Disinfection Strategies: Challenges to Meet Changing Requirements

The design variables for determining the appropriate disinfection strategy have changed over the years due to changes in technology, regulations and discharge points. The one-size-fits-all disinfection strategy no longer applies, and economics may not be the key factor in the selection of a disinfection technology. Historically, chlorine has been the most common method of disinfection' however it us use is under scrutiny due to concerns with chlorine transport from the chemical manufacturer to the point of use carries quantifiable risks, chlorine gas can be toxic, hypochlorite solution is corrosive, chlorine residual in treatment plant effluent can harm aquatic systems, and chlorine addition to wastewater can result in formation of undesirable disinfection byproduct (DBPs). Alternative disinfectants such as ultraviolet (UV) light, ozone, chlorine dioxide, and chloramines are often considered in reuse and recharge applications, primarily to address chlorine residual and/or DBP issues, i.e. trihalomethane (THM), haloacetic acids (HAA), and nitrosodimethylamine (NDMA) formation. For the Fountain Hills Sanitation District, issues with THMs forced them to evaluate alternative disinfection strategies. The challenge in selecting alternative disinfection strategy was the multiple reuse and recharge discharge points which often had conflicting requirements. To address the FHSD disinfection needs, disinfection alternatives were combined. For projects as complex as the FHSD disinfection project, a decision mapping model such as Criterion Design Plus can help simplify the design making process.