DESIGN OF THE LARGEST UV INSTALLATION IN THE U.S.

A major expansion of the 100 MGD Wayne County Michigan, Wyandotte Wastewater Treatment Facility is almost complete which will allow the facility to provide treatment for peak wet weather flows (100 year storm) of 225 MGD. To provide disinfection for a range of wastewater flow from 60 to 225 MGD, a “blended flow” concept was developed. Peak wet weather flows up to 225 MGD will receive preliminary treatment (screening and grit removal). Up to 75 MGD of flow will bypass primary treatment. Only 125 MGD will receive secondary treatment. However, the innovative design of the blending facilities provides preferential secondary treatment for the preliminary flows that bypassed primary treatment. The plant's NPDES permit requires compliance with secondary effluent standards even during peak wet weather flow periods.A unique ultraviolet disinfection system design has been provided which is the largest of its type in the US. The system is expected to provide disinfection that meets permit requirements for flows up to 175 MGD. Extensive flow modeling and pilot disinfection studies of the Wyandotte wastewater system determined that the monthly fecal coliform limit of 200/100ml and the weekly limit of 400/100ml could be met even when occasional daily effluent fecal coliform levels during peak flow events were as high as 1000/100ml. Also, the UV system was designed to disinfect the “blended flow” which will have varying concentrations of fecal coliforms from the primary and secondary wastewater.