Study On The Fate Of Antiseptics In Sewage Treatment Systems And Model Simulation

Antiseptics are additives commonly used in daily chemical products,mainly to kill microorganisms,prevent the corruption of goods,and influence the performance or quality when we use the products.Parabens,triclocarbon(called TCC for short),and triclosan(called TCS for short)are commonly used antiseptics.And studies have shown that parabens are suspected of having estrogenic activity,whereas TCC and TCS may have toxic effects on human hepatocyte DNA.As the main place for sewage treatment,sewage treatment system is very important to the removal of antiseptics.However,there are few studies on the fate of antiseptics in sewage treatment systems.In this paper,A wastewater treatment plant of A/O process with primary sedimentation tank in Harbin City and B wastewater treatment plant of A/O process without primary sedimentation tank were chosen as research objects,and the detection and analysis of parabens,TCC,and TCS in different treatment process compartments and diffenent phases were conducted.And using the Simple Treat4.0 environmental multi-media model to simulate the liquid phase concentration,total concentration and removal pathway.The research results show that 100% of parabens,TCC,and TCS can be detected in different process sections and phases of wastewater treatment plants,and methylparaben(called Me P for short)is the most major parabens in the influent.The TCC concentration is also significantly higher than that of TCS.It is related to the fact that Me P is the most used preservative,and the allowable concentration of TCC in products is also significantly higher than that of TCS.Most of parabens exist in the liquid phase.Because of their small value of octanol-water partition coefficient(called Kow for short)they are difficult to be adsorbed into solids.On the contrary,TCC and TCS have larger Kow values and are easily adsorbed into solids.The removal efficiency of parabens,TCC,and TCS in A/O process was high in the presence/absence of primary sedimentation tanks.The difference was that parabens were mainly removed in the aerobic biochemical treatment process,and the biodegradation rates of Me P,ethylparaben(called Et P for short)and propylparaben(called Pr P for short)decreased in turn.Whereas TCC and TCS are mainly removed by the primary sedimentation and excess sludge,and the TCC removal rate is higher than that of TCS.The main removal pathway of parabens is biodegradation,while the main removal pathway of TCC and TCS is solid adsorption(primary sedimentation tank + excess sludge).The primary sedimentation had few effect on the removal of parabens,but was the main removal pathway for TCC and TCS.The prediction results of the Simple Treat4.0 model for parabens,TCC,and TCS are generally consistent with the measured results,and they are suitable for parabens and have a certain gap and need further improvement for TCC and TCS.The sensitivity analysis showed the input parameter that has the greatest im pact on the biodegradation pathway is the biodegradation rate constant,and the input parameter that has the greatest effect on the sludge adsorption pathway is organic carbon adsorption coefficient(called Koc for short).After modifying the model parameters,the Koc of the TCC is reset to 316228,the corresponding partition coefficient in sewage(called Kps for short)and partition coefficient in activated sludge(called Kpas for short),Kpas are changed to 56921,72732;the Koc of the TCS is reset to 100000,and the corresponding Kps and Kpas are changed to 18000 and 23000,respectively.And then Simple Treat4.0 can predict the results much closer when compared to the actual measurement.