System solves disinfection by-product challenge at Butte-Silver Bow
The Basin Creek Reservoir in Butte, Mont., served its community with pristine water from both sides of the Continental Divide for nearly 100 years. In 2010, a pine beetle infestation killed most of the trees surrounding the reservoir, many of which fell into the water, increasing the natural organic matter (NOM) level. As a result, Butte-Silver Bow (BSB) Water Utility received a violation notice from the Montana Department of Environmental Quality for exceeding the Maximum Contaminant Limit (MCL) for a certain type of disinfection by-product (DBP). This violation prompted the construction of the Basin Creek Water Treatment Plant (WTP).
In order to maintain the use of the reservoir, filtration needed to be added to reduce the NOM and in turn, the DBPs. Initial efforts focused on site selection, pilot testing, hydraulic analysis, distribution system modeling, and process selection. Based on these initial efforts, a pressurized membrane filtration process was selected and, ultimately, an Aqua MultiBore® C-Series ceramic membrane system was procured by BSB to produce safe and secure drinking water.
The elevation difference between the reservoir and the distribution system allowed the opportunity to use gravity as the driving power to run the filtration plant. The C-series ceramic membrane offers high pressure ratings, allowing BSB to better capitalize on the gravity power. The reservoir pushes water through the membrane and directly into town, so when users in the city turn on their showers or water their lawns, more water flows through the Basin Creek WTP. HDR’s Project Design Manager Nathan Kutil said, “It’s very unique in that it is on-demand, but it is also powered by gravity.” Jim Keenan, chief operator of the new plant, added, “It saved a lot of infrastructure cost and a lot of pumping cost. That was a big advantage of this design.”
“It’s the first ceramic membrane, gravity-powered, on-demand plant in the country,” said Keenan. “We’ve been really pleased with how well the system works and how efficient it is. I really think that we have the most durable, longest-lasting, superior-quality product and I am really excited about that. I think it’s the future of water plants and the example is right here in Butte, Mont.”
Design Characteristics
Butte’s primary membrane system consists of four trains, each with 100 modules arranged in ten 10-module rows. The backwash water from this system is settled and treated with a backwash recovery train consisting of two 6-module rows. For both systems, each row has a complete set of valves such that it operates independently of the other rows; therefore, backwashes and cleanings are performed on one row at a time with the other row(s) in the train remaining in filtration. WW
Since 1969, Aqua-Aerobic Systems Inc. has led the water and wastewater treatment industry by providing advanced solutions in aeration and mixing, biological processes, cloth media filtration, membranes, disinfection, and process control. To learn more, visit www.aqua-aerobic.com.
