Biodegradable COD Research Articles

Avaliação da biotratabilidade do efluentede branqueamento de polpa celulósicapor processos aeróbios e anaeróbios

Os efluentes da planta de branqueamento da produção de pasta celulósica apresentam, além de elevadas concentrações de matéria orgânica em termos de Demanda Química de Oxigênio (DQO) e Demanda Bioquímica de Oxigênio (DBO) e cor, compostos com elevada toxicidade, o que torna o tratamento destes efluentes problemático. O objetivo do presente artigo é avaliar a biotratabilidade dos efluentes de branqueamento ácido e alcalino de polpa celulósica kraft por processos aeróbios e anaeróbios por meio da caracterização, utilizando parâmetros convencionais e coletivos. Os resultados de DQO inerte, biodegradabilidade aeróbia e anaeróbia, distribuição de massas molares, produtos microbianos solúveis e substâncias poliméricas extracelulares indicaram a baixa biotratabilidade dos efluentes

Biodegradation characteristics and size fractionation of landfill leachate for integrated membrane treatment

The fate of organics and nitrogen during the biological treatment with MBR and subsequent membrane filtration processes (nano filtration, NF; reverse osmosis, RO) were investigated for a landfill leachate. The chemical oxygen demand (COD) and total Kjeldahl nitrogen (TKN) removal performances of membrane bioreactor (MBR) were obtained to be around 89% and 85%, respectively. The effluent COD of MBR was measured to be 1935mg/L (30kDa) which is much lower than experimentally determined soluble inert COD of 3200mg/L using 0.45μm filter. The readily and slowly biodegradable COD fractions were estimated to be 17% and 52% of raw influent COD, respectively. The respirometry based modeling test performed on raw leachate exhibited much slower degradation kinetics compared to municipal wastewater. A unique subset of model parameters was extracted from batch respirometry by using acclimated MBR sludge. The sequential ultrafiltration (UF) experiments (particle size distribution, PSD) revealed that most of the organics was below 2nm filter mesh size. In addition, NF/RO post treatment after MBR system was required to increase COD and total nitrogen (TN) removal performances up to 99%. Relatively lower salt rejection rates around 94% was obtained for RO system as a post treatment of MBR system.

Investigation of the impacts of thermal pretreatment on waste activated sludge and development of a pretreatment model

This study investigated the impacts of high pressure thermal hydrolysis (HPTH) pretreatment on the distribution of chemical oxygen demand (COD) species in waste activated sludge (WAS). In the first phase of the project, WAS from a synthetically-fed biological reactor (BR) was fed to an aerobic digester (AD). In the second phase, WAS from the BR was pretreated by HPTH at 150 °C and 3 bars for 30 min prior to being fed to the AD. A range of physical, biochemical and biological properties were regularly measured in each process stream in both phases. The COD of the BR WAS consisted of storage products (XSTO), active heterotrophs (XH) and endogenous decay products (XE). Pretreatment did not increase the extent to which the BR WAS was aerobically digested and hence it was concluded that the unbiodegradable COD fraction, i.e. XE, was unchanged by pretreatment. However, pretreatment did increase the rate of degradation as it converted 36% of XH to readily biodegradable COD (SB) and the remaining XH to slowly biodegradable COD (XB). Furthermore, XSTO was fully converted to SB by pretreatment. Although pretreatment did not change the VSS concentration in the downstream aerobic digester, it did decrease the ISS concentration by 46 ± 11%. This reduced the total mass of solids produced by the digester by 21 ± 8%. A COD-based HPTH pretreatment model was developed and calibrated. When this model was integrated into BioWin 3.1®, it was able to accurately simulate both the steady state performance of the overall system employed in this study as well as dynamic respirometry results.

Modeling hydrolysis of slowly biodegradable organic compounds in biological nutrient removal activated sludge systems

Hydrolysis is an important process in biological wastewater treatment and is known to be the rate-limiting step in organic carbon removal from municipal or industrial wastewater. The influence of the readily biodegradable chemical oxygen demand fraction in biological wastewater treatment systems has been extensively investigated, but little is known about the effects of slowly biodegradable substrate (XS) on denitrification and enhanced biological phosphorus removal. The biodegradation of XS is initiated by hydrolysis, which is an integral part of activated sludge models, such as the Activated Sludge Model no. 2d (ASM2d). This process is slower than heterotrophic growth and thus becomes the rate-limiting step for the biodegradation of organic compounds. The aim of this study was to evaluate different concepts of modeling the hydrolysis process using the original and modified version of ASM2d. Batch test results obtained at a large biological nutrient removal (BNR) plant in Gdansk (Poland) provided an experimental database for comparison of the two model predictions. Both models were compared in terms of their predictions for the most important process rates in BNR activated sludge systems. In comparison with the orginal ASM2d, the modified model had no or only minor effect on the predicted nitrate utilization rate, phosphate release rate and anoxic/aerobic phosphate uptake rate, but better predicted the oxygen uptake rate. The average ARDs (average relative deviations) were 19.0 and 29.3% (original ASM2d) vs. 13.4 and 20.4% (modified ASM2d), respectively, for the settled wastewater without pretreatment and after coagulation-flocculation.

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

Treatment of wastewater using a sequencing batch reactor

The aim of this study was to evaluate the efficiency of two sequencing batch reactors (R1 and R2) at removing nutrient (N and P) and chemical oxygen demand (COD). The two reactors (R1 and R2) were of the same design, operating under identical cycles and had a sludge retention time of 5 d. In R1, the substrate was sewage enriched with cooked and triturated cereals. In R2, the substrate was raw sewage mixed with triturated discarded excess sludge. Respirometry tests were performed to compare the biodegradability of the substrates used during the experimental period. The efficiency of R1 in removing soluble P and N-ammonia was considerably higher (90.4 and 97.2%, respectively) than reactor R2 (60 and 39.2%, respectively). While the effluent generated by R1 contained only minor amounts of N-nitrite and N-nitrate (0.5±0.4 and 1.7±0.8 mg L−1, respectively). The concentrations of nitrite and nitrate in the effluent from R2 were 2 and 7 times higher. The lack of biodegradable COD available for denitrification was responsible for the high concentrations of nitrite and nitrate in the effluent of R2.

Laboratory-scale anaerobic sequencing batch reactor for treatment of stillage from fruit distillation

This work describes batch anaerobic digestion tests carried out on stillages, the residue of the distillation process on fruit, in order to contribute to the setting of design parameters for a planned plant. The experimental apparatus was characterized by three reactors, each with a useful volume of 5 L. The different phases of the work carried out were: determining the basic components of the chemical oxygen demand (COD) of the stillages; determining the specific production of biogas; and estimating the rapidly biodegradable COD contained in the stillages. In particular, the main goal of the anaerobic digestion tests on stillages was to measure the parameters of specific gas production (SGP) and gas production rate (GPR) in reactors in which stillages were being digested using ASBR (anaerobic sequencing batch reactor) technology. Runs were developed with increasing concentrations of the feed. The optimal loads for obtaining the maximum SGP and GPR values were 8-9 gCOD L(-1) and 0.9 gCOD g(-1) volatile solids.

Monitoring of slaughterhouse wastewater biodegradation in a SBR using fluorescence and UV–Visible absorbance

The aim of this study was to demonstrate that the effectiveness of slaughterhouse wastewater treatment by activated sludge could be enhanced through the use of optical techniques, such as UV–Visible absorbance and fluorescence spectroscopy, to estimate the hydraulic retention time necessary to remove the biodegradable chemical oxygen demand (COD). Two experiments were conducted. First, a batch aerobic degradation was performed on four wastewater samples collected from four different cattle processing sites in order to study the changes in the spectroscopic properties of wastewater during biodegradation. Second, a sequencing batch reactor was used in order to confirm that the wastewater fluorescence could be successfully used to monitor wastewater biodegradation in a pilot-scale experiment. Residual blood was the main source of organic matter in the wastewater samples. The absorbance at 416nm, related to porphyrins, was correlated to the COD during wastewater biodegradation. The tryptophan-like/fulvic-like fluorescence intensity ratio was related to the extent of biodegradation. The COD removal efficiency ranged from 74% to 94% with an hydraulic retention time (HRT) of 23h. A ratio of tryptophan-like/fulvic-like fluorescence intensities higher than 1.2 indicated incomplete biodegradation of the wastewater and the need to increase the HRT.

Investigation of the Impacts of Thermal Pretreatment on Waste Activated Sludge and Development of a Pretreatment Model

This study investigated the impacts of high pressure thermal hydrolysis (HPTH) pretreatment on the distribution of chemical oxygen demand (COD) species in waste activated sludge (WAS). In the first phase of the project, WAS from a synthetically-fed biological reactor (BR) was fed to an aerobic digester (AD). In the second phase, WAS from the BR was pretreated by HPTH at 150 °C and 3 bars for 30 min prior to being fed to the AD. A range of physical, biochemical and biological properties were regularly measured in each process stream in both phases. The COD of the BR WAS consisted of storage products (XSTO), active heterotrophs (XH) and endogenous decay products (XE). Pretreatment did not increase the extent to which the BR WAS was aerobically digested and hence it was concluded that the unbiodegradable COD fraction, i.e. XE, was unchanged by pretreatment. However, pretreatment did increase the rate of degradation as it converted 36% of XH to readily biodegradable COD (SB) and the remaining XH to slowly biodegradable COD (XB). Furthermore, XSTO was fully converted to SB by pretreatment. Although pretreatment did not change the VSS concentration in the downstream aerobic digester, it did decrease the ISS concentration by 46 ± 11%. This reduced the total mass of solids produced by the digester by 21 ± 8%. A COD-based HPTH pretreatment model was developed and calibrated. When this model was integrated into BioWin 3.1(®), it was able to accurately simulate both the steady state performance of the overall system employed in this study as well as dynamic respirometry results.

Performance of heterotrophic partial denitrification under feast-famine condition of electron donor: A case study using acetate as external carbon source

Recently, the combination of anammox and post heterotrophic partial denitrification (nitrate to nitrite) was increasingly popular to treat anammox effluent with excessive nitrate, whereas achieving nitrite accumulation stably was a major bottleneck for post-denitrification. This work focused on the performance of heterotrophic partial denitrification under acetate feast-famine condition. The results showed that readily biodegradable COD to nitrate (RBCOD/NO3-) ratio of 2.5 facilitated an ideal nitrite accumulation ratio (NAR) of 71.7% under complete nitrate reduction. When RBCOD/NO3- ratio was below 3.5, in terms of efficiency and nitrite accumulation, higher NAR obtained during exogenous denitrification identified that the external acetate depletion was the optimal ending point of denitrification, which could be indicated by pH accurately. The indication of pH realized NAR of 60% ideally under batch-flow mode with RBCOD/NO3- ratio of 2.7, which might promote the scale-up of partial denitrification. Furthemore, alkaline environment (pH 9.0–9.6) repressed N2O emission even during endogenous denitrification.

Effect of Ozone and Ozone/Fenton in the Advanced Oxidation Process on Biodegradable Characteristics of Semi‐aerobic Stabilized Leachate

AbstractThis study investigated the effects of O3 and O3/H2O2/Fe2+ in the advanced oxidation processes (AOPs) on the biodegradable and soluble characteristics of semi‐aerobic stabilized solid waste leachate. The biodegradability (BOD5/chemical oxygen demand, COD) ratio improved from 0.034 to 0.05 and 0.1 following O3 and O3/H2O2/Fe2+, respectively. Fractions of biodegradable COD(bi) (24%), non‐biodegradable COD(ubi) (76%), soluble COD(s) (59%), biodegradable soluble COD(bsi) (38%), non‐biodegradable soluble COD(ubsi) (62%), and particulate COD (PCOD) (41%) in stabilized leachate were also investigated. The fraction of COD(bi) increased to 28 and 36% after applying O3 and O3/AOPs, respectively. COD(S) increased to 59% after O3 and to 72% after O3/AOPs, whereas COD(bsi) increased to 38 and 51% after O3 and O3/AOPs, respectively. The removal efficiency of COD(S) was obtained at 5% after O3 alone and improved to 51% following ozone‐based AOPs, whereas the removal efficiency of PCOD improved from 25% after O3 to 71% after ozone‐based AOPs.

Modeling biodegradation characteristics of grey water in membrane bioreactor

The study evaluated the fate of grey water in a membrane bioreactor (MBR). It mainly involved the evaluation of system performance based on modeling biodegradation characteristics of grey water. The investigation was conducted on grey water using a pilot-scale MBR operated at a sludge age of 60 days. The system secured full removal of biodegradable organics with only 10mg/L residual COD in the effluent, suitable for reuse. Model calibration of cyclic dissolved oxygen profiles fitted the experimental data and defined all related model coefficients with a lower maximum growth rate and lower hydrolysis rates compared with domestic sewage. Model simulation using process kinetics confirmed full removal of available biodegradable COD and generation of soluble microbial products. Significantly, higher soluble COD levels in the bulk liquid compared with the process effluent could be explained by means of cake filtration in the membrane, capturing larger fractions of soluble residual COD. Consequently, entrapment and partial biodegradation of soluble residual organics ensured the very low levels of effluent COD.

Modeling organic matter stabilization during windrow composting of livestock effluents

Composting is a complex bioprocess, requiring a lot of empirical experiments to optimize the process. A dynamical mathematical model for the biodegradation of the organic matter during the composting process has been developed. The initial organic matter expressed by chemical oxygen demand (COD) is decomposed into rapidly and slowly degraded compartments and an inert one. The biodegradable COD is hydrolysed and consumed by microorganisms and produces metabolic water and carbon dioxide. This model links a biochemical characterization of the organic matter by Van Soest fractionating with COD. The comparison of experimental and simulation results for carbon dioxide emission, dry matter and carbon content balance showed good correlation. The initial sizes of the biodegradable COD compartments are explained by the soluble, hemicellulose-like and lignin fraction. Their sizes influence the amplitude of the carbon dioxide emission peak. The initial biomass is a sensitive variable too, influencing the time at which the emission peak occurs.

Removal of readily biodegradable substrate in super fast membrane bioreactor

The study investigated performance characteristics of super fast membrane bioreactor (MBR) in removing readily biodegradable substrate. MBR experiments were adjusted to extremely high rate operation at steady-state, with all combinations of sludge retention times between 0.5–2.0d and hydraulic retention times between 0.5–2.0h. Substrate feeding was adjusted to 200mg/L and involved a synthetic mixture representing the readily biodegradable COD fraction in domestic sewage. Effluent COD always remained below 25mg/L with an average value of 15mg/L under all tested operating conditions. Respirometric analyses indicated complete biodegradation of available substrate so that the effluent COD was essentially composed of soluble microbial products. High rate MBR operation also limited substrate storage below 10mg/L and generation of proteins and carbohydrates down to 1.5–4.5mg COD/L. Significant differences in the residual soluble COD levels between permeate and reactor volume showed that effective COD removal relied on biodegradation as well as on membrane filtration, which entrapped soluble microbial products with relatively larger particle sizes. Parallel 16s rRNA experiments based on PCR-DGGE methodology revealed significant changes in the composition of the microbial community as a function of the sludge retention time, an observation with possible implications on different biodegradation kinetics depending on the characteristics of the microbial community.

Use of Bio-Amp, a commercial bio-additive for the treatment of grease trap wastewater containing fat, oil, and grease

This research investigated the application of Bio-Amp, a commercial bio-additive for the treatment of fat, oil, and grease (FOG) in a grease trap, and evaluated potential impacts of treated effluent on downstream collection system and treatment processes. Results show that after Bio-Amp treatment, FOG deposit formation was reduced by 40%, implicating a potential reduction of sewer line blockages. Chemical oxygen demand (COD), total nitrogen (TN), total phosphorus (TP) and total fatty acids were reduced by 39%, 33%, 56%, and 59%, respectively, which represents an overall loading reduction of 9% COD, 5% TN and 40% TP received by the treatment plant from all the dining halls. On the other hand, readily biodegradable COD fractions significantly increased, which implies a potential improvement on Bio-P removal. Overall, the results showed that application of Bio-Amp in grease trap provides potential reduction of sewer line blockages, and can also alleviate downstream treatment burden.

Performance of intermittently aerated up-flow sludge bed reactor and sequencing batch reactor treating industrial estate wastewater: A comparative study

In this study, an innovative aerobic/anoxic sludge bed bioreactor with two feeding regimes, continuous-fed (an up-flow sludge bed reactor (USBR)) and batch fed (sequencing batch reactor (SBR)), was evaluated for the treatment of an industrial estate wastewater with low BOD5/COD ratio. The process performance in the two regimes was compared. Two numerical independent variables (retention/react time and aeration time) were selected to analyze, model and optimize the process. Response surface methodology with central composite design (CCD) was used with five levels of hydraulic retention time (HRT)/react time (12–36h) and aeration time (40–60min/h). In order to analyze the process, ten dependent parameters as the process responses were studied. As a result, HRT/react time showed a decreasing impact on the responses measured in both hydraulic regimes, USBR and SBR. The USBR showed better performance than the SBR in removal of total COD, slowly biodegradable COD, total nitrogen and total Kjeldahl nitrogen.

Treatment of concentrated fruit juice wastewater by the combination of biological and chemical processes

Concentrated fruit juice industries use a wide volume of water for washing and fruit processing, generating a large volume of wastewater. This work studied the combination of an aerobic biological process with a chemical coagulation/flocculation step to treat a high concentrated fruit juice wastewater. This wastewater presents a good biodegradability (BOD5/COD = 0.66) allowing a chemical oxygen demand (COD) removal above 90% in most reactors. The best results in aerobic biological treatment were obtained in reactors initially loaded with 2 g VSS L−1 of biomass concentration and 20 g COD L−1 of organic matter concentration. Three different kinetic models were evaluated (Monod, Haldane and Contois). The Haldane-inhibition model was the one that best fitted the COD biodegradation. AQUASIM© software allowed calculate the following kinetic constants ranges for aerobic biodegradation: K s: 6–20 g COD L−1; v max: 2.0–5.1 g COD g−1 VSS day−1 and K i values: 0.10–0.50 g COD L−1. These constants corresponds to maximum removal rates (v*) between 0.11 and 0.26 g COD g−1 VSS day−1 for substrate concentrations (S*) from 0.77 to 3.16 g COD L−1. A tertiary coagulation/flocculation process improved the efficiency of the biological pre-treatment. Ferric chloride was selected as best compromise to treat this wastewater. Optimal conditions were 0.44 g L−1 of coagulant at pH = 5.5, achieving 94.4% and 99.6% on turbidity and COD removal, respectively.

Simultaneous removal of carbon and nutrients from an industrial estate wastewater in a single up-flow aerobic/anoxic sludge bed (UAASB) bioreactor

Simultaneous removal of carbon and nutrients (CNP) in a single bioreactor is highly significant for energy consumption and control of reactor volume. Basically, nutrients removal is dependant to the ratio of biochemical oxygen demand to chemical oxygen demand (BOD5/COD). Thus, in this study the treatment of an industrial estate wastewater with low BOD5/COD ratio in an up-flow aerobic/anoxic sludge bed (UAASB) bioreactor, with an intermittent regime in aeration and discharge, was investigated. Hydraulic retention time (HRT) of 12–36 h and aeration time of 40–60 min/h were selected as the operating variables to analyze, optimize and model the process. In order to analyze the process, 13 dependent parameters as the process responses were studied. From the results, it was found, increasing HRT decreases the CNP removal efficiencies. However, by increasing the BOD5 fraction of the feed, the total COD (TCOD), slowly biodegradable COD (sbCOD), readily biodegradable COD (rbCOD), total nitrogen (TN), and total phosphorus (TP) removal efficiencies were remarkably increased. Population of heterotrophic, nitrifying and denitrifying bacteria showed good agreement with the results obtained for TCOD and TN removal. The optimum conditions were determined as 12–15 h and 40–60 min/h for HRT and aeration time respectively.

Performance of tubular reverse osmosis for the desalination/concentration of a municipal solid waste leachate

Municipal solid waste leachate (MSWL) has the potential to pollute the water environment and to affect biological treatment processes adversely if not properly handled. Reverse osmosis (RO) has the ability to remove both organics and inorganics effectively from effluents. Therefore, RO was evaluated for the treatment of MSWL. It was found that both cellulose acetate and polyamide RO membranes should function effectively for the treatment of the leachate and that it should be possible to control membrane fouling with chemical cleaning. The polyamide membranes, however, performed somewhat better than the cellulose acetate membranes for the treatment of the leachate. The quality of the treated leachate with the exception of ammonia-nitrogen and COD should comply with the quality requirements for discharge into the water environment. Biological treatment processes are effective in complete removal (to only traceable levels) of ammonia-nitrogen and biodegradable COD. The quality of the treated effluent further complies with the quality requirements (chloride and heavy metals) for discharge into the municipal biological treatment system. The capital and operational cost of a 250 m3/d tubular reverse osmosis (TRO) plant is estimated at R1.95 m. and R11.45/m3, respectively.

Treatment of Domestic-Strength Wastewater Using a Horizontal Flow Biofilm Reactor System

The 45-days’ laboratory start-up study examined the performance of a novel horizontal flow biofilm reactor (HFBR) system in the treatment of a synthetic domestic-strength wastewater. In this study, the sheets were alternately offset to make sure the wastewater flowed horizontally along each sheet and vertically shifted down through the reactor. Biofilms developed on the sheets and purified the wastewater. In order to obtain the HRT while the flow rate changed, we calculated the ratiocination between the flow rate and the system HRT. The system was easy to construct and start, did not clog and could be used for biodegradable COD removal.