The effect of hydraulic retention time (HRT), solar radiation and seasonality on the removal efficiency of 18 emerging contaminants has been studied in a biological filtration pilot plant based on Daphnia sp. The pilot plant consisted of a homogenization tank and two lines, A and B, each with four 1 m(3) tanks. One of these lines was directly exposed to sunlight whereas the other line was covered. Our results suggest that biodegradation and photodegradation are the most important removal pathways, whereas sorption makes a minor contribution. The removal efficiency ranged from no detectable removal to more than 90%. The kinetics of the degradation process was fit to a first order kinetic, with half-lives from 0.6 to 42 days, depending on the particular compound. However, a scaling effect comes into play as the pilot plant was found to be more efficient than a similar full-scale polishing pond.
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