The Study On The Characteristics Of Denitrification Inhibiting SRB Sludge Granulation Process And Its Microbial Community

Sulfate reducing bacteria (SRB) is a kind of bacteria,which can reduce sulfate，sulfite and thiosulfate to hydrogen sulfide under anaerobic conditions.SRB is widelyexists in the oil field.It can produce S2-which causes serious equipment corrosionphenomenon of the crude oil refilling and transportation pross,which bring seriouseconomic loss. At the same time, hydrogen sulfide transformed from S2-can overflowinto the air, which causes a serious threat to the personal safety of the oil field workersand the surrounding environment. Therefore, looking for effective inhibition method ofSRB is an important task to solve the problem of oil field.The paper was based on the previous research results of denitrification inhibitingSRB. We used a two-stage-continuous flow UASB reactor to analyze and discuss thesulfate reduction and denitrification inhibiting process. The reactor start-up completedin90days. After the reactor started successfully, sulfate reduction process worked welland a mature and stable granular sludge blanket appeared, SO42-removal rate reached93%and remained stable, effluent S2-concentration stably reached120mg/L,SRBconcentration in system reached800000CFU/100ml,and ORP dropped to-350mV.After adding sodium nitrite, bacteria survival environment changed quickly, the processof denitrification inhibiting was promoted rapidly, S2-concentration dropped to about19mg/L, the foul smell was weakened obviously, H2S inhibition rate reached94.7%, ORProse to-120mV.SRB quantity is decreased obviously and its activity was restrainedeffectively.In the condition that hydraulic loading was0.5m3/（m2d）,, the granular sludge in two stages was the densest when the SO42-concentration was1500mg/L, NO2-concentration was600mg/L. Most of the granular sludge are ellipsoid with smoothborder and in the particle size of1~2mm, VSS/SS value are73.8%and76.6%, SVIvalue are16.7mL/gSS and13.3mL/gSS, the sludge which sinking speed between20~70m/h are78%and83%, two-dimensional fractal dimension are both greater than1.96.Sludge granulation increase the SO42-removal rate from40~60%to85~90%, the S2-removal rate from50~70%to70~90%; the fastest SO42-consumption rate reaches96.81mgSO42-/g VSS h, the NO2-consumption rate reaches79.51mgSO42-/g VSS h.The granular sludge could maintain a higher consumption rate, at the same time, itincreased the resistance load potential and increases the operation effect greatly.Microorganism growth situation was analyzed by SEM(Scanning ElectronMicroscope). The results show that different species of microorganism distribute indifferent regions, and the special mass transfer channel was in the inside of granularsludge. Bacillus at the UASB-1granular sludge surface, brevibacterium and vibrio werethe chief bacteria at the UASB-2granular sludge surface. Sulfurimonas species werefound in UASB-2, which can use sulfide and nitrate, nitrite at the same time, and has thefunction of simultaneous desulfurization and denitrification. Desulfobacter,Desulfovibrio, Desulfacinum were the mainly SRB in seed sludge.After sludgedomestication, Desulfobulbus and Desulfovibrio were the dominant genera in UASB-1sludge. They were effectively inhibited after denitrification inhibiting. Compared withGenband reference strains, bacterias live in same reactor have a closer affinity betweenspecies, which show that microbial community characteristics and structure have greatrelationship with their survival environment.