Co-PIs: Miki Hondzo, Raymond M. Hozalski, and Mike Semmens
Funding Agency: St. Paul Regional Water Services
Background
Saint Paul Regional Water Services (SPRWS) installed a hypolimnetic aeration system for Vadnais Lake . The dissolved oxygen (DO) measurements in the hypolimnion from 2004 to 2006 suggest that the lake has low hypolimnetic DO concentrations, 0.1-0.9 mg/L, during stable stratification in the summer. Although the aeration system is in continuous operation, the field DO results suggest that the aerated water with high DO concentration is not delivered to the sediment-water interface. Therefore, low DO concentrations are maintained at the sediment-water interface in a relatively thick fluid layer (about 2 m high). The existing layer provides a reducing rather than an oxidizing environment for the chemical species at the sediment-water interface. This environment promotes phosphorous release and subsequent algal growth in the lake. Thus, the low DO conditions in the hypolinion may have a profound impact on taste and odor problems associated with algal growth.
Objectives
The major objectives of this study are:
• a verification of the hypolimnetic aeration design for Vadnais Lake ;
• a proposal for the remediation of the existing design;
• a proposal for a new on-line aeration system; and
• a design for a new water quality monitoring system over the Internet.
