DNR report calls for Rockwell City to limit nutrients, other elements from entering water treatment plant

An engineer told Rockwell City officials last week their preliminary waste water treatment plant permit from the state will require reducing the amount of some nutrients and elements found in the water entering the plant. Tom Grafft, an engineer with ISG, which is helping the city with its water treatment plant permitting process, said the news wasn’t unexpected, and the city has some options to reach the Iowa Department of Natural Resource’s preferred levels. DNR officials, looking at water samples from the plant, found higher levels of ammonia nitrogen, chloride and copper than the department would like to see, Grafft said. First, he added, he wanted city officials to know they will be able to work with DNR to possibly recalibrate some of DNR’s stated levels, which will give the city a little leeway.
The higher-than-expected copper levels were a surprise, Grafft said. Those levels usually rise from metal finishing or powder coating. He speculated work at North Central Correctional Facility in Rockwell City could be contributing to those copper levels. Council members agreed, noting inmates at the prison do powder coating.
Grafft said if that’s the case, city officials can approach prison administrators to talk about ways to prevent the copper from entering the waste water system, which could reduce the levels enough to meet DNR’s requirements.
For chloride levels, Grafft said public education, particularly for people with water softeners, is a key. Softeners working at their most efficient, on metered models instead of releasing the salt to soften the water on a timer, can reduce chloride levels, he said.
The next step in the process is for city officials, ISG and DNR officials to meet and discuss the levels and new permit, then draft a strategy to address the changes DNR is requiring, Grafft said.
Once issued, the city’s waste water treatment plant permit will last for five years.
Read the full story in the January 10 edition.