DESIGN AND OPERATION OF AN ULTRAVIOLET DISINFECTION SYSTEM FOR A MUNICIPAL WASTEWATER TREATMENT PLANT IN YPSILANTI, MICHIGAN

As part of an expansion to an average flow of 45.9 million gallons per day (174 mld), the supervisory board of the Ypsilanti (Michigan) Community Utilities Authority Wastewater Treatment Plant elected to install ultraviolet disinfection as a replacement for the existing chlorination/dechlorination processes. This paper presents the methodology used in selecting the best system based on not only the life cycle costs and operation and maintenance considerations, but also the participation of the stakeholders. Following evaluation and pilot testing, a lowpressure, high intensity system was selected, based on life cycle cost, reliability, safety, and ease of operation. The design incorporated efficiency, redundancy and reliability in selecting the number of channels, rows of lamps and modules. Consistently good results have been obtained with the full-scale system since start-up in May 2003. This paper presents full scale performance data for 11 months since the start-up.