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Department of Civil Engineering, Environmental Engineering Cell, Indian Institute of Engineering Science and Technology (IIEST), Shibpur, Howrah-711 103, West Bengal, India E-mail : cbiswabandhu@yahoo.com, debabrata@civil.iiests.ac.in, dmazumder@hotmail.com Manuscript received 16 June 2017, revised 15 November 2017, accepted 17 November 2017 Anaerobic Digestion (AD) can be considered as the most appropriate Municipal Solid Waste Man­agement (MSWM) technique, since it is capable of not only stabilizing a significant quanta of generated waste at once but also ensures generation of biogas, which is a non-conventional source of energy. A major part (40–50%) of the generated Organic Fraction of the Municipal Solid Waste (OFMSW) is constituted of Fruit and Vegetable Waste (FVW). In the present study, an attempt has been made to understand the performance of a three-stage lab-scale anaerobic digester for stabilizing FVW. FVW was procured from numerous house­holds and from the guest-house kitchen of Indian Institute of Engineering Science and Technology, Shibpur (IIESTS). The feasibility of FVW to undergo anaerobic digestion was established after physical characteriza­tion of the procured FVW on individual and composite basis. The performance evaluation of the lab-scale AD system was based on the batch study results of pH, alkalinity and soluble Chemical Oxygen Demand (sCOD). Mesophilic temperature regime was selected for carrying out all the batches. The following substrate utiliza­tion rates (k) were obtained : 0.168 d–1, 0.6 d–1, and 0.56 d–1, respectively for the hydrolytic, the acidogenic, and the methanogenic reactors.

Bioremoval of H2S from gas streams became popular in recent years because of high process efficiency and low operational costs. To expand the scope of these processes to gas streams containing volatile organic sulfur compounds, like thiols, it is necessary to provide new insights into their impact on overall biodesulfurization process. Published data on the effect of thiols on biodesulfurization processes are scarce. In this study, we investigated the effect of methanethiol on the selectivity for sulfur production in a bioreactor integrated with a gas absorber. This is the first time that the inhibition of biological sulfur formation by methanethiol is investigated. In our reactor system, inhibition of sulfur production started to occur at a methanethiol loading rate of 0.3 mmol L(-1) d(-1). The experimental results were also described by a mathematical model that includes recent findings on the mode of biomass inhibition by methanethiol. We also found that the negative effect of methanethiol can be mitigated by lowering the salinity of the bioreactor medium. Furthermore, we developed a novel approach to measure the biological activity by sulfide measurements using UV-spectrophotometry. On the basis of this measurement method, it is possible to accurately estimate the unknown kinetic parameters in the mathematical model.

Pulp and paper industry generates large quantity of sludge, up to 1 m 3 /ton paper produced. Anaerobic digestion (AD) is a potential treatment to stabilize sludge and produce biogas for renewable energy. The aim of this study was to investigate the potential of AD of paper sludge (PS) generated from primary and secondary wastewater treatment and to compare the effect of cow manure to paper sludge. For the reactor with PS only, biogas production was observed starting on the 5 th day with 6.3% of methane with a steady increase. The cumulative methane yield attained to 14.7 ml/g volatile solid (VS) until day 28. The second reactor containing PS and cow manure produced methane 269 ml/g VS until day 28. This study shows a more optimal AD process of paper sludge mixed with cow manure due to a more optimum C/N ratio and also higher VS.