Stormwater Symposium

Oral

396364 - Advanced Stormwater Treatment for Phosphorus Removal - Starkweather Creek, Madison, WI

Tuesday, June 5
4:00 PM - 5:30 PM
Location: Mirage Room
Co-Authors: Lauren Striegl, Madison, WI – City of Madison, Public Works

Introduction and Objectives
Traditional stormwater treatment systems are giving way active treatment processes. Treatment technology is moving into advanced processes to achieve high removal rates of nutrients.
Eutrophic conditions in Midwest lakes cause serious impacts. The City of Madison must meet aggressive phosphorus reduction requirements to achieve TMDL goals. The City of Madison investigated an innovative treatment system to divert wet-weather flows from an urban stream and treat the water using coagulant achieving enhanced phosphorus removal. A detailed feasibility study was completed in February 2017 and final design of the system is now underway.
Approach, Methodology, Results
The feasibility study included the following components and conclusions:
1. Event sampling at Starkweather Creek and bench scale testing evaluated several coagulants and select an optimal compound and concentration for phosphorus reduction (aluminum chlorohydrate at 5 mg Al/L). Total phosphorus reductions averaged 85%.
2. Performed continuous rain / runoff modelling to predict long term average annual treatable runoff volume (3,500 acre feet) and the target maximum treatment flow rate (100 cfs) for the system.
3. Combined monitored phosphorus concentrations, treatment efficiency, and treatment volume to estimate potential phosphorus load reductions (1,650 lbs./yr.).
4. Developed a design with automated controls, channel diversion weirs, treatment inlet diversion, pump station, rapid mixing chamber, settling pond, and discharge back to stream.
5. Estimated capital ($5.79 MM) and annual operations ($351,000) costs for the system.
The system will be activated through rain gauges which trigger weirs and gates to route channel water through the treatment process.
Summary
The presentation will cover the project’s background, design decisions, and public involvement. The focus will be on the challenges of siting, testing, and designing a high-level treatment system with automated controls. This work provides MS4s with a new approach to meeting phosphorus control goals.

James Bachhuber


Brown and Caldwell

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396364 - Advanced Stormwater Treatment for Phosphorus Removal - Starkweather Creek, Madison, WI



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