Assessment of di-(2-ethylhexyl)phthalate (DEHP) Removal in a Rotating Biological Contactor and Activated Sludge Process Treating Domestic Wastewater

Abstract

Di-(2-ethylhexyl)phthalate (DEHP) is one of the most representative persistent micro-pollutants detected in the sewage sludge. In the present study, the presence of DEHP and its removal in various treatment units of a sewage treatment plant (STP) including an attached growth biological system i.e., a rotating biological contactor (RBC) and a suspended growth biological system i.e., activated sludge process (ASP) were investigated. Representative samples of sewage and sludge were collected at each stage of the STP for 2 years to explore the DEHP flow in the dissolved (DEHP_d) and adsorbed (DEHP_a) phases. The combination of RBC with a final clarifier was responsible for 50.4 and 58.2% of DEHP_d and DEHP_a removals, respectively. Both DEHP_d and DEHP_a removals were greater in RBC compared to ASP, demonstrating that an attached growth biological system is more efficient in the removal of DEHP compared to the suspended growth biological system. A good correlation between DEHP and organic matter removal was observed by using Pearson-correlation matrix approach.

Keywords:

• di-(2-ethylhexyl)phthalate
• mass balance
• persistent micro-pollutants
• sewage treatment plant

ACKNOWLEDGMENTS

The authors would like to thank the National Science Council, Republic of China for financial support (Grant NSC-89-2211-E-009-013) and the operators of the Min-Shen sewage treatment plant for their support throughout this study.

Notes

^a DEHP in dissolved phase.

^b DEHP in adsorbed phase.

^c n = 5.

^a Calculations are based on measured DEHP concentrations before and after each wastewater treatment unit.

^b Calculations are based on mass concentrations of DEHP in sludge treatment unit.

∗Value reported in [ ] is calculated based on the changes of DEHP concentration in dissolved phase.

^a Figures in bold indicates a significant correlation, p < 0.05.