Simultaneous methane and phosphorus recovery from waste activated sludge: Critical role of pretreatment by ethylenediaminetetraacetic acid disodium salt in anaerobic digestion

Abstract

This study proposes an innovative ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) pretreatment strategy for simultaneous methane and phosphorus (P) recovery from waste activated sludge (WAS). Pretreatment with 7.5 mmol/L EDTA-2Na disrupted sludge floc structures via metal-chelating effects, enhancing short-chain fatty acids (SCFAs) by 1.4-fold and methane production by 1.3-fold during anaerobic digestion. After EDTA-2Na pretreatment, 48.9 % of total phosphorus (TP) was released from the sludge in the methane-production phase, and in the phosphorus recovery phase, another 32.3 % of TP was released under the synergistic promotion of EDTA-2Na pretreatment and acidification. Recovered P crystallized as vivianite with 81.1 % efficiency and 73.1 % purity. This approach demonstrates sustainable sludge management by integrating methane and P recovery through EDTA-2Na pretreatment in anaerobic digestion.