The effect of hydraulic retention time in onsite wastewater treatment and removal of pharmaceuticals, hormones and phenolic utility substances

Micropollutants such as pharmaceuticals, hormones and phenolic utility chemicals in sewage water are considered to be an emerging problem because of increased use and observed adverse effects in the environment. The study provides knowledge on the removal efficiency of micropollutants with a range of physical and chemical properties in three commercially available onsite wastewater treatment facilities (OWTFs), tested on influent wastewater collected from 2500-person equivalents in Bildchen, Germany. A longer hydraulic retention time would in theory be expected to have a positive effect, and this study presents results for three different OWTFs in full-scale comparable tests under natural conditions. A range of 24 different pharmaceuticals, five phenols and three hormones were analysed. Flow-proportional consecutive sampling was performed in order to determine the removal efficiency. Twenty-eight substances were detected in the effluent wastewater out of 32 substances included. Average effluent concentrations of Simvastatin, Oestrone, Oestradiol and Ethinylestradiol were above the indicative critical-effect concentration of pharmacological effect on fish in all facilities. Average effluent concentrations of both Diclofenac and Oestradiol were higher than the Environmental Quality Standards applied in Sweden (190-240 times and 9-35 times respectively). The removal efficiency of micropollutants was high for substances with high logKow, which enhance the adsorption and removal with sludge. Low removal was observed for substances with low logKow and acidic characteristics, and for substances with stabilising elements of the chemical structure. Facilities that use activated sludge processes removed hormones more efficiently than facilities using trickling filter treatment technique. Moreover, longer hydraulic retention time increased the removal of pharmaceuticals, hormones, turbidity and total nitrogen. Removal of Caffeine, Ibuprofen, Oestrone, Naproxen and Oestradiol, was strongly correlated to the sludge and particles removal. Thus, the efficiency of the tested OWTFs could be improved by adjusting the technical methods and increasing the hydraulic retention time.

Authors: Ejhed H, Fång J, Hansen K, Graae L, Rahmberg M, Magnér J, Dorgeloh E, Plaza G. ; Full Source: Science of the Total Environment. 2017 Nov 9; 618:250-261. doi: 10.1016/j.scitotenv.2017.11.011. [fusion_builder_container hundred_percent=”yes” overflow=”visible”][fusion_builder_row][fusion_builder_column type=”1_1″ background_position=”left top” background_color=”” border_size=”” border_color=”” border_style=”solid” spacing=”yes” background_image=”” background_repeat=”no-repeat” padding=”” margin_top=”0px” margin_bottom=”0px” class=”” id=”” animation_type=”” animation_speed=”0.3″ animation_direction=”left” hide_on_mobile=”no” center_content=”no” min_height=”none”][Epub ahead of print][/fusion_builder_column][/fusion_builder_row][/fusion_builder_container]