Whitley Burchett

Chemicals Versus Energy: Sorting Out Operation Costs for
Tertiary Recycled Water Disinfection

(Presented at the WateReuse Association Symposium XIV,
Long Beach, CA, September 1999)

Paul Friedlander: Whitley, Burchett & Associates
Talyon Sortor: Fairfield-Suisun Sewer District

ABSTRACT

An understanding of the operation cost trade-offs between recycled water disinfection alternatives is important to the feasibility of recycled water use. Chlorination is the most common method for disinfecting wastewater to meet State tertiary recycled water requirements. Ultraviolet (UV) disinfection is increasingly being used as an alternative to chlorination. This paper presents an evaluation of operation costs for disinfection using chlorine gas, sodium hypochlorite, medium-pressure UV, and a newer technology - low-pressure, high-intensity UV - for a wastewater treatment plant in Fairfield, California. The results of the evaluation highlight both the trade-offs between chemical-intensive and energy-intensive disinfection technologies and between different chlorination and UV systems. Chlorine gas operation costs are significantly less than hypochlorite chlorination, even with the added costs of meeting regulatory risk management plan requirements. UV dosage regulatory requirements result in UV operation costs being significantly higher than for either chlorination alternative. Medium-pressure UV systems are the most expensive to operate due to the inherent energy inefficiency of medium-pressure lamps.