Effect of Type of Coagulants on Removal Efficiency and Removal Mechanisms of Antibiotic Resistance Genes in Anaerobic Digestion of Primary Sludge Produced Via a Chemically Enhanced Primary Treatment Process

Abstract

Investigating the potential impact of the trivalent coagulant cations on the removal mechanisms, removal efficiencies and removal patterns of antibiotic resistance genes (ARGs) during anaerobic digestion (AD) of chemically enhanced primary treatment sludge (CEPTS) was performed using polyaluminium chloride (PACl), ferric chloride (FeCl₃) and mixed FeCl₃-PACl. The removal efficiency of the total 23 ARGs and intI1 improved to 72.1% in AD of primary sludge with 100 mg/L FeCl₃ and was the lowest (only 54.4%) in AD of primary sludge with 25 mg/L PACl. The removal of ARGs in AD of CEPTS with addition of single or mixed types of Al-based coagulant began to increase rapidly at the onset of batch operation. On the other hand, the rapid increase in the removal efficiency of ARGs in AD with FeCl₃ began somewhat later than in other ADs and the maximum removal efficiency was reached later than in other ADs.