Filtration of Detained Stormwater through Sand and Alum Sludge for Water Quality Control

Stormwater detention systems as they are frequently designed do not provide good water quality control of stormwater runoff. A filtration media to be used in conjunction with detention ponds to improve their pollutant removal efficiencies was tested at the University of Central Florida and found to be effective. The filtration media, which consisted of a mixture of sand and alum sludge, substantially improved effluent water quality. Average reductions of over 80 % were observed in concentrations of dissolved orthophosphorus, total orthophosphorus and total phosphorus. Reductions were also experienced in iron, aluminum, copper and zinc concentrations. A prototype filtration model is presently being tested on the Lake Eola watershed in Orlando, Florida. A stormwater management and design aid computer program originally written by Tim Curran (Curran 1980) to calculate stormwater hydrographs and retention volumes, and updated by the author to also calculate detention volumes will incorporate results from the prototype study