Rockland County Sewer District
Rockland County, NY
EDR is providing engineering planning services to Rockland County Sewer District No. 1 in order to satisfy compliance with a modified SPDES permit. The District is required to produce an engineering report, including evaluation of alternatives, to upgrade their 29 mgd Orangeburg wastewater treatment plant to meet stringent ammonia and total residual chlorine limits in accordance with their SPDES permit. The engineering report will establish a basis of design for significant improvements to their Orangeburg WWTP. This report is continuing the District’s efforts in a parallel manner to appeal the ammonia limits as issued, since a potentially more cost-effective solution to meet water quality limits is viable with a modification to their existing outfall. CORMIX modeling done for the current discharge location of the District’s outfall supports the conclusion that a modification to the existing outfall, addition of diffusers, would meet water quality limits and eliminate the need to upgrade the Orangeburg plant for ammonia removal. This alternative will be included in the June 2026 report, since it may save significant capital investments.
EDR’s work includes a detailed condition assessment of the existing unit processes and equipment at the Orangeburg plant and their future performance capability. Several new treatment process alternatives are being evaluated including innovative treatment technologies to improve CBOD and ammonia removal as well as adding on new processes that repurpose the existing treatment trains.