Analysis On Microbial Community Constructure Of Activated Sludge In The Different Conditions Of Ns

Organic matter-sludge loading rate （Ns） has significant influence on the sludgecharacteristics and wastewater treatment efficiency. This paper studied the removalefficiency of COD, NH3-N and TN of the SBR and the microbial communitystructural succession of the sludge in it. The SBR was operated at different Nsconditions by controlling the influent organic matter concentration, the sludgeconcentration and the hydraulic retention time. In this paper the Ns was controlled at0.02⁰.03,0.10⁰.23,0.37⁰.48,0.55⁰.73,1.08¹.38,1.45¹.84and1.91².56kgCOD·（kgMLSS·d）^-1.The study showed that the removal rate for pollutants was discrepant in differentconditions. The COD removal rate was the highest and stayed constant above90%when Ns was0.55⁰.73kgCOD·（kgMLSS·d）^-1, but it decreased with increasing Ns.Ns also had an obvious impact on ammonia removal. The effluent ammoniaconcentration was under0.5mg·L^-1at0.02⁰.73kgCOD·（kgMLSS·d）^-1. But theremoval sharply decreased after exceeding1.08kgCOD·（kgMLSS·d）^-1. In addition,total nitrogen （TN） removal rate was the highest and stayed above60%when NSwasin range of0.37⁰.73kgCOD·（kgMLSS·d）^-1.The study showed that the total removalefficiency was the best when NSwas0.55⁰.73kgCOD·（kgMLSS·d）^-1.The changes of the biology diversity and the microbial community structurewere regular as well. The DGGE graph of total bacteria showed that the number ofmicrobial species was the least at0.02⁰.03kgCOD·（kgMLSS·d）^-1, and the number ofspecies increased with increasing Ns. The biology diversity in the activated sludgesystem reached the peak under1.46¹.84kgCOD·（kgMLSS·d）^-1, but when the Nsincreased to higher level, the index showed a trend of decreasing. The DGGE ofammonia oxidizing bacteria revealed an opposite change from the DGGE of totalbacteria. The number of species for ammonia oxidizing bacteria was the highest andhad better quality at0.02⁰.03kgCOD·（kgMLSS·d）^-1. When Ns increased to1.08¹.38kgCOD·（kgMLSS·d）^-1, the bacteria was being repressed seriously, thediversity decreased rapidly and many of the bacteria deceased from the system.Moreover, the total bacteria categorizing analysis divided the microbes in different Nsinto three groups corresponding to the reactor operating process. The total bacteria banding sequencing results showed that most bacteria were uncultured bacteriumfrom the municipal sewage. And facultative anaerobic bacteria including Gammaproteobacterium and Enterobacteriaceae had been keeping the stable dominant strainstatus and played an important role for the removal of pollutants in SBR system.Real-time quantitative PCR technology was applied to analyze total bacteria anddenitrifying bacteria in the stage of0.02⁰.03kgCOD·（kgMLSS·d）^-1. The quantity ofthe total bacteria and the denitrifying bacteria were falling sharply in very low organicload condition, and the denitrification effect reduced with the sludge concentrationabating without adding external carbon source.