O uso de fotoinativação como alternativa para o uso de biocidas e controle de consórcio de bactérias redutoras de sulfato em água produzida de campos de petróleo na bacia do recôncavo baiano

Abstract

The oil and gas industry annually faces significant equipment losses and product quality degradation due to the presence of sulfate-reducing bacteria (SRB), which are common in marine environments. To mitigate these impacts, biocides are frequently employed. However, these compounds can interact unpredictably with the environment, affect biodiversity, require continuous application—thereby increasing operational costs—and promote SRB resistance and adaptation through stress induced by the biocides. In this context, this study evaluated the application of the photoinactivation technique (PI) using the double salt of zinc chloride with 1,9-dimethylmethylene blue (DMMB) as a photosensitizer (PS). Five different concentrations of DMMB (0.050, 0.250, 0.500, 0.750, 1.0, 1.5, and 2.0 μg/mL) were tested in combination with Laser light under varying exposures (8.0, 10.0, 12.0, 14.4, and 21.6 J/cm²) on an SRB consortium predominantly composed of Gram-negative bacteria. For bacterial cultivation, a modified Postgate C medium (without ferrous sulfate) was used, and cell quantification was performed using 100 μL aliquots of the consortium analyzed with a spectrophotometer (λ = 600 nm) under anaerobic and light-free conditions at room temperature. Statistical analyses included two-way ANOVA and interaction ANOVA to evaluate the separate and combined effects of the PS and Laser light on PI efficacy. Groups treated exclusively with DMMB showed microbial reduction only at concentrations above 1.0 μg/mL, while lower concentrations and groups exposed solely to Laser light did not exhibit significant effects, showing no microbial reduction. The combined application of PI resulted in antimicrobial activity across all groups, with inhibition rates exceeding 50% (p <0.05) for DMMB concentrations above 1.5 μg/mL. ANOVA analyses indicated that the technique’s efficacy significantly depends on DMMB concentration and light intensity, with a positive interaction between these factors. Microbial reductions of 70.6% (range: 55.7–70.6%; mean: 66.7%) were observed with 1.5 μg/mL of DMMB, and 70.1% (range: 65.0–70.1%; mean: 68.2%) with 2.0 μg/mL under a light intensity of 21.6 J/cm². The results demonstrate that the photoinactivation technique is a promising alternative to biocides in the oil and gas industry, standing out for its ease of application, low potential to induce bacterial resistance, environmental safety, and compatibility with other strategies for controlling SRB populations.