Relative evaluation of FeCl3 salts and its nanoparticles on methane yield and sulphide inhibition control during biomethanation of distillery spent wash

Abstract

Distillery spent wash (DSW), a complex wastewater rich in sulphates, organic matter and other contaminants when treated through anaerobic digestion process leads to digester failures due to sulphide inhibition and organic shock loading. Therefore, this work demonstrated the biomethanation of DSW to optimize the initial organic load (IOL) and substrate to inoculum (S/I) ratio in phase I experiments. In phase II, the impact of additives i.e., FeCl3 salts and its nanoparticles at optimized S/I ratio was investigated. The impact of S/I ratio, organic load and additives materials on methane yield, quality of biogas (H2S and CH4), microbial diversity and organic matter removal has been studied thoroughly. Results in phase I experiments disclosed that the dilution of wastewater to reduce COD/SO42− ratios favoured the process and the optimum IOL at which the maximum CH4 yield of 0.7 and 0.6 L/g CODR that can be achieved was 70 g/L and 35 g/L at an S/I ratio of 2:1 compared to control i.e., 0.3 L/g CODR. However, the H2S and CH4 in biogas ranged between 2 and 2.4 % and 60–64 % respectively. From phase II experiments, comparable CH4 yields of 0.67 and 0.65 L/g CODR were obtained by the application of FeCl3 NPs and salts at optimized IOL and S/I ratio but the H2S in biogas substantially decreased to <0.05 % and the CH4 improved to 72 %. Therefore, addition of FeCl3 either in the form of salts or NPs favoured biomethanation process and enhanced the overall performance.