Optimization of synergistic microwave and zero-valent iron co-pretreatment for anaerobic digestion of waste activated sludge

초록

This study optimized co-pretreatment of microwave temperature (TMW) and zero-valent iron dosage ([ZVI]) to enhance anaerobic digestion (AD) of waste activated sludge (WAS). WAS was pretreated at TMW = 100, 150, or 200 degrees C and [ZVI] = 1, 3, or 5 g/L using a central composite design. Optimal co-pretreatment (TMW = 168 degrees C and [ZVI] = 5 g/L) reduced the ratio of volatile solids (VS) to total solids by 21.5 %, increased the solubilization ratio seven-fold, removed 53.5 % of phosphate compared to WAS partly because of lignin fragmentation. Biochemical methane potential identified optimal conditions (TMW = 164 degrees C and [ZVI] = 4.8 g/L), enhancing VS removal by 70.9 %, methane yield by 60 %, and reducing hydrogen sulfide by 82.4 % compared to Control. Kinetic analysis indicated 61-108 % increase in maximum methane production rate. Microbial analysis revealed increased acetoclastic methanogens and decreased hydrogenotrophic methanogens. Thus, microwave-ZVI co-pretreatment enhanced WAS biodegradability and AD efficiency.

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