Comparison of nitrifying populations between a lab-scale system and an industrial system treating coking wastewater

Abstract:

Molecular analysis of community structure can help diagnose problems in malfunctioning full-scale wastewater treatment system. A lab-scale A₁-A₂-O fixed biofilm system with highly efficient nitrification (NH₃-N removal at 95.2%) was set up as a reference for an industrial system with poor performance of nitrification (NH₃-N removal efficiency at -106%) for treating coking wastewater. Composition of nitrifying bacteria of biofilm samples in aerobic reactors of the two systems was compared by 16S rDNA clone library analysis. The composition of clone library of the lab-scale system indicate Nitrosomonas europaea-Nitrosoccus mobilis cluster and sublineage Ⅰ of Nitrospira genus are dominant ammonia and nitrite oxidizers in this process respectively. However, there were no clones related to nitrifying bacteria in clone library of the industrial system which suggested low abundance of nitrifying bacteria in this system. Further, Real-Time PCR with Taqman probe revealed that 16S rDNA copy number of Nitrospira in aerobic reactor of the lab-scale system was 3.4×10^{6/μg DNA of biofilm which is 300 times higher than that in the industrial system. The absence of Nitrosomonas and Nitrospira in the industrial system leads to poor performance of nitrification. Building up of a high population level of Nitrosomonas and Nitrospira in aerobic reactor is the key to improve efficiency of nitrification of the industrial system.}