Project overview
Most stormwater ponds release phosphorus from sediments when the dissolved oxygen (DO) concentration is below 1 mg/L. This proposal will investigate how aerator/mixing systems affect pond DO, and the cost-effectiveness of installing such systems. A demonstration project evaluating three types of aeration/mixing technology is proposed to determine which approaches can most cost-effectively be applied to ponds. The project will develop new installations of the three different systems with two or three cities. These three systems will be assessed and compared to two different systems that will use the nano-bubble technology of Moleaer, Inc. in the City of Savage, as part of an ongoing MSRC project. This project will develop criteria that can be used in remediating ponds for release of phosphorus from the pond sediments via management to increase DO concentration and thereby reduce phosphorus release from the sediments. The benefits of the most common and promising methods for mechanically introducing more DO will be assessed, providing a basis to develop cost/benefit estimates for these approaches. The project will provide information to expand the currently limited toolbox for stormwater pond remediation and provide water quality managers with the tools and guidance necessary to make an informed decision about how to manage their stormwater ponds. Better management of the ponds could more than pay for itself, especially if the previously observed sediment consolidation and the associated increase in depth of the pond under higher DO conditions occur, which would delay the dredging requirement.
Research questions
- How effective are aerator/mixing systems at adding oxygen to the bottom of stormwater
ponds? - How effective are aerator/mixing systems at reducing water quality problems in water in and released from stormwater ponds?
- Can the impact of aeration/mixing also consolidate the sediments to the point where dredging can be put off for a few years and save the owner substantial dredging funds?
- How does the cost of these aerator/mixing systems compare with other remediation techniques for various sizes of stormwater ponds?
Key innovations/contributions
This study will help us understand the degree to which pond aeration and mixing systems are effective at reducing water quality problems and nutrient export. This information will be used to develop recommendations for the best practices for designing and installing aeration/mixing systems.
What does this mean for Minnesota?
We propose to study the effectiveness of five aeration/mixing technologies in stormwater ponds to determine their effectiveness at oxygenating stormwater pond sediments to reduce phosphorus release from those sediments, in order to understand their cost-effectiveness as a sediment phosphorus release remediation technology so that stormwater pond managers can consider given aeration/mixing technologies as a stormwater pond management technology to better avoid phosphorus release into receiving water bodies.