Characteristics of Nitrobacteria in SBR with Trace N2H4 Addition

Abstract

A sequencing batch reactor (SBR) was conducted to perform nitrification process. The influence of long-term trace hydrazine (N2H4) addition (about 3 mg·L-1) on ammonium oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) in nitrifying sludge was investigated. The result indicated that Nitrosococcu, Nitrosomonas and Nitrosospira were related to AOB, and Nitrobacter was related to NOB in nitrifying sludge with N2H4 addition, respectively. The estimates of AOB population (in dry sludge) with N2H4 addition decreased from 1.0×109 to 2.09×104 copies·g-1, and those of NOB decreased from 1.28×107 to 2.56×105 copies·g-1. AOB was more sensitive to environmental factors than NOB, the effect of inhibition and toxicity on nitrobacteria caused more loss of AOB abundances than that of NOB, but quantitative real-time PCR could not determine the inhibition of N2H4 on microbial activity of AOB and NOB. The nitrobacteria activity was destroyed with long-term trace N2H4 addition, and the reactor collapsed. Consequently, it was possibly unable to inhibit NOB activity by controlling the added N2H4 concentration, and further take off NOB in nitrification process for improving nitrogen removal.