Decrease of antiandrogenic activity in gray water and domestic wastewater treated by the MBR process

In order to figure out the variation of the androgens/antiandrogens in wastewater treatment, androgenic/antiandrogenic activities were investigated in two membrane bioreactors (MBR) treating gray water and domestic wastewater, respectively, in Beijing city, China. The androgens and antiandrogens were extracted from water and solid samples by a solid phase extraction (SPE) method and the androgenic/antiandrogenic activities were detected with a recombined androgen receptor (AR) yeast assay. The results showed that there were no androgenic induction activities either in water or in solid samples, but all samples exhibited obvious antiandrogenic activities. The antiandrogenic activities in the suspended solids contributed to 27.4% of the total antiandrogenic activities in gray water and 37.7% in domestic wastewater. Although the concentration of flutamide equivalent (FEQ) of the domestic wastewater (3.1 mg L⁻¹) was about three times higher than that of the gray water (1.1 mg L⁻¹) in the liquid phase, the effluent FEQ of the two processes was comparable, and the concentrations were 53.7 ± 2.4 μg L⁻¹ and 68.9 ± 6.0 μg L⁻¹, respectively. By mass balance analysis, a total of 1825.2 mg FEQ antiandrogens flowed into the gray water and 4914.1 mg flowed into the domestic wastewater treatment process every day. More than 95% of the influent antiandrogens in the liquid phase was removed in both systems. And only 64.5 mg and 69.0 mg FEQ antiandrogens flowed out of gray water and domestic wastewater treatment processes every day. Biodegradation was considered to be the crucial antiandrogen removal mechanism in MBR, which contributed to 98% of the antiandrogen removal in the gray water treatment plant, and 91% in the domestic wastewater treatment plant.