Effects of nitrate treatment on a mixed species, oil field microbial biofilm

Abstract

Biofilms of bacteria, indigenous to oil field produced water, were grown in square section, glass capillary flow cells at 45 degrees C. Initially, in situ image analysis microscopy revealed predominantly coccoid bacteria (length-to-width ratio measurements (l (c):w (c)) of bacterial cells gave a mean value of 1.1), while chemical measurements confirmed sulphate reduction and sulphide production. After nitrate ion addition at 100 and 80 mg/l, in the two repeat experiments respectively, the dominance of rod-shaped bacteria (mean l (c):w (c) = 2.8) was observed. This coincided with the occurrence of nitrate reduction in the treated flow cells. Beneficially, no significant increase in biofilm cover was observed after the addition of nitrate. The dominant culturable nitrate-reducing bacterium was Marinobacter aquaeolei. The l (c):w (c) ratio measured here concurs with previously reported cell dimensions for this organism. Several Marinobacter strains were also isolated from different oil fields in the North Sea where nitrate treatment has been applied to successfully treat reservoir souring, implying that this genus may play an important role in nitrate treatment.

Prokaryotic Community Structure and Sulfate Reducer Activity in Water from High-Temperature Oil Reservoirs with and without Nitrate Treatment

“…In addition to microbiologically influenced corrosion and reservoir souring, the efficiency of oil production is decreased due to plugging by SRP biomass and precipitated metal sulfides (12,39). Besides the use of broadspectrum biocides or inhibitors for sulfate reduction, the addition of nitrate effectively decreased the net production of H 2 S in model column studies (15,20,38) and field trials (7,53). The mechanisms by which nitrate addition might affect souring control are (i) the stimulation of heterotrophic nitrate-reducing bacteria (hNRB) that outcompete SRP for electron donors, (ii) the activity of nitrate-reducing, sulfide-oxidizing bacteria (NR-SOB), and (iii) the inhibition of SRP by the production of nitrite and nitrous oxides (21,51).…”

Efeito da aplicação de nitrato na redução biogênica de sulfeto sob diferentes concentrações iniciais de bactérias redutoras de nitrato e sulfato

“…Para as respostas Y1 e Y2, correspondentes aos tempos de incubação de 7 e 14 dias, respectivamente, observa-se que o modelo matemático foi altamente significativo, conseguindo explicar 99,6 e 93,6% da variação total em torno da média, sendo os valores de F calculado (184,78 e 11,72) maiores que os valores de F crítico (6,26 (19,0). Sendo assim, pode-se aferir que para o tempo de incubação de 28 dias, o modelo não se ajustou bem aos dados.…”

“…As células microbianas sésseis encontram-se imersas em uma matriz exopolimérica que pode dificultar a difusão do nitrato. 19 de ácido ascórbico como agente redutor, a fim de se estabelecer condição de anaerobiose. Todos os componentes foram solubilizados em água produzida e o pH do meio ajustado em 7,0 ± 0,5 com adição de NaOH 1,0 mol L -1 .…”

Vertical Distribution of Bacterial Communities in the Indian Ocean as Revealed by Analyses of 16S rRNA and nasA Genes

“…Previous studies have found that the Marinobacter group is of significance for nitrate assimilation and is positively correlated to nitrate concentration [9]. Marinobacter strains have been applied to successfully treat reservoir souring [20]. Marinobacter associated with Alteromonadales were abundant in the water column, indicating an important role in nitrate assimilation in the Indian Ocean.…”