Recovery of Dissolved Methane From Anaerobic Membrane Bioreactor Using Degassing Membrane Contactors

At present, the recovery and utilization of methane from anaerobic wastewater treatment systems as a source of energy are well-researched and widely adopted for a more sustainable system approach. However, not all methane produced in an anaerobic treatment system is completely recovered; subsequently, dissolved methane present in the effluent can be released into the environment and contribute to greenhouse gas accumulation in the atmosphere and reduce the system's methane yield. Many studies have already investigated and discussed the factors affecting the production of dissolved methane, as well as the techniques for its recovery. Among the recovery techniques, the use of degassing membrane contactor is most preferred for wastewater treatment application. However, reported data in the literature is limited to certain types of wastewater characteristics and anaerobic systems. Studies on membrane-based recovery of dissolved methane from AnMBR effluents are reviewed in this paper. For the case of the degassing membrane contactor, porous, or micro-porous membranes provides higher dissolved methane recovery efficiency than non-porous. However, porous membranes are more susceptible to pore wetting problem. Among the different operating conditions of degassing membrane contactors, liquid velocity, or flow rate greatly affects the recovery, wherein higher velocity decreases the recovery efficiency of dissolved methane. Consequently, research priorities aimed at development of degassing membrane to accommodate higher liquid velocity and to reduce pore wetting. Moreover, energy analysis of the AnMBR with degassing membrane system should be analyzed for performance in full-scale applications

Alkali Pretreatment and Enzymatic Hydrolysis of Australian Timber Mill Sawdust for Biofuel Production

This study investigated the potential use of alkali pretreatment of sawdust from Australian timber mills to produce bioethanol. Sawdust was treated using 3–10% w/w NaOH at temperatures of 60, 121, and −20°C. Two pathways of production were trialled to see the impact on the bioethanol potential, enzymatic hydrolysis for glucose production, and simultaneous saccharification and fermentation (SSF) for ethanol production. The maximum yields obtained were at 121°C and −20°C using 7% NaOH, with 29.3% and 30.6% ethanol yields after 0.5 and 24 hr, respectively, these treatments yielded 233% and 137% increase from the 60°C counter parts. A notable trend of increased ethanol yields with increased NaOH concentration was observed for samples treated at 60°C; for example, samples treated using 10% NaOH produced 1.92–2.07 times more than those treated using 3% NaOH. FTIR analysis showed reduction in crystallinity correlating with increased ethanol yields with the largest reduction in crystallinity in the sample treated at −20°C for 24 hr with 7% NaOH

Anaerobic Codigestion of Municipal Wastewater Treatment Plant Sludge with Food Waste: A Case Study

The aim of this study was to assess the effects of the codigestion of food manufacturing and processing wastes (FW) with sewage sludge (SS), that is, municipal wastewater treatment plant primary sludge and waste activated sludge. Bench scale mesophilic anaerobic reactors were fed intermittently with varying ratio of SS and FW and operated at a hydraulic retention time of 20 days and organic loading of 2.0 kg TS/m3·d. The specific biogas production (SBP) increased by 25% to 50% with the addition of 1%–5% FW to SS which is significantly higher than the SBP from SS of 284±9.7 mLN/g VS added. Although the TS, VS, and tCOD removal slightly increased, the biogas yield and methane content improved significantly and no inhibitory effects were observed as indicated by the stable pH throughout the experiment. Metal screening of the digestate suggested the biosolids meet the guidelines for use as a soil conditioner. Batch biochemical methane potential tests at different ratios of SS : FW were used to determine the optimum ratio using surface model analysis. The results showed that up to 47-48% FW can be codigested with SS. Overall these results confirm that codigestion has great potential in improving the methane yield of SS