Anaerobic co-digestion of sewage sludge with other organic wastes (India)

Anaerobic co-digestion of sewage sludge (SS) with other organic wastes, such as landfill leachate (LL) and food waste (FW), has been explored in this study as a sustainable and potential treatment strategy. Such an approach balances the C/N ratio and macro- and micro-nutrient availability in the feed, which are the common limitations in the anaerobic digestion of SS as the sole substrate.
Optimizing the substrate ratio has been the primary objective, followed by treatment efficiencies and increasing the methane yield. The SS was co-digested with LL with two pre-treatments, i.e., thermal pre-treatment at 70°C for 60 mins and pulsed electric field pre-treatment at different voltages for 15 mins. It was concluded that pre-treated substrates effectively increased the total and volatile solids and COD reduction efficiencies than the untreated substrates. The effectiveness of feed addition at different times of anaerobic co-digestion was also explored. SS was opted to be a co-substrate to FW, acting as a buffer with its high alkalinity to prevent quick acidification in the digester. There has been a minor increase in pH by adding the co-substrate at the time of pH drop rather than in the initial phase. The COD, volatile fatty acids, and methane yield results pave the path for further study into SS as a co-substrate for FW.