Figure 10.

A schematic diagram illustrating the interaction of NRB and SRB in a souring environment. The mechanism of nitrate injection includes the augmentation of heterotrophic nitrate-reducing bacteria to outcompete SRB for available nutrients, promotion of nitrate-reducing sulfide-oxidizing bacteria to directly oxidize sulfide, and SRB inhibition through the resultant nitrite. The yellow arrows illustrate the biosurfactant injection and the prolonged effective duration of nitrate that helped nitrate/nitrite reach deeper zone in the system, resulting in long-term suppression of SRB activities and better souring control. Reproduced with permission from Fan et al. [82]. © 2019 Elsevier Ltd., Amsterdam, The Netherlands.