Improvement of sewage sludge hazardous characteristics using physical, physicochemical and biodegradation methods

Abstract

New developments in the area of wastewater treatment together with increasing numbers of households connected to wastewater treatment plants have resulted in a considerable increase of sewage sludge production. Physical and physicochemical processes applicable within the primary treatment to sewage sludge conditioning are able to reduce its dangerous characteristics. These processes can be used individually or in combination with biodegradation. The aim of our study was to evaluate the use of UV radiation, the electrostatic field, the action of high-heat plasma and combination of these methods for reduction of contamination of sewage sludge with PCBs, PAHs and heavy metals. Another approach included a biodegradation treatment with bacteria. The effects of physical, physicochemical and biodegradation treatments on sewage sludge characteristics were measured both by chemical analysis and with the Vibrio fischeri acute toxicity test. All samples of sewage sludge were toxic before degradation. Combination of physical, physicochemical and biodegradation processes was identified as the most effective method for reducing toxicity of sewage sludge. Combination of physical, physicochemical and biodegradation processes is an innovative approach in biodegradation treatment. It also improves the utilization of sewage sludge after reducing its toxicity.