Filtration & Water Quality
Pumped from the shores of Lake Michigan, raw lake water is delivered to the filtration plant pre-filtered using infiltration (submerged) intakes as described in “Plant History”. The average turbidity level for our raw water is 0.09 NTU's. At the filtration plant, the treatment technique is "Direct Filtration"; there are no sedimentation basins after flocculation.
The water is filtered through eight (8) General Filter cells, each with a filtration area of 304.5 square feet and designed for a filtration rate of 6.6 gallons per minute per square foot. This increased our overall plant capacity by 50% which will provide safe and reliable drinking water over the next projected 15 to 20 years. Each filter cell contains 52 inches of anthracite coal. The pre-treatment stage at the plant consists of chlorination, aluminum sulfate (alum) and a non-ionic polymer additive as coagulants. Suspended particles, alum and polymer precipitate are trapped on the filter bed and after approximately 160 hours of filtration the filter is removed from service and then backwashed. Backwashing is completed in 20 minutes, which is enough time to break up and remove all impurities trapped on top of the filter. Our filters use water and air (multi-wash) during backwashing and are capable of filtering to waste once placed back into service. This process enables the operator to provide extremely low turbidity water to our customers.
Turbidity (suspended material in water) for filtered water remains well below our goal of 0.10 NTU (nephelometric turbidity unit) during normal filtration conditions. Filtered and Tap Water averages <0.05 NTU. Our operators consistently provide clean and clear water to our customers 24 hours a day by monitoring turbidity levels, temperatures, and other chemical and physical parameters.
Water Quality
The Northwest Ottawa Water Treatment Plant and its operators are certified and approved for microbiological analysis on Total Coliform, Fecal Coliform, and Heterotrophic Bacteria. Our laboratory has an operator available 24 hours a day. There are five shift operators that perform laboratory analysis and monitor water pumpages for all of Northwest Ottawa's customers. Our operators also perform routine physical parameter testing as well as state and EPA required testing for tap water and process water.
The complete filtration and pumpage system is monitored using a supervisory control and data acquisition (SCADA) computer system covering over 300 alarm notifications.
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