Analysis On The Influence Of SRT On Microbial Community Construture Of Phosphorus Removing Bacteria

Sludge retention time(SRT) is the key factor influencing on the survivalenvironment of activated sludge microorganisms and the important parameter ofdesign and operation of the process. The purpose of the study lies in exploringremoval efficiency of COD, NH4+-N, TN and TP and change law of microbialcommunity structure adjustment by running the SBR and adjusting SRT10d,15d,20dand30d respectively.The study shows that the removal rate of COD is always above80%and doesn’tappear obvious difference in different SRT. The fluctuation of system removal effectis less and the system can resist impact of influent COD load at the long sludge age.The effluent ammonia is the highest to25.9mg/L at sludge age of10d. The average is7.3mg/L at sludge age of30d, the concentration declines steadily and removalefficiency is improved at the long sludge age. The total nitrogen removal rate is on therise like ladder type with increasing SRT and is similar to the ammonia nitrogenremoval. The removal rate is not ideal for20%at sludge age of10d, the average is53%at sludge age of30d when system has the best effect. The total nitrogen removalis disappointing because a large amount of residual ammonia nitrogen inhibitdenitrification resulting from ammonia nitrogen removal doesn’t ideal at the shortsludge age and denitrifying bacteria doesn’t have enough carbon source for CODbeing consumed quickly. Total phosphorus removal effects are better and reach morethan74%at sludge age of10d and15d. The effluent concentration is more than5mg/L and the removal rate falls to31%when the function of phosphorus removalweakens at sludge age of30d. The number of nitrifying bacteria increases withlengthening sludge age, which results in more nitrate nitrogen promotingdenitrification. Phosphate accumulating organisms(PAOs) are at a disadvantagebecause of struggling for organic matter with denitrifying bacteria.The DGGE graphs show that the diversity of Acidobacteria is rich and the stripenumber of Actinobacteria is less and single slightly. By calculation, their diversityindex is above0.8and the diversity changes of Acidobacteria fluctuate strongly. Withsludge age shortening the diversity index of Acidobacteria rebounds, and there is adownturn in the Actinobacteria, indicating that Acidobacteria more adapts to the environment of short sludge age and Actinobacteria is relatively more suitable forlonger resident environment. Similarity comparison shows that Acidobacteria andActinobacteria are the largest difference with raw sludge at sludge age of10d, and thesimilarity indexes are29.5%and45.8%respectively. Dominant strains of theAcidobacteria and Actinobacteria change more frequently and the similarity betweenany two samples are on the low side. By clustering analysis, the Acidobacteria andActinobacteria are divided into two groups, the division generally follow change ruleof the sludge age, but the similarity of ethnic groups is very low. By means of DNAsequencing we found that the Acidobacteria belongs to uncultured bacterium whosehomologous bacterium mostly appears in the soil system.