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USING VISUAL PLUMES PREDICTIONS TO MODULATE COMBINED SEWER OVERFLOW (CSO) RATES
Citation:
Frick, W E. AND D. L. Denton. USING VISUAL PLUMES PREDICTIONS TO MODULATE COMBINED SEWER OVERFLOW (CSO) RATES. Presented at First Interagency Conference on Research in the Watersheds, Benson, AZ, October 28-30, 2003.
Impact/Purpose:
A main objective of this task is to combine empirical and physical mechanisms in a model, known as Visual Beach, that
â— is user-friendly
â— includes point and non-point sources of contamination
â— includes the latest bacterial decay mechanisms
â— incorporates real-time and web-based ambient and atmospheric and aquatic conditions
â— and has a predictive capability of up to three days to help avert potential beach closures.
The suite of predictive capabilities for this software application can enhance the utility of new methodology for analysis of indicator pathogens by identifying times that represent the highest probability of bacterial contamination. Successful use of this model will provide a means to direct timely collection of monitoring samples, strengthening the value of the short turnaround time for sampling. Additionally, in some cases of known point sources of bacteria, such as waste water treatment plant discharges, the model can be applied to help guide operational controls to help prevent resulting beach closures.
Description:
High concentrations of pathogens and toxic residues in creeks and rivers can pose risks to human health and ecological systems. Combined Sewer Overflows (CSOs) discharging into these watercourses often contribute significantly to elevating pollutant concentrations during wet weather, particularly following extended periods of dry weather during which pollutants accumulate, or after seasonal applications of pesticides that cause high concentrations in retention structures and flood control basins drained by the CSOs. In many instances the discharges from the CSOs are controlled by pumps that run intermittently in response to water level elevations in the retention basins. These pumps usually run at full volume, modulated only in quantum fashion when more than one pump serves the overflow structure. The either no-flow or high-flow mode of operation is insensitive to conditions in the ambient flow or the effluent, and to results that might be achieved to ameliorate the impact of pathogens or toxic residues by controlled and optimum mixing of CSO effluent and ambient streams. In principle, plume models simulating the mixing process in real time based on continuously measured stream levels and CSO volumes, together with variable flow pumps, could be used to blend the effluent with the receiving stream in a way that mitigates the impact of the CSO on the downstream environment. The Visual Plumes model is used on a CSO discharging to urban Arcade Creek in Sacramento, California to demonstrate the potential benefits that could be realized from the implementation of this kind of control strategy and technique.