Enhanced nitrite build-up in proportion to increasing alklinity/NH4+ ratio of influent in biofilm reactor

Abstract

When the alkalinity/NH4+ ratio increased from 4.1 to 9.4, the ammonium removal rate increased from 45 to 90 mg NOx-N l(-1) h(-1). An increase in alkalinity/NH4+ ratio was a major reason for higher pH and free ammonia (FA) concentration in the reactor. The high concentration of FA showed a selective inhibition for Nitrobacter, which caused enhanced nitrite build-up in a biofilm reactor.