Design and Start-up of North America's First Sidestream Nitrogen Removal Plant

There are three wastewater treatment plants in the City of Winnipeg. Undigested solids from the three plants are processed centrally at the North End Water Pollution Control Centre (NEWPCC). Raw solids are added to mesophilic anaerobic digesters and the digested solids dewatered using centrifuges. The centrate from the centrifuges is discharged to the head-end of the NEWPCC. Although the centrate flow is only about 2 ML/d, or one percent of the total flow to the NEWPCC, it contributes an estimated 1,700 kg TKN/d, which is about 30 percent of the total nitrogen load to the plant.The Province of Manitoba has issued a license which limits the total nitrogen (TN) in the centrate discharged to the head-end of the plant to a maximum of 174 kg/d. In order to meet this limit, a dedicated sidestream centrate nitrogen removal facility was installed. The facility was completed in September 2008.This paper presents the rationale for the design of the centrate nitrogen removal facility, discusses the start-up and commissioning of the plant, and describes the changes in the mainstream final effluent quality resulting from the installation of the sidestream plant.