Environmental and ecological risk assessment of municipal sewage sludge management using a sustainable solar drying system

Abstract

Providing a cost-effective and suitable way for sewage sludge refinement with the purpose of reducing environmental impacts or reutilization of sewage sludge can be an important issue for researchers. This study is inclined at bringing an economical and sustainable solution to sludge management in a municipal wastewater treatment plant. Three types of sludges were collected for the experiments: raw sludge was collected during winter (R.S.), digested sludge was collected during winter (D.S.1), and digested sludge was collected during summer time (D.S.2). This study proposes replacing mechanical drying by a solar drying system. Experimental analysis was carried out to determine the total solids (TS), volatile solids (VS), heavy metals concentration, and pollution index (index of geo accumulation, contamination factor, ecological risk factor). The solar drying system was demonstrated to be very efficient with the three samples achieving a dry solid content of 96.96% for R.S., 96.75% for D.S.1, and 93.60% for D.S.2. after solar drying. While pollution index calculations showed that all three sludges present a low potential ecological risk.