OTTUMWA — Nitrates dumped into the river upstream don’t do Ottumwa Water and Hydro any good, officials say, but the amounts released by cities pale in comparison to what rain washes into the river.
Tim Albert, production manager at the Ottumwa water plant, ran some numbers after a weekend report said cities frequently return the nitrates they remove from the Des Moines River after purifying water for their cities. He said the peak last summer involved “unprecedented levels, like we’ve never seen before.”
Nitrates, which largely get into rivers from fertilizer runoff, must be below 10 mg per liter to meet federal safety standards. The worst day last summer saw Ottumwa levels at 14.4 mg per liter.
Cities upstream, including Des Moines, have the ability to remove nitrates from the water. But the Associated Press reports most cities that do so then dump the solutions containing the nitrates back into the river. Eventually, that arrives at downstream cities.
Ottumwa doesn’t do that. It can’t.
“Ottumwa doesn’t actually have the equipment to remove the nitrates from the water,” Albert said.
Ottumwa handles the issue by diluting the river water with water from Ottumwa’s backup source. Blending enough low nitrate water with high nitrate water results in levels that pass safety regulations. The city uses the same basic approach when the water is too muddy.
Scale explains why Albert isn’t overly concerned about upstream cities. Would it be nice if they didn’t dump nitrates back into the water? Of course. But the AP cited an estimate from Des Moines Water Works officials that the city dumped about 13,500 pounds of nitrates back into the river last year.
Ottumwa had about 14.28 billion gallons of water flowing by the city on the worst nitrate day of 2013, which Albert called “an absolutely astronomical amount of water.” That included 205,000 pounds of nitrates on that one day, more than 15 times the amount Des Moines officials say their city dumped in the entire year.