Effect of disintegration pretreatment of sewage sludge for enhanced anaerobic digestion

Abstract

A sludge disintegration technology, presented in this paper, consists of pretreatment of the sludge before its anaerobic digestion. Disintegration of sludge has been recently incorporated into the wastewater treatment plant’s (WWTPs) process scheme in some countries to improve a hydrolysis phase of digestion. Better energy recovery is of crucial importance in the overall sludge disposal. This technology intensifies biogas production and improves the quality of digested sludge. The authors present results of their experiments, performed on sludge samples taken from the Gdańsk WWTP, Poland. During experiments mixture of primary and waste activated sludge (WAS) taken from the aerobic bioreactor was used. The sludge was disintegrated mechanically in a laboratory scale by using a ultrasound generator Hielsher, Germany (the frequency was 24 kHz). The concentration of chemical oxygen demand (COD) was obtained according to standard methods and the degree of sludge disintegration (DD) in supernatant was calculated. The anaerobic digestion experiment was carried out in laboratory scale using two reactors (volume ca. 30 dm3 of each), with hydraulic retention time (HRT) of 15 days and under mesophilic conditions. The quantity and quality of produced biogas was measured. Results showed 20% increase of biogas and 10% increase of methane produced generated during anaerobic digestion process of disintegrated sludge compare to untreated one.