White Papers | Potable Water Storage Reservoirs

Ice Prevention in Potable Water Storage Tanks with Solar-Powered Active Mixing

Water bodies, like human bodies, require good circulation to function properly” (Hudnell, 2009). Quiescent waters in potable water storage tanks are associated with water quality problems such as thermal stratification, biofilms, excessive disinfection byproducts and disinfectant residual loss. Ice formation in distribution-system reservoirs is another challenge faced by water utilities in northern climates during winters. Thick layers of ice often form at the surface in storage tanks during prolonged periods of subfreezing weather.

Increasing Contact Time and Reducing Short-Circuiting In a Clearwell Tank

In 2005 the City of Bend, Oregon’s Water Division commissioned a new reservoir, known as Outback Reservoir #2, which functions as a clear well. The reservoir is welded steel above ground tank, which is 120 feet in diameter and has a maximum depth of 35.4 feet. The reservoir has a capacity of 2.9 million gallons (MG), however typical operating depth is about 26.6 feet or approximately 2.23 MG. The well was designed with separate inlet and outlet pipes, which are located directly opposite each other at the bottom of the tank.

Mixing, De-Stratification, And Break-Point Chlorination

The San Francisco Public Utility Commission (SFPUC) is an innovative leader in potable water distribution system research and operation. The SFPUC continually strives to improve water quality by conducting research and implementing operational improvements to surpass increasingly stringent regulatory standards. In 2002, the SFPUC planned a 2004 transition to chloramines as a secondary disinfectant to reduce disinfection byproduct concentrations. The SFPUC anticipated nitrification problems when chloramine decayed, releasing free ammonia to the water.