Challenge
Heart of the Valley Sewerage District in Kaukauna, Wisconsin required high-purity water to test plant effluent for biochemical oxygen demand (BOD) and other contaminants. Testing is required to ensure that the effluent meets state and federal guidelines before discharge into the Fox River.
Laboratory manager Chad Giackino tests the facility's effluent daily, using a pure water sample as a benchmark. He used a still to make the pure water; however, it proved unreliable. Many different impurities would often remain in the water that came out of the still, such as organics, inorganics, biological products and microorganisms. Besides yielding unreliable results, the still increased testing time because the tests often had to be repeated.
The village treats groundwater from a semi-confined aquifer via 16 production wells at depths from 55-65 feet below the surface. The well water is piped to a 200-gallon-per-minute (gpm) water treatment facility where it's treated to remove dissolved contaminates using two reverse osmosis (RO) treatment units that produce 140 gpm at 70% recovery. After RO treatment, the water is disinfected, aerated, and stored for potable water use.
Due to discharge limits and brine reject volume with the two RO systems from the late 1990s, the water treatment plant had to be shut down. The island needed to move quickly to minimize the cost of purchasing water from the mainland.
Solution
Giackino switched to a PURELAB® Option-R point-of-use laboratory system. This system produces water that is higher in quality (Type II: between 10 and 15 megohm-cm) than double-distilled water (typically 1.0 megohm-cm). It includes pretreatment, RO and ion exchange technologies to purify the water. A prefilter removes chlorine and particulates, the high-flux RO membrane results in high flow rates and maximizes efficiency, and the purification cartridge pack removes organic and inorganic impurities. An ultraviolet lamp keeps bacteria counts low, as does the 0.2-micron point-of-use filter. Water inside the system is recirculated to maintain quality.
Results
Since switching from the still to the point-of-use system, Giackino has found that the quality of water in his benchmark samples has been much higher and much more predictable.
" I rarely see any depletion in my benchmark samples and on the odd occasion that I do, it's minimal. The point-of-use water system gives much more reliable results, and I have to repeat far fewer tests. "
*Evoqua features ELGA LabWater systems. PURELAB® is a trademark of ELGA LabWater.