Suitability of Wastewater Sludge for Utilization in the Leningrad Region (Russia)

Abstract

Insufficient wastewater treatment causes serious problems for the environment and health in the Leningrad Region. Even though wastewater treatment has been improving during the last decade, almost no attention has been paid to the wastewater sludge treatment. Nutrient emissions from the organic wastes, including wastewater sludge, are among the most significant sources of the eutrophication of the Baltic Sea. Disposal of sludge causes also significant greenhouse gas emissions, polluting local water resources and filling up the landfill sites. Currently the main treatment method of wastewater sludge in Russia is so called aging. This means that sludge is stored in piles from some months up to some years, and after that the sludge is disposed to landfills. In order to develop wastewater sludge treatment, it is essential to know the properties of the material treated. In Russia, wastewater sludge is often expected to contain high amounts of heavy metals. This is a significant challenge for material or energy recovery from the sludge. Different possible treatment methods of wastewater sludge are discussed in this paper. The properties and composition of wastewater sludge from two different municipal wastewater treatment plants are defined and discussed in the paper. The main properties are volatile and total solids, moisture and ash content, inorganic compounds, heavy metal contents, and the lower heating value of dry matter. The effect of the properties on energy and nutrient recovery purposes are evaluated.