A Novel Peptide at a Very Low Concentration Enhanced Biocide Treatment of Corrosive Biofilms

ABSTRACT

Microbiologically influenced corrosion (MIC) is caused by problematic biofilms in many industries, especially the oil and gas industry. In this work, a novel peptide (labeled as “Peptide A”) was used to enhance tetrakis hydroxymethyl phosphonium sulfate (THPS) biocide to treat the corrosive sulfate reducing bacterium (SRB) Desulfovibrio vulgaris and a tough field biofilm consortium (labeled as “Consortium II”) on C1018 carbon steel coupons. This peptide was synthesized based on the active sequence derived from an anti-biofilm protein produced by a sea anemone. Only 10 nM Peptide A or 18 ppb (w/w) was used in the biofilm prevention test and 10 – 100 nM was tested in the biofilm removal test. The cocktail of 50 ppm THPS + 10 nM Peptide A achieved 2 extra log reduction of SRB sessile cell count in the 7-day biofilm prevention test compared with 50 ppm THPS treatment alone. In the 3- hour biofilm removal test that started with mature biofilms, the combination of 50 ppm THPS + 100 nM Peptide A achieved 2 extra log reduction compared with 50 ppm THPS treatment alone. Peptide A alone showed no log reduction in the mitigation of biofilm Consortium II. However, in the D. vulgaris biofilm removal test, 10 nM Peptide A achieved 1-log reduction and 100 nM achieved 2 logs.

INTRODUCTION

Microbiologically influenced corrosion (MIC) is a major problem in many industries, such as the oil and gas industry.¹ MIC accounts for 20 – 40% of all corrosion damages. Billions of dollars are lost because of MIC every year in the United States.² Sulfate reducing bacteria (SRB) are often the culprit in MIC, but sometimes acid producing bacteria and other microbes are also involved. Pipeline systems are usually anaerobic because corrosive oxygen is removed. SRB can easily grow in an anaerobic environment where sulfate is available. Crude oil contains SRB³ and seawater injection can also bring SRB⁴ that cause corrosion and reservoir souring.⁵ Even in an aerobic environment, SRB can grow underneath an aerobic biofilm that provides an anaerobic local environment.