Genevieve posted on August 30, 2010 09:55
I spent a few days job shadowing a circuit rider from the Illinois Rural Water Association. A memorable stop we made was a small town in Illinois that has a reverse osmosis (RO) water treatment plant. This state-of-the art plant, which is just over 8 years old, took 3 million dollars to build. It takes two operators to run the RO plant; Mark is the lead man, and has been a water operator for 23 years, and Travis has been an operator for three years. Mark and Travis gave me a tour of the plant and explained how they work to provide their town with clean water.
From Well to Tap
Before the town updated their water supply, water in the town was said to be black. The distribution system was also outdated, built in 1889. When the town decided to build a new treatment plant, they also decided to drill new wells in order to obtain cleaner groundwater. The town drilled three 85-foot wells located about ten miles outside of town. Two of these wells are run at a time.
From the wells, the groundwater is pumped to the treatment plant and sent through iron and manganese removal sand filters. From these filters, about 600 gpm (gallons per minute) of the water is sent to an RO unit, while 215 gpm is sent to a holding tank. Of the water sent to the RO unit, 150 gpm concentrated is sent to a settling lagoon. The rest is aerated for carbon dioxide removal, mixed with the holding tank water, and sent to town. It takes about three days for the water that leaves the plant to reach the town. The town has around 1775 service connections and uses about 395,000 gallons of water a day.
Reverse Osmosis Treatment
Water that is treated with reverse osmosis is forced through the RO unit at a pressure of 134 psi. To put this into perspective, tap water runs at 50 psi. I was told that the membranes are so small that even a virus can’t fit through. Because of this, the water becomes 100% purified. RO is such an efficient process that it removes essential nutrients, so it’s necessary to add untreated water to the RO water before it is sent to town. Although the process is complex, the town’s residents are happy to have some of the highest quality tap water around.