Burns & McDonnell was retained by the St. Louis Metropolitan Sewer District (MSD) to plan and design upgrades to this plant, which has a capacity for 28 million gallons per day (MGD) average daily flow and 80 MGD peak flow.
A facility plan projected flows and waste loads to the year 2025, examined regulatory requirements and assessed the facility capacity and condition. This trickling filter plant was routinely handling 29 MGD average flows without permit violations. The rerating study found insufficient justification for a higher plant rating.
Alternatives were developed for both wastewater treatment and solids processing, as well as management of peak flows. Improvements to the secondary treatment and solids handling facilities of the plant was postponed until the next discharge permit conditions were known.
- Facility plan
- Re-rating evaluation
- Preliminary design
- Final design
- Primary clarifier rehabilitation
- New maintenance facility
- Digester gas treatment (siloxanes)
- Wetlands mitigation
- New headworks
- Screen replacement
- Grit chamber replacement
- Preaeration replacement
- Odor control
- Power feed upgrades
- Effluent pump station upgrades
- Peak flow storage
Improvements were separated into two construction phases, one called Rehabilitation and the other called Headworks. In the rehabilitation phase, a new larger maintenance building was designed. A treatment system to remove siloxanes from the digester gas was designed to extend the performance of three engine generators. The primary clarifier mechanisms were to be replaced, along with new launder covers to control odors. Utility systems, structural repairs and electrical repairs were also planned.
In the Headworks project, designs were developed for replacement of the screens, grit chambers, influent flow meter and preaeration basins, with a peak capacity of 190 MGD. The four pumps in the effluent pump station were enlarged. Four new basins storing up to 30 MG were designed to accommodate peak flows, along with the associated piping, pump stations, and control systems. A closure plan was developed for a former 24 acre biosolids lagoon, and a wetlands mitigation plan was developed for this area. A biofilter system handling 10,750 cfm was designed to control odors from the headworks and primary clarifiers.