e quan i ied such as
indi ec economic indica o s. Ope a ing cos s we e associa ed wi h
sludge managemen , chemical and ene gy consump ion, while capi al
cos s conside ed only he cons uc ion o he uni and inco po a ed in o
he o al alue o WWTP.
8.3. RESULTS AND DISCUSSION
8.3.1. Ca bon oo p in o each esiden acco ding o he di e en
was ewa e scheme
En i onmen al impac s we e only assessed o he CC and WC
ca ego ies. In his i s sec ion, en i onmen al impac s will be s udied o
he CC ca ego y. Fo his eason, i is impo an o know how much ene gy
and wa e is consumed pe esiden in each house. In Spain, ene gy and
hea ha is consumed pe inhabi an is abou 1.581 kWh and 425 kWh in
a yea (IGE, 2016). The biogas p oduced in he anae obic diges ion uni s
can be used o supply ene gy and hea o he houses. In his way, he
educ ion o he ca bon oo p in pe esiden can be es ima ed.
The esul s o he esiden ´s ca bon oo p in , depending on he
was ewa e ea men con igu a ion (cen alised o decen alised) a e
shown in Figu e 8.3. The wo s alues in e ms o hea and elec ici y a e

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262
p esen ed o Scena io 1 (cen alised case) because he e is no AD uni ;
he e o e, he e is no gene a ion o hese p oduc s. Fu he mo e, when
he AD uni is inco po a ed in o he cen alised sys em, he ca bon
oo p in can only be educed by abou 4% in e ms o hea and ene gy.
Decen alised cases show be e esul s in educing he ca bon oo p in
because he p oduc ion o ene gy and hea is highe han in cen alised
sys ems. The bes case is when acuum oile s a e inco po a ed (Scena io
4) and he educ ion is 23% o elec ici y consump ion and 66% o hea
p oduc ion. In Scena io 3 (con en ional oile s), he inc ease is also
signi ican , abou 20% o ene gy and 54% o hea . Thus, hese
decen alised sys ems help o dec ease he ca bon oo p in o a esiden
li ing in a decen alised was ewa e ea men sys em.
Figu e 8.3. Ca bon oo p in in e ms o ene gy and hea o a esiden ha
li es in a cen alised o decen alised was ewa e scheme. Scena io 1:
con en ional sys em, Scena io 2: con en ional sys em wi h AD uni ; Scena io 3:
decen alised sys em wi h con en ional oile s; Scena io 4: decen alised
sys em wi h acuum oile s
In he con ex o educing he ca bon oo p in , i is also impo an o
s udy he en i onmen al impac s in he CC ca ego y o each was ewa e
ea men scheme. The di e en was ewa e ea men schemes we e
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
Scena io 1 Scena io 2 Scena io 3 Scena io 4
CC [kg CO2eq/ esiden ]
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compa ed and, in addi ion, he main impac s o each scheme we e
analysed. As in he p e ious analysis, he cen alised cases a e he wo s
op ions because he e is no elec ici y p oduc ion (Figu e 8.4a). In
addi ion, in e ms o CC impac s, Scena io 3 (con en ional oile s) is he
bes scena io, e en be e han Scena io 4 ( acuum oile s). Ene gy
p oduc ion is highe in Scena io 4 (abou 16% han in Scena io 3),
howe e , he ene gy consump ion o he acuum oile s implies
undesi able impac s. Al hough, he ene gy consump ion is highe han in
Scena io 4, he impac s a e be e han in he con en ional sys ems.
I he subsys ems o each sys em in his ca ego y a e s udied, he
main impac is he hickening + homogenisa ion ollowed by he CAS uni
in cen alised sys ems. In he i s uni , he impac is associa ed wi h he
consump ion o polyelec oly e o ensu e good sludge dewa e ing, while
in he CAS uni , he nega i e e ec is ela ed o he consump ion o ene gy
o ae a ion. Mo eo e , he AD inco po a ion in Scena io 2 does no
ep esen a signi ican inc ease in he impac . In decen alised sys ems,
MBR ollowed by he SBR ep esen he wo s en i onmen al p o ile due
o he ene gy consump ion associa ed wi h hese uni s. In addi ion, he
acuum oile s also ha e a nega i e e ec o abou 10% o he o al
impac . Howe e , elec ici y p oduc ion minimises he o al impac o
hese sys ems wi h en i onmen al c edi s o a ound 50% in bo h sys ems
(Figu e 8.4b).
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Figu e 8.4. En i onmen al impac s o CC ca ego y o each esiden and
en i onmen al impac s o each sub-sys em ha con o ms he di e en
was ewa e ea men schemes. Scena io 1: con en ional sys em; Scena io 2:
con en ional sys em wi h AD uni ; Scena io 3: decen alised sys em wi h
con en ional oile s; Scena io 4: decen alised sys em wi h acuum oile s
8.3.2. Wa e consump ion and educ ion o he di e en
was ewa e ea men schemes
In his sec ion, he educ ion in he wa e consump ion was
e alua ed acco ding o he di e en was ewa e ea men
con igu a ions. In San iago de Compos ela, he wa e used o i iga ion
is 11.10 m3/inhabi an ·yea (IGE, 2016). Thus, as in he CC ca ego y, he
wa e necessa y o i iga ion was compa ed among he di e en
was ewa e con igu a ions pe inhabi an , in addi ion, he WC ca ego y
CHAPTER 8. ENVIRONMENTAL ANALYSIS OF SERVICING CENTRALISED AND
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and he sub-sys ems a ec ing o his ca ego y we e analysed and
compa ed.
The o al wa e used in i iga ion in his ci y is 6663 m3/d. This
numbe includes he i iga ion o pa ks, g een a eas and he p o ision o
wa e o he i e s a ions. The neighbou hood s udied equi es 216 m3/d
o i iga ion wa e . In bo h cen alised sys ems, his numbe does no
dec ease because he wa e in hese sys ems is discha ged in o he
en i onmen . Howe e , in he decen alised cases, wa e is eused o
i iga ion. The was ewa e gene a ed in Scena io 3 (con en ional oile s)
is abou 788 m3/d because hese oile s consume mo e wa e han
acuum oile s (Scena io 4), in which he was ewa e low is abou 663
m3/d. This means 100% sa ings in bo h sys ems. The e o e, he
en i onmen al impac s o ap wa e ea men would be a oided. Fo he
i iga ion o g een a eas only 216 m3/d o wa e is equi ed, his means
ha he e is an excess o wa e o abou 572 m3/d (con en ional oile s)
and 418 m3/d ( acuum oile s) ha could be used in o he si ua ions, o
example, ca go ucks o s ee cleaning, i e igh ing, among o he s.
Thus, in he case o decen alised sys ems, i is no necessa y o
pu i y he ap wa e o i iga ion, which means ha only he impac s o
he i iga ion p ocess i sel will be aken in o accoun . Howe e , in
cen alised cases he e is no wa e eco e y, so in Scena ios 1 and 2 he
impac s o i iga ion a e associa ed wi h he ea men o d inking wa e .
I he i iga ion p ocess is analysed o he di e en scena ios, he
en i onmen al esul s o he WC ca ego y show ha in he case o
cen alised sys ems he impac alues a e 0.12 m3 o wa e pe esiden ,
while o decen alised cases he nega i e e ec is abou 3.03·10-3 m3 o
wa e pe esiden . These esul s show an imp o emen o a ound 99%
in he en i onmen al p o ile because he p oduc ion and dis ibu ion o
ap wa e ha is caused by he cen alised con igu a ions in ol e la ge
en i onmen al impac s.
Figu e 8.5 shows he main esul s o he WC ca ego y o each
was ewa e ea men scheme conside ed. In addi ion, he subsys ems
SECTION II: CHANGING THE PARADIGM OF WASTEWATER TREATMENT
272
nu ien s. In addi ion, decen alised sys ems a e cha ac e ised by a lowe
sewage ne wo k compa ed o cen alised sys ems (Ophe and F iedle ,
2016). I is es ima ed ha he sewe ne wo k has an ha e a signi ican
con ibu ion o he o e all impac o cons uc ion o WWTPs (Pe i -Boix
e al., 2014). Thus, in his case, i was e alua ed how he sewe age
ne wo k a ec s he en i onmen al p o ile.
In he ci y o San iago de Compos ela, he ex ension o sewage
ne wo k is 647 km, which implies an amoun o 5 m/inhabi an . In
decen alised sys ems, his igu e is es ima ed o be abou 3.7
m/inhabi an (Kje s adius e al., 2017). I he en i onmen al p o iles a e
compa ed, as expec ed, he cen alised sys em (455 kg CO2eq/ esiden )
has 76% highe amoun ha he decen alised sys ems (108 kg
CO2eq/ esiden ). These impac s a e ela ed o he p oduc ion o conc e e
o enching and pipe ma e ial bu no only hese ac o s a e impo an ,
he e a e aken in o accoun he capaci y o he sewe ne wo k. The sewe
ne wo k in San iago de Compos ela has a highe capaci y because he e
is no sepa a ion ne wo k (was ewa e and ainwa e ), he e o e, he
capaci y o he sewe age mus be high because in his ci y he ain all is
high. On he con a y, in he decen alised sys em, al hough he e a e wo
pipes (one o BW and ano he o GW), he capaci y is educed. This
implies less en i onmen al impac s ela ed o he cons uc ion o he
pipelines, di ches o e en di ec emissions ela ed o he cons uc ion.
The in oduc ion o a sepa a e ne wo k in San iago is no simple due
o he p o ec ion o i s old own, so changing he sewage ne wo k is no a
iable op ion, bu decen alised sys ems o was ewa e and sewage can
be a good al e na i e in new neighbou hoods and can imp o e he
en i onmen al p o ile o hese ne wo ks no only in he CC ca ego y bu
in all ca ego ies, making he esiden ha e less consump ion o ca bon
and wa e in e ms o i iga ion han esiden s who choose ano he ype
o neighbou hood.

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8.4. CONCLUSIONS
In his Chap e , he ca bon oo p in and wa e consump ion o
i iga ion o a esiden li ing in a cen alised was ewa e dis ic was
compa ed o ha o a esiden who chooses o li e in a decen alised
was ewa e dis ic . The s udy was ca ied ou in he ci y o San iago de
Compos ela. In his amewo k, wo cen alised con igu a ions: (i)
con en ional sys em wi hou AD uni and (ii) a con en ional sys em wi h
he inco po a ion o AD uni we e compa ed wi h decen alised op ions:
one wi h con en ional oile s and ano he wi h acuum oile s. The
decen alised op ions show a educ ion o he esiden ca bon oo p in
by 20-23% due o elec ici y p oduc ion. Fu he mo e, wi h he
eclaimed wa e , hese sys ems can supply wa e o i iga ion o g een
a eas, so no ex a consump ion o ap wa e is equi ed. Al hough hese
new sys ems p esen mo e cons uc ion cos s and a e mo e complex, he
eco e y ime is less han in con en ional sys ems due o he eco e y o
p oduc s such as ene gy o wa e . Howe e , he inco po a ion o hese
sys ems is no easie due o he obus ness o con en ional sys ems. Thus,
he op ion o decen alised cases can be an op imal solu ion o new
buildings o esiden ial a eas.
8.5. REFERENCES
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GENERAL CONCLUSIONS AND
FUTURE PERSPECTIVES

278
Gene al conclusions and u u e pe spec i es
The main objec i e o his doc o al hesis was o analyse and
compa e di e en was ewa e ea men con igu a ions om an
en i onmen al and economic poin o iew. This opic is in line wi h he
g owing conce n o alle ia e he e ec s ela ed o clima e change and
wa e sca ci y caused by an h opogenic ac i i ies and popula ion g ow h.
In his sense, WWTPs should be included in he philosophy o he ci cula
economy and ha e eme ged as a solu ion o eco e p oduc s such as
ene gy, nu ien s and eclaimed wa e . In his con ex , wo inno a i e
s a egies o was ewa e ea men we e e alua ed: (i) one o
cen alised sys ems (Chap e 2 o Chap e 6) and (ii) one based on
decen alised was ewa e ea men schemes (Chap e 7 and Chap e 8).
I was demons a ed ha en i onmen al impac me hodologies and
economic indica o s p o ide use ul in o ma ion o assis he in eg a ion
o hese was ewa e ea men s a egies. The main indings and
conclusions d awn om he di e en sec ions ha make up his hesis
a e p esen ed below:
Sec ion I: Imp o ing cen alised was ewa e ea men sys ems.
The main objec i e is o c ea e a i ual was ewa e ea men plan ha
encompasses he bes echnologies om an en i onmen al and economic
poin o iew o cen alised sys ems. The concep ual design o a " i ual
plan " will be based on he analysis de eloped om Chap e 2 o Chap e
6 in he amewo k o i e di e en s udies de ailed below.
In Chap e 2, AD echnology was analysed a di e en scales wi h he
main objec i e o assessing he en i onmen al and economic iabili y o
his echnology. This ea men can be a good al e na i e o ea ing
sludge due o he euse o biogas as hea o ene gy as well as he po en ial
o he diges a e as a bio e ilise . In addi ion, i he amoun o sludge is
no e y high, he e a e al e na i es o imp o e he p oduc ion yield o
biogas such as he co-diges ion o sewage sludge wi h ood was e om
households, se ices o e en om he ag o- ood sec o . The e o e, his
echnology will be included in he " i ual plan " as his chap e showed
i s e iciency. Despi e he en i onmen al and economic ad an ages o AD,
CONCLUSIONS
279
sludge ea men can be a slow p ocess. As men ioned in he in oduc ion
and in Chap e 3, hyd olysis, an ini ial s age in he AD p ocess, is a limi ing
s ep, so in o de o imp o e his uni and sa e ea men ime, wo
al e na i e p e- ea men s we e p oposed: chemical and he mal
hyd olysis. In his case, he p e- ea men s p o ed o be a good
al e na i e o accele a e he hyd olysis s age and imp o e biogas
p oduc ion. I is ue ha he consump ion o elec ici y and chemicals
wo sens he en i onmen al p o ile bu , i can be compensa ed wi h he
inc ease in biogas p oduc ion. This means ha p e- ea men s can also
be a good al e na i e o he " i ual plan ". Howe e , hese p ocesses a e
s ill unde de elopmen , and mo e in o ma ion is needed o inco po a e
hese p e- ea men s in o a eal sludge line.
In Chap e 4 and 5, ea men schemes a di e en scales we e
p oposed o ea was ewa e in a ca bon neu al pe spec i e. In Chap e
4, he WWTP scale is 100,000 equi alen inhabi an s and in Chap e 5, he
WWTPs scales a e o 265,000 and 1,000,000 o equi alen inhabi an s.
As a summa y, Figu e 10.1 shows he esul s o di e en scena ios and
di e en plan sizes. This igu e may indica e he end ha plan s should
ollow o ha e mo e en i onmen ally iendly and economically iable
schemes in cen alised WWTPs. Thus, a p io i, o la ge plan s, he
con en ional scheme (PC + CAS) is he wo s scheme due o he high
ene gy consump ion o he CAS uni , and he e is less biogas p oduc ion
han in he o he scena ios. The case o RBF + CEPT + IFAS ha was
inco po a ed in he smalle plan (100,000 equi alen inhabi an s) is
in e es ing. Al hough, he e is a educ ion in ae a ion due o he
inco po a ion o IFAS echnology i is no app op ia e due o he
consump ion o chemicals in he p ima y ea men . This inco po a ion
o he chemical can inc ease he en i onmen al p o ile and economic
impac s. Fo his eason, no all schemes a e app op ia e. The bes
solu ions om an en i onmen al and economic poin o iew and ha can
y o make plan s ca bon neu al a e combina ions based on UASB and
IFAS as well as he HRAS and IFAS sequence. In he i s case, he sludge
line is no necessa y, so his implies a educ ion in land occupa ion and,
in he UASB uni , biomass g ow h is slowe han in ae obic uni s, so his
implies a educ ion in he amoun o sludge. I his scheme is no possible,
he HRAS uni allows a high OM eco e y wi h a high me hanisa ion ac o
CONCLUSIONS
280
while he subsequen IFAS s age p o ides ad an ages such as good
ni ogen emo al and low ene gy consump ion (Figu e 9.1).
Figu e 9.1. Di e en en i onmen al and economic esul s o he
was ewa e ea men schemes s udied. Bubbles ep esen he size o he plan
and he colou s co espond o di e en schemes. O ange: PC + CAS
echnologies, pu ple: RBF + CEPT+ IFAS, blue: UASB + IFAS, g een: ERBF+ IFAS,
and inally, u quoise: HRAS + IFAS
Finally, Chap e 6 is ela ed o he scale-up o an eme ging
echnology. This chap e is e y impo an in de e mining he minimum
scale o eliable LCA and economic e alua ion. In a con ex whe e
decen alisa ion is becoming inc easingly impo an , i is c ucial o e i y
his me hodology in he calcula ion o en i onmen al impac s. This s udy
can help o know whe he he LCA app oach makes sense in
decen alised schemes. A e conduc ing he s udy, he minimum olume
ha p o ides eliable en i onmen al impac s was selec ed as 0.2 m3,
while o economic indica o s, he minimum scale was 1 m3. This means
ha when decen alised sys ems a e s udied, he olume needed o ha e
consis en da a will be 0.2 m3. Smalle scales may p o ide an un ealis ic
p o ile.
-0.2
0.3
0.8
1.3
1.8
2.3
2.8
3.3
3.8
0 0.2 0.4 0.6 0.8 1 1.2 1.4
CC [kg CO2 eq/FU]
Cos [€/FU]
CONCLUSIONS
281
Sec ion II: Changing he pa adigm o was ewa e ea men . This
sec ion consis s o wo chap e s ha ocus on he possible ad an ages and
disad an ages o di e en decen alised sys ems. Thus, as in he p e ious
case, he main objec i e is o y o gi e a gene al app oach. Howe e , in
his case i is mo e complica ed han in he p e ious sec ion because, he
chap e s a e based on wo di e en pe spec i es.
Fi s , a decen alised was ewa e ea men plan based on a MBR
uni o 2,000 inhabi an s and loca ed in Tu key was e alua ed om an
en i onmen al poin o iew. In his case, he p io y o he sys em was
eused wa e in g een a eas because Tu key is a coun y wi h wa e
de ici . Fo his p opose, an indica o called AWARE was calcula ed. In
addi ion, in his analysis, cons uc ion and ope a ion phases we e s udied
o quan i y he en i onmen al impac s ela ed wi h he cons uc ion o
he decen alised sys ems. Wi h he objec i e o wa e euse in mind,
MBR is a echnology ha achie es sa is ac o y esul s on e ms o wa e
quali y. Mo eo e , he wa e euse had signi ican en i onmen al impac s
in all ca ego ies. Finally, o decen alised sys ems, he cons uc ion s age
associa ed wi h he memb ane ab ica ion can p esen high
en i onmen al impac s.
Finally, Chap e 8 ocuses on he poin o iew o he inhabi an . The
s udy om he poin o iew o he inhabi an is e y impo an because
he ci izen is inc easingly awa e ha in a changing and con inuously
g owing wo ld, an h opogenic ac i i ies mus ensu e an exhaus i e
con ol o emissions and he e o e lowe ca bon and wa e oo p in
alues. Thus, his s udy compa ed a esiden li ing in a cen alised a ea
wi h one li ing in a decen alised neighbou hood o was ewa e
ea men . The ca bon oo p in o a esiden in e ms o ene gy
consump ion can be educed by 20-23% in a eas ha inco po a e a
decen alised sys em. Addi ionally, he wa e demand o g een a eas can
be co e ed by eclaimed wa e . The e o e, he e a e no impac s ela ed
o wa e ea men and dis ibu ion. Finally, i is impo an o poin ou
ha hese plan s can be mo e lexible, and i is easy o eco e esou ces,
especially in coun ies whe e he e a e p essing p oblems o wa e
sca ci y. The e o e, hese sys ems can also be a good op ion o new
buildings o esiden ial a eas.