Pollutant removal efficiency of a retrofitted stormwater detention pond

The objectives of this study were to characterize the stormwater runoff for a residential catchment, evaluate the present detention pond removal efficiency for different pollutants, and evaluate how its efficiency can be increased by controlling the pond stormwater retention time. The analysed pollutants were total suspended solids (TSS), total metals and ammonia. Runoff pollutant concentrations were generally found to agree with literature for the small residential catchment. The design of the original pond was such that low retention times of most analysed pollutants occurred, causing a lower than expected removal efficiency when compared to similar types of ponds. The retrofitting of the pond consisted of adding a sluice gate at the outlet in order to retain stormwater for longer periods of time. The retrofit allowed drastic improvement of the removal efficiency for TSS, NH3-N and zinc, from 39 to 90%, 10 to 84%, and 20 to 42%, respectively.