Treat the source

摘要

New emphasis on maintenance, sampling, and monitoring in the Municipal Phase II National Pollutant Discharge Elimination System (NPDES) permit has sparked attention to identifying and controlling the source of pollutants contributing to the system. The upshot is a greater need for advanced stormwater treatment techniques that meet water quality standards. Most water quality issues are not related to single contributors, oil spills, or catastrophic events, but are related primarily to nonpoint source and construction site pollutant contributions. What's more, studies have shown the majority of hydrocarbon, metal, and pesticide contributions in stormwater to be associated with the fine sediment suspended in the stormwater. Based on these and other findings, municipalities have imposed numeric limits and benchmark values for pollutants. These locally prescribed values are often based on receiving waters or a watershed-focused pollutant loading perspective. The implementation of numeric standards-in categories such as values above background or percent removal-heightens the challenge of selecting the correct best management practice (BMP) or treatment train to apply to achieve the prescribed standards. In many cases, conventional BMPs are incapable of reducing turbidity and other pollutants to acceptable levels. Traditional installation of straw wattles, silt fences, and similar measures are insufficient for removing suspended particles to levels suitable for the new NPDES permit requirements.