By Cory Johnson, CH2M HILL Eastern US Practice Lead for Water Treatment
It’s always been fascinating to see that when we, as engineers, think we’ve solved one problem, a new one emerges. The discovery that chlorine disinfected water resulted in a significant decrease in water borne illnesses probably represents one of the more impactful accomplishments in public sanitation ever. But, we soon discovered that the use of chlorine also meant disinfection by-products formed through the reaction between chlorine and naturally occurring organic matter in the raw water. Thus, the EPA began regulating total trihalomethanes starting in 1979. In response, utilities made changes to treatment to reduce the concentration of TTHMs. To achieve rule compliance, some utilities responded by installing additional treatment systems to reduce the concentration of disinfection byproduct precursors. These treatment systems resulted in higher capital and operating costs, more treatment residuals requiring disposal, more chemicals being used, and more energy use. Others altered their disinfection process or opted for a low cost alternative by switching to chloramines, which simply requires addition of an ammonia feed system.
Following the 1979 regulation of TTHMs, the EPA set the bar higher by enacting the Stage 1 Disinfection/Disinfection By-Product Rule which made the total trihalomethanes limits stricter and added haloacetic acids to the list. Utilities again responded by making changes in treatment or by making a change to chloramines as the residual disinfectant. As more utilities made the switch to chloramines, utilities soon found this fix was less than perfect too. While low cost, chloramines can result in distribution system nitrification due to the small amount of free ammonia inherent in the chloramination process. The nitrification can result in significant flushing and residual loss in the distribution system. The Stage 2 Rule made compliance even more difficult for utilities, with utilities again making a choice between additional treatment systems to remove the disinfection by-product precursors or a switch to chloramines.
With a large number of utilities now having made the switch to chloramines, we are now gaining an understanding of the disinfection by-products related to chloramination, much like we did in the last century when we began to understand the health related effects of the chlorinated disinfection by-products. EPA is now assessing the impact of chloraminated disinfection by-products namely nitrosamines.
We don’t ultimately know if the regulation of nitrosamines would be part of another stage, Stage 3, of disinfection by-product regulation. But if history repeats itself, any regulation will mean additional treatment, more residuals, more energy per treated gallon, and ultimately more cost and more unintended consequences. CH2M HILL is always working to help our clients stay ahead of these regulations, even serving on the boards that help guide the EPA in setting them. We participate in industry and our own research projects to continually improve on the technologies and processes needed to help utilities meet changing regulations and maintain quality while also keeping costs affordable. While we may not exactly know now what future regulations will be, we will always be prepared to help our clients meet them.
Mr. Johnson has more than 11 years of experience in water treatment and distribution system design, optimization, construction, operations and management. At CH2M HILL, he currently serves as the US East Regional Practice Lead for Water Treatment in the Water Business Group. Over the past several years, Mr. Johnson’s work has increasingly focused on energy and chemical optimization and sustainability. He is an active member at both the national and state levels of the AWWA and is currently a member of the AWWA Energy Management Committee.