An Evaluation of Separating Combined Sewers and Its Effect on Water Quality in the Greater Milwaukee, Wisconsin Area
Abstract:In an effort to reduce combined sewer overflows (CSOs) and improve surface water quality in the greater Milwaukee area, construction of a 19.5-mile (31.4 km) inline storage system (ISS) was completed in 1994 to capture and convey for treatment, sanitary sewage and stormwater from the combined sewer service area (CSSA). Since the ISS has been in operation, a significant improvement in the area's water quality has been observed due to the capture and treatment of over 66.4 billion gallons (251 million cubic meters) of sanitary sewage and stormwater. Despite the water quality improvement in the CSSA area, the waterways are still not meeting Wisconsin Water Quality Standards. The continued occurrence of overflows (2.50 CSO's/year) perpetuates the public view that sewer separation is the solution to improve water quality.
The application of the Chemical Mass Balance (CMB) model in this study has been successful because the relative contributions of sanitary sewage and stormwater in CSOs were well determined. The relative contributions of pollutants such as metals, TSS, and E. coli were found to be higher in stormwater than in sanitary sewage. This result confirms that stormwater, not sanitary sewage, is the dominant pollutant source of these specific pollutants in the CSSA during storm events. Based on these findings, the impact of sewer separation in the CSSA would be a significant detriment to the water quality in the greater Milwaukee area because of the large pollutant contribution of uncaptured and untreated stormwater directly discharging to the local waterways instead of being captured by the ISS and treated at the treatment plants.
In the practice of sewer separation, the treatment of pollutants such as metals, TSS and E. coli is recommended prior to any discharges to waterways. Sewer separation only should be considered a viable alternative if the treatment of stormwater is supported through the use of effective stormwater best management practices (BMPs) that target the removal or reduction of metals, TSS and E. coli before stormwater is discharged to surface waters.
Keywords: AND BEST MANAGEMENT PRACTICES (BMPS); COMBINED SEWER OVERFLOWS (CSOS); COMBINED SEWER SERVICE AREA (CSSA); INLINE STORAGE SYSTEM (ISS); MILWAUKEE METROPOLITAN SEWERAGE DISTRICT (MMSD); SEWER SEPARATION
Document Type: Research Article
Publication date: 2007-10-01
- Proceedings of the Water Environment Federation is an archive of papers published in the proceedings of the annual Water Environment Federation® Technical Exhibition and Conference (WEFTEC® ) and specialty conferences held since the year 2000. These proceedings are not peer reviewed. A subscription to the Proceedings of the Water Environment Federation includes access to most papers presented at the annual WEF Technical Exhibition and Conference (WEFTEC) and other conferences held since 2000. Subscription access begins 12 months after the event and is valid for 12 months from month of purchase. A subscription to the Proceedings of the Water Environment Federation is included in Water Environment Federation (WEF) membership.
WEF Members: Sign in (right panel) with your IngentaConnect user name and password to receive complimentary access. Access begins 12 months after the conference or event
- Subscribe to this Title
- Membership Information
- About WEF Proceedings
- WEFTEC Conference Information
- Learn about the many other WEF member benefits and join today
- Ingenta Connect is not responsible for the content or availability of external websites