Effect of pretreatment using ultrasound and hydrogen peroxide on digestion of waste activated sludge in an anaerobic membrane bioreactor

Abstract

This study investigated combining pretreatment of waste activated sludge with anaerobic digestion in a submerged anaerobic membrane bioreactor. Preliminary tests revealed that a hydrogen peroxide and ultrasound pretreatment resulted in a chemical oxygen demand solubilization of 40% when a dose of 50 gH 2 O 2 /kgTS and sonication for 60 min were employed. Raw and pretreated waste activated sludge were fed to an anaerobic membrane bioreactor to determine if this increase in solubilization affected the biodegradability of the sludge. It was observed that pretreatment increased the extent to which the sludge was digested and hence it was concluded that the combined action of ultrasound and peroxide increased the biodegradable fraction of the sludge, while reducing the bioreactor and waste stream solids concentration. At a constant flux of 2.75 L/m 2 /hour, the transmembrane pressure and the fouling rate remained low and relatively constant over the course of operation, despite reduced mass flow of solids. The performance of the membrane was attributed to the fouling minimizing protocol that consisted of regular maintenance cleaning, a relaxed mode of operation, and continuous gas sparging. © 2015 American Institute of Chemical Engineers Environ Prog, 34: 1724–1730, 2015