Learn about the hidden risks of ice formation inside water storage tanks, traditional approaches for preventing ice damage and new tools for eliminating ice.
With the arrival of the U.S. Environmental Protection Agency's Stage 2 Disinfectants and Disinfection Byproducts Rule in 2006, water utilities began examining options to achieve compliance. Much of the attention has focused on ways of lowering organic matter concentrations at water treatment plants. Fortunately, distribution system O&M strategies often can be implemented quickly and inexpensively.
Stanly County, in central North Carolina, is typical of many smaller rural water utilities in the U.S. Due to excess capacity in the city water system that supplies the surrounding county, Stanly County receives finished water that is often at or above the Maximum Contaminant Level (MCL) for Total Trihalomethanes (TTHMs). Without a treatment plant of its own, Stanly County is limited to few options for bringing their water into compliance.
The Stage 2 Disinfectants/Disinfection Byproducts Rule is presenting tough choice for many water system managers. While some operators have used aeration to reduce Trihalomethanes in storage tanks in the past, it has produced encouraging but inconsistent findings. Now, a Texas utility is using PAX Water's in-tank THM removal system (TRS) with good results.
Despite flushing part of their system and periodically boosting chlorine to improve residual levels, the City of Monterey, California was on track to breach their Total Trihalomethane (TTHM) levels in the summer of 2011. After PAX Water and Utility Service Company provided a combination of active tank mixing, chemical cleaning and in-tank THM removal, Monterey was able to achive compliance.
The City of Ballinger, Texas struggled to meet compliance for Trihalomethane levels leaving their treatment plant for five consecutive years. After 10 days of operating PAX Water's TRS, an in-tank THM removal system (TRS), THM levels were reduced just above the MCL – the lowest level measured in 5 years.
Stanly County receives finished water that is often at or above the Maximum Contaminant Level (MCL) for Total Trihalomethanes (TTHMs). Without a treatment plant of its own, Stanly County is limited to few options for bringing their water into compliance. With the PAX Water TRS, an in-tank THM removal system (TRS), Stanly County's water became THM-free.
The City of Rifle, Colorado uses a solar-powered mixer to prevent summer stratification and maintain their ultimate goal of delivering better water quality to customers, while saving an estimated 2.6 million gallons of water annually.
Over the years, manufacturers of mixing systems have presented computational fluid dynamics (CFD) calculations to claim that their technology can achieve adequate mixing in water storage tanks. This case study presents calibrated CFD models, allowing for other mixing technologies to be evaluated on an apples-to-apples basis.
For most U.S. distribution systems using chloramination, nitrification is a leading water quality concern. However, by combining active mixing with regular tank maintenance and efficient operation, nitrification can be tamed in even the most challenging climates.