Miox : My Water. My World.

Residual Maintenance

The Environmental Protection Agency (EPA) requires maintenance of at least 0.2 mg/L of chlorine residual leaving the treatment plant and at least a measurable trace residual at all points in the distribution system.  The chlorine residual protects against recontamination that occurs in the distribution system through leaks and other compromises.

The Residual Maintenance Problem

Some sites with long distribution systems or dead-end lines have trouble maintaining a residual at their farthest reaches unless they dose excessively at the treatment plant. Excessive dosing is avoided since EPA maintains a maximum residual disinfectant limit (MRDL) of 4 mg/L for chlorine, and because excessive dosing causes high levels of hazardous by-products. High doses also tend to cause taste and odor complaints at taps nearest the treatment facility. Some facilities remedy residual maintenance problems by installing rechlorination booster stations at points along the treatment line. However, this adds additional cost and maintenance issues. Others have converted to chloramines, a mixture of chlorine and ammonia, but this is a weaker disinfectant, adds additional cost and safety issues, is susceptible to poor tastes and odors, and can lead to nitrification problems.

The MIOX Advantage

The chlorine residual from mixed-oxidant disinfectant endures throughout long distribution systems, and for extended periods of time. This effect is most likely tied to the removal of biofilms from distribution piping, which can dramatically reduce the oxidant demand that tends to consume residual disinfectant in the water supply. A notable example is the Cedar Knox Rural Water Project in Nebraska [Download datasheet], where the longest reach in the distribution system is 43 miles (69 kilometers) with a detention time of 6 to 7 weeks. Cedar Knox also supplies the neighboring village of Obert, resulting in an additional 3 to 4 weeks of detention. With use of chlorine gas, they struggled to maintain a residual at all points in the distribution system without exceeding residual disinfectant and TTHM limits. Several months after conversion to mixed oxidants, the water project was able to reduce their chlorine dosage by 30 to 50 percent while maintaining a stable and durable 0.4 mg/L residual at all points in the distribution system — even throughout the Village of Obert. A side benefit is that TTHMs were consistently 30 to 50 percent less than when using chlorine gas. [Hazardous Disinfection Byproducts]

The ability of MIOX technology to reduce the chlorine dosage while maintaining a more durable chlorine residual is repeated at site after site using mixed oxidants, as demonstrated in this chart. The data compares and contrasts dosages and residuals with conventional chlorine and with mixed oxidants.