Anaerobic Baffled Reactor Research Articles

Process Control and Operation Optimization of PN-SAD Coupling Process Based on SBR-ABR

This study uses three different operating phases for a sequencing batch reactor (SBR) combined with an anaerobic baffled reactor (ABR) to determine the effect of deep nitrogen and carbon removal by the "partial nitrification-anaerobic ammonium oxidation combined denitrification" (termed PN-SAD) reaction. The effluent of the SBR (NO2--N/NH4+-N ratio range of 1-1.32) was accessed directly to the single compartment ABR anammox system in phase Ⅰ. The results showed that although the anammox reaction was stable, the combined process total nitrogen (TN) removal efficiency was<80%, and the TN concentration of effluent was~20 mg·L-1. In order to increase the denitrification function in the ABR, denitrifying sludge was added to the third compartment of the ABR in phase Ⅱ. We found that the TN removal efficiency of the coupling reaction was still low. An organic carbon source should be supplied in the latter stage of anammox if deep nitrogen removal is required. Therefore, in phase Ⅲ, the effluent of the SBR (NO2--N/NH4+-N ratio of ~5) was mixed with the partial raw water (mixed water NO2--N/NH4+-N ratio of ~1.4; C/N ratio of 2.5). The mixed water was connected to the single compartment of the ABR. The PN-SAD system not only achieved a good matrix ratio at the anammox stage, but also provided a good carbon source for denitrification. The chemical oxygen demand (COD) concentration of the effluent in the whole process was 50 mg·L-1, the TN concentration of the effluent was<6 mg·L-1, and the TN removal efficiency was 95%. We conclude that the stable operation of the combined PN-SAD reaction provides the basis for deep nitrogen and carbon removal using the combined SBR-ABR process.

Full-scale study of pollutants removal in printing and dyeing wastewater based on anaerobic baffled reactor–A/O coupling process and microbial community analysis

Full-scale study of pollutants removal in printing and dyeing wastewater based on anaerobic baffled reactor–A/O coupling process and microbial community analysis

Advanced treatment of polysilicon production wastewater using the combination of coagulation, expanded granular sludge bed, anaerobic baffled reactor and biological contact oxidation processes

Advanced treatment of polysilicon production wastewater using the combination of coagulation, expanded granular sludge bed, anaerobic baffled reactor and biological contact oxidation processes

Treatment of landfill leachate using modified anaerobic baffled reactor

Landfill leachate is a highly concentrated organic wastewater with complex compositions. It is a major source of pollution potentially threatening the quality of groundwater, surface water, and life forms. The treatment of landfill leachate consists of various combination processes such as biological, chemical and physical methods. In this study, raw leachate was subjected to an anaerobic treatment using a modified anaerobic baffled reactor (MABR). Initially, the start-up of the MABR system was accomplished using meat extract as synthetic feed. The start-up of the reactor was carried out by maintaining a low chemical oxygen demand (COD) of 350 mg/L at an organic loading rate (OLR) of 0.0875 kg COD/m3/d. Once the reactor attained 99% COD removal, real wastewater (landfill leachate) was gradually fed into the MABR. The OLR was increased to 0.175, 0.375, 0.75 and 1.40 kg COD/ m3/d, respectively. The process performance of the reactor was evaluated in terms of pH, COD, color, volatile acid (VA), biogas production and heavy metal removal. Results showed that an average COD removal efficiency of 79.3% was observed when the OLR was 1.4 kg COD/m3/d. The VA concentration showed a stable profile with a very little value (38.9 mg/L of HOAc) in the effluent of the reactor for all the OLR studied. The color removal was 32%, 46%, 45.1% and 78.2% when the OLR was increased to 0.175, 0.375, 0.75 and 1.40 kg COD/m3/d, respectively. As, Cr and Fe removal was 87.5%, 88.8%, and 87.8%, respectively, when the reactor was operated at an OLR of 1.4 kg COD/m3/d. The heavy metals removal efficiency provides further evidence that heavy metals can be degraded in anaerobic environments.

Anaerobic baffled reactor to treat fishmeal wastewater with high organic content

Abstract This study focuses on the potential of anaerobic baffled reactor (ABR) for treating the fishmeal wastewater. This wastewater has a high organic content (140 g COD ⋅ L−1), which consists of 60% (w/w) oil and grease (O&G), 27% (w/w) protein, and 13% (w/w) mixture of suspended solids and soluble organic. The ABR reactor volume was 60 L. The ABR was operated with a hydraulic retention time of 20 days. During the operation period, the reactor achieved high performance with the average total and soluble COD removal of approximately 98% and 94%, respectively. The design of ABR compartmentalization advanced this high organic removal performance. There was also the symbiotic activity of specific microbial communities such as Syntrophobacter sulfatireducens and Methanosaeta observed in the reactor’s column which contributes to the high organic degradation process of ABR. Overall, this study demonstrated that the application of ABR could be used to treat fishmeal wastewater

Development of a molasses wastewater treatment system equipped with a biological desulfurization process.

In this study, a laboratory scale experiment for the treatment of synthetic molasses wastewater using a combination of an anaerobic baffled reactor (ABR) and a two-stage down-flow hanging sponge (TSDHS) reactor (ABR-TSDHS system) was conducted. The TSDHS comprised a closed-type first-stage down-flow hanging sponge (first DHS) for desulfurization and an open-type second-stage DHS (second DHS) for post-treatment of effluent from the ABR and first DHS. Effluent from the second DHS was sprinkled on top of the first DHS, whereas biogas produced from the ABR was supplied to its bottom. A chemical oxygen demand (COD) removal efficiency of 88.3% was found for the ABR-TSDHS system during the final treatment phase. The ABR achieved a maximum organic loading rate (OLR) of 3.70 kg COD/(m3 day). Most of the organic matter was degraded in the first compartment of the ABR, with methane-producing archaea as its main consumer. The biogas generated by the ABR contained high concentrations of hydrogen sulfide (up to 4,500 ppm). In the TSDHS, the first DHS achieved 87.3% hydrogen sulfide removal via dissolution into sprinkled effluent water. Dissolved sulfide in the first DHS effluent was oxidized to sulfate in the second DHS in the absence of aeration. In addition, 85.0% of the ammonia and 57.7% of the total nitrogen were removed in the second DHS via biological reactions, including sulfur-based autotrophic denitrification. Therefore, the ABR-TSDHS system can be applied to not only molasses wastewater treatment but also the desulfurization of the produced biogas.

Characterization of the start-up of single and two-stage Anammox processes with real low-strength wastewater treatment.

In order to promote the application of anaerobic ammonium oxidation (Anammox) for municipal wastewater treatment, single and two-stage Anammox processes were started up for real low-strength wastewater treatment under similar conditions for the comparison. Results showed that the anaerobic baffled reactor (ABR)-Nitritation-Anammox and the ABR-Completely Autotrophic Nitrogen removal Over Nitrite (CANON) process took 75 days and 101 days to start up with a total nitrogen removal rate of 86-92% and 81-87% under steady state, respectively. The 16S rRNA sequencing analysis revealed that the phylum of Proteobacteria dominated in CANON system and Anammox system with the relative abundance of 35.39% and 15.27%, respectively. Phylogenetic analysis showed that Anammox species, related to Ca. Brocadia Sinica JPN1 and Ca. Kuenenia stuttgartiensis, dominated in these two systems, respectively. The nitrogen removal performance of two-stage process was 5% higher than that of single stage process, while the start-up period and dominated Anammox species were different.

Configuration and rapid start-up of a novel combined microbial electrolytic process treating fecal sewage

Most of the developing countries are in need of sanitary toilets due to insufficient supporting facilities and proven technology mainly on disposal of fecal sewage. A microbial fuel cell (MFC)-microbial electrolytic cell (MEC) coupling with an anaerobic baffle reactor (ABR) was used to realize simultaneous removal of nitrogen and carbon in fecal sewage and complete energy recycling. Configuration and rapid start-up of the ABR-MFC-MEC process treating fecal sewage was systematically studied. Results showed that the application of an external voltage of 0.5 V can shorten the start-up time and improve hydrogen production rate to 3.42 × 10−3 m3-H2/m3/d in the MEC unit, where the double-chamber MFC can drive MEC completing the synchronous coupling start-up. In the single and double chamber systems, bio-electrochemical processes both enhanced shock resistance capacity of the whole ABR-MFC-MEC process during coupled operation, with chemical oxygen demand (COD) removal rates of 99.2% and 98.9% for the single and double chamber systems respectively. Based on results of biological analysis, the coupled system has a distinct selective effect on microbial population and each unit has high microbial diversity to enhance the stability and resistance of the whole system for treatment of feces and urine.

A simplistic approach of algal biofuels production from wastewater using a Hybrid Anaerobic Baffled Reactor and Photobioreactor (HABR-PBR) System.

The current technologies of algal biofuels production and wastewater treatment (e.g., aerobic) process are still in question, due to the significant amount of fresh water and nutrients requirements for microalgae cultivation, and negative energy balance in both processes, especially when considered in the context of developing counties around the world. In this research, a simplistic sustainable approach of algal biofuels production from wastewater was proposed using a Hybrid Anaerobic Baffled Reactor (HABR) and Photobioreactor (PBR) system. The study suggests that the HABR was capable of removing most of the organic and solid (>90% COD and TSS removal) from wastewater, and produced a healthy feedstock (high N: P = 3:1) for microalgae cultivation in PBRs for biofuels production. A co-culture of Chlorella vulgaris, Chlorella sorokiniana, and Scenedesmus simris002 showed high lipid content up to 44.1%; and the dominant FAMEs composition (C16-C18) of 87.9% in produced biofuels. Perhaps, this proposed low-cost technological approach (e.g., HABR-PBR system) would connect the currently broken link of sustainable bioenergy generation and wastewater treatment pathway for developing countries.

Evaluation of recycled paper mill effluent digestion in a modified anaerobic hybrid baffled (MAHB) reactor: reactor performance & kinetic studies

Recycled paper mill effluent (RPME) consists of various organic and inorganic compounds. In this study, modified anaerobic hybrid baffled (MAHB) bioreactor has been successfully used to anaerobically digest RPME. The anaerobic digestion was investigated in relation to methane production rate, lignin removal, and chemical oxygen demand (COD) removal, with respect to organic loading rate (OLR) and hydraulic retention time (HRT). The analysis using kinetic study was carried out under mesophilic conditions (37 ± 2 °C) and influent COD concentrations (1000–4000 mg L−1), to prove its practicability towards RPME treatment. First-order kinetic model was used to clarify the behavior of RPME anaerobic digestion under different OLRs (0.14–4.00 g COD L−1 d−1) and HRT (1–7 d). The result shows that the highest COD removal efficiency and methane production rate were recorded to be 98.07% and 2.2223 L CH4 d−1, respectively. This result was further validated by evaluating the biokinetic coefficients (reaction rate constant (k) and maximum biogas production (ym)), which gave values of k = 0.57 d−1 and ym = 0.331 L d−1. This kinetic data concludes that MAHB presented satisfactory performance towards COD removal with relatively high methane production, which can be further utilized as on-site energy supply.

Anaerobic digestion of sludge filtrate using anaerobic baffled reactor assisted by symbionts of short chain fatty acid-oxidation syntrophs and exoelectrogens: Pilot-scale verification

The growing amount of sewage sludge from wastewater treatment plant is an emerging challenge in China. The efficient anaerobic digestion of sludge filtrate generated from hydrothermally pretreated sewage sludge can promote the disposal of sewage sludge. Herein, a pilot-scale anaerobic baffled reactor (ABR) assisted by symbionts of short chain fatty acid-oxidation syntrophs (SFAS) and exoelectrogens was developed to improve its stability and efficiency for filtrate treatment. The results demonstrated that the symbionts of exoelectrogens and SFAS, which were enriched by introduction of electrodes in the ABR system, promoted the degradation of butyric, propionic and acetic acids. Therefore, the COD removal efficiency increased from 74.1% to 86.6% and the methane content increased from 81.5% to 92.2% with methane production rising from 241 to 282 mL/g CODremoved. Furthermore, the economic evaluation indicated that the energy consumption of electrodes was 0.600 kWh/m3 of sludge filtrate, the net energy profited from increased methane was 2.344 kWh/m3 of sludge filtrate. These results confirmed that the ABR system assisted by symbionts of SFAS and exoelectrogens was feasible for treatment of sludge filtrate in terms of both technical and economic level through pilot-scale verification.

Continuous Bioethanol Production Using Uncontrolled Process in a Laboratory Scale of Integrated Aerobic–Anaerobic Baffled Reactor

The expensiveness of bioethanol has made it unattractive and uncompetitive for alternative energy sources. Therefore, several ways to reduce the production cost of bioethanol become interesting topics, e.g. increasing its productivity. This research investigated the performance sensitivity of a laboratory scale of integrated aerobic–anaerobic baffled reactor (IAABR) towards the residence time. The ethanol productivity was monitored to know the optimum residence time. The difference residence times were varied between at 19.2 h and 26.7 h by using difference volume of fermenters i.e. 10 and 100 l, respectively. Molasses as a medium was fed into a reactor containing one compartment of aerobic fermentation and three compartments of anaerobic fermentation. Total sugar and bioethanol concentration were measured for each compartment to determine the production yield to sugar consumption and bioethanol productivity. The fermentation process was conducted at 30 °C, medium pH (4-5), and feed sugar concentration of 170 g/l. The results showed that the optimum residence time in this investigation range is 19.2 h. The ethanol productivity was recorded at 4.63 g/l.h and the production yield to sugar was obtained at 46 % (equivalent to 86 % of theoretical yield) with average feeding of molasses at 0.52 l/h.

Evaluation of key factors for residual rubber coagulation in natural rubber processing wastewater

Key factors for residual rubber coagulation in natural rubber (NR) processing wastewater were evaluated via a laboratory-scale system comprising an anaerobic baffled reactor (ABR) and a downflow hanging sponge (DHS) reactor (ABR–DHS system). Hydraulic retention time (HRT), seeding of the core rubber, and existence of air are selected as key factors for rubber coagulation. In the ABR, longer HRT and seeding of the core rubber was not affected for rubber coagulation. Only biodegradable substances were consumed in the ABR. On the other hand, the DHS reactor achieved high removal efficiency of residual rubber by both coagulation and biological degradation. In addition, seeding of the core rubber to the DHS reactor enhanced rubber coagulation. The genera Gordonia, known as a rubber-degrading bacteria, were detected from the retained sludge in the DHS reactor. Therefore, the wastewater–air and wastewater–core rubber contacts are considered as key factors for residual rubber coagulation in the NR wastewater treatment. Furthermore, biodegraded residual rubber was considered as carbon source for denitrification in the DHS reactor.

Start-up and Stable Operation of CANON Coupled with Denitrifying Phosphorus Removal

A process coupled completely autotrophic nitrogen removal over nitrite (CANON)with denitrifying phosphorus removal in a modified anaerobic baffled reactor (ABR) coupled with a membrane bioreactor (MBR), inoculated with ordinary activated sludge, was proposed for treating artificial wastewater with ammonia 200 mg·L-1 and COD/TN=1. This experiment studied the start-up of the process and its nitrogen and phosphorus removal efficiency by controlling the recycle ratio and increasing it from 50% to 200% step by step, with a temperature of (25±1)℃ and pH of 7.5±0.2. The results showed that the anaerobic part in the ABR consumed 70% COD, and resulted in a quick start-up of partial-nitrification at 21 d under low DO and high ammonia nitrogen. Then, by controlling the intermittent aeration (exposure stop ratio:2 h:2 h, DO 0.3-0.4 mg·L-1), the start-up of the CANON part in the coupling process was successfully achieved at 132 d, such that the concentration of nitrates in the electron acceptor of the ABR anoxic section increased steadily, and finally the coupling process started successfully at 160 d. With stable operation, the TN removal load in the MBR reached 0.22 kg·(m3·d)-1, and the average removal efficiency of COD, TN, and PO43--P was 87.0%, 90.4%, and 81.8%, respectively. The batch experiment estimated that the denitrifying phosphate accumulating organisms (DPAOs) using nitrates as electron acceptors in the ABR accounted for 68% of the phosphate accumulating organisms (PAOs). The DPAOs, ammonia-oxidizing bacteria (AOB), and anaerobic ammonium oxidizing bacteria (AnAOB) have been developed in the system and have good simultaneous nitrogen and phosphorus removal efficiency.

The addition of lamella in anaerobic baffled reactor used for decentralized municipal wastewater treatment

An anaerobic baffled reactor (ABR) represents a low-cost system for decentralized wastewater treatment in a developing country. Despite the advantages of ABR units such as low operating and maintenance costs, this system requires sufficient land to construct it. In particular of an urban area, land availability is limited and therefore acquire modification in ABR design. This study aimed to test the addition of lamella for further reduction of solids particle in domestic wastewater, and therefore it could reduce the size of ABR settler. A lab-scale of an ABR lamella with a dimension of 75 cm length, 20 cm width, and 40 cm height used in the experiment. A 20 L/d of raw municipal wastewater taken from the existing ABR in Kampong Bareng, Malang (Indonesia) used to feed the lab-scale of the ABR lamella. The experiment was conducted in two months and the sample of raw and treated wastewater collected from the ABR lamella for ten times from September to October 2018. The samples were taken from the inlet, lamella compartment, and the outlet. The results showed that the addition of lamella reduced the concentration of TSS and BOD for 95% and 90% respectively. While these results could help further reduction of organic and solids particle of wastewater that meet the treated wastewater regulation. The concentration of TSS and BOD as treated wastewater were 19 mg/L and 18 mg/L respectively. Although the ABR could reduce the nutrient concentration, the level still higher than the global standard for N and P.

DISCRIMINATION OF TOMATO PLANTS (SOLANUM LYCOPERSICUM) GROWN UNDER ANAEROBIC BAFFLED REACTOR EFFLUENT, NITRIFIED URINE CONCENTRATE AND COMMERCIAL HYDROPONIC FERTILIZER REGIMES USING MULTI-SOURCE SATELLITE

Abstract. We evaluate the detection and discriminative strength of three different satellite spectral settings, namely, HyspIRI, the forthcoming Landsat 9 and Sentinel 2-MSI, in mapping tomato (Solanum lycopersicum) plants grown under hydroponic system using humanexcreta derived materials (HEDM), namely, anaerobic baffled reactor (ABR) effluent and nitrified urine concentrate (NUC) and commercial hydroponic fertilizer mix (CHFM) as nutrient sources. Partial least squares – discriminant analysis (PLS-DA) and discriminant analysis (DA) were applied to discriminate tomatoes grown under these different nutrient sources. Results of this study showed that spectral settings of HyspIRI sensor can better discriminate tomatoes grown under different fertilizer regimes when compared to Landsat 9 OLI and Sentinel-2 MSI spectral configurations. For instance, based on DA algorithm, HyspIRI exhibited high overall accuracy of 0.99 and a kappa statistic of 0.99 whereas Landsat OLI and Sentinel-2 MSI exhibited over accuracies of 0.94 and 0.95 as well as kappa statistics of 0.79 and 0.85, respectively. Further, the performance of DA was significantly different (α = 0.05) from that of PLS-DA based on the MaNemar tests. Overall, the performance of HyspIRI, Landsat 9 OLI-2 and Sentinel-2 MSI data seem to bring new opportunities for crop monitoring at farm scale.

Performance evaluation of fixed bed anaerobic baffled reactor and its upgrading by integrated electrocoagulation process for municipal wastewater treatment

Anaerobic baffled reactor is efficient for wastewater treatment, while it lacks efficient nutrient removal and must be upgraded. The present study aimed to evaluate performance of fixed-bed media anaerobic baffled reactor (FABR) for municipal wastewater treatment. The performance of the integrated electrocoagulation process in the FABR (E-FABR) was also investigated. The large bench-scale five of sectional FABR reactor was assessed continually to the hydraulic retention times (HRTs) of 40, 30, and 20 hours, respectively to meet the effluent disposal standards using the HDPE-2H media in the FABR. After determining the optimum HRT, EP was integrated in 4th section of the FABR to improve the performance. At the E-FABR, the steel-steel and aluminum electrode pair (Al-Al) was evaluated at the current densities of 0.05-0.5 mA/cm2 (HRT=20 hours). The performance of FABR decreased with reduced HRT from 40 to 30 and 20 hours. At the optimum HRT (30 hours), the reactor met the TSS, COD, and BOD effluent discharge standards. The mean steady-state removal of TSS, COD, BOD5, total nitrogen, and total phosphorus was 93±0.5%, 91±0.8%, 93.4±1%, 16±1%, and 28±0.7%, respectively. The E-FABR with the steel and aluminum electrodes at the current densities of 0.3 and 0.1 mA/cm2 and HRT of 20 hours decreased the TSS, COD, BOD, SO4, and TP concentrations to the effluent discharge standard limits. Therefore, the FABR is an efficient system for municipal wastewater treatment, and E-FABR with aluminum electrodes and extremely low current density could easily treat wastewater to the effluent discharge standards.

Evaluation of an anaerobic baffled reactor for pretreating black water: Potential application in rural China

Black water is highly concentrated human waste water but represents only a minor portion of domestic sewage. A modified type of anaerobic baffled reactor (ABR) was studied to assess its potential for pretreating black water in rural China. The classification of microbial structure was also investigated to confirm its potential in application. The structure of the ABR was modified according to demand for application in practice. A hydraulic retention time (HRT) of 48 h was chosen as the optimal HRT after comparison among 24 h, 36 h, 48 h, and 72 h. Under the 48 h HRT, the ABR achieved average removal efficiencies of 94.05% of chemical oxygen demand (COD), 28.78% of total nitrogen (TN), 14.21% of ammonium nitrogen (NH4+-), and 32.54% of total phosphorus (TP) during 112 days of continuous operation. Samples from three different compartments were collected after 60-day continuous operation for bacterial and archaeal community investigation by 16S rRNA. Abundant degradation-related bacteria and methanogenic archaea were found in the ABR. The three samples had similar bacterial compositions at phylum, class, and genus levels, but the percentages of bacteria differed among the compartments. The distribution of archaea showed succession with the flow direction. In general, the ABR shows good performance under an HRT of 48 h and shows good potential for practical application.

Regulating acidogenesis and methanogenesis for the separated bio-generation of hydrogen and methane from saline-to-hypersaline industrial wastewater

Given the limitations of acidogens and methanogens activities under saline environments, this work aims to optimize the main operational parameters affecting hydrogen and methane production from saline-to-hypersaline wastewater containing mono-ethylene glycol (MEG). MEG is the main contaminant in several saline industrial effluents. Anaerobic baffled reactor (ABR), as a multi-stage system, was used at different temperatures (i.e., 19–31 °C [ambient] and 35 °C), organic loading rates (OLRs) of 0.6–2.2 gCOD/L/d, and salinity of 5–35 gNaCl/L. Mesophilic conditions of 35 °C substantially promoted MEG biodegradability (92–98%) and hydrogen/methane productivity, even at elevated salinity. Hydrogen yield (HY) and methane yield (MY) peaked to 258 and 140 mL/gCODadd, respectively, at OLR 0.64 gCOD/L/d and salinity up to 20–25 gNaCl/L. An immobilized sludge ABR (ISABR), packed with polyurethane media, was further compared with classical ABR, resulting in 1.8-fold higher MY, at 35 gNaCl/L. Microbial analysis showed that introducing attached growth system (ISABR) substantially promoted methanogens abundance, which was dominated by genus Methanosarcina. Among bacterial genera, Acetobacterium was dominant, particularly in 1st compartment, representing MEG-degrading/salt-tolerant genus. At high salinity up to 35 gNaCl/L, the multi-phase and attached growth configuration can efficiently reduce the induced salt stress, particularly on methanogens, towards balanced and separated acidogenesis/methanogenesis. Overall, producing hydrogen and methane from anaerobic treatment of MEG-based saline wastewater is feasible at optimized parameters and configuration.

Anaerobic digestion of sludge filtrate assisted by symbionts of short chain fatty acid-oxidation syntrophs and exoelectrogens: Process performance, methane yield and microbial community

Sludge filtrate is a kind of special organic wastewater generated from hydrothermally pretreated sewage sludge. The efficient treatment of sludge filtrate can promote the development of sludge recycling technology. Herein, the anaerobic baffled reactor (ABR) assisted by symbionts of short chain fatty acid-oxidation syntrophs (SFAS) and exoelectrogens was applied to treat the sludge filtrate. The influence of fermentation temperature and promotion of methanogenesis via symbionts were focused. The results showed that the COD removal efficiency and methane yield of the ABR system assisted by symbionts at 35 °C (R3) were 11.7% and 11.0% higher than the one at 55 °C (R2), respectively. And the COD removal efficiency and methane yield of the R2 system were 9.1% and 12.9% higher than the traditional ABR system at 55 °C (R1), respectively. Large abundances of exoelectrogens such as Thermincola and Geobacter were found in the R2 and R3 systems, respectively. Moreover, ample Syntrophobacter, Syntrophomonas and Methanobacterium were detected in both R2 and R3 systems. The present research revealed the importance of SFAS, exoelectrogens and hydrogenotrophic methanogens for the improvement of methanogenesis. Besides, the mesophilic condition is conducive to enhancing the methanogenesis rate of sludge filtrate.