Evaluation Of Proprietary Stormwater Treatment Devices In Field And Laboratory Conditions

Proper stormwater management acknowledges both water quantity and water quality. Historically, stormwater quantity and quality have been separately considered; runoff was routed as quickly as possible into the nearest body of water. Although this alleviates potential flooding concerns, water quality is often compromised. Common stormwater quality problems include gross pollutants, sediment, nutrients, and heavy metals. The chronic elevated presence of these pollutants is detrimental to the environment. As a result, the government has passed legislature to protect waterways. The passage of the National Pollution Discharge Elimination System (NPDES) permit requires that municipalities implement stormwater treatment techniques, known as Best Management Practices (BMPs). Unfortunately, the NPDES document suggests treatment to the maximum extent possible, a vague description at best. This thesis reports a two-part study that endeavors to evaluate three of these proprietary treatment units manufactured by Stormceptor, BaySaver Separation Systems, and Continuous Deflective Separator (CDS) Technologies, Inc. to determine their performances. Each manufacturer produces a separator system that physically removes contaminants through the use of hydrodynamic flow principles. Phase I of the study focuses on monitoring two Stormceptor units and a CDS device in field conditions, while the second phase of the study evaluates each of the three treatment systems under laboratory conditions. The data analyses from the field study show the importance of proper maintenance. Storm events monitored after sump material removal showed great improvement over storm events occurring some time after the sump material removal. Furthermore, the treatment devices show a greater ability to remove pollutants from smaller storm events when compared with larger storm events. It is suggested that large storms cause scour of sediment previously trapped within the sump of the devices. An increase in the total suspended solid and nutrient concentrations, which were higher than the influent concentrations, was observed in both the field and laboratory studies. This could be explained by the fact that organics trapped by the treatment system decompose over time, therefore producing nutrient-rich water in the sump of the devices with higher concentration than the subsequent storm events. Some results are close to the minimum detection limit of the parameters being tested and small differences between influent and effluent load exaggerate the percent load differences. Consequently, there is little statistical significance between influent and effluent data, thus the data are summarized utilizing two methods. The methods include graphical representation of concentration and percent load difference, a method that normalized storms based on event size. In addition, a mass balance of gross litter was performed during the laboratory study