AWWA JAW62337

Hundreds of water utilities using chloramines experience problems with nitrification, including loss of total chlorine residual, destruction of free ammonia, increases in nitrite concentration, and potential bacteriological problems. An effective and reliable nitrification control strategy can help eliminate these concerns and make the use of chloramines simpler than it has been in the past. For utility managers looking for cost-effective ways to control nitrification, this article offers a promising method, application of sodium chlorite. Results of a six-month pilot study in Tucson, Arizona, demonstrated that continuous feed of chlorite ion was effective at controlling nitrification even at concentrations as low as 0.1 mg/L. Until now, no widely usable control method was available to control nitrification. Each utility had to handcraft its own individual solution. Although the cost of sodium chlorite is relatively high compared with other water treatment chemicals, the small doses needed to control nitrification make the cost of this chemical more reasonable. Many water providers using chloramines are all too familiar with the extensive maintenance and sampling costs associated with uncontrolled nitrification, as well as the loss of confidence that can arise from a Total Coliform Rule violation or a boil water advisory. In comparison with these kinds of costs, the expense of sodium chlorite and chemical feed systems may seem a bargain. Includes 18 references, tables, figures.