The purposes of this study were (1) to characterize the SMPs under a number of simulated stressful conditions, (2) to evaluate the formation of DBPs resulting from chlorination of SMPs under these stressful conditions, and (3) finally to examine the mutagenicity of SMPs before and after chlorination under each of these conditions.
2. Materials and methods
2.1. Batch experiments and preparation of SMPs
Activated sludge was collected from an aeration tank in a municipal wastewater treatment plant, and used as inoculums for the reactor. Five series of batch experiments (one normal state (NS) and four simulated stressful conditions of HA, HS, HM and HT) were conducted in this study.
The cultured activated sludge was added into five 5-L reactors filled with synthetic wastewater to a final EPZ-6438 concentration of about 2000 mg/L to create NS wastewater. The synthetic wastewater contained the following substances (in mg per L): glucose (800), (NH4)2SO4 (189), KH2PO4 (35), CaCl2 (0.37), MgSO4 (5.07), MnCl2 (0.27), ZnSO4 (0.44), FeCl3 (1.45), CuSO4 (0.39), CoCl2 (0.42), Na2MoO4 (1.26), NaBr (0.26) . (NH4)2SO4, NaCl and CrCl3 were added into one of the NS wastewater samples to create simulated stressful condition of HA (500 mg/L ammonia nitrogen (NH4+-N)), HS (5% NaCl) and HM (50 mg/L CrCl3) solutions, respectively. HT was the NS samples conducted at elevated temperature of 45 °C. Each reactor was incubated for 6 h at 25 °C followed by a precipitation time of 30 min. Supernatant was then collected and filtered through a 0.45 μm filter paper. The filtrate was defined as SMPs .