Analysis of Properties and Possibilities of Environmental Use of Municipal Sewage Sludge—A Case Study

Abstract

The formation of sewage sludge is an inherent effect of the wastewater treatment process. Their composition is characterized by high variability and depends mainly on the properties of wastewater, technologies of their treatment and methods of processing sediments. Without knowing the properties of sewage sludge, it is difficult to choose the appropriate method for their utilization or disposal.The aim of the study was to analyze the physical and chemical properties of sewage sludge from a selected municipal wastewater treatment plant and to assess the possibility of their use in environment. A municipal sewage treatment plant, located in mountainous terrain (Gorlice, Poland, Malopolska Voivodship) was selected for the study. The research were conducted in the years 2011–2016, on dehydrated sludge, after aerobic stabilization.Analysis of the results showed a high variability and a relatively low level of the sludge pH, which could be the result of improperly performed stabilization process. Among the analysed properties of sludge from the wastewater treatment plant in Gorlice, high variability was also demonstrated by the dry matter content and organic compounds. The maximum contents of some of the analysed heavy metals were relatively high, but did not exceed the limits specified for sludge used to fertilize the land, utilized for agricultural purposes, which apply to the most stringent conditions. However, the maximum content of zinc significantly exceeded the limit value at the agricultural use of sewage sludge. This limits the possibility of using sludge and makes it necessary to look for other methods of utilization.