Isolation And Characterization Of Thermophilic Sulfate Reducing Bacteria And Study On The Growth Inhibition

This study focused on a strain of thermophilic sulfate reducing bacteria (SRB-HT) isolated from Henan oil field, and developed some inhibitive methods against SRB-HT. The study could be divided into three parts:1. Isolation and characterization of thermophilic sulfate reducing bacteriaA strain of thermophilic sulfate reducing bacteria was isolated from Henan oil field and morphological and physiological characterizations were conducted. Single factor experiments were performed to determine the effect of pH, temperature, salinity, redox potential, and carbon source on the growth of SRB-HT. Results indicated that SRB-HT is with very strong capability of reducing sulfate, the optimal temperature 60℃, the optimal pH neutral, the optimal carbon source sodium citrate, the optimal salinity Og/L, and the optimal reducing agent sodium hyposulfite. Under the optimal conditions, the culture medium becomes black after 2 days, the growth of the strain reaches the utmost after 3 days, and the maximal production of H2S appears after 4 days of culture.2. Chemical methods against SRB-HT growthThree chemicals (namely HCHO, H2O2 and CaO2) were employed to investigate their inhibitive effects on SRB-HT. Results indicated that 20mg/L HCHO or 15mg/L H2O2 is enough for effective inhibition against SRB-HT. Besides, the optimal dosage of CaO2for the effective inhibition is determined by orthogonal experiments, and the mechanism of inhibition is preliminarily predicted. Results indicated that CaO2 of 0.1%is sufficient for effective inhibition and the inhibition period could be as long as two weeks. The mechanism could be summarized from three aspects:First, slow release of oxygen from CaO2 creates an aerobic environment against the growth of SRB-HT; Second, oxygen oxidizes H2S produced by SRB-HT; Third, slow dissolution of CaO2 elevates the overall pH to a level not suitable for SRB-HT growth.3. Biological methods against SRB-HT growthIn order to find out the minimal inhibitive dosage of nitrate against SRB-HT, different concentrations of nitrate were added into the medium to inhibit the growth of SRB-HT and the production of H2S. Besides, the inhibitive effect of nitrate in the presence of a nitrate reducing bacteria (NRB-HT) was investigated. Results indicated that low concentration of nitrate alone could inhibit the growth of SRB-HT, but the inhibition period was short. When NRB-HT was added simultaneously, the inhibition period was prolonged obviously. Nitrate of 0.01%could inhibit the growth of SRB-HT as long as 8 days. So nitrate in combination with NRB-HT serves as a very effective method against SRB-HT and may provide an economical way against corrosion problem caused by SRB in oil field.