A synergistic D-tyrosine and tetrakis hydroxymethyl phosphonium sulfate biocide combination for the mitigation of an SRB biofilm.

Microbiologically influenced corrosion (MIC) is a major problem in various industries such as oil and gas, and water utilities. Billions of dollars are lost to microbiologically influenced corrosion (MIC) each year in the US. The key to MIC control is biofilm mitigation. Sulfate-reducing bacteria (SRB) are often the culprits. They are also involved in souring and biofouling. SRB biofilms are notoriously difficult to eradicate. Due to environmental concerns and increasing costs, better biocide treatment strategies are desired. Recent studies suggested that D-tyrosine and some other D-amino acids may signal biofilm dispersal. Experimental results in this work indicated that D-tyrosine is an effective biocide enhancer for tetrakis hydroxymethyl phosphonium sulfate (THPS) that is a green biocide. Desulfovibrio vulgaris (ATCC 7757) was used in biofilm prevention and biofilm removal tests. It was found that 100 ppm D-tyrosine alone and 50 ppm THPS alone were both ineffective against the SRB biofilm. However, when 1 ppm D-tyrosine was combined with 50 ppm THPS, the synergy between the two chemicals successfully prevented the establishment of the SRB biofilm on C1018 mild steel coupon surfaces in batch treatment tests. It also eradicated established SRB biofilms from coupon surfaces in both 1 and 3-h shock treatment tests.