Synergetic treatment of sewage sludge and food waste for biogas generation and heavy metals immobilization via anaerobic digestion and pyrolysis

In this study, a novel method was proposed for synergetic treatment of sewage sludge and food waste. First, the sewage sludge was hydrothermally treated to improve its dewaterability. The separated filtrate from hydrothermally treated sewage sludge (HS) and food waste co-digested for biogas generation. The obtained digestate residue (DR) was used for co-pyrolysis with sludge filter cake from HS for heavy metals immobilization. The obtained results showed that the methane yield of filtrate was significantly increased with addition of food waste and the lag phase during the digestion of food waste was shortened during co-digestion. In terms of heavy metals immobilization, the heavy metals in sewage sludge were immobilized during co-pyrolysis process. Moreover, the higher DR content led to better immobilization effect. These above results provided the feasibility for more efficient and safer synergetic treatment of sewage sludge and food waste.