Specific Oxygen Uptake Rate Research Articles

Changes in enzymatic and microbiological activity during adaptation of a conventional activated sludge (CAS) to a CAS-oxic-settling-anaerobic (OSA) adapted process

The production of excess sludge in the conventional activated sludge (CAS) process is an important aspect of the operation of wastewater treatment plants. The oxic-settling-anaerobic (OSA) process is one of the most promising strategies among those to achieve a reduction in the excess sludge produced. Cell decay occurs at a low oxidation–reduction potential and subsequent degradation reactions seem to be the major causes of sludge reduction in the OSA process. As a consequence of previous exposure of the sludge to anaerobic conditions in the sludge holding tank, an increase of enzymatic and microbiological activity in the aeration reactor could enhance the degradation of the released material. In this study, the results of a pilot plant running sequentially as a CAS and a CAS-OSA system are shown not only in the terms of the crucial aspect of excess sludge reduction, but also in terms of enzymatic and microbiological activities in the sludge from the aeration tank. Specifically, the application of the OSA strategy with a sludge anaerobic exposure time (SAET) of 5.5 h achieved a 33.6% reduction of the produced sludge in comparison with the CAS approach. Similarly, this system showed an average increase of 23.2, 22.6 and 7.59% in the specific oxygen uptake rate (SOUR), dehydrogenase, and protease activity, respectively, and a negligible change in glucosidase activity compared to the conventional process. At the same way, the OSA process with a SAET of 8 h led to a reduction of 38.9% of produced sludge and an average increase of 27.9, 11.31, 28.7 and 26.57% in SOUR, dehydrogenase, protease, and glucosidase activity, respectively, compared to control unit.

Effects of black liquor shocks on activated sludge treatment of bleached kraft pulp mill wastewater

Kraft pulp mills use activated sludge systems to remove organic matter from effluents. Process streams may appear as toxic spills in treatment plant effluents, such as black liquor, which is toxic to microorganisms of the activated sludge. The present study evaluates the effects of black liquor shocks in activated sludge systems. Four black liquor shocks from 883 to 3,225 mg chemical oxygen demand−COD L−1 were applied during 24 hours in a continuously operating lab−scale activated sludge system. Removal efficiencies of COD, color and specific compounds were determined. Moreover, specific oxygen uptake rate (SOUR), sludge volumetric index (SVI) and indicator microorganisms were evaluated. Results show that the addition of black liquor caused an increase in COD removal (76−67%) immediately post shock; followed two days later by a decrease (−19−50%). On the other hand, SOUR ranged between 0.152 and 0.336 mgO2 g−1 volatile suspended solids−VSS• min−1 during shocks, but the initial value was reestablished at hour 24. When the COD concentration of the shock was higher than 1,014 mg/L, the abundance of stalked ciliates and rotifers dropped. Finally, no changes in SVI were observed, with values remaining in the range 65.8−40.2 mL g−1 total suspended solids−TSS during the entire operating process. Based on the results, the principal conclusion is that the activated sludge system with the biomass adapted to the kraft pulp effluent could resist a black liquor shock with 3,225 mgCOD L−1 of concentration during 24 h, under this study's conditions.

Biomass viability: An experimental study and the development of an empirical mathematical model for submerged membrane bioreactor

This study investigates the influence of key biomass parameters on specific oxygen uptake rate (SOUR) in a sponge submerged membrane bioreactor (SSMBR) to develop mathematical models of biomass viability. Extra-cellular polymeric substances (EPS) were considered as a lumped parameter of bound EPS (bEPS) and soluble microbial products (SMP). Statistical analyses of experimental results indicate that the bEPS, SMP, mixed liquor suspended solids and volatile suspended solids (MLSS and MLVSS) have functional relationships with SOUR and their relative influence on SOUR was in the order of EPS>bEPS>SMP>MLVSS/MLSS. Based on correlations among biomass parameters and SOUR, two independent empirical models of biomass viability were developed. The models were validated using results of the SSMBR. However, further validation of the models for different operating conditions is suggested.

Rapid start-up and improvement of granulation in SBR

BackgroundThe aim of this study is to accelerate and improve aerobic granulation within a Sequencing Batch Reactor (SBR) by cationic polymer addition.MethodsTo identify whether the polymer additive is capable of enhancing granule formation, two SBRs (R1 and R2, each 0.15 m in diameter and 2 m in height) are used by feeding synthetic wastewater. The cationic polymer with concentration of 30 to 2 ppm is added to R2, while no cationic polymer is added to R1.ResultsResults show that the cationic polymer addition causes faster granule formation and consequently shorter reactor start-up period. The polymer-amended reactor contains higher concentration of biomass with better settling ability (23% reduction in SVI15) and larger and denser granules (112% increase of granular diameter). In addition, the results demonstrate that the cationic polymer improve the sludge granulation process by 31% increase in Extracellular Polymer Substance(EPS) concentration, 7% increase in Specific Oxygen Uptake Rate(SOUR), 18% increase in hydrophobicity, and 17% reduction in effluent Mixed Liquor Suspended Solid(MLSS) concentration.ConclusionsConcludingly, it is found that using the cationic polymer to an aerobic granular system has the potential to enhance the sludge granulation process.

Poly‐3‐hydroxybutyrate production by Azotobacter vinelandii strains in batch cultures at different oxygen transfer rates

AbstractBACKGROUNDPoly‐3‐hydroxybutyrate (PHB) is a polyester that can be accumulated by Azotobacter vinelandii. This polymer is a biodegradable thermoplastic material used for producing plastics for packaging, biobased films, and biocompatible implants.RESULTSPHB produced by wild‐type A. vinelandii and a mutant OP strain were evaluated at different agitation rates. The oxygen transfer rate (OTR) evolution was characterized in cultures grown at 300, 400, 500 and 600 rpm, showing for the first time the OTR evolution in cultures of mutant OP. Under the conditions evaluated, the cultures were limited by oxygen. In the cultures grown with the OP strain, lower OTR and specific oxygen uptake rate were obtained, indicating a lower necessity for oxygen for growth in this mutant. A higher amount of PHB can be produced by decreasing the OTR. A maximum PHB of 79% on dry weight was observed in the cultures with the wild‐type strain, whereas the highest PHB productivity (0.18 g L−1 h−1) was obtained in cultures of A. vinelandii OP conducted at 600 rpm.CONCLUSIONThe amount of PHB produced during the period of oxygen limitation can be controlled by the OTR, opening the possibility to evaluate this parameter as a criterion for scaling‐up PHB production by A. vinelandii. © 2015 Society of Chemical Industry

Influence of powdered activated carbon addition on water quality, sludge properties, and microbial characteristics in the biological treatment of commingled industrial wastewater

A powdered activated carbon–activated sludge (PAC–AS) system, a traditional activated sludge (AS) system, and a powdered activated carbon (PAC) system were operated to examine the insights into the influence of PAC addition on biological treatment. The average COD removal efficiencies of the PAC–AS system (39%) were nearly double that of the AS system (20%). Compared with the average efficiencies of the PAC system (7%), COD removal by biodegradation in the PAC–AS system was remarkably higher than that in the AS system. The analysis of the influence of PAC on water quality and sludge properties showed that PAC facilitated the removal of hydrophobic matter and metabolic acidic products, and also enhanced the biomass accumulation, sludge settleability, and specific oxygen uptake rate inside the biological system. The microbial community structures in the PAC–AS and AS systems were monitored. The results showed that the average well color development in the PAC–AS system was higher than that in the AS system. The utilization of various substrates by microorganisms in the two systems did not differ. The dissimilarity index was far less than one; thus, showing that the microbial community structures of the two systems were the same.

Application of a novel respirometric methodology to characterize mass transfer and activity of H2S-oxidizing biofilms in biotrickling filter beds

The elimination capacity of gaseous H2S biofiltration can be limited either by mass transfer or bioreaction in the biofilm. Assessment of the biological activity of immobilized cells (biofilm) usually implies morphological and physiological changes during the adaptation of cells to respirometric devices operated as suspended cultures. In this study, respirometry of heterogeneous media is advised as a valuable technique for characterizing mass transport and biological activity of H2S-oxidizing biofilms attached on two packing materials from operative biotrickling filters. Controlled flows of liquid and H2S-containing air were recirculated through a closed heterogeneous respirometer allowing a more realistic estimation of the biofilm activity by the experimental evaluation of the oxygen uptake rate (OUR). Specific maximum OUR of 23.0 and 38.5mmol O2 (g biomass min)−1 were obtained for Pall rings and polyurethane foam, respectively. A mathematical model for the determination of kinetic-related parameters such as the maximum H2S elimination capacity and morphological properties of biofilm (i.e., thickness and fraction of wetted area of packing bed) was developed and calibrated. With the set of parameters obtained, the external oxygen mass transport to the wetted biofilm was found to limit the global H2S biofiltration capacity, whereas the non-wetted biofilm was the dominant route for the gaseous O2 and H2S mass transfer to the biofilm. Oxygen diffusion rate was the limiting step in the case of very active biofilms.

Respiration and enzymatic activities as indicators of stabilization of sewage sludge composting

The objective of this work was to study the evolution of physico-chemical and microbial parameters in the composting process of sewage sludge (SS) with pruning wastes (PW) in order to compare these parameters with respect to their applicability in the evaluation of organic matter (OM) stabilization. To evaluate the composting process and organic matter stability, different microbial activities were compared during composting of anaerobically digested SS with two volumetric ratios, 1:1 and 3:1 of PW:SS and two aeration techniques including aerated static piles (ASP) and turned windrows (TW). Dehydrogenase activity, fluorescein diacetate hydrolysis, and specific oxygen uptake rate (SOUR) were used as microbial activity indices. These indices were compared with traditional parameters, including temperature, pH, moisture content, organic matter, and C/N ratio. The results showed that the TW method and 3:1 (PW:SS) proportion was superior to the ASP method and 1:1 proportion, since the former accelerate the composting process by catalyzing the OM stabilization. Enzymatic activities and SOUR, which reflect microbial activity, correlated well with temperature fluctuations. Based on these results it appears that SOUR and the enzymatic activities are useful parameters to monitor the stabilization of SS compost.

Short-term effects of TiO2, CeO2, and ZnO nanoparticles on metabolic activities and gene expression of Nitrosomonas europaea

Nanosized TiO2 (n-TiO2), CeO2 (n-CeO2), and ZnO (n-ZnO) and bulk ZnO were chosen for a 4-h exposure study on a model ammonia oxidizing bacterium, Nitrosomonas europaea. n-ZnO displayed the most serious cytotoxicity while n-TiO2 was the least toxic one. The change of cell morphologies, the retardance of specific oxygen uptake rates and ammonia oxidation rates, and the depression of amoA gene expressions under NP stresses were generally observed when the cell densities and membrane integrities were not significantly impaired yet. The TEM imaging and the synchrotron X-ray fluorescence microscopy of the NPs impacted cells revealed the increase of the corresponding intracellular Ti, Ce or Zn contents and suggested the intracellular NP accumulation. The elevation of intracellular S contents accompanied with higher K contents implied the possible activation of thiol-containing glutathione and thioredoxin production for NP stress alleviation. The NP cytotoxicity was not always a function of NP concentration. The 200mgL−1 n-TiO2 or n-CeO2 impacted cells displayed the similar ammonia oxidation activities but higher amoA gene expression levels than the 20mgL−1 NPs impacted ones. Such phenomenon further indicated the possible establishment of an anti-toxicity mechanism in N. europaea at the genetic level to redeem the weakened AMO activities along with the NP aggregation effects.

Characterizing the metabolic trade-off in Nitrosomonas europaea in response to changes in inorganic carbon supply.

The link between the nitrogen and one-carbon cycles forms the metabolic basis for energy and biomass synthesis in autotrophic nitrifying organisms, which in turn are crucial players in engineered nitrogen removal processes. To understand how autotrophic nitrifying organisms respond to inorganic carbon (IC) conditions that could be encountered in engineered partially nitrifying systems, we investigated the response of one of the most extensively studied model ammonia oxidizing bacteria, Nitrosomonas europaea (ATCC19718), to three IC availability conditions: excess gaseous and excess ionic IC supply (40× stoichiometric requirement), excess gaseous IC supply (4× stoichiometric requirement in gaseous form only), and limiting IC supply (0.25× stoichiometric requirement). We found that, when switching from excess gaseous and excess ionic IC supply to excess gaseous IC supply, N. europaea chemostat cultures demonstrated an acclimation period that was characterized by transient decreases in the ammonia removal efficiency and transient peaks in the specific oxygen uptake rate. Limiting IC supply led to permanent reactor failures (characterized by biomass washout and failure of ammonia removal) that were preceded by similar decreases in the ammonia removal efficiency and peaks in the specific oxygen uptake rate. Notably, both excess gaseous IC supply and limiting IC supply elicited a previously undocumented increase in nitric and nitrous oxide emissions. Further, gene expression patterns suggested that excess gaseous IC supply and limiting IC supply led to consistent up-regulation of ammonia respiration genes and carbon assimilation genes. Under these conditions, interrogation of the N. europaea proteome revealed increased levels of carbon fixation and transport proteins and decreased levels of ammonia oxidation proteins (active in energy synthesis pathways). Together, the results indicated that N. europaea mobilized enhanced IC scavenging pathways for biosynthesis and turned down respiratory pathways for energy synthesis, when challenged with excess gaseous IC supply and limiting IC supply.

Impact of Nanoparticle Silver in a Sequencing Batch Reactor Removing Phosphorus and Ammonia

AbstractThe effect of nanoparticle silver (AgNP) in a sequencing batch reactor (SBR) removing phosphorus and ammonia was analyzed. The amount of 500 μg/L of AgNP did not significantly change the soluble chemical oxygen demand or specific oxygen uptake rates during the batch tests. Furthermore, 300 μg/L of AgNP had no effect on phosphorus, ammonia, or chemical oxygen demand removal during continuous dosing. Analysis by inductively coupled plasma-mass spectrometry determined that the lab-scale SBR removed over 80% of influent AgNP during continuous dosing. It was also determined that the North End Water Pollution Control Centre in Winnipeg, Canada, removed just under 50% of influent AgNP, and that half of the reduction occurred before secondary treatment.

Lead toxicity to the performance, viability, and community composition of activated sludge microorganisms.

Lead (Pb) is a prominent toxic metal in natural and engineered systems. Current knowledge on Pb toxicity to the activated sludge has been limited to short-term (≤24 h) toxicity. The effect of extended Pb exposure on process performance, bacterial viability, and community compositions remains unknown. We quantified the 24-h and 7-day Pb toxicity to chemical oxygen demand (COD) and NH3–N removal, bacterial viability, and community compositions using lab-scale experiments. Our results showed that 7-day toxicity was significantly higher than the short-term 24-h toxicity. Ammonia-oxidizing bacteria were more susceptible than the heterotrophs to Pb toxicity. The specific oxygen uptake rate responded quickly to Pb addition and could serve as a rapid indicator for detecting Pb pollutions. Microbial viability decreased linearly with the amount of added Pb at extended exposure. The bacterial community diversity was markedly reduced with elevated Pb concentrations. Surface analysis suggested that the adsorbed form of Pb could have contributed to its toxicity along with the dissolved form. Our study provides for the first time a systematic investigation of the effect of extended exposure of Pb on the performance and microbiology of aerobic treatment processes, and it indicates that long-term Pb toxicity has been underappreciated by previous studies.

Mineralization of Quinoline by BDD Anodes: Variable Effects and Its Effluent Characteristics

BDD anodes were selected for quinoline mineralization and influence of operating parameters, such as current density, initial quinoline concentration, supporting electrolyte, and initial pH was investigated. Based on the consideration of quinoline removal efficiency and average current efficiency, at initial quinoline concentration of 50 mg L−1and pH of 7, the optimal condition was confirmed as current density of 75 mA cm−2, electrolysis time of 1.5 h, and Na2SO4concentration of 0.05 mol L−1by orthogonal test. At different electrolysis time, its effluent characteristics were focused on. The biodegradability (the ratio between BOD5and COD) was enhanced from initial 0.02 to 0.57 at 90 min. The specific oxygen uptake rate was used to assess effluent toxicity, and the value gradually reduced with decreasing effluent organic concentration with mean value of 5.51, 4.19, and 2.20 mgO2 g−1MLSS at electrolysis time of 15, 30, and 45 min, respectively. Compared with control sample (prepared with glucose), the effluent of quinoline mineralization showed obvious inhibition effect on microorganisms at electrolysis time of 15 min, and then it was significantly faded at 30 min and 45 min.

Effect of algae growth on aerobic granulation and nutrients removal from synthetic wastewater by using sequencing batch reactors

The effect of algae growth on aerobic granulation and nutrients removal was studied in two identical sequencing batch reactors (SBRs). Sunlight exposure promoted the growth of algae in the SBR (Rs), forming an algal–bacterial symbiosis in aerobic granules. Compared to the control SBR (Rc), Rs had a slower granulation process with granules of loose structure and smaller particle size. Moreover, the specific oxygen uptake rate was significantly decreased for the granules from Rs with secretion of 25.7% and 22.5% less proteins and polysaccharides respectively in the extracellular polymeric substances. Although little impact was observed on chemical oxygen demand (COD) removal, algal–bacterial symbiosis deteriorated N and P removals, about 40.7–45.4% of total N and 44% of total P in Rs in contrast to 52.9–58.3% of TN and 90% of TP in Rc, respectively. In addition, the growth of algae altered the microbial community in Rs, especially unfavorable for Nitrospiraceae and Nitrosomonadaceae.

Effect of n-hexane extracted from food wastewater on biological substrate adsorption in wastewater treatment

The purpose of this study was to assess the effects of n-hexane contained in food wastewater on biological substrate adsorption (substrate bio-sorption). To achieve the purpose, microbial activity was assessed based on substrate removal characteristics and specific oxygen uptake rates (SOUR) at different concentrations of injected n-hexane. The X-ray photoelectron spectroscopy (XPS) was applied for an overall observation of n-hexane effects on substrate bio-sorption. The result showed that with higher n-hexane levels, the TBOD5 concentrations increased in the effluent, thereby pushing down substrate removal efficiencies. The SOUR values fell from its maximum 86.4–38.6 mg O2/g MLVSS h, which indicates that microbial activity was affected by n-hexane injection. In addition, the sludge injected with n-hexane was analyzed by XPS, and it was found that carbon elements (especially C–C and C–H) were gradually reduced on the sludge surface. The injection of n-hexane is assumed to inhibit microbial substrate adsorption, consequently reducing extracellular polymeric substances. Therefore, n-hexane needs to be removed sufficiently through a pre-treatment process in food waste-to-resource facilities.

Effluent characteristics of advanced treatment for biotreated coking wastewater by electrochemical technology using BDD anodes.

Effluent of biotreated coking wastewater comprises hundreds of organic and inorganic pollutants and has the characteristics of high toxicity and difficult biodegradation; thus, its chemical oxygen demand cannot meet drainage standards in China. A boron-doped diamond anode was selected for advanced treatment of biotreated coking wastewater, and considering the efficiency of the removal of total organic carbon and energy consumption, optimal conditions were obtained as current density of 75 mA cm(-2), electrolysis time of 1.5 h, and an electrode gap of 1.0 cm in an orthogonal test. Effluent characteristics were investigated at different electrolysis times. The ratio of the 5-day biochemical oxygen demand (BOD5) to the chemical oxygen demand increased from an initial value of 0.05 to 0.65 at 90 min. Fluorescence spectra were used to evaluate the evolution of refractory organics. Two fluorescence peaks for raw wastewater, corresponding to an aromatic protein-like substance II and humic acid-like substance, weakened at 30 and at 90 min, only the former was detected. The specific oxygen uptake rate was used to assess effluent toxicity, and an obvious inhibition effect was found at 15 min; then, it was significantly faded at 30 and 45 min. The BOD5/NO3 (-)-N ratio increased from an initial value of 0.48 to 1.25 at 45 min and then gradually dropped to 0.69 at 90 min. According to the above effluent characteristics, it is strongly suggested that electrochemical technology using boron-doped diamond anodes is combined with biological denitrification technology for the advanced treatment of biotreated coking wastewater.

Specific oxygen uptake rate as indicator of cell response of Rhodococcus erythropolis cultures to shear effects

Specific oxygen uptake rate, qO2, on Rhodococcus erythropolis IGTS8 cultures has been measured under different fluid dynamic conditions in a STBR, changing stirrer speed, between 100 and 700rpm, and air flow rate, between 1 and 10Lmin−1. Experimental results indicate that qO2 values for R. erythropolis cultures can be influenced by the fluid dynamics inside the bioreactor. Under non oxygen-limited conditions, the oxygen consumption rate by the cells does not depend on the oxygen transfer rate; hence, the specific oxygen uptake rate is constant. However, when the stirrer speed is increased over a limit value, around 450rpm in the culture studied, a change is clearly detected and, as higher stirrer speeds are used, specific oxygen uptake rate suffers a significant decrease. Nevertheless, when the hydrodynamics are varied changing the air flow rate, between 1 and 10Lmin−1, this variable does not affect the oxygen uptake rate. According to these results, specific oxygen uptake rate measurement provides a good indication of whole stress generated by the hydrodynamic conditions into the bioreactor. A simple method to determine changes into the cell response due to the fluid dynamic environment in the bioreactor is herein proposed. According to this method, shear effects on the culture can be detected by the change on specific oxygen uptake rate measured at laboratory scale, employing the usual gas in-gas out dynamic method. This assay combines oxygen transfer, oxygen uptake rate and possible cell damage in a one simple method that can considerably simplify and accelerate fundamental research on the development and scale-up of bioprocesses.

Rapid evaluation of algal and cyanobacterial activities through specific oxygen production rate measurement

Extant respirometry enables rapid determination of sludge decay coefficients and chemical biodegradability in wastewater treatment systems. This study extends its use to phototrophic systems to determine phototrophic decay rate and photosynthetic activity through the measurements of specific oxygen uptake rate (SOUR) and specific oxygen production rate (SOPR), respectively. With a sufficient CO2 supply (4.0mM of NaHCO3) and pH control (from 7 to 8) at the light intensity of 50±5μmolm−2s−1 and the temperature of 23±1°C, the specific growth rates of cyanobacteria (Microcystis aeruginosa) and green algae (Chlorella vulgaris) were 0.92±0.11 and 0.79±0.14d−1, respectively. The decay coefficients of M. aeruginosa and C. vulgaris were 0.08±0.04 and 0.08±0.03d−1, respectively. Compared to batch phototrophic growth studies that often last longer than 10 days, the proposed SOPR measurement enables rapid determination of algal/cyanobacterial growth kinetics within minutes and is capable of determining phototrophic growth under different environmental and stress conditions (e.g., pH, nitrogen sources, chemical and metal exposure). As demonstrated here, ammonium was a preferred nitrogen source for the growth of M. aeruginosa and C. vulgaris because reducing power (energy) is needed to convert nitrate to ammonium before nitrogen uptake by the phototrophs. M. aeruginosa was more susceptible than C. vulgaris to inhibition by heavy metal copper. At the concentration of 10mg Cu2+/L, cupric ions had no effect on algal growth but inhibited cyanobacterial growth by 66.4%.

Avoiding overfeeding in high cell density fed-batch cultures of E. coli during the production of heterologous proteins

Heterologous protein production often causes a significant metabolic burden in Escherichia coli cells which manifests itself in a substantial decrease in their physiological characteristics such as the maximal specific growth rate on a given substrate, the maximal substrate uptake rate as well as the maximal specific oxygen uptake rate. In high-cell-density cultures, the substrate feed rate must be adapted to this changing capabilities of the cells in order to avoid overfeeding and thus the formation of by-products that inhibit the cell performance further. This requires the precise knowledge about the changes in these specific rates, particularly during the product formation phase.In order to precisely investigate the time profile of the critical specific substrate uptake rate σcrit of microorganisms, i.e. the maximal rate at which the cells can fully oxidize their substrate, a new online tracking technique is presented. The feed rate F is modulated in such a way that the specific substrate uptake rate σ is linearly raised towards its critical value σcrit. When this is reached the feed rate is automatically reduced and the procedure is repeated. In this way the method automatically follows the changing time profile of σcrit during the entire cultivation and avoids significant acetate formation rates. This procedure considerably increases the identifiability of σcrit. The high precision of the technique also results from replacing the pO2 measurements that seem to suggest themselves for monitoring maximal oxygen uptake rate, by measuring the total oxygen consumption rate tOUR, which is available at a much higher signal-to-noise ratio and is not as prone to distortions. An important advantage of measuring tOUR is that it allows keeping pO2 controlled at its optimal value. The applicability of the new tracking technology is demonstrated at E. coli cultures. The resulting σcrit(t) profile allows determining the substrate feed rate profile and other key variables that can be used for advanced feedback control in protein production processes. The technique can be considered a PAT tool and is well suited to industrial fermentations.

Effects of filtration modes on membrane fouling behavior and treatment in submerged membrane bioreactor

Relaxation or backwashing is obligatory for effective operation of membrane module and intermittent aeration is helpful for nutrients removal. This study was performed to investigate effects of different filtration modes on membrane fouling behavior and treatment in membrane bioreactor (MBR) operated at three modes i.e., 12, 10 and 8min filtration and 3, 2, and 2min relaxation corresponding to 6, 5 and 4cycles/hour, respectively. Various parameters including trans-membrane pressure, specific cake resistance, specific oxygen uptake rate, nutrients removal and sludge dewaterability were examined to optimize the filtration mode. TMP profiles showed that MBR(8+2) with 8min filtration and 2min relaxation reduced the fouling rate and depicted long filtration time in MBR treating synthetic wastewater. MBR(12+3) was more efficient in organic and nutrients removal while denitrification rate was high in MBR(8+2).