North American Experience with Centrate Treatment Technologies for Ammonia and Nitrogen Removal

The discharge of ammonia and nitrogen to receiving bodies of water is becoming more strictly regulated at municipal wastewater treatment plants throughout North America. The dewatering of anaerobically digested biosolids creates a reject water stream (often referred to as centrate or dewatering filtrate) that can contribute to an additional 15 to 20 percent of the ammonia load to a facility. If not managed properly, the reject water stream can have a significant impact on secondary treatment performance in terms of nitrification and nitrogen removal. The objective of this paper is to document and summarize reject water treatment experience at facilities in North America. Much of the groundbreaking work in this field has been lead by the City of New York Department of Environmental Protection (NYCDEP) and a summary of their work over the past 15 years is provided herein. In addition, this paper provides a summary of other North American facilities that have carried out or are currently carrying out pilot or full-scale application of these technologies. The information presented in this paper will be useful to practitioners in the municipal wastewater industry who are considering the implementation of centrate/reject water treatment for their facilities and wish to gain a better understanding of where it has been practiced at North American facilities.