Research Supports Design of the Largest Ozonation Facility in the United States. The Southern Nevada Water Authority (SNWA) is in the process of installing 900 mgd (3,400 Ml/d) of ozone facilities at their Alfred Merritt Smith and River Mountains Water Treatment Facilities. However, the formation of bromate from ozonating bromide-laden water posed a challenge to future operations. SNWA retained the Carollo Black & Veatch joint venture team and initiated a research project to examine the operation of ozone followed by biological filtration. The research project included one year of pilot testing conducted at the existing ozone pilot plant on its Alfred Merritt Smith Water Treatment Plant site.

The research goals included the following:

• Develop an implementation plan for full-scale ozone / biological filtration at the Alfred Merritt Smith Water Treatment Plant.
• Determine an optimum bromate mitigation technique.
• Determine the approximate ozone dosage required to achieve 2-log Cryptosporidium inactivation.
• Determine the effects of variable-rate filtration on the operation of the biological filters.
• Determine the effects of temperature changes in the lake on biological filtration.

The research project led to a patent-pending bromate control technique that used chlorine and ammonia addition prior to the ozone contactors. The project team developed an innovative solution that will potentially allow SNWA to meet disinfection goals without exceeding the bromate MCL of 10 ppb.

Carollo Black & Veatch also provided design of the full-scale ozonation facilities under construction at the Alfred Merritt Smith Water Treatment Plant. The facilities will provide pre-ozonation for the 600 mgd (2,271 Ml/d) treatment plant, and were also designed under a program to expand Las Vegas Valley's water supply system.

When the ozone facilities are put into service later this year, they will be the largest ozonation installation in the United States. Its design required the integration of the massive ozone complex into the existing plant processes with minimal hydraulic and construction disruption.