Research Project Information

Research Project Summary Information

Selector Contact Stabilization Process for WWTP:Town of Rosendale Municipal Wastewater (ST7056-1)

Town of Rosendale


The Town of Rosendale, Ulster Co., New York, owns and operates a municipal wastewater treatment plant (WWTP) that serves a sewer district in a largely residential area. The township was approached by a regional developer with a plan that would, when combined with current flows, exceed the rated capacity of the existing WWTP. The Rosendale WWTP has traditionally experienced poor mixed liquor settleability, due to dissolved oxygen and nutrient limitations. Plant operators typically resort to chlorination of the return activated sludge (RAS) to avoid solids wash-out under critically high biological oxygen demand loading and sustained wet weather flows. In an effort to improve plant operation and efficiency, the Selector Contract Stabilization Process (SCS) process was demonstrated at full-scale at the Rosendale facility.

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Project Description

The Selector Contract Stabilization Process (SCS) was developed to 1) increase wastewater treatment plant capacity without construction of new process tankage, 2) improve operations of activated sludge biological treatment processes, 3) reduce aeration energy use, and 4) enhance process stability, particularly as a result of enhanced biological mixed liquor settleability.


The SCS process reduces the potential for total suspended solids exceedences, which could be discharged to the receiving stream. The SCS process should reduce the capital cost of potential future upgrades needed to treat greater flows at the plant. The demonstration was expected to enhance the promotion of SCS to other similar sites in New York State.

Project Results

The primary objectives were to demonstrate increased capacity and improved process performance at the Town of Rosendale WWTP. These objectives were achieved; the SCS process was found to be superior to the WWTP’s existing extended aeration process. The SCS process sufficiently treated 59,000 gallons per day (gpd) in one half the plant’s existing tankage; extrapolated to both tanks, this equals a capacity of approximately 118,000 gpd, which is in excess of the targeted capacity of 105,000 gpd. In addition to the process benefits, the demonstration provided the Rosendale WWTP operators with first-hand knowledge of operating the SCS process. The data and other information collected during the demonstration can be used to prepare a detailed engineering design for a permanent conversion of the Rosendale WWTP to the SCS process.


Town of Rosendale
Rosendale Sewer District P.O. Box 423
Rosendale, NY 12472

Principle Investigator

Mark Green

Universities Involved


Project Type:

Product Demonstration

Technologies Types:

Waste Management and Pollution Prevention
Water/Wastewater treatment systems

NYSERDA Contact Information

Kathleen O'Connor


R&D - Environment & Energy Res

Contract Details

Start Date: 1/11/2010
Project Status: Active
Contract Number: ST7056-1

Last Updated: 11/13/2013