Evaluation of municipal sewage treatment systems for pollutant removal efficiency by measuring levels of micropollutants

In order to evaluate the municipal sewage treatment systems used at Harbin municipal sewage treatment plant for their pollutant removal efficiency, raw sewage and effluent samples at different treatment stages from the sewage treatment systems were taken, priority pollutants (PPs) were identified and quantified using gas chromatography–mass spectrometry (GC–MS) and inductively coupled plasma-atomic emission spectrograph (ICP-AES). The test results indicated that there were one hundred and fifty species of organic pollutants identified in the raw sewage sample, and only ten species of PPs in all the sewage samples. The levels of dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), di-n-octyl phthalate (DnOP) in the sewage samples were 0.779–0.111 μg l−1, 1.977–0.022 μg l−1, 6.411–2.194 μg l−1 and 7.152–2.953 μg l−1, respectively, and most of these phthalate esters (PAEs) were removed through anaerobic/aerobic (A/O) process; The levels of alachlor, acetochlor, atrazine were 0.074–0.021 μg l−1, 0.160–0.096 μg l−1 and 0.238–0.184 μg l−1, respectively, and the total removal efficiency of atrazine was poorest through the sewage treatment systems. The levels of Cu, Cr, Se, Hg, Ni and Zn were 0.0030–0.2327 mg l−1. It is therefore concluded from these results that the sewage treatment systems were efficient in removing most of the organic and inorganic compounds in this study, and so, the discharged effluent could cause little of the secondary pollution of the aquatic environment.