Reverse Osmosis Water Treatment Plant Improvements: Oakland, Iowa

In 2012, it became clear to city officials that the water treatment system in Oakland, Iowa, was no longer meeting its water supply demands. As businesses, including a large food production facility, required more water it was evident upgrades were necessary to sustain the community water operation. The City of Oakland hired Snyder & Associates to complete an extensive assessment, rehabilitation, and expansion of the existing water treatment system. This project included renovations of specific plant components and the construction of a new Reverse Osmosis (RO) treatment process.

Water Treatment Systems: Updates, Additions, and Renovations

In the years leading up to its revision, the plant treated all water by a lime softening process — a method that uses calcium hydroxide, or limewater, to soften water by removing calcium and magnesium ions. As regulations tightened, this was no longer the best means of treatment as it does not efficiently treat all water contaminants entering the facility.

The source water wells supplying this plant are a mixture of shallow alluvial and deep wells ranging anywhere from 40 to 3,000 foot deep. With that expansive range of depths comes a variety of water qualities and chemistries. Our team determined that a combined system approach could effectively treat water from both types of wells.

This combined system includes two different treatment processes — a new reverse osmosis system and the conversion of the previous lime softening plant to an iron and manganese removals system. To aid in the transition to a multi-system facility, our engineers modified multiple piping systems to direct source water to the specific treatment process best suited for its water chemistry. This meant that water from the deep wells is guided to the RO system, while the shallow well water is directed through the iron and manganese removals system.

Water Treatment through Reverse Osmosis Systems

Once deep well water reaches the RO system, it’s placed under high pressure which pushes it through an extremely fine porous membrane. During this process, pollutants are filtered out and flushed away, resulting in clean water.

At this plant, our team installed a RO system that produces about 325 gallons of permeate water per minute. This system primarily pulls water from the North wellfield where well depths are mixed and water often contains higher levels of iron, manganese, radium-226, and hardness. Once treated, the water leaves with no hardness, radium, or contaminants.

Transitioning to an Iron and Manganese Removal System

The lime softening plant previously used for the city’s water treatment already contained aspects required for iron and manganese removal. Instead of building a completely new system, the Snyder & Associates team modified what was present to meet the new design standard.

Due to its geological landscape, Iowa water naturally contains iron and manganese and the majority of wells near the plant were no exception. To remove those unwanted minerals, the water is first oxidized with added aeration and sodium permanganate chemicals. Together, these cause a reaction with the metals, forming particles similar to rust flakes that can then be removed through sand gravity filtration. This system treats around 700 gallons of water per minute from the area’s shallow alluvial wells, producing a filtered product.

Creating the Perfect Water Quality Mixture

Water from the various wells is treated independently by the two processes, utilizing the vital benefits of each system. The RO process provides effective hardness reduction for deep well water but can create water chemistry, pH, and stability concerns. Comparatively, water treated by the iron and manganese removal system is naturally higher in pH, making the water alkaline.

To achieve the best product, finished water from each treatment system is mixed in a new 173,000 gallon 70-foot diameter ground storage reservoir. The combination of water from each method creates a balanced finished product that is ready for distribution. High service pumps draw water from the tank to be sent to the distribution system for community use.

Results Post Water Treatment Plant Renovation

Since the completion of the upgrades, the Oakland plant has seen an increase in daily water production along with higher overall water quality. The water is now softer than what was created by the former system and regularly contains lower concentrations of ions. This provides a more consistent water product for businesses and general public use.

Currently, the Oakland community uses around 750,000 gallons of water from the plant per day. Snyder & Associates was able to use the existing plant, reworking its features and adding new systems to meet the community’s drinking water supply needs.