Posts Tagged ‘Agrotoxins’April 22, 2016
On Earth Day, Des Moines Water Works Reflects on Resources Spent to Manage Agrotoxins in Source Waters
This Earth Day, as nitrate concentrations in the Des Moines and Raccoon Rivers continue to rise, Des Moines Water Works reflects on the vast resources spent to manage the persistent agrotoxins in the waters of the state.
Des Moines Water Works continues to meet and exceed regulatory requirements for safe drinking water for 500,000 central Iowa customers; however, not without a cost to our ratepayers. In 2015, Des Moines Water Works operated its Nitrate Removal Facility for a record-setting 177 days, surpassing the previous record of 106, set in 1999. Due to the significant costs to operate the facility and the rising nitrate concentration in Des Moines’ source waters, Des Moines Water Works has also invested a significant amount of capital funds in projects for natural nitrate removal or avoidance:
- The natural denitrification strategies include Water Works Park ponds, former gravel pits near Des Moines Water Works’ L.D. McMullen Water Treatment Plant, and most recently, a constructed wetland pilot project in Water Works Park. If the one-acre pilot wetland is 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.
In this natural process, nitrate is consumed and converted to nitrogen gas by the life processes of microorganisms. Although the ultimate source of water is the Raccoon River, this approach maximizes the time the water is in off-river storage and allows the nitrate concentration in the river water to be reduced via biological reduction.
- To avoid high nitrate water in a particular source water, Des Moines Water Works has also invested capital funds for projects that provide access to water with very little nitrate levels – Aquifer Storage and Recovery (ASR) wells – or water with lower nitrate concentration – Des Moines River – that can be blended with other water sources in order to meet drinking water quality standards.
Des Moines Water Works’ two ASR wells (a third one is currently being constructed) store finished water in wells for distribution to customers at a later date. Although originally developed to smooth out spikes in treatment demand during high customer demand periods, the ASR wells have been utilized to meet customer demand during high nitrate levels.
The Des Moines River Intake facility was constructed to provide additional raw water supply for the Fleur Drive Water Treatment Plant. With the Saylorville Reservoir upstream from the intake, the nitrate concentration in the Des Moines River is almost always lower than the Raccoon River. Access to the Des Moines River provides Des Moines Water Works with another lower nitrate water supply option that was not available prior to construction of this facility.
- Des Moines Water Works’ newest treatment plant – Saylorville Water Treatment Plant – uses reverse osmosis membranes that removes nitrate from the water, without the use of a side-stream nitrate removal facility.
Ultimately, the best way to reduce nitrate concentration in the Des Moines and Raccoon Rivers is nutrient management on farms and watershed protection to prevent agrotoxins from directly entering surface waters. Des Moines Water Works follows this concept by practicing agricultural best management practices on 100 acres of leased farm land on Maffitt Reservoir property, including the use of cover crops and adjusted rental rates for the tenant to install conservation practices.
Des Moines Water Works remains vigilant in protecting the source waters that produce drinking water for central Iowans. On this Earth Day and every day, Des Moines Water Work is committed to producing water you can trust for life, even with adverse water quality conditions. Des Moines Water Works asks all Iowans to Think Downstream.