You Think Effluent UV Disinfection is Easy! Difficulties in Validating Existing UV Process and Plant Capacity Under New Regulations

The revised Title 22 Guidelines of the California Department of Public Health (CDPH) require revalidating UV disinfection systems for water reuse applications. Elsinore Valley Municipal Water District received CDPH approval for its 0.3 m3/s (cubic meters per second) (8.0 mgd) Regional Wastewater Reclamation Facility (RWRF) without full-scale bioassay testing; the plant capacity was significantly down rated. The District decided to conduct a full-scale bioassay test to recover the lost capacity and thus avoid significant expansion expenditures. The full-scale test results discussed here validated the existing UV system capacity, prevented capacity down-rating and established an Operations Plan to continually deliver the UV dose to comply with the design criteria (100 mJ/cm2) under CDPH approved operating conditions of flow, water quality, and lamp output. A recommendation for the water reuse industry is; to design full-scale facilities with ability to verify Ddose, including sampling access points, handling facilities for test-flow collection and storage and monitoring for flow split verification.