Abstract

Municipal and industrial wastewater treatment plants (WWTP) produce sludge that contains around 5% of solids. Sludge requires further treatment before final disposal, which is limited because of the contents of heavy metals, nutrients, and some pathogens. A solution for more efficient biosolids management is urgent. The main objective of this study is revitalization of biosolids focussing on dewatering, metals and organic matter reduction as well as pathogen destruction to reduce the hazard associated with disposal or reuse. Subsequently a new cost-effective method combining all processes into one technology is investigated. The feasibility of using electrokinetic processes was evaluated out at lab scale. Six cells were filled up with biosolids from the WWTP in Laval (Quebec). Di-ammonium-phosphate was added to two cells. The DC power supply was connected to 5 cells (one cell was left without connection as a control cell) and the desirable potential gradients were set up at 0.5 V/cm, 1.0 V/cm, and 1.5 V/cm in respective cells. During 10 days of experiment, electrical parameters were measured and water was collected from the cathode area. At the end of the experiment, the biosoilds were subjected to physico-chemical analysis. No fecal coliforms were observed in cells with fertilizer. Results showed the capability of dewatering by 95%. The highest solids content was achieved in the cell with the highest voltage in the presence of fertilizer. The removal of organic matter reached 47%. The experiment showed the best removal for lead (below detection limit). The transport of other metals (Cu, Ni, Zn, Cd, and Fe) was also observed. For the optimal removal condition, which is in the cell with potential 1.5 V/cm in the presence of fertilizer, the consumption of energy was 220 kW.h/m 3 of biosolids or $6.62/m 3 of biosolids.