DEMFIL - treatment of stormwater for recreational use

Decoupling of stormwater (road runoff) in a residential area has been implemented in order to reduce flooding and to increase the hydraulic capacity of a lake with a high recreational value. The object here was to evaluate a disc filter technology in combination with a green polymer for flocculation for its feasibility of particle removal.

Secondary, the particulate pollution in the separate road runoff should be assessed. The road runoff was found not to be highly contaminated with particle pollution, here measured as turbidity and total suspended solids (TSS). The particles were generally small (< 10 μm) and negatively charged. The disc filtration was hampered during the winter season and by the large fraction of small particles, but supplementing it with flocculation increased the removal efficiencies.

The inlet particle concentrations (mg/L) affected the removal efficiencies, and events with inlet concentrations < 10 mg TSS/L or FNU had no statistically significant removal of the particle pollution whereas the events with the highest concentrations yielded among the highest removal efficiencies. The green polymer is as efficient as previously tested commercial coagulant/ flocculent and the disc technology is promising but need to be further tested with higher hydraulic loadings.