185
ACTA UNIVERSITATIS AGRICULTURAE ET SILVICULTURAE MENDELIANAE BRUNENSIS
Volume LVIII 21 Numbe 5, 2010
RELATIONSHIP BETWEEN CENTRIFUGATION
AND DRYING OF SLUDGE AND
THE ORGANIC HALOGENS
K. H ich, B. G oda
Recei ed: May 12, 2010
Abs ac
HRICH, K., GRODA, B.: Rela ionship be ween cen i uga ion and d ying o sludge and he o ganic halogens. Ac a
uni . ag ic. e sil ic. Mendel. B un., 2010, LVIII, No. 5, pp. 185–190
This wo k is ocused on de e mina ion o adso bable o ganic halogens (AOX) concen a ion in he di-
ges ed sludge om he sewage ea men plan and he losses o his componen du ing dewa e ing
and d ying o sludge. D ying o he sludge om was ewa e ea men plan is no ex ended oo much
in Czech Republic. In his wo k, he AOX a e moni o ed, because AOX is one o he limi s es aining
use o he sludge on an ag icul u al land. Ano he eason is echnological demand o using he sludge
in cemen p ocessing, because chlo ine in AOX can cause dec ease in a hea ans e eff ec in a ce-
men kiln. I is clea om he esul s ha bo h cen i uged and d ied sludge om he sewage ea -
men plan B no ulfi lled limi s o using sludge on ag icul u e land. They can also be compos ed,
in case hey mee o he equi emen s. I no , i is a possibili y o co-incine a ion in cemen kiln. In
such case, limi o o al chlo ine including he AOX is equi ed oo. This limi was no exceeded. An-
o he aim was o calcula e a mass balance o AOX du ing he cen i uga ion and d ying p ocesses.
I was ound ou , ha a e cen i uga ion he main pa o AOX emained in he cen i uged sludge
(96.4 %). The es was d awn-off wi h ejec wa e . 60 % o AOX in he ejec wa e we e dissol ed com-
pounds. A simila si ua ion occu ed du ing he d ying p ocess. Mo e han 99 % o AOX was bound in
he d ied sludge. The ai and apo ised wa e con ained such quan i y o AOX, which co esponded
wi h he amoun o he dus in he ai and he amoun o pa icles o sludge in apo ised wa e .
adso bable o ganically bound halogens, cen i uga ion, d ying, sludge, was e wa e
Sludge is a mix u e o wa e and solids sepa a ed
om he was e wa e in a ious ways. Sludge is
abou 1–2 % o he ea ed was e wa e ; howe e , i
con ains 50–80 % o he ini ial pollu ion in he was e
wa e (Ku il, Dohányos, 2005; Malý, Malá, 2006).
The ideal s a us would be o use all sludge as e -
ilize o ag icul u al land o eplace mine al e -
ilize s. Howe e , sludge con ains pollu ion o igi-
nally p esen in he sewage. This limi s i s use on
ag icul u al land, which is modifi ed by egula ion
in Czech Rep. (co esponds wi h Eu opean egula-
ion), speci ying he concen a ion o hea y me als,
PCBs, and AOX. Compos ing is ano he op ion o
ea ing he sludge. The equi emen s on he sludge
a e simila . I he sludge con ains he abo e pol lu-
an s, i is possible o dispose i in a haza dous was e
landfi ll. In his case, he p oduce o sludge pays
o i and he e o e he looks o o he choices. One
o hem is co-incine a ion o he sludge in he ce-
men wo k. Du ing he incine a ion p ocess, chlo-
ine om sludge eac s o chlo ides and u he
wi h subs ances in he combus ion gases. A ising
p o duc s adhe e o he u nace, cause de e io a-
ion o he hea ans e in he u nace, and educe
i s eff ec i eness. Main pa o his chlo ine is o in-
o ganic o igin, bu he e a e he adso bable o ganic
bound halogens – AOX, oo. They a e o ganic com-
pounds con aining halogen elemen s, usually chlo-
ine a oms.
Many a icles we e published abou AOX, bu
he majo i y is aimed a analysing concen a ion o
AOX in indus ial was e wa e and sludge. Com-
monly highe amoun s o AOX a e in effl uen s om
ex ile o pape ac o ies. These effl uen s a e usually
186 K. H ich, B. G oda
being ea ed di ec ly in he own ea men plan s.
Con en o AOX in sludge om u ban was e wa-
e was men ioned in (Shoma , 2007), who s udied
he concen a ion o AOX in was e wa e and sludge
in sewe sys em o Gaza S ip. I ollows om his a -
icle ha some AOX compounds can o m di ec ly
du ing he ea ing p ocess, especially in anae obic
anks. O he au ho s ocused a he a he me ho do-
lo gy AOX analysis in he sludge (K ysell e al., 2008)
and he AOX concen a ion in i e s, such as (Kacz-
ma czyk, Niemiycz, 2005).
As al eady no ed, his wo k was aimed on moni-
o ing he AOX in he cen i uging and d ying p o-
cesses. Sampling was made a he municipal was e
wa e ea men plan (WWTP) in B no-Modřice,
which has sludge ea men including cen i uga-
ion and d ying. I s capaci y is 400 housand popula-
ion equi alen s (p. e.).
Sludge ea men a WWTP Modřice
To al olume o he diges ion anks is 14 960 m3.
They a e equipped by gaseous seal lamina ed oo .
Tank diame e is 20 me e s wi h conical bo om wi h
8 m dep h. Diges ion anks a e fi ed wi h a e ical,
slow, no mal s i e . Hea ing o he anks on em pe-
a u e 35 °C is ca ied ou by h ee hea -exchange s
sludge/sludge and wo hea -exchange s sludge/wa-
e .
Two pa allel cen i uges Guina d D5LLC wi h ca-
paci y 36 m3 . h−1 pe uni we e used o dewa e ing
o sludge. Abou 670 m3 . d−1 o sludge wi h 57 g . l−1
d ied ma e a e p ocessed on a e age. D ie NARA
NPD14W ype wi h indi ec hea ing consis s o ho-
i zon al case ough equipped wi h wo hollow o-
a ing spindles wi h hollow paddles. Ho oil (180–
210 °C) fl ows inside he case, spindles, and paddles.
Re en ion ime o he sludge in he d ie is abou 4
hou s. S eam wi h cap u ed dus om he sludge
(3.43 m3 . h−1) is lead o a gas sc ubbe . Condensa e
wi h empe a u e o 85 °C is fi lled in o sludge/wa-
e hea exchange and se es as main sou ce o
hea o diges ion anks. D ied sludge o he amoun
28 . d−1 and 88–92 % d y ma e is cooled o 40 °C
and ca ied wi h he sys em o spindles ou o p e-
pa ed con ai ne s. P oduced sludge is sampled and
ca ied away o i s fi nal use. The whole p oduc ion
o d ied sludge is used as an al e na i e uel in a ce-
men wo k. A he ime o cemen ac o y s oppages,
cen i uged sludge is used as a ma e ial o indus-
ial compos s.
Acco ding o he alues ob ained om he WWTP
ope a o , he a e age AOX concen a ion in aw
was e wa e was 0.138 mg . l−1 in 2007. The concen-
a ion dec eased o 0.050 mg . l−1 in ea ed wa-
e . The ma e ial balance was calcula ed on he ba-
sis o knowledge o wa e fl ow h ough he WWTP
and i can be said ha 59.6 % o AOX a e cap u ed
in he sludge and 40.4 % emain in wa e . The daily
quan i y o AOX in sludge was 7359 g.
MATERIAL AND METHODS
Selec ion o sampling si es
Eigh si es we e selec ed (see fi g. 1): (1) s abilized
sludge en e ing he cen i uges, (2) wa e om cen-
i uges, (3) sludge en e ing he d ye (cen i uged
sludge), (4) he cooling wa e en e ing he gas sc ub-
be , (5) indus ial wa e en e ing he gas sc ubbe , (6)
he mix u e o wa e and condensa e lea ing he gas
sc ubbe , (7) d ied sludge, (8) ai in he d ye build-
ing be o e i en e s he fi l e s o deodo izing (no
ma ked in he fi gu e).
Concen a ions o AOX we e analysed im me dia-
e ly a e sampling. In case his was no possible,
he samples we e ozen and analysed as soon as
possible.
Ai was sampled by he HS-SPME me hod (head
space – solid phase mic o ex ac ion), in which
he sampled ai was caugh in o a p epa ed con-
aine and allowed o eac on a fi b e imp egna ed
so ben . The sample was hen analysed by gas ch o-
ma og aphy.
1: Sampling si es in he cen i uga ion and d ying p ocesses
Rela ionship be ween cen i uga ion and d ying o sludge and he o ganic halogens 187
Analysis o AOX
Analysis o aqueous samples was ca ied ou ac-
co ding o ČSN EN 1485: Wa e quali y: The de e -
mina ion o adso bable o ganically bound halogens.
The ECS 1200 Eu oglas analyze was used. In case o
sludge samples ea men , he sludge is p e-d ied o
130 °C, mixed wi h wa e and u he ea ed simi-
la ly o aqueous samples.
RESULTS AND DISCUSSION
Resul s published in his wo k we e measu ed
du ing he yea 2007. Daily a e age o s abilized
sludge d y ma e in measu ed samples anged be-
ween 3.12 up o 3.57 % ( able Ia and Ib) wi h he a e-
a ge o 3.38 %. The common alue is no o e eaches
10 % (Dohányos e al., 2007), usually a e age d y ma -
e in he sludge is 5.1 % (Malý, Malá, 2006). Highe
d y ma e con en causes anspo pipeline p ob-
lems. O ganic pa o he d y ma e in he moni-
o ed sludge was abou 52.1 % (usually abou 46 % –
Chudoba e al., 1991).
As shown in fi g. 2, he AOX con en in sludge is
below he limi alue o sludge disposal as e i li-
ze , and hus om he pe spec i e o AOX con en ,
he sludge can be used o e ilize ag icul u al land.
As al eady indica ed, co-incine a ion in a cemen
u nace is possible. The cemen ac o y is equi ed
o ha e a maximum o al chlo ine le el which does
no exceed 0.08 % w . This is equi alen o 0.8 g o-
al chlo ine in one kilog am o d y ma e . The mea-
su ed samples o sludge we e sui able o he ce-
men ac o y. I co esponds wi h he da a ob ained
om he WWTP ope a o : in 2008, he o al chlo ine
le el was usually only 0.052 % w .
Da a ha ep esen he AOX way h ough cen-
i uga ion p ocess a e so ed in able Ia and Ib. Ta-
ble II shows he alues om sludge d ying. Du ing
cen i uga ion, wa e was emo ed and he d y ma -
e o sludge inc eased. The wa e con en in dewa-
e ed sludge was be ween 72,6 % and 79,0 % (a e a ge
77,1 %). Mo e han 99 % o d y ma e emained in
he sludge and 29.97 m3 . h−1 cen i uged wa e fl ew
off . The cen i uged sludge con ained mo e han
96 % o AOX ed in o he cen i uge. 99.6 % o AOX
in he cen i uged sludge was bound in solid phase,
while in case o s abilized sludge he pe cen age was
only 96.8 %. P opo ion o insoluble AOX in ejec
wa e was abou 32 % o o al AOX con en . The a e-
a ge concen a ion o dissol ed AOX in sludge was
242 mg . m−3, he a e age concen a ion o AOX in
sludge solids was abou 260 mg . kg−1, which co e-
sponds wi h he li e a u e da a: 300 ± 162 mg . kg−1
(min. = 68 mg . kg−1, max. = 199 mg . kg−1) (Malý, Malá,
2009). Adso p ion capaci y o solid sludge may cause
he accumula ion o ce ain subs ances con ained in
was e wa e , such as non-pola hyd oca bons, en-
sides, polycyclic a oma ic hyd oca bons (PAHs),
AOX, and hea y me als. The e o e, hei p opo -
ion in solids o sludge is highe han in he aqueous
phase. PAHs, AOX and PCB a e no signifi can ly de-
composed.
The si ua ion du ing he d ying is a simila as in
case o he cen i uga ion. The majo i y (abou 99 %)
o AOX con ained in cen i uged sludge emains in
he d ied sludge. A negligible amoun is e ained
in apo ised wa e . These AOX a e p obably dis-
2: Concen a ion o AOX in cen i uged and d ied sludges: compa ison wi h he Czech egula ion No. 504/2004 Coll.
188 K. H ich, B. G oda
sol ed, jus like in he ejec wa e . Highe quan i ies
han in apo ised wa e a e con ained in he ai ou -
fl ow. This is caused by high concen a ion o dus in
he ai ou fl ow. The daily p oduc ion o dus is on
a e age 120 kg. Abou 17 g AOX escape in o he ai
wi h he dus e e y hou . This dus is sepa a ed in
a gas sc ubbe and hus he ai in he d ye building
mee s he pe missible exposu e limi (PEL) o dus
specifi ed in Go e nmen Dec ee No. 361/2007 Coll.
( he AOX limi is no se ).
I: Cen i uga ion p ocess
Da e 04/14 04/15 06/09 06/10 10/10 10/11 10/12 10/13 10/14 10/15 10/16 10/
24–25
In e al [h] 20 20 20 20 24 24 24 24 24 24 24 20
S abilized sludge, inle o he cen i uge
Quan i y [m3]829 825 808 806 734 723 739 720 821 755 795 716
D y ma e [kg.m−3]30.4 32.1 39.3 35.7 33.8 35.4 33.3 34.6 31.2 33.0 32.0 34.9
AOX [mg.kg−1 d.m.*] 186 202 300 189 253 279 274 246 281 256 285 321
AOX [g] 4687 5349 9526 5438 6277 7141 6743 6128 7198 6378 7250 8021
Cen i uged sludge
D y ma e [%] 21.0 22.3 27.4 25.4 22.9 22.3 23.2 23.4 22.6 23.0 23.9 24.4
AOX [mg.kg−1 d.m.*] 151 141 138 156 242 259 255 235 268 246 273 312
AOX [g] 4255 4628 9331 5213 6131 7006 6581 5990 7043 6239 7061 7826
Rejec wa e
Quan i y [m3]710 708 693 694 626 609 633 614 709 648 690 614
Suspended solids [g.m−3]395 493 542 447 380 450 300 290 450 500 580 475
AOX [mg.m−3]609 1020 282 325 233 222 256 225 219 215 274 319
AOX [g] 432 722 195 225 146 135 162 138 155 139 189 196
* d.m. – d y ma e
II: D ying p ocess
Da e 10/10 10/11 10/12 10/13 10/14 10/15 10/16 10/24–25
In e al [h] 24 24 24 24 24 24 24 20
Cen i uged sludge, inle o he d ie
Quan i y [ ] 107 114 105 106 112 107 104 101
D y ma e [%] 22.9 22.3 23.2 23.4 22.6 23.0 23.9 24.4
AOX [mg.kg−1 d.m.*] 249 276 269 242 278 253 281 316
AOX [g] 6131 7006 6581 5990 7043 6239 7061 7826
D ied sludge
D y ma e [%] 91.4 91.5 91.7 92.1 91.5 92.3 91.9 90.8
AOX [mg.kg−1 d.m.*] 239 256 253 231 264 241 269 300
AOX [g] 5833 6458 6148 5677 6660 5892 6622 7390
Vapo ized wa e
Quan i y [m3]80.2 85.9 78.6 79.0 84.4 80.4 77.2 73.7
AOX [μg.m−3]0.110 0.136 0.178 0.114 0.146 0.167 0.165 0.269
AOX [g] 8.84 11.70 13.99 8.99 12.34 13.44 12.75 19.80
Ai om d ie
Quan i y [m3]31104 31104 31104 31104 31104 31104 31104 31104
Dus in ai , d ied ma e [kg] 118 97 106 124 72 121 132 174
AOX [mg.kg−1 d.m.*] 239 256 253 231 264 241 269 300
AOX [g] 28.2 24.8 26.8 28.7 19.0 29.1 35.6 52.3
* d.m. – d y ma e
Rela ionship be ween cen i uga ion and d ying o sludge and he o ganic halogens 189
CONCLUSIONS
The a e age con en in solids o diges ed sludge in was e wa e ea men plan B no is abou
260 mg . kg−1.The mos o AOX (96.8 %) is bound in suspended pa s o sludge du ing he cen i uga-
ion and. 3.2 % o AOX emains in ejec wa e , 68 % o o al amoun in o m o dissol ed subs ances.
Du ing he d ying, 99 % o AOX emained in d ied sludge. The es (1 %) was di ided be ween apo-
ised wa e and dus in ou fl ow.
F om AOX concen a ion poin o iew, bo h cen i uged and d ied sludge ulfi ls he legal equi e-
men s se o hei use on ag icul u al land, in o compos , and co-incine a ion in cemen wo ks.
SOUHRN
Vz ah mezi ods řeďo áním a sušením kalu a o ganickými halogenidy
Ta o p áce byla zaměřena na zjišťo ání koncen ace adso bo a elných o ganických halogenidů
(AOX) kalu z čis í ny odpadních od a hodnocením koncen ačních změn AOX e yhnilém kalu
při jeho od odňo ání a sušení kalu. V České epublice není sušení čis í enských kalů příliš ozšíře-
ným způsobem. Jedním z dů odů, p oč byly sledo ány AOX kalu, byl en, že koncen ace ěch o lá-
ek je jedna z limi ujících hodno při yuži í kalu na zemědělské půdě. Obdobně je omu u použi í
kalu do zakládek kompos u. Sušený kal může bý docela dobře spolu-spalo án cemen ářském p o-
cesu. I zde šak je z echnologického hlediska omezeno množs í celko ého chlo u, espek i e AOX
obsaženého kalu. Na celko ém chlo u kalu se podílejí edle AOX i ano ganické chlo idy. Chlo
se při spalo ání přeměňuje na akz ané „nálepy“ a zho šuje přes up epla přes s ěny pece. P o y-
počí ání bilančních o nic p o ods řeďo ání a sušení bylo z oleno sedm odbě ných mís , ak, aby
byly pok y y šechny s upy a ýs upy z ěch o p ocesů. Vzo ky ody a kalu byly pod obeny analýze
na přís oji ECS Eu oglas 1200. Dále byla získána p o ozní da a, jako množs í ody a kalu, k e é p o-
cházelo p ocesy. Z ýsledků analýz je jasné, že ods ředěný a sušený kal splňuje limi y AOX p o po-
uži í kalu na zemědělské půdě. Mohou bý edy i kompos o ány, pokud splňují os a ní požada ky.
Z hlediska obsahu chlo u, espek i e AOX, je možné yuží kal při spolu-spalo ání cemen á ně.
Z bilančních ýpoč ů yplynulo, že během ods řeďo ání zůs á á ě šina podílu AOX kalu (96,4 %).
Zby ek je ods aněn ods ředěné odě. Přes 99 % pe ných čás ic zůs á á ods ředěném kalu. V p o-
cesu sušení zůs á á sušeném kalu přes 99 % AOX. Zby ek je ozdělen mezi os a ní ýs upy (odpa-
řená oda, od áděný zduch). V ods ředěné odě oří hla ní podíl ozpus né o my AOX. Podobně
omu bude i odpařené odě. AOX o zduší od áděném ze sušá ny jsou ázány na p acho é čás ice.
adso bo a elné o ganické halogeny, ods řeďo ání, sušení, kal, odpadní oda
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Add ess
Ing. Ka el H ich, Fakul a s a ební, Ús a chemie, Vysoké učení echnické B ně, Žižko a 17, 602 00 B no,
Česká epublika, e-mail: h ich.k@ ce. u b .cz, p o . Ing. Boři oj G oda, D Sc., Ús a zemědělské po a inář-
ské a en i onmen ální echniky, Mendelo a uni e zi a B ně, Zemědělská 1, 613 00 B no, Česká epublika,
e-mail: bo i oj.g [email p o ec ed]

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