Pond Treatment with Spent Lime to Control Phosphorus Release from Sediments

Sedimentation ponds that accumulate particles and phosphorus in stormwater runoff are a standard
and widely applied storm water best management practice. However, just as internal loading occurs in
lakes during warm summer periods when the potential for oxygen depletion is greatest, aging ponds
have the potential to release more phosphorus than is captured during summer months (Watershed
Protection Techniques, Technical Note 102). Dredging is a potential, but expensive, option to improve
pond performance, but phosphorus release may occur long before a pond is filled with sediment. Areal
applications of alum and iron can control phosphorus release, but incur raw material production costs.

In cooperation with SPRWS, City of White Bear Lake, RWMWD, and VLAWMO staff, Barr Engineering
proposes this study to evaluate the application of spent lime (amorphous calcium carbonate from
drinking water treatment) to pond sediments to reduce phosphorus release during warm summer
months. Spent lime can reduce phosphorus release by forming calcium phosphate and potentially by
increasing the pH of the treated sediments to facilitate iron and aluminum phosphate binding. This
study includes a laboratory and a field component and is intended to validate large-scale applications.
The laboratory component includes the addition of spent lime at a range of doses to phosphorus rich
pond sediment to determine optimal spent lime dosing. The field component involves the addition of
spent lime to two ponds and monitoring to determine the magnitude of reduced phosphorus release,
evaluate cost-effective methods for areal application and quantify the benefits of this water treatment
byproduct.

2019 Midproject Presentation .pdf

Project Staff: 

Project Lead: Greg Wilson,,Barr Engineering Company, gwilson@barr.com; 952-832-2672

Co-Investigators: Keith Pilgrim, Erin Anderson-Wenz, Kevin Menken and Tyler Olsen
Barr Engineering Company

Field Staff: Eric Korte and Lyndsey, Ramsey Washington Metro Watershed District (RWMWD)
Tyler Thompson and Brian Corcoran, Vadnais Lake Area Watershed Management Organization (VLAWMO)

Spent Lime/Lab Jeremy Erickson