EVALUATION OF THPS BIOCIDE EFFICACY ON BIOFILM CONTROL AT DIFFERENT EXPOSURE TIMES

摘要

The efficacy of shock treatment, using tetrakis hydroxymethyl phosphonium sulphate (THPS) commercial biocide, was evaluated for the control of biofilms formed on the surface of AISI 1020-carbon steel. The assays were carried out in a dynamic system (looping) in order to simulate the internal conditions of industrial pipelines. A decrease in the sessile numbers of aerobic, anaerobic and sulfatereducing (SRB) bacteria and filamentous fungi were observed in the presence of biocide at the different tested exposure times (1, 2 and 3 hours)., the efficacy of the biocide was proportional to the exposure time, whereas the aerobic microorganisms were more resistant than the anaerobes. A considerable reduction of the SRB population was detected soon after the first 1-hour biocide application, while a pronounced reduction of the other microbial groups examined was observed only after four consecutive 3-hour applications. The obtained results confirm the broad spectrum of THPS action, especially with regard to its efficacy on BRS, which demonstrates the capacity of this biocide of diffusing into the polysaccharide matrix of the biofilm without losing its antimicriobial properties; thus guaranteeing control over the microorganisms which are the main cause of microbiologically influenced corrosion process.