Inhibiting sulfate reducing bacteria activity by denitrification in an anaerobic baffled reactor: Influencing factors and mechanism analysis

For controlling the equipment corrosion of hydrogen sulfide produced by the microbe in oilfield system, denitrification was used to inhibit the sulfate reduction in a continuous flow anaerobic baffled reactor. The influencing factors and running effects of this process inhibition were investigated. Batch experiments were conducted to study the inhibitory mechanisms. The results indicated that SO^2-₄/NO^-₃ ratio and relative Chemical Oxygen Demand (COD) content were the two most important environmental factors affecting the inhibitory effect. The inhibitory effect increased with decrease of SO^2-₄/NO^-₃ ratio. The lower COD content benefited to increase the inhibitory effect. The inhibitor could act only in 1-3 chambers with the effective inhibitory time of 2.3-6.9 h. The inhibitory effect could be reflected by the system oxidation reduction potential (ORP). Denitrification predominated with the ORP in the range of -50 mV to -150 mV, while sulfate reduction predominated with the ORP in the range of -300 mV to -400 mV. Three inhibitory mechanisms were observed in the experiments: competitive inhibition for carbon source, nitrite-N inhibition, and oxidation by autotrophic denitrifying bacteria.