Municipal Water Treatment

Disinfection Creates New Problems

In the summer of 2003, the EPA activated the second phase of the Disinfection Byproducts Rule (DBPR). Until the establishment of the DBPR, the EPA had been concerned only with how much (or how little) municipal facilities were removing from the water. Little attention was given to what was added to the water in the treatment process and the subsequent reactions taking place within. Studies completed throughout the 1970's and 1980's provided revealing insight as to the problematic disinfection byproducts formed upon injecting chlorine, chloramines and chlorine dioxide into contaminated water. Discovery of the dangers of Trihalomethanes (THMs) and Haloacetic acids (HAAs) led the EPA to form the DBPR, part of the larger Microbial Disinfection Byproduct Rule (M-DBR).

The DBPR is of great concern to the operators and engineers of the over 170,000 public water systems throughout the U. S. The reason being is that, with small exception, chlorine is the primary disinfectant applied to raw water throughout the U. S. Chlorine is also the single contributing factor in the production of THMs and HAAs in treated water.

The residents of Las Vegas receive their drinking water from Southern Nevada Water Authority (SNWA). The SNWA treats 490 MGD of water from the Colorado River with two facilities, both utilizing ozone for disinfection. Because of this, the amount of THMs and HAAs has dropped to record lows. Ron Zegers, director of SNWA stated, "It has improved the water's clarity by 10 times of what it was before we started the system."

Prior to 1974 only a handful of treatment facilities were employing ozone as a disinfectant and to remove color and odor. Following The Safe Drinking Water Act (SDWA), the number has grown dramatically. As of 2000, over 250 drinking water plants use ozone within the United States. That number is expected to double within the next few years with the finalization of the DBPR.

Click here to find out more about the DBPR.