Occurrence, removal and risk assessment of steroid hormones in two wastewater stabilization pond systems in Morogoro, Tanzania

The present study investigated the occurrence and removal of 10 steroid hormones (4 androgens, 3 progestagens and 3 estrogens) in two WSP systems, Mafisa and Mzumbe in Morogoro, Tanzania. All 10 steroid hormones were detected in the influent of both WSP systems in the dry as well as in the rainy season. The concentrations of steroids in influent wastewater ranged from 0.1 ng/L for 17-OH-pregnenolone to 445 ng/L for estrone and from below limit of detection for 17-OH-pregnenolone to 45 ng/L for estrone in effluent. During dry season, the overall mean ± standard deviation removal efficiency for the 10 steroids were 70 ± 21% for Mzumbe WSP and 97 ± 3% for Mafisa WSP. During the rainy season the overall mean removal efficiency for all the steroid hormones were 52 ± 32% for Mzumbe WSP and 94 ± 8% for Mafisa WSP. Risk was characterized by calculating the risk quotients (RQs) for fish and humans. 46% of the total RQs calculated were above one, indicating high risk. Low RQs were estimated for androgens and progestagens but the estrogen concentrations measured in the WSP systems and Morogoro River indicated a high risk for fish. However, estrogens appeared not to pose an appreciable risk to human health from water intake and fish consumption. The results indicated that WSP systems are quite effective in removing steroid hormones from wastewater. Thus, low technology systems such as WSP systems are suitable techniques in low income counties due to relatively low costs of building, operating and maintaining these systems.