Wastewater Characteristics of a Cattle Zootechnical Farm – A Case Study

BULETINUL INSTITUTULUI POLITEHNIC DIN IAŞI Publicat de Universitatea Tehnică „Gheorghe Asachi” din Iaşi Volumul 71 (75), Numărul 3, 2025 Secţia CHIMIE şi INGINERIE CHIMICĂ DOI: 10.5281/zenodo.17357071 WASTEWATER CHARACTERISTICS OF A CATTLE ZOOTECHNICAL FARM – A CASE STUDY BY CRISTINA-ALEXANDRA HAIVAS and CARMEN ZAHARIA “Gheorghe Asachi” Technical University of Iaşi, “Cristofor Simionescu” Faculty of Chemical Engineering and Environmental Protection, Iaşi, Romania Received: June 13, 2025 Accepted for publication: August 15, 2025 Abstract. This research highlights the waste types and their principal characteristics produced from the main activities in an investigated livestock farm, especially collected wastewaters from different zootechnical activity sectors. Six monitoring sectors were selected to assess the level of polluting load from the discharged effluents. Constant control of the main imposed quality indicators (pH, COD, BOD, total solids, ammonia, extractible substances) is obviously required and periodically reported to water regulatory management authority, as well as the establishment of viable and efficient directions utilized for the wastes treatment and recovery on-site (direct possible use). The limiting norms of the quality indicators controlled in a few sectors (mainly 4 control sectors) are far exceeded and the trend is to increase the polluting loads, which requires the adoption of serious local treatment measures and the continuation of monitoring the quality status of the effluents generated on the livestock farm. Keywords: environmental protection, wastewater, livestock farm, quality indicators. Corresponding author; e-mail: cr[email protected] Corresponding author; e-mail: carme[email protected] 10 Cristina-Alexandra Haivas and Carmen Zaharia 1. Introduction Livestock farming practices in Romania have been accompanied by a significant increase in waste production which places a heavy burden on the environment. Thus, environmental pollution has become an important limiting factor for the sustainable and efficient development of modern agriculture and connected industries all over the countries (Biagini and Betta, 2024; Richards and Yabar, 2023; Tinitana-Bayas et al., 2024; Valverde-Orozco et al., 2024; Verlicchi et al., 2019; Xiaoyuan et al., 2024; Zaki et al., 2023). Therefore, the Romanian livestock industry was rapidly developed because of population growth, market demand, and good practice policy support. The production pattern has gradually changed from household farms into large-scale and high-intensity farms, such that a large-scale pig farm which raises 50 × 104 pigs, a cattle farm for milk which has 10 x 100 cattle and a poultry farm with 100 × 104 chickens. A special attention was giving to collected and uncollected wastewaters (WWs) produced in different zootechnical activity sectors onto the farm emplacement. Generally, the statistics indicated that the chemical oxygen demand (CODCr) and NH4-N (ammonia) discharges from livestock industry sources commonly account for 45% and 25% of total discharges, respectively. This environmental pollution caused by the high organic and inorganic loads of zootechnical effluents has become an important limiting factor for sustainable and efficient development of the agricultureand zootechny-based industries in Romania (Filote et al., 2021; Zimmo et al., 2002; Zaharia, 2022). Usually, animals such as cows are raised in modern shelters where a proper microclimate is maintained, which must ensure maximum milk and weight gain in a minimum time. The normal trend in the removal of waste and liquid residues from cattle consists, on the one hand, in maintaining the best possible hygienic and sanitary conditions in the shelters, and on the other hand in saving labor and energy, the costs of which are included in the costs of the final product, milk, meat and/or derived products. Since one of the ways of removing fresh residues / wastes from shelters uses the washing water (i.e. either use of the jet, or through the "water cushion" system in which the fresh residues / wastes fall through the interspaces of the discontinuous floor - grill type), the characteristics of the effluents produced in each sector of activity and the ones which are stagnant in the collectors of each building or sector of activity acquire a special importance, and compliance with the quality requirements imposed on the wastewater discharged or taken over by an operator to the local municipal wastewater (WW) treatment plant becomes mandatory in maintaining a sustainable environmental management of the livestock farm. This paper aims to present and briefly discuss the main characteristics of all effluents produced in a cattle farm specialized in milk production, collected from all sectors of activity on the farm site. Information regarding the compliance Bul. Inst. Polit. Iaşi, Vol. 71 (75), Nr. 3, 2025 11 with the quality requirements of the aquatic environment nearby imposed by the authorized water management responsible will be presented and discussed in comparison with the quality norms inscribed in the environmental legislation corresponding to the quality of the treated wastewater discharged by an economic agent. Directions to be followed in order to comply with the quality norms of the WW discharged from the site of the investigated farm will be mentioned and immediate solutions which are imposed for its sustainable management will be underlined, too. 2. Experimental and study objective 2.1. Case study location: a Romanian zootechnical farm It is evaluated a Romanian cattle zootechnical farm which is located near a small village (in Northern-Eastern part of the Moldavian macro-region No. 2), disposing of an available environmental and water management authorization. The livestock farm (cattle for milk production) / dairy farm has an average area of 25 ha with 6 animal production sheds (stalls) (3000 at the time of the authorization permit). The water consumed on the farm site comes from three controlled underground sources (4 boreholes) and from the local centralized water supply system. Commonly, the produced wastewater amount per head of animal and day is around 25-30 L. The livestock farm has an internal sewage system for the produced wastewaters in each activity sectors (Fig. 1), i.e. six separate collectors in each farm building that are drained periodically (every 4 months) and two aerated lagoons for the entire urine produced (Zaki et al., 2023) (diluted with rainwater). The faecal wastes are locally treated and stocked on a concrete platform. Faecal waste and sewage are not applied to crop land and not directly discharged into the environment; thus, it minimizes the pollution of soil, surface water and groundwater (Voicea et al., 2020). (a) (b) Fig. 1 ‒ Feeding (a) and cleaning (b) sectors of the studied zootechnical farm complex. 12 Cristina-Alexandra Haivas and Carmen Zaharia The wastewater flow in each farm building can vary in range of 1000 – 4300 L/day, and the registered mean and maximum WW flow is of 3.28 m3/day and 4.30 m3/day, respectively. The WW characteristics, meaning the values of imposed WW quality indicators, must be periodically controlled but at least two times per year reported to the water management authority. 2.2. Analysis methods used for the characterization of collected wastewater For WW characterization were used a few specific quality indicators which were determined by internationally approved standards, mainly consisting in certain physical-chemical analytical analysis methods. Thus, the WW produced and collected in each farm building and rainwater collectors is usually twice controlled per year for certain quality indicators recommended by the water management authority such as pH, total solids (TS), chemical oxygen demand (CODCr), biochemical oxygen demand (BOD5), ammonia and extractible substances (ES), analysed according with the international approved standards. Determination of pH (pH units): the pH value is directly recorded and read using a Hanna pH-meter (Combo pH & EC waterproof). Determination of CODCr (mg O2/L): it was used the closed reflux, colorimetric method (SR ISO 15705) at small scale with closed tubes, based on WW sample oxidation at 150⁰C for 2 h with help of a digestion/oxidant solution (i.e. 1.5 mL K2Cr2O7 / HgSO4 / H2SO4 solution, as catalyst was considered HgSO4 and as oxidant – K2Cr2O7) and chloride-inhibitor solution (Ag2SO4 / H2SO4) followed by cooling and absorbance reading at 600 nm under a blank prepared the same as the WW sample. Data calculation is considering the calibration curve CODCr (mg O2/L) = f(A600), plotted using potassium hydrogen phthalate as COD stock solution (i.e. 1000 mg O2/L). Determination of BOD5 (mg O2/L): it was used the standard method to determine the relative oxygen requirements of WW sample for degradation of its organic matter (carbonaceous demand) during 5-d incubation period and presence of microorganisms as well as the oxygen used to oxidize inorganic matter such as sulfides, ferrous iron and even reduced forms of nitrogen (nitrogenous demand). The seeding (e.g., domestic wastewater with a population of microorganisms) and dilution (with phosphate buffer, MgSO4, CaCl2 and FeCl3, standard check for NH4Cl and glucose-glutamic acid) procedures provide an estimate of BOD5 at pH 6.5 to 7.5. The dissolved oxygen (DO) is measured initially and after incubation (using the standard iodometric method with azide modification, or membrane electrode method), and BOD is computed from difference between initial and final DO. Determination of total solids content (TS) (mg/L): the standard gravimetric method was used by filtration on solid paper support of a certain WW sample volume and after support drying and weighting at room temperature, followed by calculation of retained solids amount per sample volume. Bul. Inst. Polit. Iaşi, Vol. 71 (75), Nr. 3, 2025 13 Determination of ammonia content (mg NH4+/L): it was used the standard spectrometric method (SR ISO 7150-1) based on absorbance measurement at 650 nm of WW sample treated sodium salicylate and hypochlorite in the presence of sodium nitroso-prussiate (i.e. sodium nitrosopenta cyanoferrate (III)). The ammonia content is calculated using the calibration curve CN-NH4+ = f(A650). Determination of extractible substances in organic solvent (ES) (mg/L): it was used the gravimetric method based on extractible substances’ extraction using as organic solvent the petroleum ether. After solvent evaporation at room temperature the used extraction vessel is weighted and ES content calculated. 3. Results and discussion The wastewater produced at cattle farms has a high concentration of pollutants that can negatively influence the quality of the receptors. The literature mentions an average amount of undiluted residues / wastes of 23 L/animal head x day, or 5 kg of residues / wastes (solid and liquid) per 100 kg of living animal weight, as an annual average of the daily amount excreted by animals, in general (Antoniu et al., 1987). In dairy cows, the daily quantity of residues/wastes represents 7% of the animal's weight, the humidity being 87.5%, the dry matter in feces is 5.7 kg/day, and in urine it is 0.48 kg/day. Urine represents about 30% of the total residue / waste. Unlike pigs and other animals on a livestock farm, ruminants' stomachs contain bacteria that allow cellulosic feed to be used. Compared to the feed consumed, the quantities of manure produced by cattle are large. The urine produced by herbivores has a pronounced alkaline character. Growing animals and dairy farmers (Fig. 2) retain more nitrogen, phosphorus and calcium from their feed than fattening animals, which thus lose a large amount of nutrients in their excrement. (a) (b) Fig. 2 – Some activities onsite of zootechnical farm producing wastewater. (a) food preparation and support-bed cleaning; (b) milking activity sector. 14 Cristina-Alexandra Haivas and Carmen Zaharia In general, the literature reports high average concentrations of chlorides in waste (liquid and solid) from cattle (i.e., around 2500 mg/L) as well as high concentrations of other soluble ions (sodium, potassium, calcium) (Antoniu et al., 1998) that can influence a possible direction of recovery in agriculture of the treated wastewater produced on the cattle farm. As consequence, the characterization of zootechnical WW or final effluent from each productive building is imposed and the values of some important quality indicators periodically reported to the water management authority centre for evaluation (especially, validation of respecting the imposed environmental norms in the farm compliance plan). The real pollution status due to the waste from cattle farm (liquid and/or solid) is expressed by physicalchemical and bacteriological indicators such as total suspended solids (TSS), COD, BOD5, content of nutrients, total number of total coliforms, other bacterial population types etc. For the studied zootechnical farm there were considered 6 sampling sectors for WW analysis, mainly from the 6 final collectors of buildings with specific activities such as 1-Administration building; 2-Protocol building; 3Cafeteria shop building; 4-Milking parlor building; 5Pharmaceutical warehouse building, and 6-Mechanical workshop building. The mean annual values of the studied WW quality indicators controlled in the time period of 2022-2023 are summarized in Tables 1 and 2. Table 1 Characteristics of collected wastewaters from the studied zootechnical farm in 2022 Quality Indicators BUILDING pH COD (mg O2/L) BOD5 (mg O2/L) TS (mg/L) Ammonia (mg NH4+/L) ES (mg/L) Test method Year 2022 1-Administration 7.61 ±0.7 223.0 ±75 66.90 ±23 31.5 ±3.5 0.93 ±0.88 235.00 ±105.0 SR EN ISO 10523:2012 2-Protocol 7.30 ±0.10 598.80 ±257.0 179.63 ±77.0 92.5 ±54 2.02 ±1.97 66.00 ±6.0 SR ISO 6060:1996 3-Cafeteria 7.16 ±0.16 1550.5 ±263.5 775.16 ±132 132.5 ±39 113.02 ±113 107.00 ±46.0 SR EN ISO 5815-1:2020 4-Milking parlor 7.36 ±0.37 4103.0 ±393 2051.0 ±197 443.5 ±19 210.52 ±210 185.00 ±60.0 SR EN 872:2005 5Pharmaceutical warehouse 7.73 ±0.17 664.5 ±285.5 269.31 ±111 62.02 ±48 16.02 ±16 82.00 ±54.0 SR ISO 7150-1:2001 6-Mechanic workshop 7.88 ±0.06 327.5 ±68.5 98.5 ±20 48 ±38 14.02 ±14 49.00 ±30.0 SR 7587:1996 M.A.C.* 6.5-8.5 500.00 300.00 350 36.42 30.0 * norms (NTPA 2) As shown in Table 1 (for 2022 year), the values of analysed quality indicators exceed the maximum admissible concentration according to the Bul. Inst. Polit. Iaşi, Vol. 71 (75), Nr. 3, 2025 15 imposed norms only in the case of WW produced and collected from the milking parlor (4-building) for COD, BOD, TS, ammonia, ES and also cafeteria (3building) for COD, BOD and ES, and all were indicating high organic compounds content and local presence of extractible substances from fuel and oils especially from mechanical maintenance and repairs’ service. Special comparative findings for each analysed WW characteristics are mentioned below: ‒ For pH: the lowest value recorded was 7.16 at 3-Cafeteria and the highest value recorded was 7.88 at 6-Mechanic workshop. These values are in range with permissible limits of 6.5 – 8.5. ‒ For COD (mg O2/L): the lowest value recorded was 223.0 at 1Administration collector and the highest value recorded was 4,103.0 at 4-Milking parlor; values exceed by 8.20 times fold the M.A.C. and indicates a high organic load from which relative large fractions are biodegradable, meaning more than 50%. ‒ For BOD5 (mg O2/L): the lowest value recorded was 66.90 at 1Administration building and the highest value recorded was 2,051.0 for 4Milking parlour building; values exceed by 6.83 times fold the M.A.C. and are originated in biodegradable organics from metabolic animal activities, animal products and others. The ratio COD/BOD varied in the range of 2.00-12.33, and ratios higher than 4 indicate that WW may contain also non-biodegradable organics or refractory ones. ‒ For TS (mg/L): the lowest value recorded was 31.5 at 1-Administration and the highest value recorded was 443.5 at the 4-Milking parlour sector; values exceed by 1.26 times fold the M.A.C. and can be separated in time by different mechanical operations (sedimentation, filtration, flotation, etc.). ‒ For ammonia (mg NH4+/L): the lowest value recorded was <0.05 and the highest value recorded was 210.52 at the 4-Milking parlour sector; values exceed by 5.78 times fold the M.A.C. and are predominantly produced after degradation/ decomposition processes developed in the collectors (in stationary status) and mixture of urine with water washing, among others. ‒ For ES (mg/L): the lowest value recorded was 49 at the 6-Mechanical workshop sector (on a hill platform) and the highest value recorded was 185 at the 3-Cafeteria sector (downstream of the hill platform, collecting also a part of rainwater passed through the fuel deposit platform); values exceed by 6.16 times fold the M.A.C. and are explained by the presence of oils, fuel and fuel-derivate products. It seems that there are exceeding of maximum admissible concentrations in four collectors from buildings of studied zootechnical farm in 2022, meaning protocol (2), cafeteria (3), milking parlor (4) and pharmaceutical warehouse (5) for COD and extractible substances (ES). All analysed quality indicators are exceeding the admissible norms only in the final collector from the milking parlor sector. 16 Cristina-Alexandra Haivas and Carmen Zaharia Table 2 Characteristics of collected wastewaters from the studied zootechnical farm in 2023 Quality Indicators BUILDING pH COD (mg O2/L) BOD5 (mg O2/L) TS (mg/L) Ammonia (mg NH4+/L) ES (mg/L) Test method Year 2023 1-Administration 7.17 ±0.1 1041.92 ±623 312.43 ±186 153.00 ±139.0 3.52 ±3.47 68.00 ±20.0 SR EN ISO 10523:2012 2-Protocol 7.61 ±0.23 944.82 ±164 277.92 ±65 117.00 ±87.0 11.52 ±11 70.00 ±24.0 SR ISO 6060:1996 3-Cafeteria 6.85 ±0.13 2006 ±506 601.80 ±151 126.00 ±10.0 102.52 ±10 188.00 ±16.0 SR EN ISO 5815-1:2020 4-Milking parlor 7.70 ±0.3 21728 ±634 10864 ±31 2565.00 ±121.0 174.52 ±174 108.00 ±4.0 SR EN 872:2005 5Pharmaceutical warehouse 8.10 ±0.21 288.28 ±37 87.0 ±11 49.00 ±41.0 22.0 ±22 67.00 ±15.0 SR ISO 71501:2001 6-Mechanic workshop 7.80 ±0.05 381.73 ±115 114.5 ±34 54.00 ±42.0 18.52 ±18 34.00 ±4.0 SR 7587:1996 M.A.C.* 6.5-8.5 500.00 300.00 350 36.42 30.0 *norms (NTPA 2) As shown in Table 2 (for 2023 year), the values of analyzed quality indicators exceed the maximum admissible concentration according to imposed norms only in the case of WWs produced and collected from the milking parlor (4-building) and cafeteria (3-building) for COD, BOD, TS, ammonia and ES. Some findings are underlined as follows ‒ pH: the lowest value recorded was 6.85 at 3-Cafeteria and the highest value recorded was 8.10 at 5-Pharmaceutical. These values are in the range of permissible limits (6.5 - 8.5). ‒ COD (mg O2/L): the lowest value recorded was 381.73 at 6-Mechanical workshop sector and the highest value recorded was 21,728 at the 4-Milking parlor sector; values exceed by 43.45 times fold the M.A.C. are due to all types of organic matter accumulated in time in the final WW collectors in which more than 50-70 % is biodegradable. ‒ BOD5 (mg O2/L): the lowest value recorded was 87.0 at the 5Pharmaceutical sector and the highest value recorded was of 10,864 at the Milking parlor sector; values exceed by 36.21 times fold the M.A.C. which indicates a possible future trend perspective for valorization of organics for biogas and other energetical products’ production. ‒ TS (mg/L): the lowest value recorded was 49 at the 5-Pharmaceutical warehouse and the highest value recorded was 2,565 at the 4-Milking parlor Bul. Inst. Polit. Iaşi, Vol. 71 (75), Nr. 3, 2025 17 collector; values exceed by 7.32 times fold the M.A.C. and can be locally separated, if wanted. ‒ Ammonia (mg NH4+/L): the lowest value recorded was <0.05 and the highest value recorded was 174.52 at the 4-Milking parlor sector; values exceed by 4.79 times fold the M.A.C. and are caused by local biological treatment processes acting on site. ‒ ES (mg/L): the lowest value recorded was 34 for the 6-Mechanical workshop and the highest value recorded was 188 for 3-Cafeteria; values exceed by 6.26 times fold the M.A.C. and must be reduced by application of the prevention measures. (a) (b) (c) (d) Fig. 3 – Exceeding values referring to C.M.C. of all analyzed quality indicators in 2022-2023 for some collectors. (a) 5-Milking parlor; (b) 3-Cafeteria; (c) 5Pharmaceutical warehouse and (d) 2-Protocol building. COD (mg O2/L) BOD (mg O2/L) TS (mg/L) Ammonia (mg/L) ES (mg/L) 0 5000 10000 15000 20000 25000 2022 2023 Exceedings of analyzed quality indicators at the 5-Milking Parlor collector COD BOD TSAmmonia ES 0 500 1000 1500 2000 2022 2023 Exceedings of analyzed quality indicators at the 3-Cafeteria collector COD BOD5 TS Ammonia ES 0 50 100 150 200 2022 2023 Exceedings of quality indicators at the 5-Pharmaceutical warehouse collector COD BOD5 TSAmmonia ES 0 100 200 300 400 500 2022 2023 Exceedings of analyzed quality indicators at the 2-Protocol collector