Illinois utility addresses water quality problems using versatile tanks
There is iron in your well water, you are sitting on a fault line, and your soil is silty. This was the situation facing the Anna-Jonesboro Water Commission (AJWC), a wholesale water supplier to several municipalities and rural water districts in Southern Illinois, which prevailed against the challenges of nature with help from its allies Aquastore, CST and J.T. Blankinship Eng.
Element 1: Iron Contamination
“The Illinois EPA put us under review due to restraints we had on aeration capacity, which stems from the high iron content in our water source,” said Casey Johnson, superintendent of AJWC. “At 24 parts per million, it’s the highest concentration in the region.”
Even though AJWC has filtration capacity, the Illinois EPA advised that the high iron levels put stress on its aeration capacity, which could hamper supply—for example, not being able to meet increased demand in the event that a neighboring district has a failure or if a new manufacturing facility were to open in the area.
“The plant had been de-rated to about 1.4 million gallons a day (gpd) from its original capacity of 2 million,” said Ted Beggs, president of J.T. Blankinship Eng. “So we worked with Aquastore to develop a system that would improve the aeration of the incoming water and increase filtration capacity.”
Beggs and his firm have worked for years with Cady Aquastore, the authorized CST dealer in DeKalb, Ill. Cady Aquastore has extensive experience with aeration systems, having designed and installed approximately two dozen for water districts over the last 25 years, according to Dave Hemauer, Cady Aquastore project manager.
“Our aeration system is a big value-added feature because it’s fully integrated with the storage tank and complements the treatment process,” Hemauer said. “Forced aeration is superior to gravity tray systems because the forced air speeds up oxidation, while gravity systems rely on the water percolating over trays, which require frequent maintenance and backwashing.”
Armed with their expertise and intimate knowledge of AJWC’s requirements, the crew from J.T. Blankinship and Cady Aquastore built an aeration system to attach to the top of a new Aquastore tank. The system features two powerful fans that force air on the water and promote rapid oxidization. The iron settles at the bottom of the tank, and the oxidized water is pumped into a clarifier.
“It has greatly improved our overall treatment capability,” Johnson said. “Using air pressure to force water to oxidize makes it easier to treat. If you have iron or manganese underground, it’s definitely worth the investment. We’ve gone from between 0.30 and 0.40 mg/L iron content when the water reaches the clarifier to almost zero, so I’d say we’ve tripled the amount of oxidation.”
AJWC typically treats 800,000 to 1.2 million gpd, but with the Aquastore tank and aeration system, it now has the ability to reach 2 million gpd.
Elements 2 & 3: Shake & Soil
AJWC’s treatment facility is located in the New Madrid seismic zone and stands on weak soils, so Cady Aquastore engaged the services of a structural engineer who specializes in designing platforms for problematic foundations. Together, they evaluated a range of possible earthquake-and-soil scenarios. One involves the outlet pipe from the aerator to the tank becoming obstructed or compromised, causing the aerator to fill with water and become top-heavy.
“When you face these risks, you have to calculate the conditions under which a structure could fail and design against it,” Hemauer said. “Our goal was to get the foundation and tank to perform as a single unit and withstand the stress of shaking and shifting soil.”
The Aquastore tank is engineered for durability and construction is simple. The roof is assembled first and then lifted with a jacking system so the individual steel panels can be bolted underneath. Crews work at ground level and require only a few feet of space around the foundation. An Aquastore goes up quickly, and if an owner anticipates needing increased capacity, the entire tank can be designed to add panel courses for future installation at the bottom of the tank shell.
It also stands up to the harsh Midwest weather. The glass coating applied in the factory makes an Aquastore resistant to extreme cold and heat. Its seamless surface prevents cracking that can attract rust, and the absence of corrosion and leakage greatly mitigates the chance of hazardous runoff or leaching. There is no need to repaint, and maintenance costs are relatively low.
Johnson can testify to Aquastore’s reliability and quality. He has a 1.2-million-gal ground storage tank manufactured by CST and installed in 1994, and he says he has never had a single issue or problem with it.
“If there should be a problem, they’re easy to reach and responsive,” Johnson said. “The less we have to worry about storage or aeration, the easier it is to do our job.”