Allocation of supplementary aeration stations in the Chicago waterway system for dissolved XXXX improvement.

@entity26 @entity262
The @entity262 ( @entity262 ), used mainly for commercial and recreational navigation and for urban drainage, is a 122.8 km branching network of navigable waterways controlled by hydraulic structures. The @entity262 receives pollutant loads from 3 of the largest wastewater treatment plants in the world, nearly 240 gravity Combined Sewer Overflows (CSO), 3 CSO pumping stations, direct diversions from Lake Michigan, and eleven tributary streams or drainage areas. Even though treatment plant effluent concentrations meet the applicable standards and most reaches of the @entity262 meet the applicable water quality standards, Dissolved @entity26 (DO) standards are not met in the @entity262 during some periods. A Use Attainability Analysis was initiated to evaluate what water quality standards can be achieved in the @entity262 . The UAA team identified several DO improvement alternatives including new supplementary aeration stations. Because of the dynamic nature of the @entity262 , the DUFLOW model that is capable of simulating hydraulics and water quality processes under unsteady-flow conditions was used to evaluate the effectiveness of new supplementary aeration stations. This paper details the use of the DUFLOW model to size and locate supplementary aeration stations. In order to determine the size and location of supplemental aeration stations, 90% compliance with a 5 mg/l DO standard was used as a planning target. The simulations showed that a total of four new supplementary aeration stations with @entity26 supply capacities ranging from 30 to 80 g/s would be sufficient to meet the proposed target DO concentration for the North Branch and South Branch of the Chicago River. There are several aeration technologies, two of which are already being used in the @entity262 , available and the UAA team determined that the total capital costs of the alternatives range from  35.5 to  89.9 million with annual operations and maintenance costs ranging from  554,000 to  2.14 million. Supplemental aeration stations have been shown to be a potentially effective means to improve DO concentrations in the @entity262 and will be included in developing an integrated strategy for improving water quality in the @entity262 .
