Development of an electrokinetic method of dewatering and upgrading sludge to class A/excellent quality biosolids: Comparison of aerobic and anaerobic municipal sludge.

摘要

Biosolids are organic-rich residuals resulting from the wastewater treatment processes. Thousands of tons of biosolids are produced every year currently in Canada and the U.S., which should be treated and disposed of safely according to the strict environmental standards. This study aims to investigate different sludges and generate Class A biosolids due to electrokinetic (EK) simultaneous dewatering and inactivation of pathogenic organisms such as Salmonella spp. and Fecal coliforms.; Bench scale experiments had been conducted operating under batch regime in the environmental research laboratory at Concordia University. Ten cells were set up with three different types of sewage sludge: primary, secondary (attached growth culture and suspended culture), and anaerobic digested sludge. They were taken from Auteuil Wastewater Treatment Plant, Laval, Quebec, and R.O. Pickard Environmental Centre, Ottawa, Ontario. The characterization of the sludge was performed followed by electrokinetic system (EK) tests and data analysis. A conditioning liquid was also added to five cells. Low and high potential such as 1 V/cm and 1.5 V/cm were applied to the cells. Blower system was integrated into the EK for four cells. In order to access the dewatering, disinfection efficiency and other applications of EK system, parameters such as total solids contents, Fecal coliforms, pH, Salmonella spp, and anions concentration were analyzed. The highest total solids (TS) content (98.5% TS) was achieved in the cell with combined primary and secondary sludge where the lower voltage gradient, conditioner and blower system were applied. No Fecal coliforms were detected after treatment in most of the EK cells. The highest log reduction of Salmonella spp. was achieved in the EK cell with anaerobic digested sludge, under lower voltage gradient. In general, Salmonella spp. log-reduction was found to be between 6 and 11 in EK cells. The cells without the conditioner exhibited Salmonella spp. inactivation mostly in the anode area, while the cells with conditioner observed the inactivation of Salmonella spp. in cathode area. Different types of biosolids were observed having different responses to the EK system in terms of dewatering efficiency and pathogen inactivation. It was concluded that the anaerobic digested sludge had better inactivation of Salmonella spp. and achieved higher dewatering efficiency under lower voltage gradient. The mixed sludge had better inactivation of Salmonella spp. under higher voltage gradient, while the lower voltage gradient yielded higher dewatering efficiency.; This study showed that Electrokinetic dewatering can be applied simultaneously to upgrade both aerobic and anaerobic digested sludge to Class A/Exceptional Quality biosolids.