Abstract

Biosolids, the end product of municipal wastewater treatment contains many of the constituents removed from the influent wastewater. Constituents of wastewater sludge include organic contents, nutrients, pathogens, metals, and toxic organics. Concentration of heavy metals in sewage sludge is one of the major issues of public concern, when sludge is applied on land. Municipalities in cold climate regions face specific problems during winter months due to snow and severe weather conditions when land application of biosolids becomes difficult or impossible. The major goal of this research was to investigate the impact of extremely low winter temperatures as faced on the Canadian prairies on the functionality of electrokinetic processes and to assess technical feasibility of the electrokinetic method for the removal of metals from municipal biosolids in extreme cold winter condition. Biosolids in rectangular polyethylene cells were subjected to electrokinetic processes at -8 and -15{493}C ambient temperatures. Tests were carried out both biosolids alone and biosolids mixed with conditioning liquid. Metal contents analyses of biosolids samples after the application of electrokinetics indicated excellent movement of metal ions towards the cathode. Concentrations of cadmium, copper, lead, nickel and zinc in the cathode areas were found respectively 195%, 97%, 118%, 26% and 1686% higher than the concentrations in the anode areas in cells that showed the best movement of the respective metals. Use of conditioning liquid slowed down the biosolids freezing process. A 10% concentration increase of the conditioning liquid helped to extend the working period of the electrokinetic processes in freezing biosolids by 15%, thus the conditioning liquid enhanced the performance of the system and helped to obtain better movement of metals.