Advanced stormwater treatment - comparison of technologies

In traditional wet ponds for stormwater management, the dissolved and colloidal bound pollutants are as a general rule only poorly removed. However, it is these fractions that are most mobile in the aquatic environment and which are most easily bio-accumulated. In the context of this project, different technologies for reducing dissolved pollutants and pollutants associated with fine particles and colloids were tested in full scale. For this purpose, 3 treatment facilities were constructed managing between 8.8 and 25.8 reduced ha. All facilities contained a wet detention pond and sand filters. In one facility the water from the sand filters was led through fixed media sorption filters. In another facility the pond bottom was enriched with iron salts. In the last facility aluminum was added to the incoming stormwater. The treatment train consisting of wet detention pond, sand filter and sorption filter was efficient in reducing nutrients, heavy metals and PAHs. Accidentally, the facility equipped with this treatment train received extremely high concentrations of copper and other heavy metals, which were consistently reduced to very low levels, proving an efficient safeguard against those pollutants. The treatment train consisting of wet detention pond with iron enriched bottom sediments followed by a sand filter and the treatment train consisting of aluminum addition to the stormwater entering the wet pond and followed by a sand filter, proved to be efficient in reducing suspended algae of the wet detention pond. Compared to the fixed media filters, the treatment trains were, however, less efficient with respect to removing heavy metals.