May 9, 2016

Natural Denitrification Wetland Pilot Project

During 2015, Des Moines Water Works operated the Nitrate Removal Facility for a record-setting 177 days, eclipsing the previous record of 106 days set in 1999. The Nitrate Removal Facility is used to reduce source water nitrate concentrations to below 10 mg/L, a level established by the United States Environmental Protection Agency (EPA), for our 500,000 central Iowa customers.

Des Moines Water Works has been working with a consultant to evaluate nitrate trends in the raw water sources. These trends indicate that nitrate concentrations will continually increase without regulation upstream, reaching levels where the existing Nitrate Removal Facility will be unable to provide sufficient removal to meet the EPA’s drinking water standards.

In an attempt to evaluate alternative nitrate removal technologies, Des Moines Water Works is constructing a pilot wetland in 2016. This pilot project will be a one acre surface flow wetland located in Water Works Park. The pilot will be used to test the efficiency of nitrate removal through natural processes. Testing of the pilot will help staff understand how a full scale wetland would react to changes in temperature and flood events, along with any other water quality concerns.

Pilot wetland under construction in Water Works Park

In late April, DMWW staff planted 20,000 cattails and bulrush plants in the pilot wetland area.

If successful, Des Moines Water Works will consider converting a large portion (up to 80-acres) of Water Works Park into constructed wetlands, with the goal of providing natural denitrification, and ultimately protecting the health of our customers.

The consultant is also recommending several nitrate removal measures, including expansion of the current ion exchange denitrification facility. The funds needed for nitrate mitigation in the recently announced five year capital improvement plan total $70 million. An additional $10 million will be needed beyond the five year outlook, for a total of $80 million in infrastructure investments in order to meet the safe drinking water standard for nitrate.

 

Posted by: Laura Sarcone No Comments
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