Concerns about water quality and possible intentional contamination of water distribution systems are making on-line monitoring an increasingly important priority for many water utilities. The city of Ann Arbor (Mich.) evaluated different water quality monitoring parameters, tested multiple manufacturers' monitoring equipment, and evaluated how to effectively locate monitoring equipment within the distribution system to address these two concerns. A suite of modeling tools was used in this case study. Total chlorine, ultraviolet absorbance at 254 nm, conductivity, and dissolved oxygen were selected for monitoring based on pilot testing. When balancing costs and benefits, four stations for monitoring water quality and four stations for monitoring contamination events were found to be sufficient for the city. Only one location was common between water quality and security sites, and the number of security monitors needed was not affected by system demands. It was confirmed that it is critical to minimize response time in order to mitigate the effects of a contamination event.
The Detroit Water & Sewerage Department (DWSD) collection system and WWTP serves the majority in Southeastem Michigan. This collection system has been modeled in detail since 1987. The primary model used for these evaluations has been the US EPA Stormwater Management Model (SWMM). While this model provides significant capability, the combined sewer evaluations performed for this area have required modifications both to the methods used to prepare the model and changes to the calculations performed by the model. This chapter highlights the changes that have been made to the model to provide an appropriate evaluation of the collection system performance. Many of the new features added to the SWMM model have been driven by the need to evaluate different methods to control combined sewer overflows. Some changes were required by the sheer scope of the modeled area and by the complexity ofthe collection and treatment system. The changes made include better methods to simulate flow routing; improved algorithms to simulate dry weather flow (DWF), rainfall dependent inflow/infiltration (RDIII), and their seasonal variation; better methods to evaluate regulators, outfaHs, and storage; and finally, better fonnats used to present the output to fairly evaluate t~e different con.sidered. Miilly of these ,.
A SWMM computer model was developed for the Detroit Water and Sewerage Department (DWSD) collection system to gain an understanding of overflows of combined and wet sanitary sewage (Camp, Dresser and McKee, 1993). This system serves both the City ofDetroit and surrounding communities, with a service area of 800 square miles (2067 km 2), which includes both combined and separated service areas. It contains a number of complex interconnections, loops, and overflow points within the system. Both SWMM EXTRAN and SWMM TRANSPORT were used to provide estimates of overflows within the system, while SWMM RUNOFF was used to compute the wet-weather inflows from the combined sewer service areas. The SWMMEXTRAN model was developed for specific calibration and design events. The use of EXTRAN enabl.ed a more detailed analysis of the complex hydraulic interactions within the large collection system. The information gained from this analysis was used as a basis for the continuous modeling. A continuous SWMM model was developed to
An accurate dye dilution testing protocol using Rhodamine WT was developed and used to quantity flow meter accuracy in the Greater Detroit Regional Sewer System. Over 150 tests were performed on 3 7 flow meters in conjunction with a set of good metering practice principles. A summmy of the accuracy for each of the seven technologies tested before and after good metering practice is given. The seven technologies assessed are electromagnetic induction meters (magmeters
Flow data collected from over twenty metered sites in Detroit, Michigan are used to determine the source of flows fi:om districts tributary to the Detroit Water & Sewerage Department (DWSD) collection system through a flow balance analysis. Criteria developed for selecting data include precipitation, snowmelt, and basin dewatering. The Greater Detroit Regional Sewer System (GDRSS) model, a hydraulic and hydrologic model of Detroit's sewer collection system, was used to refine the rainfall-based criteria. Specifically, it was used to determine the time required for the system to return to dry weather flow (DWF) conditions after one or a series of rainfall event'l. As a result of model simulations, relationships were developed to represent time-to-dly as a function of the rainfall amount of single-or multiple-day rainfall events. These relationships are a key component of the overall data selection for the flow balance, and provide an objective approach to characterizing DWF in the DWSD collection system.
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