What is the treatment process at the Joint Water Commission?
The treatment process consists of a series of steps. First, raw water is drawn from the Tualatin River Intake and pumped directly to a mixing tank where chlorine and alum are added. The chlorine serves as a disinfectant and the addition of alum causes small particles to adhere to one another (called ‘floc’) making them heavy enough to settle in a sediment basin. After settling, polymer is added for turbidity removal (turbidity is a common measure of the clarity of water). Activated carbon is also periodically added at this point, when needed to remove irregular taste and odor. The water is then filtered through layers of fine coal and silicate sand. As suspended particles are removed, turbidity disappears and clear water emerges. Removing turbidity is the best protection against cryptosporidium, since the cysts containing the crypto are also removed in the filtering process. Chlorine is added again at this point as a precaution against any bacteria that may still be present. (We carefully monitor the amount of chlorine, adding the lowest quantity necessary to protect the safety of your water without compromising taste.) Finally, caustic soda (used to adjust the final pH and alkalinity) is added and the finished water is pumped from clearwell storage to either the Fernhill Reservoirs or directly into a transmission line to be fed to one of the JWC member agencies or wholesale customers.