Multicriteria Analysis of the Effects of Sewage Sludge Conditioning Prior to the Dewatering Process

Abstract

Dewatering of sewage sludge is a key operational element of wastewater treatment plants and has major economic implications, as it entails the costs of thickening, transport, and disposal. The aim of this study was to determine the influence of selected polyelectrolytes and their dosages on dewatering efficiency and to present an innovative, multicriteria method of result evaluation using radar charts. In this research, 10 different polyelectrolytes were assessed in terms of sludge dewaterability, considering conditioning parameters including Specific Resistance to Filtration (SRF), Capillary Suction Time (CST), and centrifugation performance. The results were presented in the form of radar charts, enabling both an overall evaluation of the effectiveness of each product and an assessment of their suitability for specific dewatering technologies, such as belt filter presses and centrifuges. The analysis showed that polyelectrolytes with higher cationic charge provided better dewatering performance. The proposed visualization method allows us to analyze the effects across different conditioners and technologies. The best sludge conditioning effect (maximum radar chart area) was achieved with Praestol 665, a polyelectrolyte with a high cationic charge level. This method is a practical tool for selecting the optimal agent for sewage sludge dewatering.