Dissolved Air Flotation: Efficient Removal of Micropollutants from Stormwater Runoff

Abstract

Stormwater runoff washes off a considerable amount of pollutants from the surfaces of urban catchment areas. Most of the pollutants are transported particlebound and it is well known that solids of a small grain size (suspended solids) serve as their host carrier. In the traditional design, the stormwater sewer of a separate system discharges into an intermediate sedimentation tank at the outfall of the receiving water to reduce the pollutants load. Due to the extended sedimentation time of small particle, this type of stormwater treatment facility is incapable of removing finer, polluted solids fractions. A demonstration project has shown that chemical coagulation and liquid/solid separation by dissolved air flotation results in an efficient removal of pollutants and allows recovery of the natural waters.