Containment of Biogenic Sulfide Production in Continuous Up‐Flow Packed‐Bed Bioreactors with Nitrate or Nitrite

Abstract

Produced water from the Coleville oil field in Saskatchewan, Canada was used to inoculate continuous up-flow packed-bed bioreactors. When 7.8 mM sulfate and 25 mM lactate were present in the in-flowing medium, H(2)S production (souring) by sulfate-reducing bacteria (SRB) was prevented by addition of 17.5 mM nitrate or 20 mM nitrite. Changing the sulfate or lactate concentration of the in-flowing medium indicated that the concentrations of nitrate or nitrite required for containment of souring decreased proportionally with a lowered concentration of the electron donor lactate, while the sulfate concentration of the medium had no effect. Microbial communities were dominated by SRB. Nitrate addition did not give rise to changes in community composition, indicating that lactate oxidation and H(2)S removal were caused by the combined action of SRB and nitrate-reducing, sulfide-oxidizing bacteria (NR-SOB). Apparently the nitrite concentrations formed by these NR-SOB did not inhibit the SRB sufficiently to cause community shifts. In contrast, significant community shifts were observed upon direct addition of high concentrations (20 mM) of nitrite. Strains NO3A and NO2B, two newly isolated, nitrate-reducing bacteria (NRB) emerged as major community members. These were found to belong to the epsilon-division of the Proteobacteria, to be most closely related to Campylobacter lari, and to oxidize lactate with nitrate or nitrite as the electron acceptor. Thus the mechanism of microbial H(2)S removal in up-flow packed-bed bioreactors depended on whether nitrate (SRB/NR-SOB) or nitrite (SRB/NR-SOB as well as NRB) was used. However, the amount of nitrate or nitrite needed to completely remove H(2)S was dictated by the electron donor (lactate) concentration, irrespective of mechanism.

Oil Field Souring Control by Nitrate-Reducing Sulfurospirillum spp. That Outcompete Sulfate-Reducing Bacteria for Organic Electron Donors

“…This was shown by Hubert et al (16) with a bioreactor injected with 25, 12.5, or 6.25 mM lactate and 7.8, 4.7, or 3.0 mM sulfate. Because SRB were a prominent component in all bioreactor communities that were analyzed (16), it was concluded that souring control was due primarily to NR-SOB activity, as in Fig. 1A.…”

“…All cultures originated from the water produced from the Coleville oil field located near Kindersley, Saskatchewan, in western Canada. The water produced from the oil field sampled in August 2000 was used to inoculate bioreactors in previous studies (15,16) from which most strains described here were isolated. A sample of the water produced obtained in April 2002 was used to inoculate the bioreactor in the present study and was also plated directly for further strain isolations.…”

“…1A. The goals of the current work are to (i) determine the properties of the main NRB present in a similar bioreactor experiment and (ii) evaluate whether SRB remain dominant community members at sulfate concentrations lower than those used in previous work (16), i.e., to determine the lower limit of the sulfate concentration at which effective sulfur cycling can still occur.…”

Acetate Production from Oil under Sulfate-Reducing Conditions in Bioreactors Injected with Sulfate and Nitrate

“…Studies of souring and its control with nitrate or nitrite have mostly used VFA or lactate as the electron donor for nitrate and sulfate reduction (15,19,21,33,34,45,46). Only Myhr et al (18) also used an oil-flooded bioreactor.…”

“…Souring of oil fields is unwanted and can be prevented or reversed by the injection of nitrate, stimulating heterotrophic nitrate-reducing bacteria (hNRB) and sulfide-oxidizing nitrate-reducing bacteria (6,7,(15)(16)(17)(18)(19)(20)(21). Both NRB activities produce nitrite as an intermediate, inhibiting dissimilatory sulfite reductase Dsr, the highly conserved enzyme that produces the sulfide (22)(23)(24).…”