Evaluation of Wet Weather Auxiliary Treatment Alternatives to Increase Plant Capacity

The Milwaukee Metropolitan Sewerage District is evaluating alternatives to increase the South Shore Water Reclamation Facility wet weather treatment capacity from 300 to 450 million gallons per day. In this study, side-by-side testing of biological contact treatment, chemically enhanced sedimentation, and compressible media filtration was conducted to define treatment performance and design criteria for treating wet weather flows. Wet weather testing showed that all three treatment schemes could achieve the target effluent water quality goals with biological contact achieving the lowest effluent concentrations. Based upon testing results, chemically enhanced sedimentation, biological contact, and ballasted biological contact were evaluated for full-scale implementation. Chemically enhanced sedimentation is recommended for full-scale implementation based upon lowest cost and least impact to existing and anticipated treatment facilities and plant operations.