Sewage sludge dewatering by electric field

Abstract

During the cleaning and further treatment of municipal wastewater, sediments are formed, which are extremely dangerous from a sanitary and hygienic point of view, poorly dewatered, have high humidity (over 90%), large volumes (up to 3% of wastewater consumption), contain organic substances, pathogens, heavy metals, etc. In Ukraine, at most wastewater treatment plants, sewage sludge is mostly piled up on sludge sites after minimal treatment. Effective processing and disposal of sewage sludge in order to reduce the negative impact on the environment, as well as the use of sewage sludge as secondary raw materials, is an actual, complex and urgent task. The key link in the existing process of treatment and disposal of sewage sludge is their dewatering. When designing facilities for the treatment and disposal of sewage sludge, advanced technologies should be used, the use of which is based on scientific and technical research. The article reviews the results of research on the intensification of existing mechanical methods of sewage sludge. One of the most effective methods of intensifying the process of dewatering sewage sludge is electro-dewatering, which involves the application of an electric field during mechanical dewatering of sludge. Electro-dewatering technology makes it possible to reduce the humidity of sediments to 20...40%, reduce the concentration of heavy metals and pathogens in sediments, etc. The purpose of this work is to study the possibility of electro-dewatering of activated sludge from secondary settling tanks of municipal wastewater treatment plants in Lviv. Empirical research methods were used. A laboratory scale has been designed for electro-dewatering of sewage sludge. Activated sludge with a moisture content of 98% was studied. It is shown that the effect of activated sludge dewatering, depending on the duration of its treatment, is an S-shaped curve that resembles a kinetic autocatalytic reaction with three periods: induction, main, and fading. The possibility of electro-dewatering of sewage sludge with a maximum dewatering effect of 60% has been proven. Therefore, it is proposed to carry out mechanical dewatering of city sewage sludge using an electric field.