An integrated approach for waste activated sludge management towards electric energy production/resource reuse

This study developed an integrated approach for electric energy harvest/resource reuse from waste activated sludge (WAS) pretreated by enzymolysis based on anaerobic fermentation and microbial fuel cells (MFCs). WAS solubilization by the 3-h enzymatic pretreatment (a blend of hydrolytic enzymes caused over 5300 mg/L soluble COD release) prompted volatile fatty acid (VFA) production with 3580 mg COD/L after 10-d fermentation. After solid-liquid separation, fermentation liquid with high VFA content was fed into MFCs for electric energy production, while solid residues were used for making building materials (such as blended cements). Results showed that the electricity conversion efficiency of fermentation liquid (VFA) reached 1.254 kW h/kg COD with over 90% organics removal and solid residues could be consumed potentially as qualified substitutes for producing cements. As such, this study may provide some new thinking on future WAS management towards electricity harvest/resource reuse with zero secondary wastes discharge.