By PERRY BEEMAN
DES MOINES, Iowa, Oct. 3, 2000 (The Des Moines Register) — The Des Moines Water Works takes nitrates out of river water when the compounds are at high levels so that household taps serve safe water.
The utility then dumps the nitrates, which are considered health threats, into the Raccoon River. They float down to Ottumwa's water plant and beyond.
The waterworks has followed the practice since it opened a nitrate- removal system in 1992. The state suggested that the plant flush the nitrates back into the river to avoid a more expensive technique.
The nitrate-removal plant is used only when nitrates in the Des Moines and Raccoon rivers are high. The system has not kicked in this year because of dry conditions. The past few years, nitrates have hit record levels and the plant has run overtime.
The technique leaves the river downstream with the same nitrate level as upstream from the Des Moines plant. The amount of nitrates pulled from the river, and put back, is tiny compared with the 600 tons of nitrate that sometimes pass by the water plant in the Raccoon daily, General Manager L.D. McMullen said.
When nitrate levels are high, the system pulls water from the Des Moines and Raccoon rivers and removes a half-ton of nitrates a day before pouring the compounds into the Raccoon.
McMullen, who has campaigned to keep farmers, yard-keepers and others from letting excessive nitrates run into the river, tried to avoid flushing nitrates back into the river.
When engineers designed the plant, they considered several chemical techniques that would have permanently removed the nitrates from the water pumped from the river. However, most cost 10 times what engineers expected to pay for disposal, McMullen said.
The Iowa Department of Natural Resources told waterworks officials that returning the nitrates to the river was acceptable, McMullen said.
Some scientists say nitrates can rob babies' blood of oxygen, and may cause miscarriages and cancers.
Ottumwa is the only downstream Iowa town using the Des Moines River for drinking water. The Raccoon dumps into the Des Moines in the capital city.
Nitrates in Des Moines River have exceeded the limit for drinking water sometimes, but the Ottumwa water plant has been able to dilute the supply to safe levels by adding water from local lagoons, said general manager Doug Drummey.
Drummey said Des Moines' practices are fine with him.
The Raccoon River is one of the biggest contributors to the so- called dead zone off Louisiana, scientists say. There, in the nation's best shrimping groups, nitrogen rushing down the Mississippi feeds algae that rob the waters of oxygen when they die. That leaves a large area without much fish or plant life from spring to fall each year.
Water from the Raccoon ends up in the Mississippi.
Reporter Perry Beeman can be reached at (515) 284-8538 or mailto:[email protected]
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