Full-Scale Reverse Osmosis Water Treatment System: Atkins, Iowa

Engineering Excellence Honor Award, ACEC, 2012

Water System Study Finds High Nitrite Levels in Raw Water

Snyder & Associates prepared a Water System Study for the City of Atkins, Iowa to address capacity issues, hardness, hydrogen sulfide, rising radium levels, and periodic excursions of nitrite levels occurring in its distribution system. While preparing the report, it was determined that the source of high nitrite levels was raw water with ammonia levels up to 8 mg/L, which was the highest level in the state at the time. The City’s current plant didn't have the ability to remove nitrate and its Silurian well had just recently been drilled, so utilizing the existing plant or changing water sources were not valid options for resolving the issue. As a result, it was determined a new water treatment plant was needed.

Reverse Osmosis Pilot Yields Strong Results for Reducing Ammonia

First, a biological filtration pilot was conducted to determine if the system would efficiently remove contaminants as a less expensive, easy method to provide stable water. However, it did not reduce ammonia to the desired level and actually raised nitrites by 4-6 mg/L to exceed the limit of 10 mg/L.  Next, a reverse osmosis pilot was commissioned. It achieved a satisfactory reduction in ammonia and nitrate, with secondary benefits of hardness and radium removal. While reverse osmosis technology has been utilized for years, it's just becoming affordable and practical for municipalities to install. With the ability to consistently remove 85-90 percent of various water contaminants, reverse osmosis systems are well-suited to serve as a long-term solution to meet both current and future drinking water regulations without major improvements or cost involved.

Achieving Water Stability without Blending in an RO System

Project challenges included addressing the Iowa DNR’s concern of creating aggressive water. Typically, reverse osmosis water is blended with well water because reverse osmosis water in an unaltered state can be very corrosive. Unfortunately, due to the levels of ammonia present in Atkins well water, blending was not possible. To resolve the issue, chemical addition was utilized to stabilize the water, which made Atkins the first water treatment plant in the state of Iowa to be 100 percent reverse osmosis without blending. Designed by Snyder & Associates, the new treatment facility features a full-scale reverse osmosis treatment system, aeration, an 80,000-gallon clearwell, and extensive chemical addition. In addition, odor scrubbing was added to the new facility due to the plant’s location on a main street in town. The location also drove the architectural look and design of the building to be more aesthetically pleasing than typical treatment facilities.

Client Satisfaction Spurs ACEC Honor Award for Reverse Osmosis Design

Snyder & Associates provided a number of services for the project including evaluation of the existing system, a preliminary engineering report for improvement options, design and construction documents, letting assistance, construction administration, observation, and start-up assistance. Since completion, Snyder & Associates continues to address operational questions in addition to assisting with regular maintenance and equipment troubleshooting. In 2012, the Atkins Water Treatment Plant project was selected to receive an Honor Award from the American Council of Engineering Companies (ACEC), following a competition among engineering firms throughout Iowa. In selecting Snyder & Associates, the ACEC cited several aspects of the project as examples of engineering excellence but highlighted, in particular, its solution to address a complex issue with ultimate client satisfaction in mind.