Effect of fish waste augmentation on anaerobic co-digestion of sludge with food waste.

The effect of sudden augmentation with fish waste (FW) on an operating anaerobic digester was investigated. Fifteen repeated FW spikes (FWS) composed of 1% or 5% FW per working volume of digester were suddenly fed into semi-continuous operation of a mixture of sludge and food waste. Overall process efficiency was not inhibited by FW augmentation. The bacterial community were clustered differently in the 5% FWS treatment than in the control and 1% FWS. Protein-degrading bacteria (Porphyromonadacea, Family XI, and Family XII) were commonly found in the 5% FWS treatment. Their proportions positively correlated with numbers of other bacteria and dominant methanogens (Methanosaeta and Methanospirillum), showing their important role in FWS digestion. FWS caused a shift of bacteria community, but an increase in archaeal concentration. Therefore, sudden addition of an appropriate amount of FW to existing digesters did not provoke process failure. This result contributes an ecologically-benign method to process FW.