Non-biodegradable COD Research Articles

Treatment of hospital wastewater using aerobic granular sludge technology: Removal performance and microbial dynamics

Hospital wastewater contains several contaminants of emerging concern that cannot be removed by conventional treatment processes. Many of these emerging contaminants are pharmaceutical compounds, which are found in hospital wastewater at high loads. The presence of these toxics affects to the performance of biological processes in receiving wastewater treatment plants. This research evaluated the capability of the aerobic granular sludge technology to remove pharmaceutical compounds from hospital wastewater in a single chamber, which to date has not been investigated with real hospital wastewater. Despite the high non-biodegradable organic matter content, COD and BOD5 removal reached 75 % and 100 %, respectively. Nitrogen removal ranged from 70 %–90 %, and phosphate removal was maximum 50 %. The technology was able to efficiently remove antibiotics, antiepileptic and antidepressant drugs, whereas non-steroidal anti-inflammatory drugs were removed and released under oscillating patterns. The granular biomass increased in size, but it reduced the settling velocity. Bacterial and fungal communities were acclimated to pharmaceutical inlet, whereas the archaeal population had a progressive adaptation over time. The aerobic granular sludge technology is therefore a viable approach to enhance the disposal of real hospital wastewater prior to discharge into the urban wastewater network.

Diazinon and MCPA photo-reduction with sulfite excitation under UV irradiation and reducing agents’ generation

Diazinon (DIZ) and 4-Chloro-2-methylphenoxyacetic acid (MCPA) herbicide and widely used in agricultural lands. Present study investigates diazinon and 4-chloro-2-methylphenoxyacetic acid photo-reduction via UV/Sulfite (US) in as Advanced Reduction Processes (ARP). The ideal pH was Molar ratio of sulfite: DIZ or MCPA 1:1 and, 20 min reaction time, and pH 9, in which about 100 % reduction of DIZ and MCPA with a concentration of 10 mg L−1 was achieved and the optimal conditions were considered. Kinetic investigation increasing DIZ and MCPA concentration from 5 to 20 mgL−1, kobs increase about from 0.151 to 0.234 for DIZ and from 0.231 to 0.589 min−1. Also, reaction rate (robs) increases about from 0.755 to 4.68 for DIZ and from 1.155 to 11.78 mg L−1.min. The amount of energy consumption in DIZ solution increased from 5 to 20, respectively, from 0.73 to 2.37, and in the reduction of MCPA from 0.47 to 1.49 kWh per cubic meter. According to experiments performed in 30 min with the US process, COD levels were reduced by about 46 % of both pollutants. It is important to note that the BOD/COD ratio rose from about 0.20 to 0.48 after 30 min. Since the index of biodegradability has grown high, it can be concluded that non-biodegradable COD (NBDCOD) convert to biodegradable COD (BDCOD) and toxicity is lower than of before of treatment. This study has been very suggesting that the UV/sulfite method produces effluent with a non-toxic and ecologically beneficial manner by biological treatment or discharge directly in environment.

Performance of sulfur-based autotrophic denitrification process for nitrate removal from permeate of an MBR treating textile wastewater and concentrate of a real scale reverse osmosis process

Textile is one of the industrial sectors generating the highest amount of wastewater with various polluting substances. Lately, water reuse in textile industries, especially, with the reverse osmosis (RO) process following membrane bioreactor (MBR) treatment has been applied more commonly. In this study, an autotrophic sulfur-based denitrifying column performance was evaluated, for the first time, for nitrate reduction from permeate of a lab-scale MBR receiving real textile wastewater and from the concentrate stream of a real scale-RO plant used for recovering water from textile wastewater. Nitrate concentration in the MBR effluent and RO concentrate averaged 35 ± 3 and 12 ± 2 mg-N/L, respectively. With the sulfur-based column bioreactor, quite high (≥90%) denitrification performances were attained both for MBR effluent and RO concentrate up to nitrate loadings of 0.432 and 0.12 g-N/(L.d), respectively. COD present in wastewater was not utilized in the column bioreactor, which illustrates no or minimal contribution of heterotrophic denitrification. Alkalinity concentration in the wastewater was enough to buffer the acid formation during autotrophic denitrification. Sulfate was generated accompanied by nitrate reduction and sulfide was formed at low nitrate loadings. In the batch tests, the denitrification rates for the MBR effluent and RO concentrate were 0.31 and 0.28 g-N/(g-VSS.d), respectively, which were relatively higher than the ones observed for the synthetic nitrate-contaminated groundwater. Autotrophic sulfur-based denitrification is a promising and robust process alternative even for textile RO concentrate with high concentrations of salinity, non-biodegradable COD, and color.

Effect of ozonation on COD fractionation of wastewater from poultry processing industry

The objectives of this study were to evaluate the effect of ozonation on the solubility and biodegradability of wastewater from poultry processing industry. In addition, the wastewater also characterized based on the COD fractionation. The wastewater sample used was collected from Advance Chicken Processing (M) Sdn. Bhd., Perlis, Malaysia. Ozonation process was carried out in a semi–batch glass reactor which has a 2 L volume. The COD fractionation of poultry wastewater indicated that non-biodegradable COD is predominant compare to other fractions. However, the wastewater is containing higher percentage biodegradable COD comprehensively. It is expected that ozonation treatment would transform both particulate and soluble non-biodegradable COD towards biodegradable constituent that easily remove by biodegradation. The removal of COD was significant at ozonation duration up to 5 min. However, COD removal efficiency was only increased slightly with the increased of the ozonation duration after 5 min. This may be due to the fact that ozonation for long time would possibly producing constituent that inhibit ozone dissociation.

Biological treatment of reverse osmosis concentrate from low salinity water

With increasing water demand and growing scarcity of potable water, the reuse of water recovered from low salinity water like sewage or surface water is becoming an important issue from both technical and economic points of view. The reverse osmosis (RO) membrane processes widely used for water recovery inevitably produce RO concentrate having very high concentrations of salts and other materials of concern. Disposal to nature or feeding back into the recovery facility can be an option, but may have an impact on environment and raise legal problems. This study deals with the biological treatment of RO concentrate produced during water reclamation processes. The RO concentrate studied had low BOD5 and T-P, but high T-N and COD concentrations. The sequencing batch reactor (SBR) process and the modified Ludzack-Ettinger (MLE) process were compared in controlled lab-scale experiments. The pilot-scale plant was operated to evaluate the performance of the SBR process under more realistic conditions. Kinetic parameters such as specific substrate utilization rate (SSUR), specific nitrification rate (SNR), and specific denitrification rate (SDNR) were obtained, and empirical equations were derived relating these parameters to the food-to-micro-organism (F/M) ratio. These parameters could prove useful tools for process design, operation, and improvement of anoxic and aeration tanks. Non-biodegradable COD components in the RO concentrate turned out to be hard to remove, which implies some physical or chemical process (e.g. flocculation, precipitation, or adsorption) may be needed in addition to the biological treatment process.

Effect of ozone and ozone/persulfate processes on biodegradable and soluble characteristics of semiaerobic stabilized leachate

This study investigated the effects of O3 and O3/S2O82− in the advanced oxidation process (AOPs) on the biodegradable and soluble characteristics of semiaerobic stabilized solid waste leachate. The biodegradability (BOD5/COD) ratio improved from 0.034 to 0.05 and 0.29 following O3 and O3/ S2O82−, respectively. Fractions of biodegradable COD(bi) (24%), nonbiodegradable COD(ubi) (76%), soluble COD(s) (59%), biodegradable soluble COD(bsi) (38%), nonbiodegradable soluble COD(ubsi) (62%), and particulate COD (PCOD) (41%) in stabilized leachate were also investigated. The fraction of COD (bi) increased to 28 and 39% after applying O3 and O3/ S2O82− in AOPs, respectively. COD(S) increased to 65 after O3 and to 72% after O3/AOPs, whereas COD (bsi) increased to 38 and 55% after O3 and O3/AOPs, respectively. The removal efficiency of total COD was obtained at 15 after O3 alone and improved to 72% following ozone‐based AOPs, whereas PCOD reduced from 41 to 35 after O3 and 28% after ozone‐based AOPs. Ozone/Prsulfate is an efficient method for degradation of stabilized leachate, enhanced biodegradability and improved biodegradable and soluble characteristics of stabilized leachate. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 184–191, 2014

Combined coagulation–flocculation and sequencing batch reactor with phosphorus adjustment for the treatment of high-strength landfill leachate: Experimental kinetics and chemical oxygen demand fractionation

The treatability of high-strength landfill leachate is challenging and relatively limited. This study examines the feasibility of treating high-strength landfill leachate (chemical oxygen demand [COD]: 7,760–11,770 mg/L, biochemical oxygen demand [BOD5]: 2,760–3,569 mg/L, total nitrogen [TN] = 980–1,160 mg/L) using a sequencing batch reactor (SBR) preceded by a coagulation–flocculation process with phosphorus nutritional balance under various mixing and aeration patterns. Simulations were also conducted to define kinetic parameters and COD fractionation. Removal efficiencies reached 89% for BOD5, 60% for COD, and 72% for TN, similar to and better than reported studies, albeit with a relatively lower hydraulic retention time (HRT) and solid retention time (SRT). The coupled experimental and simulation results contribute in filling a gap toward managing high-strength landfill leachate and providing guidelines for corresponding SBR applications. Implications: The treatability of high-strength landfill leachate, which is challenging and relatively limited, was demonstrated using a combined coagulation–flocculation with SBR technology and nutrient balance adjustment. The most suitable coagulant, kinetic design parameters, and COD fractionation were defined using coupled experimental and simulation results contributing in filling a gap toward managing high-strength leachate by providing guidelines for corresponding SBR applications and anticipating potential constraints related to the non-biodegradable COD fraction. In this context, while the combined coagulation–flocculation and SBR process improved removal efficiencies, posttreatment may be required for high-strength leachate, depending on discharge standards and ultimate usage of the treated leachate.

A Comparative Study on Performance of Two Aerobic Sequencing Batch Reactors with Flocculated and Granulated Sludge Treating an Industrial Estate Wastewater: Process Analysis and Modeling

In this study, the performance of two aerobic sequencing batch reactors (SBR) in removing carbon and nutrient (N & P) from Faraman’s industrial estate wastewater (FIW) with flocculated and granulated sludge was compared. The comparison study was performed by varying two significant independent variables (aeration time and mixed liquor volatile suspended solids (MLVSS)). The experiments were conducted based on a central composite design (CCD) and analyzed using response surface methodology (RSM). The region of exploration for the process was taken as the area enclosed by aeration time (6-24 h) and MLVSS (2000-7000 mg/L) boundaries. The results showed that the granulated sludge system was more efficient than the flocculated sludge system in removing the nonbiodegradable COD (nbCOD), total nitrogen (TN), total phosphorus (TP) and other sludge studied characteristics. The performance of both systems was almost the same for COD removal in FIW with a maximum removal of about 70 %.

The effect of primary sedimentation on full-scale WWTP nutrient removal performance

Traditionally, the performance of full-scale wastewater treatment plants (WWTPs) is measured based on influent and/or effluent and waste sludge flows and concentrations. Full-scale WWTP data typically have a high variance which often contains (large) measurement errors. A good process engineering evaluation of the WWTP performance is therefore difficult. This also makes it usually difficult to evaluate effect of process changes in a plant or compare plants to each other. In this paper we used a case study of a full-scale nutrient removing WWTP. The plant normally uses presettled wastewater, as a means to increase the nutrient removal the plant was operated for a period by-passing raw wastewater (27% of the influent flow). The effect of raw wastewater addition has been evaluated by different approaches: (i) influent characteristics, (ii) design retrofit, (iii) effluent quality, (iv) removal efficiencies, (v) activated sludge characteristics, (vi) microbial activity tests and FISH analysis and, (vii) performance assessment based on mass balance evaluation. This paper demonstrates that mass balance evaluation approach helps the WWTP engineers to distinguish and quantify between different strategies, where others could not. In the studied case, by-passing raw wastewater (27% of the influent flow) directly to the biological reactor did not improve the effluent quality and the nutrient removal efficiency of the WWTP. The increase of the influent C/N and C/P ratios was associated to particulate compounds with low COD/VSS ratio and a high non-biodegradable COD fraction.

Evaluation of the reject waters from co-digestion of solid wastes from agro-industries in a municipal WWTP

Overcapacities of anaerobic digesters at municipal WWTPs are frequently used for the treatment of organic wastes in order to increase the biogas production. However, "co-digestion" of organic wastes leads to additional nitrogen loading and to additional loads of non-biodegradable COD. The effects of (co-) digestion of organic wastes from agro-industries (slaughterhouses, dairies and leather industry) on the wastewater cycle have been evaluated in full-scale investigations at Leoben WWTP with a capacity of 90,000 pe where the methane production was increased from 700 to more than 1700 Nm3 CH4 per day. For this evaluation, mass balances for COD and nitrogen have been applied to estimate the fluxes of these substances. Application of this method is described in detail. As the additional loadings, it was found that related to methane production less nitrogen is released from the organic wastes than from the waste sludge. While the ammonia nitrogen load in the effluent from sludge digestion was about 100 g NH4-N per Nm3 of CH4 produced, in the effluent from the digestion of organic wastes only 70 g NH4-N/Nm3 CH4 were found. The decrease in the COD removal efficiency after digestion of the organic wastes started was not regarded as significant enough to be seen as a consequence of the treatment of external substrate.

Leachate detoxification by combination of biological and TiO2-photocatalytic processes

Landfill leachates are a problematic wastewater due to their variable concentration, volume changing in time and presence of refractory and hazardous components. In this paper, the results of a new approach to photocatalysis assisted by biological process for the detoxification of stabilised landfill leachate are presented. The biologically pre-treated leachate still contained a significant amount of non-biodegradable COD and TOC amounting to 500 and 200 mg/L, respectively. The 300 min of photocatalytic treatment (UVC/TiO2) brought about a significant decrease in more than 80% refractory organics remaining in leachate. The effect of pH and catalyst loading on mineralisation, colour removal rate and biodegradability (BOD/COD) improvement in the photoreactor were discussed. The bio-accessibility of formed photocatalytic oxidation intermediates was confirmed by oxygen uptake rate (OUR) measurements. Consequently, a part of COD was successfully removed in post-biological treatment.

Soluble substrate concentrations in leachate from field scale MSW test cells

We have monitored non-biodegradable soluble COD of leachates derived from two different landfill test cells, which were constructed at Odayeri Sanitary Landfill and operated with (C2) and without (C1) leachate recirculation for 1080 days. Refuse height and the placement area of test cells were 5 m and 1250 m 2 (25 m × 50 m), respectively. For leachates of both cells, initial inert soluble COD fraction ( f non) increased from it is initial value of 0.01 to around 0.1 after 300 days of operation. Due to the development of anaerobic conditions, the value showed an increasing trend and the maximum value of 0.4 was reached on day 600. Several suitable models were also fitted to the experimental data on the basis of statistical reasoning. So as to evaluate the goodness of obtained fits, the calculated values of the sum of squares due to error (SSE), R-square, the residual degrees of freedom (DFE), adjusted R-square, and root mean square errors (RMSE) associated with the model results were compared. Logistic model for C1 test cell and Gompertz model for C2 test cell gave the best fits to the experimental data. Moreover, using the fitted model parameters, pollution loads, and BOD/COD ratios in leachates from C1 (control) and C2 (recirculation) cells were estimated and deeply discussed. The results of the study can be satisfactorily used to predict change in the composition of leachate over time, which may help to obtain better effluent quality in biological treatment of leachate.

Aerobic Co-Treatment of Landfill Leachate with Domestic Wastewater

Addition of landfill leachate to a domestic wastewater treatment system may have negative impacts since leachate is a highly concentrated wastewater both in terms of inorganic and organic pollutants. The aim of this study was to investigate the effluent quality in the cotreatment of sanitary landfill leachate and domestic wastewater and the improving effect of powdered activated carbon (PAC). The volumetric ratio of leachate was varied from 5 to 25% (v/v). Batch activated sludge (AS) reactors were fed with leachate and domestic wastewater. Parallel AS + PAC reactors also contained PAC, which was added at the dose of 100-3,500 mg L-1. The nonbiodegradable soluble COD (SCOD) in leachate was decreased to very low levels by this addition. Experiments were also conducted in Semi-Continuously Fed Batch (SCFB) and Continuous-Flow (CF) activated sludges with recycle. In both types of operations, effluent COD and ammonium nitrogen concentrations increased when the leachate input increased. In all cases, the positi...

Bioremediation post-photo-oxidation and coagulation for black liquor effleunt treatment

In an attempt to achieve water suitable for recycling from paper-mill effluent, photo-Fenton's advanced oxidation and chemical coagulation were investigated as options to remove both non-biodegradable COD and color from pre-bioremediated block liquor effluent. It was found that at the first bioremediation COD removal ranged from 35–98% and TSS removal ranged from 12–89%. Almost 20% of the heavy metals were removed. Photo-Fenton's UV advanced oxidation and lime coagulation combination treatment achieved complete removal of COD, TSS and color. It was able to remove 80–100% COD, 70–100% TSS and 77–100% color. The removal of heavy metals was enhanced to reach >80% removal. Two potentialmicrobial species out ofthe eight tested strains were the most dominant species in the three media. Diplodia oryzae and Phaerochaete chrysosporium NRRL6364 enhanced the post-physicochemical treatment to reach optimum clean-up after 12 days of incubation at 32°C They produced a medium-grade recycled water. Operating costs are outlined.

Viability of microbial mass in a submerged membrane bioreactor

In this study the viability of biomass in a submerged membrane activated sludge system (sMBR) which treats domestic wastewater was investigated by dealing with non-biodegradable COD, specific oxygen uptake rate and MLVSS during operation for 100 days. It was shown that the viability of biomass in the bioreactor was reduced at the 50% level because of the accumulation of inert compounds and the reduction in the activities of poor biomass. After inoculating the bioreactor again, the specific OUR increased because of young biomass entering into the bioreactor. It was shown that there was an exponential relationship between OUR and MLVSS and there was a logarithmic relationship between specific OUR and MLVSS.

Impact of landfill leachate on the co-treatment of domestic wastewater

Landfill leachate and domestic wastewater were co-treated in batch activated sludge reactors and the ratio of leachate varied from 5 to 20% (v/v). The leachates had a non-biodegradable COD fraction of at least 20%. An increase in leachate adversely affected the co-treatment and it was concluded that the leachate ratio should never exceed 20% of the total wastewater or 50% of the initial COD. The initial Total Kjeldahl Nitrogen (TKN) and the free ammonia level were identified as factors influencing the completion of nitrification.

The Treatment of a High Strength Pulp and Paper Mill Effluent for Wastewater Re-Use

In an attempt to achieve water of a quality suitable for in-house re-use, chemical coagulation, ozone and activated carbon adsorption were investigated as options to remove both non-biodegradable COD and colour from the effluent of an activated sludge plant treating papermill waste water. Chemical coagulation was investigated using jartests and the results were scaled-up to a 6 m3 hr−1 pilot plant. This was able to remove 70% of the COD and 90% of colour using alum and it produced an effluent with a COD of 50 mg l−1 and colour of 40 Pt-Co units. Ozone dosed at 60 mgO3 l−1 could remove 90% of the colour but had a poor COD reduction. Isotherm tests of activated carbon adsorption showed a very high removal efficiency at 1.18 kg activated carbon m−3 product, but this dosage incurred an excessive cost. Chemical coagulation followed by dissolved air flotation (DAF) and multimedia filtration proved the most suitable tertiary treatment process train. Operating conditions were optimised for the chemicals applied, their dosages and the optimum pH. The process produced a medium grade recycled water suitable for re-use in the recycled fibre plant, and outline operating costs of producing this water were determined.

Two-phase anaerobic treatment of cane-molasses alcohol stillage

Anaerobic treatment of cane-molasses alcohol stillage was studied in a thermophilic two-phase system comprising two bioreactors for the acidogenic and methanogenic phases respectively in comparison with the single-phase process. The experiments were conducted with HRT ranging from 36.0 to 9.0 days for single-phase and from 32.7 to 5.6 days for two-phase, corresponding to organic loading rates of 3.452 to 14.487 and 4.646 to 20.022 kgCODm−3day−1 respectively. The treatment efficiency was essentially maintained at BOD5 and COD removal of over 85% and 65% respectively in the two-phase process even with higher substrate loading. The acidogenic phase provided satisfactory conversion of initial COD to VFA averaging 15.6% in the degree of acidification. The methanogenic culture pH of both systems was maintained in a range of 7.4 to 7.8 through self regulation. The methane content of the biogas generated from the two-phase process was significantly higher by about 17% than that from the single-phase process, both decreasing with increasing substrate loading and shorter HRT. The mean overall methane yield was found to be 0.168 m3CH4(STP)kg−1 CODadded or 0.292 m3CH4(STP)kg−1 VSadded from two-phase methanogenesis, compared to 0.055 m3CH4(STP)kg−1CODadded or 0.082 m3CH4(STP)kg−1VSadded from single-phase fermentation. However, methane yield in the two-phase process was enhanced only at COD loading rates higher than 2.9 kgm−3day−1 or VS loading rates higher than 1.8 kgm−3day−1. The ultimate methane yield was evaluated graphically to be 0.216 m3CH4(STP)kg−1CODadded, or 0.401 m3CH4(STP)kg−1 VSadded. This indicated a methane yield efficiency of 73-78% for the two-phase anaerobic digestion of cane-molasses alcohol stillage, which was composed of 24.2% and 28.2% of non-biodegradable COD and VS respectively. Kinetic evaluation of the experimental data provided θm (minumum SRT) and K (kinetic constant) values as 6.6 days and 0.166 respectively based on COD, or 7.0 days and 0.160 respectively based on VS. Application of the two-phase anaerobic process on full scale at an industrial treatment plant for alcohol stillage showed mean treatment efficiency in terms of BOD5 and COD reduction of 84.3% and 63.2% respectively at an average loading rate of 5.1 kgCODm−3day−1, which was in good agreement with the bench-scale studies, considering the great variation in the raw wastewater characteristics typical of an industrial operation.

Two-phase anaerobic treatment of cane-molasses alcohol stillage

Anaerobic treatment of cane-molasses alcohol stillage was studied in a thermophilic two-phase system comprising two bioreactors for the acidogenic and methanogenic phases respectively in comparison with the single-phase process. The experiments were conducted with HRT ranging from 36.0 to 9.0 days for single-phase and from 32.7 to 5.6 days for twophase, corresponding to organic loading rates of 3.452 to 14.487 and 4.646 to 20.022 kgCODm−3day−1 respectively. The treatment efficiency was essentially maintained at BOD5 and COD removal of over 85% and 65% respectively in the twophase process even with higher substrate loading. The acidogenic phase provided satisfactory conversion of initial COD to VFA averaging 15.6% in the degree of acidification. The methanogenic culture pH of both systems was maintained in a range of 7.4 to 7.8 through self regulation. The methane content of the biogas generated from the two-phase process was significantly higher by about 17% than that from the single-phase process, both decreasing with increasing substrate loading and shorter HRT. The mean overall methane yield was found to be 0.168 m3CH4(STP)kg−1CODadded or 0.292 m3CH4(STP)kg−1 VSadded from two-phase methanogenesis, compared to 0.055 m3CH4(STP)kg−1CODadded or 0.082 m3CH4(STP)kg−1VSadded from single-phase fermentation. However, methane yield in the two-phase process was enhanced only at COD loading rates higher than 2.9 kgm−3day−1 or VS loading rates higher than 1.8 kgm−3day−1. The ultimate methane yield was evaluated graphically to be 0.216 m3CH4(STP)kg−1CODadded, or 0.401 m3CH4(STP)kg−1VSadded. This indicated a methane yield efficiency of 73–78% for the two-phase anaerobic digestion of cane-molasses alcohol stillage, which was composed of 24.2% and 28.2% of nonbiodegradable COD and VS respectively. Kinetic evaluation of the experimental data prOVided am (minumum SRT) and K (kinetic constant) values as 6.6 days and 0.166 respectively based on COD, or 7.0 days and 0.160 respectively based on VS. Application of the two-phase anaerobic process on full scale at an industrial treatment plant for alcohol stillage showed mean treatment efficiency in terms of 8005 and COD reduction of 84.3% and 63.2% respectively at an average loading rate of 5.1 kgCODm−3day−1, which was in good agreement with the bench-scale studies, considering the great variation in the raw wastewater characteristics typical of an industrial operation.

Fate of residuals in nitrification-denitrification treatment of piggery wastewaters

A careful appraisal of piggery wastewaters should be made mainly because of their high content of organic constituents together with the nitrogen and stringent effluent limitations involved. Specific emphasis should be given to the COD of the wastewater as it contains, aside from a biodegradable portion, a residual fraction which persists throughout the treatment process. Experimental evaluations indicated that the effluent of a laboratory-scale SBR contained significant amounts of non-biodegradable COD. Since SBR was primarily operated to achieve nitrification-denitrification, a method previously developed for the assessment of the influent soluble inert COD, S1 was modified in a way to reflect the possible impact of the nitrification and denitrification processes. The paper also summarizes the performance of SBR with respect to its nitrogen removal potential from piggery wastewaters.