Optimizing operational parameters in MEC system for enhanced methane production and reduced dissolved methane from dairy wastewater

While anaerobic digestion (AD) has been considered as a commonly used method for methane recovery from dairy wastewater, part of methane is lost as dissolved form (D-CH4) with the effluent, reducing overall efficiency of methane recovery and increasing greenhouse gas emissions. In this study, a hybrid system of microbial electrolysis cell (MEC) and AD was utilized to enhance the recovery of methane, the influence of organic loading rate, sludge concentration, particle size, and temperature on methane production and the D-CH4were investigated. The system recorded a 42.04% enhancement in the rate and an 18.13% enhancement in methane production at an applied voltage of 0.8 V. Microbial analysis showed that voltage-dependent enrichment of Bacteroides and Methanobacterium species likely played a synergistic role in enhancing methanogenesis. The temperature was found to have the most desirable impact on the solubility of methane. The elevated temperatures could enhance microbial activity and methane production rates, which increase methane partial pressure in the liquid phase and thus elevate dissolved concentrations despite the decrease in solubility.