Westchester Joint Water Works (WJWW) obtains approximately half of its supply from New York City’s water system at Rye Lake – a branch of Kensico Reservoir that has been impacted by local surface water runoff. While the City’s Kensico supply is included under USEPA’s Filtration Avoidance Determination for the Catskill/Delaware systems, water withdrawn by WJWW at Rye Lake was not granted a filtration waiver. Although WJWW had evaluated and implemented several nonfiltration alternatives, the New York State Department of Health (NYSDOH) issued WJWW a consent order to filter the Rye Lake supply.

WJWW faced many challenges in meeting the consent order. It did not own property suitable for siting a 20-mgd facility. WJWW also needed a cost-effective, operator-friendly, robust filtration facility that could both fit and be permitted on land available for purchase.

These challenges were overcome by a comprehensive study involving site selection, treatment process evaluation, pilot plant testing on Rye Lake water, and conceptual design. This study enabled the project to progress from a regulatory mandate to a comprehensive plan for a state-of-the-art immersed membrane filtration plant, projected to go online in early 2008.