Electrochemical pretreatment (EPT) of waste activated sludge: Extracellular polymeric substances matrix destruction, sludge solubilisation and overall digestibility.

Anaerobic digestion (AD) of waste activated sludge (WAS) is widely used for stabilisation, mass reduction and resource recovery. However, AD performance is often hampered by the poor digestibility and slow degradation rate for WAS. A series of bench-scale tests was conducted using innovative electrochemical pretreatment (EPT) method to enhance the destruction of the extracellular polymeric substances (EPS) matrix and anaerobic digestibility. The results showed that the EPS matrix destruction was enhanced by 15-30% after EPT for 0.5 h at voltages of 8-15 V. The highest improvement in hydrolysis rate and overall digestibility was achieved at EPT of 15 V for 1.5 h, which was determined as 59% (from 0.27 to 0.43 d-1) and 28% (from 105 to 134 mL CH4/g VSSadded) respectively, compared with the WAS treatment without EPT. The economic analysis showed 1 h, 12 V EPT was more economically feasible.