An innovative method of removing phosphorus has been put to the test in Long Lake Park in the City of Apple Valley. Past land uses, combined with the watershed area draining to Long and Farquar Lakes, provides too much phosphorus for the lakes to assimilate. The large amount of phosphorus results in excessive algae in the lakes.
Iron-enhanced sand filters are a relatively new technology. The filters are proving to be effective at removing large amounts of phosphorus compared to other more commonly used practices. Traditional water quality practices have focused on treating particulate-bound phosphorus, which addresses only a portion of the total phosphorus load. Iron filings mixed with sand allow for the treatment of dissolved phosphorus and particulate-bound phosphorus.
The City of Apple Valley and the Vermillion River Watershed Joint Powers Organization (VRWJPO) identified the portion of the watershed draining to the lakes that was contributing a large amount of phosphorus to the lakes and developed a project that would address the issue. City park land was given up to construct the filters for the benefit of the lakes. Long Lake drains into Farquar Lake, and is the primary source of phosphorus in Farquar Lake. The project reduces phosphorus loads in Long Lake, which results in improved water quality for both lakes.
Look for the interpretive sign (pictured) in Long Lake Park.