Thermal Treatment of Sewage Sludge

This article provides the results of several series of experiments on the combustion of mechanically dehydrated sewage sludge as one of the ways to solve the problems of sludge storage, treatment and disposal. Solving this problem requires the development and implementation of new technologies and methods for the treatment, processing and disposal of sewage sludge, which would be more efficient and economically sound. Non-treated sewage sludge contains toxic substances such as heavy metals, organic pollutants and pathogenic microorganisms that can be dangerous to living organisms and ecosystems. In addition, sewage sludge accumulated at landfills occupies huge territories, which causes additional problems in terms of land use, since about 100 million tons of liquid sludge (2 million tons by dry weight) are generated annually at Russian wastewater treatment plants. The research on the thermal disposal of sludge were conducted at the sewage treatment plants of one of the cities in the region at a small experimental unit with vertical sludge supply and with a side point flame source. A number of experiments revealed that mechanically dehydrated sludge is able to burn without an external flame source at a humidity of 69.9%; with a decrease in the sludge humidity its calorific value increases. In the process of sludge burning ash is obtained with a volume at least 5 times smaller than the initial volume of sludge which makes it possible to increase manifold the utilization rate of sludge piles.