City Installs On-Site Sodium Hypochlorite Generating System

The City of Tempe, AZ, recently replaced the gaseous chlorine disinfection systems at its Johnny G.

Jan 1st, 2006

The City of Tempe, AZ, 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 ClorTecTM 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 percent solution and has a total storage capacity of 42,000 gallons. The South Tempe WTP system produces 2,250 lb/day of sodium hypochlorite at a 0.8 percent solution and has a total storage capacity of 30,500 gallons. 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.

Paper Designed to Assist With Wet Weather Negotiations

The National Association of Clean Water Agencies (NACWA) has released its Financial Capability and Affordability in Wet Weather Negotiations White Paper.

The White Paper provides an in-depth review of existing EPA guidance on affordability-related issues and recommends modifications to existing policy and practice on wet weather compliance and its financial impacts. Through detailed Case Studies, the White Paper also provides information for, and guidance on, affordability negotiations and details viable approaches for reducing the financial impacts of wet weather projects on low-income households.

NACWA commissioned the White Paper to:

− Provide a critical review of the U.S. Environmental Protection Agency’s established policies and guidance on financial capability assessments for wet weather programs;

− Offer practical guidance to clean water agencies for discussions with state and federal regulators on current policies and practices related to consideration of financial capability;

− Suggest modifications to EPA’s assessment methods and enforcement practices - particularly the importance of expanding financial capability considerations to include the breadth of wet weather related compliance requirements facing a community;

− Through Case Studies, provide a succinct overview of the experiences of clean water agencies assessing financial capability in the context of negotiating Clean Water Act (CWA) wet weather consent decrees; and

− Provide general guidance on the relationship between financial capability and low-income affordability, and suggest approaches to addressing low-income affordability concerns.

NACWA’s Executive Director, Ken Kirk, stated that, “When short implementation schedules are coupled with a zero overflow philosophy, many public utilities find it all the more essential to make affordability and financial capability arguments. This White Paper reviews a broad sampling of clean water agency wet weather negotiations and highlights various techniques for making successful affordability arguments.”

The White Paper can be found on the NACWA website at www.nacwa.org. WW

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