The city of Tempe, Ariz., recently replaced the gaseous chlorine disinfection systems at its Johnny G. Martinez Water Treatment Facility (WTP) and South Tempe WTP with on-site sodium hypochlorite generation. The facilities, which were commissioned in October, are each equipped with a duty and standby ClorTec on-site sodium hypochlorite generating system, manufactured by Severn Trent Services. On-site sodium hypochlorite disinfection allows the City to reduce disinfection by-product formation (DBPs) as well as the potential hazards and security risks to plant operators and the nearby communities associated with chlorine gas.
The Johnny G. Martinez WTP system produces 3,000 pounds per day (lb/day) of sodium hypochlorite at a 0.8% solution and has a total storage capacity of 42,000 gal. The South Tempe WTP system produces 2,250 lb/day of sodium hypochlorite at a 0.8% solution and has a total storage capacity of 30,500 gal. Severn Trent Services provided temporary on-site disinfection systems that were used for about a year while expanded facilities were constructed to house the new equipment. %
According to Don Hawkes, water utilities manager for the city of Tempe, "Safety, security and long-term capacity were the highest priorities in making the switch from gaseous chlorine to on-site sodium hypochlorite generation. The support we received for the temporary systems while construction was in progress was outstanding, and the new sodium hypochlorite generating systems are operating flawlessly."
Carollo Engineering was responsible for oversight engineering for the project and served as the design engineer. M.G.C. Contractors was the general contractor.