Tetra Tech CSO, a commissioned agent and in association with two French firms, designed an integrated wastewater management program for the central Île-de-France Region (population of 8 million and covering 1,900 km²) to meet water quality objectives for the Seine and Marne rivers in dry and wet weather.
Four separate solution alternatives were developed and tested to meet the water quality objectives of the receiving water bodies, namely the Marne and Seine rivers as well as the Seine and Manche estuary, for projected conditions in 2015. The alternatives used a combination of best management practices and civil works, including off line and on line storage, relief sewer trunks, satellite treatment, wastewater treatment plant construction or upgrade, as well as real time control (RTC). Water quality impact analysis and criteria comprised levels of dissolved oxygen, ammonia, nitrate, and phosphorous, and were used to design and assess the best balance of alternatives.
Tetra Tech CSO’s RTC software Csoft™ was used to analyze and optimize the four proposed alternatives to achieve the environmental objectives, as well as to manage them in a coordinated and real-time fashion. The team simulated all four of the alternatives for three rainfall events and the effects of the overflows were assessed. All interventions were analyzed for their feasibility, especially to determine appropriate sites to implement solutions in a dense urban environment. The most appropriate alternative solution was selected based on a multi-criteria analysis, including environmental and socioeconomic parameters.
In follow-up projects, Tetra Tech CSO designed and implemented a Decision Support System to help manage the large wastewater system in real time (refer to Paris real time control project).