Long Term Performance of Two Wastewater Tertiary Treatment Systems Approved for Use in the New York City Water Supply Watersheds

The Stamford and Hobart Wastewater Treatment Plants are located in the headwaters of the West Branch Delaware River feeding the Cannonsville Reservoir, an integral component of the New York City water supply system. Federal regulations require a drinking water filtration plant for the NYC water supply unless specific filtration avoidance requirements can be met. One requirement necessitated that WWTPs discharging in the NYC watershed be upgraded to tertiary treatment. The Stamford WWTP was upgraded with a two stage tertiary granular media filtration system whereas the Hobart WWTP upgrade utilized a hollow fiber microfiltration system. Both systems were designed to eliminate the discharge of pathogenic protozoans while also reducing solids and phosphorus concentrations. Over ten years of operation has proved that both systems are robust, reliable and capable of meeting design expectations. Significant long term reductions in effluent turbidity, total suspended solids, phosphorus and fecal Coliform have been achieved.