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CONSIDERATION IN THE DESIGN OF TREATMENT BEST MANAGEMENT PRACTICES (BMPS) TO IMPROVE WATER QUALITY
Citation:
Clar, M., B. Barfield, AND S. Yu. CONSIDERATION IN THE DESIGN OF TREATMENT BEST MANAGEMENT PRACTICES (BMPS) TO IMPROVE WATER QUALITY. U.S. Environmental Protection Agency, Washington, D.C., 600/R-03/103, 2002.
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Description:
For the past three decades, municipalities in the United States have successfully addressed pollution in the watershed by collecting and treating their wastewater. Currently, all municipalities provide secondary level treatment, and in some cases tertiary treatment, and industries provide best available/best practicable treatment. This has had great benefits. More rivers are meeting water quality standards, and the public health is being protected from waterborne disease. The challenge now facing us is to address pollution associated with storm water runoff, since this is now the last major threat to water quality. It is less costly to prevent the generation of polluted runoff than to treat it. Today, many municipalities are implementing low-cost best management practices (BMPs) that prevent runoff. The lowest cost BMPs, termed non-structural or source control BMPs, include practices such as limiting pesticide use in agricultural areas or retaining rainwater on residential lots (currently termed "low impact development"). There are a set of higher cost BMPs, which involve building a structure of some kind to store stormwater until it can be discharged into a nearby receiving water. These can be more costly, especially in areas where land costs are discharged into a nearby receiving water. These can be more costly, especially in areas where land costs are high. The three most commonly used structural treatment BMPs that will be discussed in the document are ponds (detention/retention), vegetated biofilters (swales and filter/buffer strips) and constructed wetlands. Two categories of treatment considered in this document are ponds and vegetated biofilters. Ponds are probably the most frequently used BMP in the United States. There are three types of pond BMPs: wet ponds (retention ponds); dry ponds (notably extended detention ponds);and infiltration basins. Three different types of vegetative biofilter BMP types are discussed: grass swales, vegetated filter strips, and bioretention cells. Grass swales include three variations: traditional grass swales, grass swales with media filters and wet swales. This document presents factors that should be considered in the design of treatment BMPs to improve water quality. The state-of-the-practice is such that existing design guides vary and the performance of treatment BMPs shows a wide range of pollutant removal effectiveness.