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South Shore Water Reclamation Facility Aeration Basin Diffuser Replacement

Milwaukee Metropolitan Sewerage District
Milwaukee, Wisconsin

Project Overview

Achieving nutrient goals, maintaining local contract limits, and minimizing energy consumption for one of the largest wastewater facilities in the Midwest.

The goal of any fine bubble aeration system is to deliver oxygen where it is needed with as little air as possible. This goal is harder to achieve in practice as activated sludge conditions are ever changing, and physical constraints impact equipment placement. The Milwaukee Metropolitan Sewerage District (District) operates two activated sludge wastewater treatment plants within the metropolitan area of Milwaukee, Wisconsin—South Shore Water Reclamation Facility (SSWRF) and Jones Island Water Reclamation Facility (JIWRF), which are the largest activated sludge treatment facilities in Wisconsin. This project focuses on the retrofit of the aeration system at the SSWRF, whose existing diffusers are reaching the end of their useful life.

The SSWRF has a design capacity of 90 mgd with a peak flow capacity of 375 mgd. Constructed in the late 1960’s, the plant has influent screening, grit removal, primary clarification, single pass step-feed aeration basins, secondary clarifiers, and chlorine disinfection. The plant was initially designed for biochemical oxygen demand and total dissolved solids removal but is currently operating as a nitrifying facility as well.

Based on the condition of the existing aeration system and corresponding performance deficiencies, the District set out to redesign the aeration system to address the challenges of the existing system while at the same time preparing for the needs identified in the 2050 facility plan. Working in partnership with Carollo, the project looked to meet the following objectives:

  • Meet the air demand of the projected flow and loading conditions identified in the 2050 Facility Plan.
  • Eliminate significant dissolved oxygen variations between basins.
  • Improve air control within each aeration basin.

The $74-million project is in the early stages of construction. The design of the new system features an entirely new aeration system, including a new diffuser pattern and associated piping, hybrid aeration controls, the addition of swing zones (mixers and baffle walls) to aid in filament management and prepare for future biological phosphorus removal, and structural modifications to equalize the sidewater depths across all the basins. Energy savings from these upgrades are projected to be 20 percent or higher depending on how the facility will be operated.

Results and Highlights

Aeration system replacement of all 28 aeration basins.

$74 million in upgrades at the 375-mgd peak flow facility.

Designed to reduce the aeration energy demand by 20 percent.

Incorporates swing zones and baffle walls for ultimate flexibility in nutrient and filament management.

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