LAUSR

Abstract The application of nitrate-mediated souring control has been proposed as a promising tool. However, the efficiency of this method remains controversial due to several unresolved issues, such as the determination of effective nitrate concentration, the optimal injection period, etc. In this study, we investigated the depletion of specific hydrocarbons as the electron donor for sulfate-reducing bacteria (SRB) and nitrate-reducing bacteria (NRB) by varying the nitrate concentration (1.5 mM and 4.5 mM) and injection timing (single, Ns; and multiple Nm) to control souring. Based on analysis of bacterial communities, genus Arcobacter was predominant, followed by NRB of family Rhodospirillaceae, which includes Thalassospira sp. By contrast, in the condition without nitrate addition (Nw/o), genus Desulfotignum was dominant. Both SRB and NRB share similar hydrocarbon preferences: toluene, ethylbenzene, and xylene. At the limiting nitrate concentration to suppress SRB activity, 1 mM, SRB could co-exist with NRB and promote a more diverse bacterial community.