AWWA WQTC58921

The Catskill and Delaware watersheds supply New York City with up to 90% of the nearly two billion gallons of water consumed daily. Although unfiltered, these upstate supplies are of high quality. Because of the high quality raw water supply and the extensive watershed protection program, the New York City Department of Environmental Protection (DEP) has been granted a Filtration Avoidance Determination (FAD) by the United States Environmental Protection Agency (EPA). As part of the FAD, the NYCDEP must proceed with the design and installation of ultraviolet (UV) disinfection facilities, even though the promulgation of regulations governing enhanced disinfection are still several years off. The purpose of this paper is to report on the feasibility of UV disinfection for large utilities and the unique set of design challenges that must be addressed. The design of a UV disinfection facility for New York City's Catskill and Delaware supplies poses several unique design challenges due to the scale of the facility (2,020 mgd), the unfiltered state of the water being treated and the relative infancy of UV technology. Challenges that have been encountered include the need to provide a facility that meets the required design goals under all operating conditions and raw water qualities, is highly reliable, and maintains the present operational flexibility of the system. Additional challenges in designing the world's largest UV disinfection facility include maintaining a schedule ahead of regulatory promulgation, maintaining operational flexibility in the overall system both now and in the future and ensuring that the UV equipment that will be provided for this facility can be validated to meet the design criteria. Includes 2 references, figures.