Reducing phosphorus (P) release from ponds that treat stormwater is a major stormwater management challenge because phosphorus is the primary limiting nutrient. Reducing P availability is necessary to prevent algal blooms and reduce or eliminate floating plants like duckweed and watermeal. Many ponds are also seen as an amenity, such that reducing algal blooms and floating plants in the ponds is an additional challenge. Sediment P release in ponds that treat stormwater reduces the overall effectiveness of the pond in capturing and retaining phosphorus, a primary function of the pond. The goal of the proposed project is to determine the effectiveness of the four most promising approaches for improving P removal in ponds: application of alum or iron to reduce P release from the sediments, and street sweeping to reduce inflowing organic material which contains labile organic P. The proposed project will also develop maintenance guidelines for these treatment technologies that considers cost-effectiveness for P reduction over time.
Project Outcomes:
- Lifetime cost and effectiveness at reducing sediment P release of alum addition in terms of mass released/cost of remediation.
- Lifetime cost and effectiveness at reducing sediment P release of iron filings addition in terms of mass released/cost of remediation.
- Lifetime cost and effectiveness at reducing sediment P release of enhanced street sweeping in terms of mass release and cost of remediation, which will be added to the USGS study to determine impact of street-sweeping upon P inflow and outflow to ponds that treat stormwater.
- Recommendations of which remediation techniques to consider for given pond characteristics to reduce P concentration in ponds that treat stormwater, including the use of the assessment tool developed in a prior study (Natarajan et al. 2022).