Willamette River Water Treatment Plant

Water Supply

Willamette River Water Treatment Plant 10350 SW Arrowhead Creek Lane Wilsonville, OR 97070 (503)-582-9655 Tours of the Willamette River Water Treatment Plant In April 2002, Wilsonville began operation of its new water treatment plant on the Willamette River. The plant is capable of processing 15 million gallons per day (mgd). Within Wilsonville, demand for water varies seasonally from a low of approximately 2 mgd in the winter to nearly 6 mgd in the peak of the summer. The plant's additional treatment capacity is available to meet growth in demand. As further backup supply, the City's water system includes storage tanks throughout town with a total combined capacity of nearly 11 million gallons. Wilsonville's former water supply (a system of 8 local wells) is also available for use in emergencies. All of Wilsonville's storage tanks and wells are covered and have security systems in place.  Operation of the Water Treatment Plant is performed under contract by Veolia Water North America.

Water Treatment Process

During the 1990's pilot tests were conducted here in Wilsonville using conventional treatment methods. These tests confirmed that under "worst case" conditions, treated water from the Willamette could consistently meet drinking water standards. As a further margin of safety, enhanced methods of treatment were tested and incorporated into the design of the multi-barrier system used at Wilsonville's water treatment plant. The resulting water supplied from this facility is even purer than required by current drinking water standards (as well as proposed future drinking water standards). The treatment facility is "over-designed" in the sense that drinking water standards can be met without such extensive treatment. Nonetheless, the plant is operated using all steps at all times - - whether or not they are all needed to meet drinking water standards. In addition, the treatment plant has redundant (i.e., back-up) systems for all these processes. Here's a brief description of the "step-by-step" process used in Wilsonville's multi-barrier water treatment facility. Intake Screens The intake screens protect fish and prevent debris from entering the treatment facility. The screens are located off the bottom of the river (to avoid bringing sediments into the treatment plant) and below the surface (to avoid bringing oils or other floating material into the treatment plant). The openings in these screens are approximately the diameter of a toothpick.   Enhanced Sedimentation Enhanced Sedimentation to remove materials that are small enough to pass through the intake screens. Conventional chemicals called coagulants cause the suspended materials to adhere to one another forming larger, heavier "floc" which settles out of the water. By adding very fine sand to the mixture, the weight of the "floc" is increased thereby causing the settling process to occur more quickly and more completely than conventional water treatment. The sand is then cleaned, recycled and reused.   Ozonation Ozonation serves multiple functions including disinfection(to kill bacteria, viruses, Giardia, Cryptosporidium); breakdown of organic chemicals; breakdown of taste/odor causing compounds; and enhanced removal of organic material by the filters. After bubbling through the water, the ozone quickly decomposes into harmless oxygen gas.     GAC Granular Activated Carbon charcoal filters (6 feet thick) further remove turbidity and pathogens; remove organic chemicals; and remove taste/odor compounds to assure consistently high quality of the treated water.   Sand Filter The Sand Filter is a "polishing" step to improve particle removal.   Secondary Disinfection Secondary Disinfection adds chlorine to prevent bacterial contamination as the treated water flows through the distribution system to customers.

Water Quality Analysis

The following Water Quality Comparison Table lists the quality of Wilsonville's treated water in relation to drinking water standards established by the U.S. Environmental Protection Agency. Further information about EPA drinking water standards can be found on the EPA's website: www.epa.gov/safewater