Denver Water selected Carollo to evaluate UV disinfection at three water treatment plants: the 275-mgd Foothills Water Treatment Plant, the 250-mgd Martson Water Treatment Plant, and the 180-mgd Moffat Water Treatment Plant.

Carollo developed UV design criteria, established UV location alternatives, reviewed commercial UV technologies, and developed conceptual designs for each facility. The evaluation also included an assessment of UV light to inactivate and control Chorella and UV with hydrogen peroxide to control seasonal taste and odor events.

Carollo's approach for Denver Water addressed important issues that directly impact implementing UV disinfection in terms of costs, reliability, and ease of use. Carollo compared the costs and benefits of applying large-scale UV reactors to smaller scale reactors currently being used by many utilities. Work included coordinating Denver Water and its state regulator to optimize UV system design and minimize UV costs by obtaining approvals to use UV reactors validated under the USEPA UV Disinfection Guidance Manual Tier 2 validation approach. Carollo used advanced life-cycle cost analysis to identify optimal UV system operational strategies and used cost-benefit analysis to rank and select the best UV system for each site. Of particular importance was using the risk analysis to evaluate the impacts of off specification performance by the UV system and identify the need for back up power using uninterruptible power supply systems.

The project followed an aggressive seven month schedule. Project deliverables included developing an implementation plan for full-scale design.