Grasslands Naturalists organized a tour of the Medicine Hat Water Treatment Plant for World Water Day on Wednesday recently. It was an inquisitive group and the tour, which was scheduled for 30 minutes, lasted nearly two hours.
The group learned about the entire process, starting at when water comes into the plant from the South Saskatchewan River to where it leaves once its clean.
The group learned that water coming in changes throughout the year. The Nephelometric Turbidity Unit is used to measure the presence of suspended products. The higher the NTU, the more solids are in the water and the dirtier it looks.
Water coming in from the river can be anywhere from 100 NTU to over 9,000 NTU. After a rainstorm, it can be around 400 NTU, but during the floods of 2013, the water coming in was closer to 9,100 NTU, which means more sediment that must be removed until it is clean enough to leave the plant. Clean drinking water has 0.05 NTU.
Several questions focused on what is added to the water, such as charcoal, alum and permanganate, which act as coagulants to remove solids from the water. Without using them the water would never be as clean, and the coagulants do not remain in the water but are removed as part of the sediment. This sediment is currently returned to the river but will now need to be further processed into a dry cake and taken to the landfill.
There were lots of questions about addition of chlorine to the water. The water treatment plant now uses UV radiation as an end-stage disinfection process, which is why is chlorine still added.
While the water is clean leaving the plant, it still goes to the reservoir and through the distribution system. Chlorine remains in the water to deal with any contamination that might occur after it leaves the plant and before coming out of the tap.
One question that couldn’t be answered was about dealing with pharmaceuticals in the water. As they are molecules and not a sediment, there isn’t a process to deal with them. It is a human-made problem and part of the solution is returning unused medication to the pharmacy for disposal and not dumping them down the toilet.
By SAMANTHA JOHNSON, Local Journalism Initiative Reporter
Original Published on Mar 23, 2023
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