Enhancement of Nitrogen Removal thru Innovative Integration Of Centrate Treatment

The City of New York has introduced a modification to it's high rate step feed aeration process that permits significant nitrogen removal. By integrating nitrification of anaerobically digested sludge dewatering centrate in a separate tank, severely constrained wastewater treatment plants were able to achieve nitrification at sludge ages below nitrifier washout. Additional process stability was conferred by integrating three novel process enhancements – (a) sidestream nitrifier production, (b) increased sludge retention via sludge storage and (c) selective inhibition of an otherwise dominant species, nitrite oxidizers, to allow for stable nitrification and to maximize denitrification performance under carbon limited conditions. Nitrifier growth rates in the modified centrate treatment process increased by 73% versus the original configuration, allowing the plant to stably remove up to 65% of the influent nitrogen load.