DES MOINES, Iowa — Most of the Iowa water treatment departments that work to remove nitrates from drinking water dump the chemical back into the water supply where other cities will have to remove it.
The law sets a safe level for nitrates in drinking water, but it doesn't dictate what must be done with nitrates after they are removed, The Des Moines Register reported (http://dmreg.co/1pybE3D).
Des Moines Water Works officials say they dumped an estimated 13,500 pounds of nitrates back into the river last year. At the same time, they were urging farmers to limit how much nitrate-rich fertilizer ran off into waterways.
Sixteen municipal water utilities in Iowa have nitrate removal systems and they spend millions of dollars each year to comply with federal drinking water standards. The majority of those utilities acknowledged dumping nitrates back into waterways.
"Symbolically, it's a troublesome issue for me," Des Moines Water Works Director Bill Stowe said. "Frankly, we're saying to the single farmer, 'Please don't do this,' and yet we're imitating the behavior we're trying to avoid."
Nitrates are a concern because they can cause health problems if they are consumed at high levels. They have been associated with diseases including leukemia and non-Hodgkin lymphoma.
The main sources of nitrates are runoff from fertilizer, leaking septic tanks, sewage and natural deposits.
Jon Martens, president of the Iowa Groundwater Association, said it is a concern that utilities are returning nitrates to rivers and streams, but he's not sure how to fix the problem.
"You take it out of one source, and you dump into another source, and it's just weird to me," said Martens, who is director of water operations for Atlantic Municipal Utilities.
Water treatment utilities generally can't recycle nitrates into fertilizers because the typical removal system uses technology known as ion exchange. The nitrate-rich residue that remains from that process contains a salt solution, which is detrimental to vegetation.
And removing nitrates naturally requires investments of millions of dollars and many acres of lands to create swamp-like areas to absorb the chemical.
The Iowa Department of Natural Resources allows utilities to put the removed nitrates back into the state's waterways because the utilities are not increasing the total about of the chemical in the water.
"You have to have a permit for treating water and then a different permit for what (chemicals) you emit, but in the case of nitrogen — at least at this point — it's kind of considered a no-net gain," said Kevin Baskins, a spokesman for the Iowa Department of Natural Resources.
In addition to the intentional dumping of nitrates, since 2007 the Iowa chapter of the Sierra Club has tracked more than 500 cases where untreated water bypassed state treatment facilities due to situations like floods, failed sump pumps and sewage leaks.
Neila Seaman, director of the Iowa Sierra Club chapter, said every one of those instances also contributes to high nitrate levels and adds costs for water treatment utilities.
"Des Moines Water Works customers like me have to pay a lot more to take nitrates out. When they put the nitrates back into the water then it potentially costs cities downstream like Ottumwa a lot of money." Seaman said. "It's a cycle."
Information from: The Des Moines Register, http://www.desmoinesregister.com