Influent Organic Loading Research Articles

Metabolomics Study of Subsurface Wastewater Infiltration System Under Fluctuation of Organic Load.

Subsurface Wastewater Infiltration System (SWIS) is a sewage ecological treatment technology with low investment, energy consumption, and operating cost. SWIS soil contains a large variety of microorganisms. The metabolic process and production of microorganisms are an important basis for qualitatively describing the process of pollutant removal. In order to discover the microbial decontamination pathways in SWIS, the metabolic profiles of soil microorganisms in SWIS were analyzed by UPLC-MS. Partial least squares-discriminant analysis (PLS-DA)and principal component analysis (PCA) pattern recognition methods were used to classify the samples. According to the model's variable importance factor (VIP value), potential biomarkers were screened and biological information contained in the metabolites was also analyzed. The correlation between metabolites and environmental factors was explored by RDA analysis. In total, 230 differential metabolites with VIP value greater than 1.5 were screened out when the influent organic load fluctuated at 250mgL-1, 400mgL-1, and 500mgL-1. After identifying and screening, 35 differential metabolites were identified and used to further analyze the metabolic pathway. It turns out that microbial metabolites in SWIS were mainly glycosides, fatty acids, amino acids, pigments, diterpenoids, and some polymers under medium and high organic loading conditions. At low organic load, the microbial metabolites in SWIS were mainly ketones, alcohols, and esters.

Performance and kinetics analysis of an aerobic sequencing batch flexible fibre biofilm reactor for milk processing wastewater treatment

In this study, a sequencing batch flexible fibre biofilm reactor (SB-FFBR) is used for efficient and cost-effective treatment of milk processing wastewater (MPW). The SB-FFBR, modified type of a typical sequencing batch reactor (SBR), is made up of eight bundles of flexible fibre as a supporting media for microorganisms'growth. The working volume and the cycle length of the bioreactor are 8 L and 24 h, respectively. The biological performance of the bioreactor is studied at 10, 3 and 10 various levels of the influent chemical oxygen demand (CODin; 610–8193 mg L−1), retention time (RT; 1, 1.6 and 2 days), and organic loading rate (OLR; 0.38–8.19 gCOD m−3d−1), respectively. From the results, the minimum COD and total suspended solids (TSS) removal efficiency of 86.8% and 77.3% were achieved at OLR of 8.2 kg COD m−3d−1, CODin of 8193 mg L−1 and RT of 1 day. While, an excellent COD and TSS removal efficiency were found to be 97.5% and 99.3%, respectively, at low OLR of 0.4 kg COD m−3d−1, CODin of 945 mg L−1 and RT of 2 days. Furthermore, the kinetic coefficients of COD removal were computed using a first order substrate removal model at different COD concentrations. The first order kinetic constant, (k), was 0.60, 0.65 and 0.357 h−1 for 500, 810 and 2000 mg COD L−1, respectively. The use of the flexible fibre as a packing material provided a huge surface area for more microorganism attachment. Therefore, the results demonstrated the SB-FFBR has acted as a suitable and effective strategy in treatment of milk processing industrial wastewater.

Impact of goethite dosed continuous stirred tank reactor on continuous methane production at different organic loading rates.

Iron oxides facilitated anaerobic digestion process has been attracted more and more attention in the renewable energy production area. In the current study, goethite was added into the continuous stirred tank reactor with glucose as the substrate. Effect of the influent organic loading rate (OLR) on the reactor performances was explored. Results showed that goethite promoted the methane production significantly (p<0.05) when OLR was changed between 1.20 and 1.80g glucoseL-1 day-1 . Compared to the control reactor, addition of goethite improved the methane production by13.4%-22.9%. The iron reduction rate had a positive correlation with the methane production rate. Microbial community analysis results showed that OLRs influenced the dominant methanogenic species in the both reactors. Methanothrix, Methanobacterium, Methanosarcina, and Methanocella were dominant under various OLR levels. PRACTITIONER POINTS: Goethite could promote the methanogenic process of glucose in the CSTRs under certain levels of OLRs. Iron reduction rate had a positive correlation with the methane production rate. OLRs influenced the dominant methanogenic species in the goethite-dosed reactors.

Anaerobic Membrane Bioreactor for Urban Wastewater Valorisation: Operative Strategies and Fertigation Reuse

In European scenario, the potential source for water supply from treated wastewater is actually estimated in 1,100 Mm3/y (EU-ENV, 2015). Anaerobic processes compared with conventional aerobic ones, cause a net reduction of the operative costs and possible reuse for fertigation purposes. The tested anaerobic pilot (HRT 6 h and T 30°C) is constituted from a UASB reactor (16 L). Increment of influent organic loading rate (OLR) was studied for 1 year from 1 to 2 kgCOD/m3/d by feeding raw wastewater (Period 1), methanol (Period 2) and fermented supernatant from cellulosic sludge (Period 3).The biogas production was assessed equal to 0.13 m3biogas/kgCOD (Period 1), to 0.57 m3biogas/kgCOD (Period 2) and to 0.24 m3biogas/kgCOD (Period 3) with methane percentages constant around 33%. UASB effluent has not the final quality to comply limit values for water reuse and fertigation, especially for microbiological parameters. Further treatments could be necessary to achieve the removals of bacteria, such as E.Coli, recalcitrant organic traces and metals. Therefore, some advanced post treatments have been studied in this paper after UASB treatments, like UV disinfection, UV coupled with H2O2 and GAC adsorption. The innovative solution is coupling UASB reactor with anaerobic submerged sidestream AnMBR (UF hollow fiber membrane with 0.03 µm of nominal pore-size and 0.5 m2 of surface area KOCH, Puron single bundle). Membrane cleaning was carried out using sodium hypochlorite solution (400 ppm) each 45 days to remove organic fouling and to recover the initial permeability of the membrane. The average operative flux at process temperature was equal to 8.8±1.9 L/h/m2 and operating TMP of 44.6±8.5 mbar was detected. The removal of E.Coli was investigated in the effluent from UASB and in the permeate from AnMBR process. At clean membrane conditions, complete removal of bacteria (99±1%) was found. Furthermore, the determination of microplastics distribution was carried out both in the experimental anaerobic pilot and in the conventional full scale aerobic treatment plant. The effluent microplastics were quantified and the removal role of the different operative units was studied.

Granulation of halophilic sludge inoculated with estuarine sediments for saline wastewater treatment

As a solution of the sludge loss in the treatment of saline wastewater, the granulation of halophilic sludge was explored in this study. The inoculated estuarine sediment was granulated to an average diameter of 1155 ± 102 μm under the selective settling pressure in the airlift sequencing batch reactor (SBR) when the influent organic loading rate (OLR) was doubled to 0.36 g COD/L·day. The results indicated that the OLR doubled the amount of total extracellular polymeric substance (EPS) and that protein was predominant in the EPS (72.8 ± 2.0%). The correlation between aggregate size and protein content was better than that between aggregate size and polysaccharide content. The amount of alginate-like exopolysaccharides (ALE) increased linearly at the mature granular stage, co-occurring with the compact and elastic structure of the granules. According to the results of 16S rRNA high -throughput sequencing, the Shannon-Weaver index of mature granule decreased by >50% compared to the inoculated sediment. Bacteria of Propionibacteriaceae family constituted 34% of the population in granules and were in symbiotic relationship with halophiles of family Rhodocyclaceae, Vibrionaceae, Flavobacteriaceae, and Cryomorphaceae. The aerobic halophilic granular sludge showed COD removal efficiency of 90.9 ± 0.8% and ammonia removal efficiency of 72.6 ± 4.0% for 30 g/L saline wastewater. An average nitrite accumulation ratio of 94.5 ± 2.9% was observed during nitrification. Granulation of halophilic sludge provides an effective solution to the saline sludge loss problem, which is a step forward to realize the biological treatment of saline wastewater by halophiles.

Coproduction of hydrogen and methane in a CSTR-IC two-stage anaerobic digestion system from molasses wastewater.

A continuous hydrogen and methane production system in a two-stage process has been investigated to increase energy recovery rate from molasses wastewater in this study. This system consisted of a continuous stirred-tank reactor for hydrogen production and an internal circulation (IC) reactor for methane production, and was studied under the influent organic loading rate (OLR) of 18, 24, 30 and 36kg COD/(m3·d) (COD: chemical oxygen demand). The maximum volumetric hydrogen production rate of 2.41 L/(L·d) was obtained at the OLR of 30kg COD/(m3·d) with a hydrogen content of 42%, and the maximum volumetric methane production rate of 2.4 L/(L·d) with a methane content of 74.45% was obtained at the OLR of 36kg COD/(m3·d) using the effluents of hydrogen fermentation as substrate. The maximum of 71.06% of the molasses wastewater energy was converted to biogas (hydrogen and methane) at the OLR of 30kg COD/(m3·d).

Effective Anaerobic Bio-Treatment of Fresh Leachate From Municipal Solid Waste Incineration Plant by Full-Scale Internal Circulation Reactor

This study aimed to investigate the effectiveness of the full-scale internal circulation (IC) reactor in biodegrading of municipal solid waste (MSW) fresh leachate under mesophilic conditions, where the anaerobic process stability, biogas yield, and sludge granulation were intensively investigated. The effects of operational parameters on the influent organic loading rate (OLR), chemical oxygen demand (COD) removal efficiency, alkalinity (ALK), pH, volatile fatty acids (VFAs) accumulation, and effluent recirculation were also studied. The results showed that the reactor operated stably and effectively. The COD removal efficiency and biogas yield could be maintained at (92.8 ± 2.0)% and (0.47 ± 0.05) m3/kg CODremoval, respectively, with the influent OLR (24.5 ± 0.9) kg COD/(m3 d) and hydraulic retention time (HRT) 2.7d during the stable operation phase. Meanwhile, this study demonstrated that 1.5–3.0 m/h would be the optimal Vup for the reactor, corresponding to the effluent recirculation of 32.5–78.0 m3/h. Moreover, it was found that the content of extracellular polymeric substances (EPS) in the anaerobic sludge increased from 50.3 to 140.7 mg/g volatile suspended solids (VSS), and the sludge had good granular performance during the reactor operation.

The influence of incorporating microbial fuel cells on greenhouse gas emissions from constructed wetlands

Microbial fuel cells (MFCs) were incorporated into constructed wetlands (CWs) in recent years aiming to enhance the wastewater treatment of CWs while simultaneously produce electricity. However, currently no information is available about the greenhouse gas (GHG) emissions from integrated CW–MFC systems during wastewater treatment. Therefore, this study investigated the influence of incorporating MFCs on GHG (especially CH4 and N2O) emissions from CWs under different external resistances, influent organic loadings and seasons. Results showed that incorporating the MFC significantly reduced the GHG emissions (by 5.9%–32.4% CO2 equivalents) from CWs by reducing 17.9%–36.9% CH4 and 7.2%–38.7% N2O emissions. The CH4 and N2O emissions from CW–MFCs significantly increased with increasing external resistance (above 500 Ω), while the CO2 emission showed the opposite trend. However, the CH4 and N2O emissions at external resistances below 500 Ω did not differ significantly. There was a significant positive correlation between the CO2 and CH4 emissions and influent organic loadings in CW–MFCs, but a significant negative correlation between the N2O emission and influent organic loadings. Influent chemical oxygen demand/total nitrogen (COD/TN) = 3 could result in a TN removal of ≥90% as well as the minimum CO2 equivalents emission in CW-MFCs. The GHG emissions from CW–MFCs showed significant seasonal variations.

Effects of hydraulic loading rate and organic load on the performance of a pilot-scale hybrid VF-HF constructed wetland in treating secondary effluent

This study evaluated the performance of a pilot-scale hybrid constructed wetland system for secondary effluent and investigated bulk organic matter characteristics. The hybrid constructed wetland consisted of a vertical-flow (VF) bed followed by a horizontal-flow (HF) bed. We also investigated the effects of hydraulic loading rates and influent organic load on the performance of the pilot-scale VF-HF hybrid constructed wetland. The results showed a high removal efficiency for suspended solids (>95%) and organic matter as determined by total organic carbon (>98.5%) and dissolved organic carbon (>70%), but no significant change in nitrogen removal was observed. The wetland treatment efficiency for suspended solids and organic matter showed a good buffer capacity even when hydraulic loading rates increased from 750 to 1500 L m−2 d−1 and 500–1000 L m−2 d−1 during the VF and HF stages, respectively. Moreover, there was no significant change in the performance when influent organic load increased eight-fold. Fluorescence excitation-emission matrix and liquid chromatography-organic carbon detection (LC-OCD) were used to investigate the dissolved organic matter characteristics in the hybrid VF-HF constructed wetland. Fluorescence excitation-emission matrix spectroscopy showed that both protein- and humic-like substances did not significantly change in the effluent when hydraulic loading rates and organic load increased by two- and eight-fold, respectively. Biopolymers determined using LC-OCD were effectively removed via the VF and HF stage wetlands, indicating the occurrence of biodegradation. Fluorescence excitation-emission matrix spectroscopy and LC-OCD provided the fate of dissolved organic matter characteristics in the hybrid VF-HF constructed wetland.

Organic loading rate (OLR) regulation for enhancement of aerobic sludge granulation: Role of key microorganism and their function

According to unique growth characteristics of various environmental microorganism specially with different substrates and their levels, aerobic sludge granulation are studied under different operation mode of influent organic loading rate (OLR), and the EPS component, sludge surface characters and functional microbes are analyzed to achieve a novel process for stable sludge granulation. Results showed that activated sludge cultivated under gradient influent OLR decreasing from 5.5 to 3.5 kgCOD m−3 d−1 achieved complete granulation with average size of 438 μm and exopolysaccharide (PS) to protein (PN) ratio over 2.0. Meanwhile, these granules had excellent flocculability and hydrophobicity with Zeta potential and contact angle of −15 mV and 110°, respectively. Principal component analysis (PCA) illustrated that microbes with function of EPS secretion enriched with decreased OLR regulation for their suitable specific growth characteristics, then promoted other microbes aggregation and sludge granulation along with the improvement of cellular surface characters and microbial niche.

Pilot-scale multi-level biological contact oxidation system on the treatment of high concentration poultry manure wastewater

Abstract A pilot-scale (5 m3/d) study was applied for the treatment of a high-strength poultry manure wastewater by using a multi-level biological contact oxidation tanks system with novel carriers. Firstly, four kinds of carriers including porous block carriers, sponge globoid carriers, fiber ball carriers, and suspend plastic carriers were compared at lab-scale experiment to choose the best performed carriers for the further application in pilot scale experiment. Then, the performance of the pollutants elimination during the whole pilot-scale reactor as well as the contribution efficiency of each tank under different influent pollutants loads were investigated. Finally, the biomass evaluation on the carriers and the mechanism of nitrogen removal were also explored. The conclusion showed that the effluent quality could satisfy the discharge standard of pollutants for livestock and poultry breeding industry (GB 18596-2001) when the influent organic load was less than 3.64 kg CODcr/(m3 d) during the pilot-scale system placed with the porous block carriers. The contact oxidation tank I dominated the average contribution efficiency of CODcr (89.2%), ammonia (69.6%), and the total nitrogen (57.3%) during the three-level biological contact oxidation tanks. The step-feed operational model was suggested to further increase the pollutants removal capacity of the following Tank II and Tank III. The oxygen-deficient environment of the biofilm and the proper three-dimensional spiral structure of the carriers were suitable for the happening of the simultaneous nitrification and denitrification occurred in the pilot-scale aerobic reactor.

Does influent surface organic loading and aeration mode affect nitrogen removal and N2O emission in subsurface wastewater infiltration systems?

This study evaluated the influence of influent surface organic loading (SOL) and aeration mode on nitrogen removal and N2O emission in subsurface wastewater infiltration systems (SWISs). Aeration developed appropriate oxygen conditions, which resulted in high COD, NH4+-N and TN removal and enhanced the abundances of amoA, nxrA, napA, narG, nirS, nirK, qnorB and nosZ under SOL rate of 21.2 and 33.8 g COD/(m2 d) compared to the non-aerated SWIS. N2O emission decreased with influent SOL rate increasing in non-aerated and aerated SWISs. The SWIS with intermittent aeration had a better performance on TN removal and lower N2O emission compared to the SWIS with continuous aeration under the same SOL rate. It could conclude that intermittent aeration is a feasible method to win high influent SOL rate, high TN removal and low N2O emission for SWISs.

Enhancement of Organic Matter Removal in an Integrated Biofilm-Membrane Bioreactor Treating High-Salinity Wastewater.

High salinity can strongly inhibit microbial activity and decrease the sedimentation ability of activated sludge. The combination of biofilm and membrane bioreactor is a practical approach towards effective removal of pollutants and low fouling rate. An integrated biofilm-membrane bioreactor (BMBR) treating mustard tuber wastewater was investigated. An average COD removal efficiency of 94.81% and ammonium removal efficiency of 96.84% were achieved at an organic load of 0.5 kg COD/(m3·d). However, the reactor showed a relatively low efficiency in total nitrogen and soluble phosphorus removal due to the lack of anaerobic environment. The increase of influent organic load resulted in a performance degradation because a balance between the degradation ability and pollution has been reached. Images of scanning electron microscopy revealed that halophilic bacteria were the dominant microbe in the system that leads to a loose sludge structure and declined settling properties. It was found that membrane fouling was the consequence of the interaction of microbial activities and NaCl crystallization.

Bacterial community analysis in upflow multilayer anaerobic reactor treating high-solids organic wastes.

A novel anaerobic digestion configuration, the upflow multi‐layer anaerobic reactor (UMAR), was developed to treat high‐solids organic wastes. The UMAR was hypothesized to form multi‐layer along depth due to the upflow plug flow; use of a recirculation system and a rotating distributor and baffles aimed to assist treating high‐solids influent. The chemical oxygen demand (COD) removal efficiency and methane (CH4) production rate were 89% and 2.10 L CH4/L/d, respectively, at the peak influent COD concentration (110.4 g/L) and organic loading rate (7.5 g COD/L/d). The 454 pyrosequencing results clearly indicated heterogeneous distribution of bacterial communities at different vertical locations (upper, middle, and bottom) of the UMAR. Firmicutes was the dominant (>70%) phylum at the middle and bottom parts, while Deltaproteobacteria and Chloroflexi were only found in the upper part. Potential functions of the bacteria were discussed to speculate on their roles in the anaerobic performance of the UMAR system. © 2017 The Authors Biotechnology Progress published by Wiley Periodicals, Inc. on behalf of American Institute of Chemical Engineers Biotechnol. Prog., 33:1226–1234, 2017

Quantitative characterization of organic diffusion using an analytical diffusion-reaction model and its application to assessing BOD removal when treating municipal wastewater in a plug flow reactor

The present study aimed to derive an analytical formula to quantify the diffusion of organic contaminant in a biofilm. The experiments were conducted to investigate the BOD degradation under the conditions of influent COD concentration from 50 to 300 mg/L, COD:N:P ratios of 100:5:1 and 100:15:3, with and without auxiliary aeration. The BOD removal rate was around 73% for non-aerated influent COD of 50 mg/L with 1-h hydraulic retention time. The BOD removal rate increased as the influent loading and hydraulic retention time increased while the influent COD was no more than 150 mg/L. Without aeration, the removal rate dropped significantly when influent COD increased to the range no less than 200 mg/L, due to the fact that the BOD diffusive flux driven by the biomass uptake was not further enhanced by higher ambient organic loading. The diffusion coefficient was calculated to be 1.12 × 10−6 m2/d with influent COD of 50 mg/L at COD:N:P ratio of 100:5:1 and 1 h hydraulic retention time and aeration, and the coefficient increased to 3.35 × 10−6 m2/d as the influent COD concentration increased to 300 mg/L. The diffusion coefficient decreased to 4.09 × 10−7 m2/d as the retention time increased to 3 h. The overall diffusion coefficients showed an increasing trend as the influent organic loading increased. The difference in diffusion coefficients between 1 and 2 h was apparently greater than that between 2 and 3 h, indicating a smaller overall diffusive flux due to a longer retention time. Further analysis revealed that BOD diffusion activity exhibited a declining trend as the wastewater travelled through the system. An analytical diffusion-reaction model was developed to characterize the diffusion behaviour, and applied to estimating the treatment efficiency for real domestic sewage. The result showed that the estimated effluent BOD concentrations were quite comparable to those from experimental measurements.

Treatment of synthetic tannery wastewater in a continuous two-phase partitioning bioreactor: Biodegradation of the organic fraction and chromium separation

A continuous two-phase partitioning bioreactor has been tested for treating a synthetic leather tannery wastewater with the objective of achieving effective removal of the organic load and complete chromium separation. The bioreactor was operated with 5.5 m of Hytrel 8206 polymeric tubing fed with a synthetic tannery wastewater consisting of 4-chlorophenol (concentration in the range of 1000–2500 mg L−1) and potassium dichromate (100 mg L−1 as Cr (VI)), and immersed in a 4 L bioreactor containing the microbial culture acclimatized to the compound. This configuration prevents the direct contact between the toxic wastewater and the microorganisms themselves, and provides the gradual organic substrate delivery through the tubing walls. Abiotic partition and mass transfer tests were performed to investigate the transport of dichromate and 4-chlorophenol across the tubing into the bulk phase of the bioreactor. No appreciable mass transfer of dichromate was detected. During biotic testing, the influent organic load in tubing has been varied in the range of 19–94 mg h−1 and the hydraulic retention time from 3 to 6 h. Achieved biological removal efficiencies were in the range of 89–95% for the highest applied loads. Process kinetics (which included consideration of both mass transfer and biological rates) were evaluated, and it was found that the increased load did not result in any decrease in 4-chlorophenol removal rate. This work has shown that the continuous two-phase partitioning bioreactor has significant potential in enhancing the biological treatment of tannery wastewater, which is a typical representative of industrial “hostile” wastewater.

Influence of operational conditions on the stability of aerobic granules from the perspective of quorum sensing

Integrated aerobic granules were first cultivated in two sequencing batch reactors (SBRs) (A1 and A2). Then, A1's influent organic loading rate (OLR) was changed from alternating to constant (cycling time was still 6h), while A2's cycling time varied from 6 to 4h (influent OLR strategy remained alternating). After 30-day operation since the manipulative alternations, granule breakage happened in two reactors at different operational stages, along with the decrease of granule intensity. Granule diameter in A1 declined from the original 0.84 to 0.32cm during the whole operation, while granules in A2 dwindled to 0.31cm on day 22 with similar size to A1. Both the amount of total extracellular polymeric substances (EPSs) and the protein were declining throughout the operation, and the large molecular weight of protein was considered closely related to the stability of aerobic granules. The relative AI-2 level decreased at the same time, and influent OLR strategy might had more evident impact on quorum sensing (QS) ability of sludge compared with starvation period. Combined with microbial results, the decline of total EPS amount in two reactors could be concluded as follows: During the reactor operation, some functional bacteria gradually lost their dominance and were eliminated from the reactors, which finally caused granule disintegration. In summary, the results further confirmed that alternating OLR and proper starvation period were two major factors in effective cultivation and stability of aerobic granules from the perspective of QS.

Quantitative impact of influent characteristics on nitrogen removal via anammox and denitrification in a landfill bioreactor case

In this paper, Quantitative Polymerase Chain Reaction (qPCR), Illumina MiSeq sequencing and 15N stable isotopic tracing methods were applied to study the effects of influent organic loading, BOD5/TN and NO2-N/NH4-N ratios on the combined nitrogen removal through denitrification and anammox. The results show that, the total nitrogen removal was above 90% at the optimum reaction condition: organic loading 0.04kg/m3·day, BOD5/TN 0.2, and NO2-N/NH4-N 1.0. Approximately 9.43% of the nitrogen removal occurred through anammox process when BOD5/TN was 0.1, and increased to 21.46% when BOD5/TN was 0.2. The anammox accounted for 10% when NO2-N/NH4-N was 0.5, and that increased to 20.72% when NO2-N/NH4-N was 1.0–1.5. hzsA was directly proportional to the influent BOD5/TN. A positive correlation between BOD5/TN and anammox microorganisms existed. Similarly, there was a positive correlation between NO2-N/NH4-N and denitrification microorganisms. Therefore, it is feasible to regulate the influent to improve nitrogen removal efficiency.

Effects of influent organic loading rates and electrode locations on the electrogenesis capacity of constructed wetland‐microbial fuel cell systems

Three novel constructed wetland‐microbial fuel cells (CW‐MFCs), based on electrode location, were developed for wastewater treatment and sustainable electricity production by embedding a MFC into a CW system. In the three CW‐MFCs, electrodes were placed in different locations, including bottom anode‐rhizosphere cathode CW‐MFC (BA‐RC‐CW‐MFC), rhizosphere anode‐air cathode CW‐MFC (RA‐AC‐CW‐MFC), and bottom anode‐air cathode CW‐MFC (BA‐AC‐CW‐MFC), to investigate the combined effects of organic loading rates (OLRs) and reactor configurations on the electrogenesis capacity of the hybrid system. All the systems operated continuously to treat five types of synthetic wastewater with increasing OLRs: 9.2, 18.4, 27.6, 55.2, and 92.0 g chemical oxygen demand (COD) m−2 d−1. The BA‐RC‐CW‐MFC failed to produce electricity at any OLR, whereas the maximum power densities of 0.79 ± 0.01 and 10.77 ± 0.52 mW m−2 were achieved in the RA‐AC‐CW‐MFC with 18.4 g COD m−2 d−1 influent OLR and in the BA‐AC‐CW‐MFC with 27.6 g COD m−2 d−1 influent OLR, respectively. The coulombic efficiencies of the RA‐AC‐CW‐MFC and BA‐AC‐CW‐MFC decreased gradually with the increase in influent OLRs. © 2016 American Institute of Chemical Engineers Environ Prog, 36: 435–441, 2017

Operation Performance of a Bioaugmented Membrane-aerated Biofilm Reactor Treating Atrazine Wastewater

A hydrophobic SPG (shirasu porous glass) membrane-aerated biofilm reactor (MABR) with genetically engineered microorganism (GEM) biofilm formed on the SPG membrane surface was applied to treat atrazine wastewater. The contaminant removal performance and its influencing factors were investigated during the stable operation of this MABR. The results indicated that the oxygen supply capacity could be increased in the SPG membrane aeration when the membrane pore size and the aeration pressure increased, which could improve the performance of COD and atrazine removals. The maximum oxygen supply capacity of hydrophobic SPG membrane with pore size of 1.5 μm was estimated to be about 22.4 g·(m2·d)-1 at aeration pressure of 70 kPa. When aeration pressure was 70 kPa and hydraulic retention time (HRT) was 1.5 h, the average COD removal efficiency was 80.1% and the average organic loading rate removed was 1.86 kg·(m3·d)-1in the MABR with 1.5 μm hydrophobic SPG membrane. Under the same operating conditions, the average atrazine removal efficiency was 62.5% and the average atrazine loading rate removed was 0.18 kg·(m3·d)-1. The COD and atrazine removal efficiencies decreased significantly at further shortened HRT and increased influent organic loading rate. DO concentration showed more significant influence on atrazine removal. The simplex genetically engineered microorganism biofilm turned into complex microbial community gradually during MABR operation, but the GEM cells could still reside in the biofilm well. Therefore, the efficient atrazine removal by GEM bioaugmentation could be maintained.