Aplicação de bacteriófagos e biossurfactante no controle de microrganismos e corrosão em sistemas de resfriamento industrial

Abstract

Corrosion in the petrochemical industry represents a significant problem, leading to considerable losses of equipment, materials, and inputs, which makes the search for new control technologies indispensable. A specific type, biocorrosion, is frequently observed in industrial cooling systems. It occurs due to the direct contact of metallic surfaces with process water, combined with favorable temperature and nutrient conditions that promote microbial growth and biofilm formation. Biofilms are communities of microorganisms enveloped in a polymeric matrix that provides them with mechanical support and protection against antibiotics, biocides, and environmental variations. These structures favor the formation of deposits, scaling, and corrosion, resulting in unplanned maintenance and inefficiency in heat transfer. Conventional control, based on chlorine gas and sodium hypochlorite, presents disadvantages such as corrosivity, environmental toxicity, and the selection of resistant microorganisms. A sustainable and promising alternative is the use of bacteriophages and biosurfactants. Bacteriophages, or phages, are viruses that exclusively infect bacteria, potentially causing the lysis of the host cell. Biosurfactants, in turn, are products of microbial metabolism with surfactant and antimicrobial properties. This study evaluated the effectiveness of bacteriophages and biosurfactants as sustainable alternatives for the control of planktonic bacteria and biofilms, and their influence on corrosion inhibition in a rack bypass reactor, a system that simulates conditions found in cooling towers. Tests were conducted using bacteria from the collection of the Laboratory of Applied Microbiology (LMA), isolated from an industrial cooling system, and phages previously isolated by the research group. Stainless steel and polyvinyl chloride (PVC) biocoupons were kept in the system for biofilm monitoring and quantification in CFU/cm². Water samples were collected periodically for evaluation of bacterial density (CFU/mL), phages (PFU/mL), and physicochemical parameters. Water corrosivity was assessed by mass loss in carbon steel coupons and by linear polarization resistance (LPR) and electrical resistance (ER) probes. The use of biosurfactants was evaluated for biofilm inhibition and removal in microplates and in the reactor. Tests conducted in synthetic water and industrial cooling tower basin water demonstrated that bacteriophages significantly reduced planktonic bacterial density (62.3% in synthetic water, 38.3% in real water) and biofilm formation on PVC (57.7%) and stainless steel (41.7%) coupons, with biofilm removal efficacy of 67.43% on stainless steel and 51.3% on PVC. Rhamnolipid showed limited efficacy in bacterial control and biofilm removal/inhibition. Notably, the combination of phages with anticorrosive products reduced the corrosion rate on carbon steel by 95.47% (0.7721 mpy), outperforming control with chemical inhibitors (1.7289 mpy). UV radiation, evaluated for purge, completely inactivated phages and bacteria at the tested doses. The results suggest that phage therapy and the application of biosurfactants, alone or in combination with anticorrosive products, are promising approaches for microbiological control and corrosion prevention in industrial cooling systems, offering a more sustainable and efficient solution.