Removal of endocrine-disrupting chemicals and conventional pollutants in a continuous-operating activated sludge process integrated with ozonation for excess sludge reduction

•Sludge ozonation was applied to a continuous-operating activated sludge process.•A zero yield of excess sludge was achieved at an ozone dose of 100 mg O3 g−1 SS.•Ozonation impacted insignificantly the removal of COD and nitrogen substances.•Sludge ozonation contributed a little more removal of target EDCs than the control.•Phosphorus recovery is necessary for the long-term sludge reduction by ozone.

Sludge ozonation is considered as a promising technology to achieve a complete reduction of excess sludge, but as yet its effects on the removal of endocrine-disrupting chemicals (EDCs) and conventional pollutants (i.e., COD, N and P) in the activated sludge process are still unclear. In this study, two lab-scale continuous-operating activated sludge treatment systems were established: one was operated in conjunction with ozonation for excess sludge reduction, and the other was operated under normal conditions as control. The results indicate that an ozone dose of 100 mg O3 g−1 SS led to a zero yield of excess sludge in the sludge-reduction system during a continuous-operating period of 45 d. Although ozonation gave a relatively lower specific oxygen uptake rate of activated sludge, it had little effect on the system’s removal performance of COD and nitrogen substances. As a plus, sludge ozonation contributed a little more removal of target EDCs (estrone, 17β-estrodiol, estriol, 17α-ethinylestradiol, bisphenol A, and 4-nonylphenol). However, the total phosphorus removal declined notably due to its accumulation in the sludge-reduction system, which necessitates phosphorus recovery for the activated sludge process.

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