Treatment Of Molasses Wastewater Research Articles

Statistical optimization of waste molasses-based exopolysaccharides and self-sustainable bioelectricity production for dual chamber microbial fuel cell by Bacillus piscis

BackgroundThe application of exopolysaccharide-producing bacteria (EPS) in dual chamber microbial fuel cells (DCMFC) is critical which can minimize the chemical oxygen demand (COD) of molasses with bioelectricity production. Hence, our study aimed to evaluate the EPS production by the novel strain Bacillus piscis by using molasses waste. Therefore, statistical modeling was used to optimize the EPS production. Its structure was characterized by UV, FTIR, NMR, and monosaccharides compositions. Eventually, to highlight B. piscis' adaptability in energy applications, bioelectricity production by this organism was studied in the BCMFC fed by an optimized molasses medium.ResultsB. piscis OK324045 characterized by 16S rRNA is a potent EPS-forming organism and yielded a 6.42-fold increase upon supplementation of molasses (5%), MgSO4 (0.05%), and inoculum size (4%). The novel exopolysaccharide produced by Bacillus sp. (EPS-BP5M) was confirmed by the structural analysis. The findings indicated that the MFC's maximum close circuit voltage (CCV) was 265 mV. The strain enhanced the performance of DCMFC achieving maximum power density (PD) of 31.98 mW m−2, COD removal rate of 90.91%, and color removal of 27.68%. Furthermore, cyclic voltammetry (CV) revealed that anodic biofilms may directly transfer electrons to anodes without the use of external redox mediators. Additionally, CV measurements made at various sweep scan rates to evaluate the kinetic studies showed that the electron charge transfer was irreversible. The SEM images showed the biofilm growth distributed over the electrode’s surface.ConclusionsThis study offers a novel B. piscis strain for EPS-BP5M production, COD removal, decolorization, and electricity generation of the optimized molasses medium in MFCs. The biosynthesis of EPS-BP5M by a Bacillus piscis strain and its electrochemical activity has never been documented before. The approach adopted will provide significant benefits to sugar industries by generating bioelectricity using molasses as fuel and providing a viable way to improve molasses wastewater treatment.

Biomethane production and microbial strategies corresponding to high organic loading treatment for molasses wastewater in an upflow anaerobic filter reactor.

Molasses wastewater contains high levels of organic compounds, cations, and anions, causing operational problems for anaerobic biological treatment. In this study, an upflow anaerobic filter (UAF) reactor was employed to establish a high organic loading treatment system for molasses wastewater and further investigated the microbial community dynamics in response to this stressful operation. The biogas production increased with an increase in total organic carbon (TOC) loading rate from 1.0 to 14g/L/day, and then it decreased with further TOC loading rate addition until 16g/L/day. The UAF reactor achieved a maximum biogas production of 6800mL/L/day with a TOC removal efficiency of 66.5% at a TOC loading rate of 14g/L/day. Further microbial analyses revealed that both the bacterial and archaeal communities developed multiple strategies to maintain stable operation of the reactor at high organic loading (e.g., Proteiniphilum and Defluviitoga maintained high abundances throughout the operation; Tissierella temporarily dominated the bacterial community at TOC loading rates of 8.0 to 14g/L/day; and multi-trophic Methanosarcina shifted as the dominant methanogen at the TOC loading rates of 8.0 to 16g/L/day). This study presents insights into a high organic loading molasses wastewater treatment system and the microbial flexibility in methane fermentation in response to process disturbances.

Application of Citeromyces siamensis for Molasses Wastewater Decolourization

Abstract Molasses, a brownish black viscous liquid, is a byproduct of the cane sugar process. It finds applications in various industries such as fertilizer production, animal husbandry, alcohol production, monosodium glutamate production, and the production of acetic acid. In Thailand, it is primarily used for alcohol production and as animal feed. However, molasses wastewater is characterized by high levels of biochemical and chemical oxygen demand, as well as suspended solids. Untreated release of this wastewater into the environment can lead to numerous environmental issues. Additionally, the presence of melanoidins in molasses wastewater makes its removal challenging, resulting in a dark colour of the treated water. Discharge of this dark-coloured water into natural water sources can lead to an abnormal discolouration of the water. This study aims to investigate the optimal conditions for utilizing Citeromyces siamensis microorganisms in the biological treatment of molasses wastewater. The experiment was conducted to determine the conditions that facilitate the reduction of colour in molasses wastewater. The findings indicate that the addition of 1 % glucose and 1 % peptone was more effective in decolourizing molasses wastewater using Citeromyces siamensis compared to other nutrient additions. While the addition of additives may incur additional costs, it remains a more economical option compared to the use of chemicals for wastewater colour removal. Furthermore, the use of the additives is considered safe for living organisms.

Statistical optimization of process conditions for pyrvinium pamoate elimination using UV/zeolite‐based nanostructures/H 2 O 2

Statistical optimization of process conditions for pyrvinium pamoate elimination using UV/zeolite‐based nanostructures/H ₂ O ₂

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.

Enhancement of lipid production and nutrient removal of Monoraphidium sp. FXY-10 by combined melatonin and molasses wastewater treatment

Abstract Molasses wastewater can be utilized for microalgae cultivation, and the harvested algal biomass is suitable for biofuel production. In this study, the effects of melatonin on the metabolism and activities of three key lipid biosynthetic enzymes of Monoraphidium sp. FXY-10 cultured in molasses wastewater were evaluated. The maximal biomass (1.21 g L−1) and lipid content (68.69%) were obtained during melatonin treatment and were approximately 1.42- and 1.15-fold, respectively, of the group not treated with melatonin. The carbohydrate and protein contents of melatonin-treated cells were also increased. MT treatment upregulated the activities of malic enzyme and acetyl-CoA carboxylase but downregulated phosphoenolpyruvate carboxylase activity, which was correlated with lipid accumulation in FXY-10. MT-treated samples showed greater potentials for removing organic carbon (92.33% chemical oxygen demand removal) and nutrients (90.07% nitrogen removal, 86.04% phosphorus removal) than the non-treated samples. Additionally, the economic feasibility of melatonin treatment demonstrated that a combined strategy is ideal for molasses wastewater treatment and biofuel production.

Investigating the synergy of integrated anaerobic digestion and photodegradation using hybrid photocatalyst for molasses wastewater treatment

Anaerobic digestion (AD) can remove the high organic load of molasses wastewater (MWW), but is ineffective in removing the characteristic dark brown colour caused by biorecalcitrant melanoidin. Ultraviolet (UV) photodegradation, can mineralise the biorecalcitrants leading to complete colour removal, but with a high-energy input and low organic load removal. This study investigated the plausibility of integrating the two processes for organic load and colour reductions. Desk scale AD and photodegradation processes were carried out in batch reactors. A hybrid photocatalyst consisting of titanium dioxide (TiO2) and zinc oxide (ZnO) was used for photocatalytic degradation. Biodegradation at thermophilic conditions in the bioreactor achieved high total organic carbon (TOC) and chemical oxygen demand (COD) reductions of 80 and 90%, respectively, but with an increased colour intensity. Contrastingly, UV photodegradation achieved a high colour reduction of 92% with an insignificant 6% TOC reduction, after 30 min of irradiation. During photodegradation, the mineralisation of the biorecalcitrant organic compounds led to the colour disappearance. The energy required for the TOC reduction was 40-fold higher than that required for the colour reduction in the same irradiation period, suggesting that the UV process was only suitable for colour reduction. Therefore, there is a possible synergy when the two processes are integrated, with AD preceding UV, where AD removes the high COD/TOC while UV removes the recalcitrant colour at a reduced cost.

Enhanced methane production through bioaugmentation of butyrate‐oxidizing hydrogen‐producing acetogens in anaerobic wastewater treatment

A feasible and readily available source of hydrogen‐producing acetogens (HPAs) was developed by obtaining microflora D83 dominated by butyrate‐oxidizing HPAs through enrichment and subculture of anaerobic sludge with the use of butyric acid. The effect of bioaugmentation of D83 both on methane production through glucose fermentation and molasses wastewater treatment was evaluated. At a bacterial number‐to‐activated sludge ratio of 1:9, inoculation of microflora D83 could enhance methane yield and production rate from glucose by a factor of 2.1 and 2.0, respectively. In treatment of normal molasses wastewater, chemical oxygen demand (COD) removal efficiency improved from 75.6% to 88.2%, and the accumulated methane yield and methane yield obtained through COD removal increased by a factor of 2.3 and 2.0, respectively. Hydrogen‐producing acetogenesis is apparently a rate‐limiting step in methanogenesis because bioaugmentation of HPAs during methane production improved not only hydrogen‐producing acetogenesis but also hydrolysis/acidogenesis and methanogenesis. © 2017 American Institute of Chemical Engineers Environ Prog, 37: 367–374, 2018

Molasses wastewater treatment and lipid production at low temperature conditions by a microalgal mutant Scenedesmus sp. Z-4

BackgroundSimultaneous wastewater treatment and lipid production by oleaginous microalgae show great potential to alleviate energy shortage and environmental pollution, because they exhibit tremendous advantages over traditional activated sludge. Currently, most research on wastewater treatment by microalgal are carried out at optimized temperature conditions (25–35 °C), but no information about simultaneous wastewater treatment and lipid production by microalgae at low temperatures has been reported. Microalgal growth and metabolism will be inhibited at low temperature conditions, and satisfactory wastewater treatment performance will be not obtained. Therefore, it is critical to domesticate and screen superior microalgal strains with low temperature adaptability, which is of great importance for wastewater treatment and biodiesel production.ResultsIn this work, simultaneous wastewater treatment and lipid production were achieved by a microalgal mutant Scenedesmus sp. Z-4 at the low temperature conditions (4, 10, and 15 °C). The results showed that algal growth was inhibited at 4, 10, and 15 °C compared to that at the optimal temperature of 25 °C. However, decreased temperature had no significant effect on the total cellular lipid content of algae. Importantly, lipid productivity at 10 °C was compromised by more net energy output relevant to biodiesel production, which demonstrated that the low temperature of 10 °C was favorable to wastewater treatment and energy recovery by Scenedesmus sp. Z-4. When molasses wastewater with optimal COD concentration of 8000 mg L−1, initial inoculation ratio of 15%, and C/N ratio of 15 was used to cultivate microalgae, the maximum removal rate of COD, TN, and TP at 10 °C reached 87.2, 90.5, and 88.6%, respectively. In addition, lipid content of 28.9% and lipid productivity of 94.4 mg L−1 day−1 were obtained.ConclusionsScenedesmus sp. Z-4 had good adaptability to low temperature conditions, and showed great potential to realize simultaneous wastewater treatment and lipid production at low temperatures. The proposed approach in the study was simple compared to other wastewater treatment methods, and this potential novel process was still efficient to remove COD, N, and P at low temperatures. Thus, it had a vital significance for the wastewater treatment in low temperature regions.

Production of Bioflocculants Prepared from Wastewater Supernatant of Anaerobic Co-Digestion of Corn Straw and Molasses Wastewater Treatment

Novel bioflocculants (BS-MBF) were prepared using the wastewater supernatant from anaerobic co-digestion of corn straw and molasses wastewater as a nutrient resource. Acetic acid and ethanol were the dominant fermentation products during the anaerobic digestion process and were estimated to be 50.5% and 30.0%, respectively, after 150 d of operation. Equal volumes of bioflocculant producing bacteria F2 (Rhizobium radiobacter) and F6 (Bacillus sphaericus) were mixed to form F+, which was inoculated to wastewater supernatant at different times. A maximum flocculation activity of 91.3% was achieved, and 2.32 g/L of purified bioflocculant was extracted when a compound medium from 110-d wastewater supernatant was used. The removal efficiencies of heavy metals from simulated electroplating wastewater were tested by using these prepared bioflocculants. The optimal conditions for heavy metal removal to BS-MBF were found to be at 374 mg/L at an initial pH of 6.0 and a contact time of 40 min. The adsorption capacities for Cu2+ and Zn2+ reached more than 90%, while for Cr6+ it reached approximately 30%. Overall, the study showed for the first time that wastewater supernatant from anaerobic co-digestion of corn straw and molasses wastewater can be used for producing bioflocculants, which can be effectively used to remove heavy metals from electroplating wastewater.

Molasses Wastewater Treatment by Microbial Fuel Cell with MnO2-Modified Cathode

Molasses Wastewater Treatment by Microbial Fuel Cell with MnO2-Modified Cathode

Enhancement of the performance of a combined microalgae-activated sludge system for the treatment of high strength molasses wastewater

The treatment of molasses wastewater, by a combined microalgae-activated sludge process, for the simultaneous organics and total nitrogen reduction, was examined. Further enhancement of the performance of the combined process was accomplished, by means of biofilm carriers or electrocoagulation. A LED light tube was immersed into the reactor tank aiming to enhance the growth of photosynthetic microalgae, while in a similar unit, biofilm carriers were added to the system, representing a moving bed bioreactor. Exposure of the activated sludge biocommunity to light source, resulted in the growth of microalgae and photoreactors exhibited higher removal rates of total nitrogen and nitrates. However, operation at longer times resulted in low effluent quality due to the presence of microalgae cells as a result of high growth rates, and potential light shading effect. Nevertheless, the moving bed system was more beneficial than the single photoreactor, as biofilm carriers provided a self cleaning capacity of the light source, reducing the effect of microalgae deposition. Advanced treatment of the biological effluents, by electrocoagulation, increased even more the process efficiency: the combined photobioreactor and electrocoagulation process resulted in about 78% COD removal and more than 35% total nitrogen removal in the effluent, where nitrates represented almost the single form of total nitrogen.

Microalgae-activated sludge treatment of molasses wastewater in sequencing batch photo-bioreactor

ABSTRACTThe aim of this work was the examination of the treatment potential of molasses wastewater, by the utilization of activated sludge and microalgae. The systems used included a sequencing batch bioreactor and a similar photo-bioreactor, favoring microalgae growth. The microalgae treatment of molasses wastewater mixture resulted in a considerable reduction in the total nitrogen content. A reduction in the ammonium and nitrate content was observed in the photo-bioreactor, while the effluent’s total nitrogen consisted mainly of 50% organic nitrogen. The transformation of the nitrogen forms in the photo-bioreactor was attributed to microalgae activity, resulting in the production of a better quality effluent. Lower COD removal was observed for the photo-bioreactor than the control, which however increased, by the replacement of the anoxic phase by a long aeration period. The mechanism of nitrogen removal included both the denitrification process during the anoxic stage and the microalgae activities, as the replacement of the anoxic stage resulted in low total nitrogen removal capacities. A decrease in the photobioreactor performance was observed after 35 days of operation due to biofilm formation on the light tube surface, while the operation at higher temperature accelerated microalgae growth, resulting thus in the early failure of the photoreactor.

Performances of microbial fuel cells fed with rejected wastewater from BioCH4 and BioH2 processes treating molasses wastewater

ABSTRACTAn integrated process involving conventional anaerobic digestion and microbial fuel cells (MFCs) has attracted attention recently to produce sustainable energy and to treat wastewater efficiently. To evaluate the possibility of CH4-producing process (BioCH4)-MFC or H2-producing process (BioH2)-MFC integrating systems, the MFC performances were investigated using rejected wastewater from a BioCH4 reactor (RWCH4) or BioH2 reactor (RWH2) treating molasses wastewater. When RWCH4 or RWH2 was fed into a single-chamber MFC reactor (designated as AC-MFCCH4 and AC-MFCH2, respectively) at different hydraulic retention times (HRT) of 1–7 d, both MFC systems showed maximum electricity production efficiencies at a HRT of 3 d. In the AC-MFCCH4 reactor, the average current density and average power density were 60.5 mA·m−2 and 8.8 mW·m−2, respectively. The AC-MFCH2 reactor generated an average current density of 71.4 mA·m−2 and an average power density of 12.0 mW·m−2. The COD removal rates were 45.7% in the AC-MFCCH4 reactor and 90.3% in the AC-MFCH2 reactor. There were no significant differences of the eubacterial community structures between the MFC systems, where Proteobacteria was remarkably dominant in both MFC systems. However, the archaeal community structures were significantly different where Methanothrix (89.3%) was remarkably dominant in the AC-MFCCH4 system, while Methanothrix (52.5%) and Methanosarcina (33.5%) were abundant in the AC-MFCH2 system. These findings demonstrate that the utilization of MFCs after the BioCH4 or BioH2 process is advantageous for energy recovery as well as COD removal from molasses wastewater.

High organic loading treatment for industrial molasses wastewater and microbial community shifts corresponding to system development

Molasses wastewater contains high levels of organic compounds, cations, and anions, causing operational problems for anaerobic biological treatment. To establish a high organic loading treatment system for industrial molasses wastewater, this study designed a combined system comprising an acidification tank, a thermophilic multi-stage (MS)-upflow anaerobic sludge blanket (UASB) reactor, mesophilic UASB reactor, and down-flow hanging sponge reactor. The average total chemical oxygen demand (COD) and biochemical oxygen demand removal rates were 85%±3% and 95%±2%, respectively, at an organic loading rate of 42kgCODcrm−3d−1 in the MS-UASB reactor. By installation of the acidification tank, the MS-UASB reactor achieved low H2-partial pressure. The abundance of syntrophs such as fatty acid-degrading bacteria increased in the MS-UASB and 2nd-UASB reactors. Thus, the acidification tank contributed to maintaining a favorable environment for syntrophic associations. This study provides new information regarding microbial community composition in a molasses wastewater treatment system.

Experimental study of degradation of molasses wastewater by biological treatment combined with ozonation

AbstractBACKGROUNDThe aim of this work was the examination of molasses wastewater treatment by the combination of activated sludge with ozonation, for the effective removal of refractories. In addition to biological treatment, samples were subjected to: (a) ozonation prior to activated sludge; (b) ozonation coupled with addition of hydrogen peroxide prior to activated sludge; (c) post‐ozonation of activated sludge effluents; and (d) ozonation applied to influents and effluents, as a pre‐ and post‐treatment of the biological process.RESULTSThe activated sludge treatment of the mixture resulted in a 48% reduction of COD, while the combination of ozone pretreatment followed by biological treatment resulted in 66.5% COD removal and the production of an effluent with 240 mg L−1 COD. Therefore, it was concluded that ozone pretreatment might contribute to the enhancement of the biodegradability of the influent. This assumption was further supported by the examination of molecular weight distribution of wastewater samples by size exclusion chromatography.CONCLUSIONThe combined biological and ozone processes resulted in effluents with similar COD values, independent of the stage of the application of the ozone treatment process, either as a pretreatment or as post‐treatment step, indicating that a fraction of the compounds of the raw influent was resistant to the particular treatment process. This recalcitrant residual exhibited high organic nitrogen content, and was responsible for the relatively moderate total nitrogen content reduction, although almost complete nitrification and denitrification took place during the biological process, as deduced by the ammonia and nitrates content of the effluents. © 2015 Society of Chemical Industry

UV/H2O2/TiO2/Zeolite Hybrid System for Treatment of Molasses Wastewater

Wastewater from molasses processing contains a large amount of coloured substances that give a recalcitrant dark brown colour and high organic load to the effluent. Photocatalytic decolourization of molasses wastewater was performed using titanium dioxide catalyst coated on the surface of South African natural zeolite using the solid-solid dispersion method. Addition of hydrogen peroxide as an oxidant was investigated and 30W UV-Clamp was used as source of irradiation. The Chemical Oxygen Demand (COD) of the wastewater treated was varied from 20 g/L to 1 g/L. Batch experiments were conducted in a thermostatic shaker fitted with the UV lamp. The effects of pH, catalyst loading, oxidant dosage and irradiation time on the COD reduction and decolourization of the Molasses Waste Water (MWW) were investigated in this study. The highest colour removal of more than 90% was achieved at pH = 4 and oxidant dosage of 1.47 mM, while low COD removal (< 20%) was observed during photodegradation. A H 2O2/UV/TiO 2 system achieved higher colour removal of 97% compared to a UV/TiO 2 system which achieved 44% while H 2O2 /UV system achieved 34% colour removal. The rate of decolourization was found to fitpseudo - first order reaction kinetics with the highest rate constant value of 1.36 x 10 -2 min -1 .

Development of Ann-Based Models to Predict Biogas and Methane Productions in Anaerobic Treatment of Molasses Wastewater

Two three-layer artificial neural network (ANN) models were respectively developed to predict biogas and methane production rates in a pilot-scale mesophilic up-flow anaerobic sludge blanket (UASB) reactor treating molasses wastewater. Eight process-related variables such as volumetric organic loading rate (OLR), influent and effluent pH, operating temperature, influent and effluent alkalinity, effluent chemical oxygen demand (COD), and volatile fatty acid (VFA) concentrations were selected for the implementation of an artificial intelligence-based approach. A tangent sigmoid transfer function (tansig) at the hidden layer and a linear transfer function (purelin) at the output layer were conducted for the proposed ANN models. Several benchmark comparisons were conducted to obtain an optimal algorithm for training the network. After backpropagation training combined with principal component analysis (PCA), the scaled conjugate gradient algorithm (trainscg) was found as the best of the 11 training algorithms. The number of neurons in the hidden layer was optimized as nine and 12 with the minimum mean squared errors (MSE) of 0.06238 and 0.06488, respectively, for the estimation of biogas and methane production rates. ANN-predicted results were also compared to the outputs of two non-linear regression models by means of several statistical indicators, such as determination coefficient (R2), unsystematic root mean-square error (RMSEU), index of agreement (IA), and fractional variance (FV). Computational results clearly demonstrated that, compared to the conventional multiple regression-based methodology, the proposed ANN-based models produced smaller deviations and exhibited superior predictive accuracy with satisfactory determination coefficients of about 0.935 and 0.924, respectively, for the forecasts of biogas and methane production rates.

Evaluation of Process Performance and Sludge Properties of an up-flow staged Sludge Blanket (USSB) reactor for Treatment of Molasses Wastewater

A combination of an acidification reactor and an up-flow staged sludge bed (USSB) reactor wasapplied to treatment of molasses wastewater. The USSB, equipped with three gas solid separators, wasselected because of superior organic removal by means of good retention of granular sludge. The combinedsystem was continuously operated at mesophilic (35°C) conditions for 600 days. The USSB achieved a highorganic removal rate of 37 kgCOD/m3 day (organic loading rate of 43 kgCOD/m3 day with 86.2% CODremoval). The USSB retained high sludge concentration of approximately 58 gVSS/L based on the reactorvolume. The retained granular sludge had good settle-ability with a sludge volume index (SVI) of 4 to 20 ml/gSS. The retained sludge possessed a sufficient level of methanogenic activities for acetate (1.2 gCOD/gVSS day) and for hydrogen (1.7 gCOD/gVSS day). Analysis of microbial community revealed that genus Methanobacterium as hydrogen utilizing methanogen and order Methanosarcinales as acetate utilizingmethanogen were detected in the retained sludge of the USSB reactor. The superior performance of the USSB was attributed to good retention of a large amount of granular sludge with high methanogenic activity.

High-rate treatment of molasses wastewater by combination of an acidification reactor and a USSB reactor

A combination of an acidification reactor and an up-flow staged sludge bed (USSB) reactor was applied for treatment of molasses wastewater containing a large amount of organic compounds and sulfate. The USSB reactor had three gas-solid separators (GSS) along the height of the reactor. The combined system was continuously operated at mesophilic temperature over 400 days. In the acidification reactor, acid formation and sulfate reduction were effectively carried out. The sugars contained in the influent wastewater were mostly acidified into acetate, propionate, and n-butyrate. In addition, 10–30% of influent sulfur was removed from the acidification reactor by means of sulfate reduction followed by stripping of hydrogen sulfide. The USSB achieved a high organic loading rate (OLR) of 30 kgCOD m−3 day−1 with 82% COD removal. Vigorous biogas production was observed at a rate of 15 Nm3 biogas m−3 reactor day−1. The produced biogas, including hydrogen sulfide, was removed from the wastewater mostly via the GSS. The GSS provided a moderate superficial biogas flux and low sulfide concentration in the sludge bed, resulting in the prevention of sludge washout and sulfide inhibition of methanogens. By advantages of this feature, the USSB may have been responsible for achieving sufficient retention (approximately 60 gVSS L−1) of the granular sludge with high methanogenic activity (0.88 gCOD gVSS−1 day−1 for acetate and as high as 2.6 gCOD gVSS−1 day−1 for H2/CO2). Analysis of the microbial community revealed that sugar-degrading acid-forming bacteria proliferated in the sludge of the USSB as well as the acidification reactor at high OLR conditions.