Sono-alkalization pretreatment of sewage sludge containing phthalate acid esters

Abstract

This work experimentally elucidates the efficiencies of sono-alkalization treatment on municipal sewage sludge. The total solids (TS) concentration of the sewage sludge was pre-adjusted at 29.7 g/L. Two parameters such as sodium hydroxide (NaOH) dosage and sonication time were considered by the central composite design (CCD) program to investigate the effect on the degradation of phthalate acid esters (PAEs) and solubilization of soluble chemical oxygen demand (SCOD). The mean concentrations of dibutyl phthalate (DBP), di-(2-ethylhexyl) phthalate (DEHP) and butyl benzyl phthalate (BBP) in the sewage sludge were 718, 41 and 8 mg/kg dry weight sludge, respectively. Sono-alkalization process was effective on the degradation of DBP but worthless for DEHP and BBP. Overall degradation of DBP in sewage sludge was estimated to be 100% at the NaOH dosage of 68 mM and sonication time of 2.2 min. Sono-alkalization was responsible for 6,000 mg/L increase of SCOD based on the decrease of volatile solids in sewage sludge.