Microbial community dynamics in bioaugmented sequencing batch reactors for bromoamine acid removal

Sphingomonas xenophaga QYY with the ability to degrade bromoamine acid (BAA) was previously isolated from sludge samples. The enhancement of BAA removal by strain QYY in sequencing batch reactors (SBRs) was investigated in this study. The results showed that augmented SBRs exhibited stronger abilities to degrade BAA than the non-augmented control one. In order to estimate the relationship between community dynamics and function of augmented SBRs, a combined method based on fingerprints (ribosomal intergenic spacer analysis, RISA) and 16S rRNA gene sequencing was used. The results indicated that the microbial community dynamics were substantially changed, and the introduced strain QYY was persistent in the augmented systems. This study suggests that it is feasible and potentially useful to enhance BAA removal using BAA-degrading bacteria, such as S. xenophaga QYY.     

Decolorization of 1-amino-4-bromoanthraquinone-2-sulfonic acid in bioaugmented membrane bioreactor

Decolorization of 1-amino-4-bromoanthraquinone-2-sulfonic acid (ABAS) in a Sphingomonas xenophaga-augmented membrane bioreactor was investigated. The results showed that sequencing bioaugmented membrane bioreactor (SMBR) could run stably for 60 days. During the process, over 99% ABAS (570 mg/L) was decolorized and 60% COD was removed. Moreover, the yellow intermediate produced in continuous operation mode was not detected in SMBR. It was probably a dimer resulting from the autoxidation of 2-amino-3-hydroxy-5-bromobenzenesulfonic acid. Ribosomal intergenic sequence analysis (RISA) of the sludge in SMBR suggested that bioaugmentation resulted in large decrease or increase of certain population and Strain QYY can persist in SMBR. The biomass of membrane surface in SMBR could be further divided into a cake layer and a dense layer. The former is mainly composed of coccus, bacillus and filamentous bacteria, which is different from suspended sludge flocs with predominant bacillus.     

Factors affecting the performance of membrane bioreactor for piggery wastewater treatment

This study was conducted to identify the factors affecting the performance of membrane bioreactor (MBR) for piggery wastewater treatment. The change of organic and nitrogen concentrations in piggery wastewater was studied to investigate the treatment efficiency. The increase of COD, BOD and NH₃–N from 1150 to 2050 mg/L, 683 to 1198 mg/L and 154 to 248 mg/L has led to the decrease of treatment efficiency. Removal efficiencies of COD, BOD and NH₃–N have decreased from 96.0% to 92.0%, 97.0% to 92.7% and 93.2% to 69.5%, respectively. The effects of biomass characteristics on membrane fouling were determined based on Pearson’s correlation coefficient (r_p). It was found that MLSS had a negative correlation with permeate flux (r_p = −0.745, at significant level of 0.05) while sludge floc size a positive correlation (r_p = 0.731, at significant level of 0.05). MLSS and sludge floc size were found to be the dominant factors that controlled the membrane filterability while sludge viscosity, EPS, SMP and SV₃₀ have taken as the sub-factors affecting membrane fouling.     

Performance of a submerged membrane bioreactor for the aerobic treatment of abattoir wastewater

The performance of a submerged membrane bioreactor (SMBR) has been investigated for abattoir wastewater (AW) treatment. The chemical oxygen demand (COD) of permeate has not exceeded 25 mg L⁻¹ providing an average COD removal of 98%. Microbiological analysis showed that the SMBR has allowed a complete removal of fecal coliforms, Listeria and Salmonella. A significant reduction in the excess biomass production was also observed. In fact, the yield of biomass production (Yobs) ranged between 0 and 0.106 g suspended solids/g COD removed.The study of the dynamic of bacterial communities using the single strand conformation polymorphism (SSCP) method showed a significant change in the population structure and revealed a correlation between the sludge production yield and the bacterial communities.     

Application of chemical precipitation and membrane bioreactor hybrid process for piggery wastewater treatment

This study was conducted to investigate the chemical precipitation (CP) and membrane bioreactor (MBR) hybrid process for the treatment of piggery wastewater. Average removal efficiencies for BOD, COD and turbidity in CP process were 64.3%, 77.3% and 96.4%, respectively. CP process had a moderate effect on NH₃–N removal (40.4%) which improved up to 98.2% mainly due to nitrification and filtration processes in MBR. The average removal efficiencies of BOD, COD and turbidity in MBR were 99.5%, 99.4% and 99.8%, respectively. Monod equation was used to explain the microbial activities in terms of specific growth rate. The specific growth rate of bacteria in aeration tank (N-batch) and anoxic tank (D-batch) were 0.013 and 0.005 d^?1 with a biomass yield of 0.78 and 0.43 mg MLSS produced/mg COD utilized, respectively. Microorganisms from the N-batch and D-batch showed a low-level of nitrifying and moderate-level of denitrifying capabilities which were 1.08 mg NH₃–N/(g MLVSS.h) and 2.82 mg NO₃–N/(g MLVSS.h), respectively. Carbohydrates were the main component in extracellular polymeric substance (EPS) compounds that could be attached to the membrane surface easily and led to membrane biofouling. The increase of MLSS, EPS and sludge viscosity concentration, decrease of sludge floc size and incomplete chemical cleaning procedure resulted in the increase of membrane resistance. Total membrane resistance increased from 3.19 × 10¹² m^?1 to 5.43 × 10¹⁴ m^?1.     

Optimized operational parameters of a pilot scale membrane bioreactor for high-strength organic wastewater treatment

A pilot-scale test was conducted in a submerged membrane bioreactor (SMBR) for 452 days to treat high-strength traditional Chinese medicine wastewater from two-phase anaerobic digest effluent. This study focuses on the effects of operational parameters on effluent quality of a SMBR. The parameters include shorter hydraulic retention time (HRT), higher influent COD concentration, higher COD loading rate and mixed liquor suspended solids (MLSS). The experimental results demonstrated that when HRT was 5 h and the influent COD was less than 3000 mg L⁻¹, the effluent quality of the SMBR evaluated from its COD content (COD_filt) could meet the accepted Chinese standards for water reclamation; when HRT was 3.2 h and the influent COD was less than 3000 mg L ⁻¹, or HRT was 5 h and the influent COD fluctuated between 3000 and 6000 mg L⁻¹, the effluent quality of the SMBR could meet the normal Chinese discharged standard. Statistical analyses showed that COD_filt correlated positively with the COD loading rate. It correlated negatively with the MLSS for MLSS values between 7543 and 13 694 mg L⁻¹. When MLSS was >13 694 mg L⁻¹ it correlated positively with COD_filt. Based on experimental values from SMBR and on values predicted by a simulation model generated using the back propagation neural network (BPNN) theory, the optimum operational parameters for the treatment of a high-strength TCM wastewater were as follows: HRT was 5 h, SRT was 100 day, COD loading rate was<20.5 kg m⁻³ d⁻¹, the range of MLSS was 7543–13 694 mg L⁻¹.     

A novel membrane bioreactor enhanced by effective microorganisms for the treatment of domestic wastewater

The activated sludge membrane bioreactor (MBR) has been shown to have some advantages for the processing and reclamation of domestic wastewater. We hypothesized that certain microorganisms, chosen for their abilities to decompose the chemical components of raw sewage, would, when coupled with the MBR, significantly improve the stability and efficiency of this system. We selected environmental bacterial strains which oxidize ammonia and nitrites and produce protease, amylase, and cellulase for the development and testing of a novel biologically enhanced MBR (eMBR). We compared the eMBR with the activated sludge MBR. With the eMBR, the average values of effluent quality were: chemical oxygen demand (COD), 40 mg/l(average efficiency of removal 90.0%); and NH₄ ⁺–N, 0.66 mg/l(average efficiency of removal 99.4%). Effluent qualities met the standard and were stable during the entire 90 days of this study. For the activated sludge MBR, the COD removal rate was 91.7%, and the NH₄ ⁺–N removal (94.8%) was less than that of the eMBR. Start-up time for the eMBR was only 24–48 h, much shorter than the 7–8 days required to initiate function of the standard MBR. The biomass concentrations of total heterotrophic bacteria and autotrophic bacteria in the eMBR did not fluctuate significantly during the course of the study. Various kinds of microorganisms will establish an ecological balance in the reactor. Compared with the activated sludge MBR, the eMBR not only produced an excellent and stable quality of effluent but also resulted in a shorter time to start-up and significantly improved the efficiency of NH₄ ⁺–N removal.     

Use of cloth-media filter for membrane bioreactor treating municipal wastewater

This study evaluated three different textile materials (Acrylate, Polyester, and Nylon) as filter media for MBR treating municipal wastewater. Chemical oxygen demand (COD) loading rates were 1.71, 1.65 and 1.84 g/l d while feed/microorganisms (F/M) ratios were 0.32, 0.31 and 0.33 in Reactor 1, Reactor 2 and Reactor 3, respectively. The actual hydraulic retention times were 8.6, 8.9 and 8.0 h in R1, R2 and R3. At 5.3-5.5 g/l mixed liquor suspended (MLSS) and 26.3 days solid retention time (SRT) the membrane bioreactors were effective in removing 93-95% of COD, 99% of total suspended solids (TSS) and turbidity, 89-94% of total kjeldahl nitrogen (TKN) and 90-96% of total ammonia nitrogen. Phosphorous removal was limited to 51-55% while faecal coliform was reduced by four logs. Quality of the treated effluents met both Saudi and Egyptian reuse standards for restricted irrigation and could be easily disinfected to meet the unrestricted irrigation standards.     

Performance of a membrane bioreactor used for the treatment of wastewater contaminated with heavy metals

In this work the performance of a Membrane bioreactor (MBR) was assessed for the removal of 3-15 mg/l of copper, lead, nickel and zinc from wastewater. The average removal efficiencies accomplished by the MBR system were 80% for Cu(II), 98% for Pb(II), 50% for Ni(II) and 77% for Zn(II). The addition of 5 g/l vermiculite into the biological reactor enhanced metal removal to 88% for copper, 85% for zinc and 60% for nickel due to adsorption of metal ions on the mineral, while it reduced biomass inhibition and increased biomass growth. The metal ions remaining in soluble form penetrated into the permeate, while those attached to sludge flocs were effectively retained by the ultrafiltration membranes. The average heterotrophic biomass inhibition was 50%, while it reduced to 29% when lower metal concentrations were fed into the reactor in the presence of vermiculite. The respective autotrophic biomass inhibition was 70% and 36%. The presence of heavy metals and vermiculite in the mixed liquor adversely impacted on membrane fouling.     

Preparation of a mesoporous silica quorum quenching medium for wastewater treatment using a membrane bioreactor

Abstract

Various quorum quenching (QQ) media have been developed to mitigate membrane biofouling in a membrane bioreactor (MBR). However, most are expensive, unstable and easily trapped in hollow fibre membranes. Here, a sol-gel method was used to develop a mesoporous silica medium entrapping a QQ bacterial strain (Rhodococcus sp. BH4). The new silica QQ medium was able to remove quorum sensing signalling molecules via both adsorption (owing to their mesoporous hydrophobic structure) and decomposition with an enzyme (lactonase), preventing MBR biofouling without affecting the water quality. It also demonstrated a relatively long life span due to its non-biodegradability and its relatively small particle size (<1.0?mm), which makes it less likely to clog in a hollow fibre membrane module.     

Lab-scale study of an anaerobic membrane bioreactor (AnMBR) for dilute municipal wastewater treatment

Anaerobic bioreactors supplemented with membrane technology have become quite popular, owing to their favorable energy recovery characteristics. In this study, a lab-scale anaerobic Membrane Bioreactor (AnMBR) was assessed in experimental treatments of pre-settled dilute municipal wastewater obtained from a full-scaled wastewater treatment plant. The MBR system was operated in continuous flow mode for 440 days. To evaluate the performance of the AnMBR under various loading rates, the hydraulic retention time (HRT) was reduced in a stepwise manner (from 2 to 0.5 days). Afterward, the mixed liquor suspended solids (MLSS) were reduced from 7,000 to 3,000 mg/L in increments of 1,000 mg/L, resulting in a decrease in solids retention time (SRT) at a constant HRT of 1.0 day. The soluble chemical oxygen demand (SCOD) concentration in the feed varied between 38 and 131 mg/L, whereas the average permeate SCOD ranged between 18 and 37 mg/L, reflecting excellent effluent quality. The AnMBR performance in terms of COD removal proved stable, despite variations in influent characteristics and HRT and SRT changes. The concentration of extracellular polymeric substance (EPS) was reduced with decreases in HRT from 42 to 22 mg VS/mg of MLSS, thereby indicating that the increased biomass concentration biodegraded the EPS at lower HRTs. AnMBR is, therefore, demonstrably a feasible option for the treatment of dilute wastewater with separate stage nitrogen and phosphorus removal processes.     

High rate treatment of terephthalic acid production wastewater in a two-stage anaerobic bioreactor

The feasibility was studied of anaerobic treatment of wastewater generated during purified terephthalic acid (PTA) production in two-stage upflow anaerobic sludge blanket (UASB) reactor system. The artificial influent of the system contained the main organic substrates of PTA-wastewater: acetate, benzoate, and terephthalate. Three parallel operated reactors were used for the second stage, and seeded with a suspended terephthalate degrading culture, with and without additional methanogenic granular sludge (two different types). The first stage UASB-reactor was seeded with methanogenic granular sludge. Reactors were operated at 37 degrees C and pH 7. During the first 300 days of operation a clear distinction between the biomass grown in both reactor stages was obtained. In the first stage, acetate and benzoate were degraded at a volumetric loading rate of 40 g-COD/L . day at a COD-removal efficiency of 95% within the first 25 days of operation. No degradation of terephthalate was obtained in the first stage during the first 300 days of operation despite operation of the reactor at a decreased volumetric loading rate with acetate and benzoate of 9 g-COD/L . day from day 150. Batch incubation of biomass from the reactor with terephthalate showed that the lag-phase prior to terephthalate degradation remained largely unchanged, indicating that no net growth of terephthalate degrading biomass occurred in the first stage reactor. From day 300, however, terephthalate degradation was observed in the first stage, and the biomass in this reactor could successfully be enriched with terephthalate degrading biomass, resulting in terephthalate removal capacities of 15 g-COD/L . day. Even though no single reason could be identified why (suddenly) terephthalate degradation was obtained after such a long period of operation, it is suggested that the solid retention time as well the prevailing reactor concentrations acetate and benzoate may have played an important role. From day 1 of operation, terephthalate was degraded in the second stage. In presence of methanogenic granular biomass, high terephthalate removal capacities were obtained in these reactors (15 g-COD/L . day) after approximately 125 days of operation. From the results obtained it is concluded that terephthalate degradation is the bottleneck during anaerobic treatment of PTA-wastewater. Pre-removal of acetate and benzoate in staged bioreactor reduces the lag-phase prior to terephthalate degradation in latter stages, and enables high rate treatment of PTA-wastewater.     

Effects of the acidogenic biomass on the performance of an anaerobic membrane bioreactor for wastewater treatment

Continuous flow experiments were performed to study the effects of acidogenic biomass development, induced by feeding with non-acidified substrate, on the operation and performance of an anaerobic membrane bioreactor (AnMBR). The AnMBR was operated at cross-flow velocities up to 1.5 m/s and fed with a gelatine–starch–ethanol mixture. A significant fraction of acidogenic biomass developed during reactor operation, which fully determined the sludge rheology, and influenced the particle size distribution. As a result, flux levels of only 6.5 l/m² h were achieved, at a liquid superficial velocity of 1.5 m/s. Even though the soluble microbial products levels in the AMBR were as high as 14 g COD/l, the observed hydraulic flux was not limited by irreversible pore fouling, but by reversible cake layer formation. Propionate oxidation was the limiting step for the applied organic loading rate. The assessed specific methanogenic activity (SMA) with propionate as substrate was, however, similar to the values found by others during thermophilic treatment of non or partially acidified substrates in granular sludge bed reactors, indicating an appropriate level of the propionate oxidation capacity.     

Hydrogenotrophic denitrification of synthetic aquaculture wastewater using membrane bioreactor

A hydrogenotrophic denitrification system was evaluated in removing nitrate from synthetic aquaculture wastewater for recirculation purposes. Two membrane bioreactor (MBR) systems, namely, aeration–denitrification system (ADS) and denitrification–aeration system (DAS) were studied with 50 mg/L of influent concentrations for both organic matter and nitrate nitrogen. The DAS achieved better removal efficiency of 91.4% total nitrogen (T-N) and denitrification rate of 363.7 mg/L.day at a HRT of 3 h compared to ADS. Further, there was no nitrite accumulation in the DAS effluent. The nitrite accumulation in ADS effluent was lesser when CO₂ was used as buffer rather than K₂HPO₄ and KH₂PO₄. Estimation of kinetic parameters of hydrogenotrophic bacteria indicated lesser sludge production compared to heterotrophic denitrification. In the DAS, membrane fouling was nonexistent in the aeration reactor that was used to produce the recirculating effluent. On the contrary, membrane fouling was observed in the denitrification reactor that supplied hydrogen to the mixed liquor. Thus, this study demonstrated DAS capability in maintaining the acceptable water quality appropriate for aquaculture, in which a closed recirculating system is typically used.     

Anaerobic submerged membrane bioreactor (AnSMBR) for municipal wastewater treatment under mesophilic and psychrophilic temperature conditions

A pilot scale anaerobic submerged membrane bioreactor (AnSMBR) with an external filtration unit for municipal wastewater treatment was operated for 100 days. Besides gas sparging, additional shear was created by circulating sludge to control membrane fouling. During the first 69 days, the reactor was operated under mesophilic temperature conditions. Afterwards, the temperature was gradually reduced to 20 °C. A slow and linear increase in the filtration resistance was observed under critical flux conditions (7 L/(m2 h)) at 35 °C. However, an increase in the fouling rate probably linked to an accumulation of solids, a higher viscosity and soluble COD concentrations in the reactor was observed at 20 °C. The COD removal efficiency was close to 90% under both temperature ranges. Effluent COD and BOD5 concentrations were lower than 80 and 25 mg/L, respectively. Pathogen indicator microorganisms (fecal coliforms bacteria) were reduced by log(10)5. Hence, the effluent could be used for irrigation purposes in agriculture.     

Experimental study of the anaerobic urban wastewater treatment in a submerged hollow-fibre membrane bioreactor at pilot scale

The aim of this study was to assess the effect of several operational variables on both biological and separation process performance in a submerged anaerobic membrane bioreactor pilot plant that treats urban wastewater. The pilot plant is equipped with two industrial hollow-fibre ultrafiltration membrane modules (PURON? Koch Membrane Systems, 30 m2 of filtration surface each). It was operated under mesophilic conditions (at 33 °C), 70 days of SRT, and variable HRT ranging from 20 to 6h. The effects of the influent COD/SO?-S ratio (ranging from 2 to 12) and the MLTS concentration (ranging from 6 to 22 g L?1) were also analysed. The main performance results were about 87% of COD removal, effluent VFA below 20 mg L?1 and biogas methane concentrations over 55% v/v. Methane yield was strongly affected by the influent COD/SO?-S ratio. No irreversible fouling problems were detected, even for MLTS concentrations above 22 g L?1.