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AbstractThe laboratory-scale UASB reactors were operated at five different hydraulic retention times (HRTs). The various sizes of granules from three different sources: a cassava factory (CS), a seafood factory (SS), and a palm oil mill (PS), having the size range of 1.5-1.7mm, 0.7-1.0mm and 0.1-0.2mm. respectively, were used as inocula for anaerobic digestion of cassava wastewater. For comparison, the first reactor with only granules from its own source (R1, CS) was treated as control. The other two reactors were inoculated with mixed granules from different sources (R2, CS+SS and R3, CS+PS). As HRT decreased from 5 days to 1 day, the organic removal efficiencies decreased from 91.49 to 43.23%, 89.36 to 45.13% and 87.23 to 32.69% for R1, R2 and R3 respectively (or inversely with increasing OLR). In this study selected mathematical models including Monod, Contois, Grau second-order and Modified Stover-Kicannon kinetic models were applied to determine the substrate removal kinetics of UASB reactors. Kinetic parameters were determined through linear regression using experimental data obtained from the steady-state experiments and subsequently used to predict effluent COD. The results showed that Grau second-order and Modified Stover-Kicannon kinetic models were more suitable than the others for predicting the substrate removal for all different sizes of granules. In addition the Upflow Anaerobic Sludge Blanket (UASB) reactor with only granules from a cassava factory gave the best performance.

Abstract Empty fruit bunches (EFB), palm oil mill effluent (POME), sewage chemical sludge and sewage biological sludge were evaluated for methane production under liquid-state anaerobic digestion (L-AD) and solid-state anaerobic digestion (SS-AD). The highest methane yield of 456 mL CH 4 g -1 VS was achieved from co-digestion POME with sewage chemical sludge at a ratio of 99:1 under L-AD. The highest methane yield of 18 mL CH 4 g -1 VS was achieved from co-digestion EFB with sewage chemical sludge at a ratio of 95:5 and EFB with sewage biological sludge at a ratio of 95:5 under SS-AD. An increasing of sewage sludge content of 6-42% in both AD systems resulted in decreasing of methane yield. The L-AD system has 2-3 times higher volumetric methane productivity than the SS-AD system. The electricity production from 1-tonne a mixture of POME and sewage chemical sludge or sewage biological sludge would be 218 MJ or 60 kWh of electricity. Anaerobic co-digestion POME with sewage sludge has great potential for biogas production.

Background Anaerobic digestion (AD) is a suitable process for treating high moisture MSW with biogas and biofertilizer production. However, the low stability of AD performance and low methane production results from high moisture MSW due to the fast acidify of carbohydrate fermentation. The effects of organic loading and incineration fly ash addition as a pH adjustment on methane production from high moisture MSW in the single-stage AD and two-stage AD processes were investigated. Results Suitable initial organic loading of the single-stage AD process was 17 gVS L−1 at incineration fly ash (IFA) addition of 0.5% with methane yield of 287 mL CH4 g−1 VS. Suitable initial organic loading of the two-stage AD process was 43 gVS L−1 at IFA addition of 1% with hydrogen and methane yield of 47.4 ml H2 g−1 VS and 363 mL CH4 g−1 VS, respectively. The highest hydrogen and methane production of 8.7 m3 H2 ton−1 of high moisture MSW and 66.6 m3 CH4 ton−1 of high moisture MSW was achieved at organic loading of 43 gVS L−1 at IFA addition of 1% by two-stage AD process. Biogas production by the two-stage AD process enabled 18.5% higher energy recovery than single-stage AD. The 1% addition of IFA into high moisture MSW was useful for controlling pH of the two-stage AD process with enhanced biogas production between 87–92% when compared to without IFA addition. Electricity production and energy recovery from MSW using the coupled incineration with biogas production by two-stage AD process were 9,874 MJ ton−1 MSW and 89%, respectively. Conclusions The two-stage AD process with IFA addition for pH adjustment could improve biogas production from high moisture MSW, as well as reduce lag phase and enhance biodegradability efficiency. The coupled incineration process with biogas production using the two-stage AD process was suitable for the management of MSW with low area requirement, low greenhouse gas emissions, and high energy recovery.

Abstract The sulfate-rich wastewater from rubber smoked sheet industry could generate hydrogen sulfide (H2S) under anaerobic condition, which created bad smell to the community and might cause toxicity and damage to the environment. The H2S can be removed from the biogas by sulfur-oxidizing bacteria (SOB) with the ability to converted H2S to sulfate. Sulfate-reducing bacteria (SRB) could remove sulfate in wastewater before anaerobic treatment for biogas production. The microbial sludge from wastewater and anaerobic digestion system was collected and test for sulfate and H2S removal efficiency. Anaerobic microbial sludge has a high ability to produced methane from gelatin with a specific methane production rate of 92.4 ml CH4 gVSS-1 day-1. Anaerobic microbial sludge has lower methane production when gelatin and sulfate used as a substrate with a specific methane production rate of 81.4 ml CH4 gVSS-1 day-1. The biomethane potential, hydrogen sulfide removal and sulfate removal in anaerobic digestion system by addition of enriched cultures of SOB and SRB were investigated. The methane yield of SRB consortium was 60.1 ml CH4/gCOD with 20% sulfate reduction from wastewater and no sulfide reduction. The methane yield of SOB consortium was 41.9 ml CH4/gCOD with no sulfate and sulfide reduction from wastewater. The addition of SRB consortium could increase methane production by reducing sulfate concentration in wastewater consequently to a reduced concentration of H2S in biogas.

AbstractSolid state anaerobic digestion is a safe and environmental friendly technology to dispose solid wastes, could produce methane and reduce the volume of wastes. Three biomass residues from palm oil mill plant including empty fruit bunches (EFB), palm press fiber (PPF) and decanter cake (DC) were evaluated for methane production by solid state anaerobic digestion. Oil palm biomass was mixed with inoculum at F/I ratio of 2:1, 3:1, 4:1, 5:1 and 6:1 based on the volatile solid (VS). Results show that among the five F/I ratios tested, the F/I ratio of 2:1 gave the highest methane yield and methane production for all biomass residues. The highest cumulative methane production of 2180 mLCH4 was obtained from EFB followed by PPF (1964mL CH4) and DC (1827mL CH4) at F:I ratio of 2:1. The highest methane yield of 144mL CH4/gVS was obtained from EFB followed by PPB (140mL CH4/gVS) and DC (130mL CH4/gVS) at F/I ratios of 2:1. Methane production from EFB, PPF and DC by SS-AD was 55, 47 and 41 m 3 CH4/ton, respectively. These results collectively suggested that EFB could be a promising substrate for methane production by SS-AD

Abstract The cultivation of Chlorella sp. TISTR 8411 on biogas effluent of seafood processing wastewater was investigated. Chlorella sp. biomass was used for biogas production by anaerobic co-digestion with seafood processing. Chlorella sp. biomass cultivated on 50, 60, 70, 80, 90, and 100% of biogas effluent was 0.184, 0.121, 0.061, 0.048, 0.039, and 0.032 g/L, respectively. The highest growth of Chlorella sp. biomass was 0.184 g/L from 50% biogas effluent. Methane yield from anaerobic co-digestion of seafood processing wastewater with 10, 20, 30, 40, and 50% v/v Chlorella sp. biomass was 131, 152, 173, 188 and 193 ml CH4/gVS, respectively. Methane yield from Chlorella sp. biomass was 44 ml CH4/gVS. Methane yield from seafood processing wastewater was 18 ml CH4/gVS. 10 times of methane yield was improve in anaerobic co-digestion seafood processing wastewater with Chlorella sp. biomass at 40 and 50 % v/v. Anaerobic co-digestion seafood processing wastewater with Chlorella sp. biomass has great potential for biogas production.

A biodiesel wastewater treatment technology was investigated for neutral alkalinity and COD removal by microbial fuel cell. An upflow bio-filter circuit (UBFC), a kind of biocatalyst MFC was renovated and reinvented. The developed system was combined with a pre-fermented (PF) and an influent adjusted (IA) procedure. The optimal conditions were operated with an organic loading rate (OLR) of 30.0 g COD/L-day, hydraulic retention time (HRT) of 1.04 day, maintained at pH level 6.5-7.5 and aerated at 2.0 L/min. An external resistance of circuit was set at 10 kΩ. The purposed process could improve the quality of the raw wastewater and obtained high efficiency of COD removal of 15.0 g COD/L-day. Moreover, the cost of UBFC system was only US$1775.7/m3 and the total power consumption was 0.152 kW/kg treated COD. The overall advantages of this invention are suitable for biodiesel wastewater treatment.

Hydrothermal liquefaction of sewage sludge to produce bio-oil and hydro-char unavoidably results in the production of high-strength organic wastewater (HTLWW). However, anaerobic digestion (AD) of HTLWW generally has low conversion efficiency due to the presence of complex and refractory organics. The present study showed that granular activated carbon (GAC) promoted the AD of HTLWW in continuous experiments, resulting in the higher methane yield (259 mL/g COD) compared to control experiment (202 mL/g COD). It was found that GAC increased the activities of both aceticlastic and hydrogenotrophic methanogens. The molecular transformation of organics in HTLWW was further analyzed. It was shown GAC promoted the degradation of soluble microbial by-products, fulvic- and humic-like substances as revealed by 3-dimensional fluorescence excitation-emission matrix (3D-EEM) analysis. Gas chromatography mass spectrometry (GC-MS) analysis showed that GAC resulted in the higher degradation of N-heterocyclic compounds, acids and aromatic compounds and less production of new organic species. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) analysis also showed that GAC promoted the degradation of nitrogenous organics. In addition, it was shown that GAC improved the removal of less oxidized, higher nitrogen content, and higher double bond equivalent (DBE) organic compounds. Microbial analysis showed that GAC not only increased the microbial concentration, but also enriched more syntrophic bacteria (e.g., Syntrophorhabdus and Synergistes), which were capable of degrading a wide range of different organics including nitrogenous and aromatic organics. Furthermore, profound effects on the methanogens and the enrichment of Methanothrix instead of Methanosarcina were observed. Overall, the present study revealed the molecular transformation and microbial mechanism in the AD of HTLWW with the presence of GAC.