Author(s): Jia Ma; James H. Lenhart; D. Wre; Karel Tracy
Linked Author(s):
Keywords: Filter Media; Ortho-Phosphate; Total Phosphorus; Activated Alumin
Abstract: Many surface water bodies around world are eutrophic and one major cause is phosphorus loading from stormwater runoff. These escalated concentrations of phosphorus are both in solution and associated with the entrained particles. Stakeholders have been seeking stormwater Best Management Practices (BMPs) which offer high removal rates of total phosphorus (TP), which is the sum of the particulate and dissolved fractions. The dissolved fraction is characterized as Ortho-Phosphate (Ortho-P). A regulatory target removal of 50-65 percent is commonly required in an effort to maintain predevelopment conditions. Many past studies of BMPs show that TP removal rates in excess of 40%are difficult, and that many technologies, even though sporadically achieving high initial TP removal rates continue to release OrthoP afterwards which reduces the overall TP reduction. Therefore, it is critical to remove and retain Ortho-P in order to reliably achieve the TP removal target. Different types of filtration media, such as iron based media, expanded clays and aluminium based media, have been evaluated with regard to Ortho-P removal. Laboratory research and subsequent field trials of activated alumina demonstrated its effectiveness for Ortho-P reduction, resulting in improved TP removal. But still, for other factors, few media are fully qualified to treat TP in stormwater runoff. In addition to effective Ortho-P and TP removal, basic media requirements such as low cost, controllable gradation and permeability, no aquatic toxicity, and cost of disposal are critical to successful commercial deployment for stormwater treatment. To develop a media that meets these requirements, nearly 100 formulations were evaluated and tested. The end result is a light weight refractory media utilizing activated alumina that provides cost effective removal of total suspended solids (TSS) and TP from stormwater. Bench scale testing showed that an average removal of 40%for treating over 2000 empty bed volumes (EBVs) of 0.5 mg/l Ortho-P influent solution. By comparison, common zeolite can only treat dozens of EBVs before exhausted. The first result from field testing showed higher than 50%of TP removal with additional field testing under way.
Year: 2010