Effect of THPS on the microbial community in a simulated crude-oil storage tank environment

Tetrakis (hydroxymethyl) phosphonium sulfate (THPS) is commonly used due to its low environmental impact and its effectiveness in preventing sulfate-reducing bacteria (SRB) growth. The treatment effect with one THPS application on the microbial community was evaluated in a batch fractionated assay containing water from a crude oil storage tank, carbon steel coupons and crude oil. The effects of the treatment were monitored for 60 days. The total number of planktonic bacteria and archaea estimated by qPCR decreased at the beginning of the treatment with THPS, however, 60 days after the application the number was higher, as were the sulfate-reducing microorganisms (SRM) and methanogens (MA). From the diversity analysis of the 16S rRNA gene, the relative abundance of the genus Desulfovibrio was higher on day 8 in the system with THPS, but by day 60 there were no differences. Among the MA, the abundance of the genus Methanocalculus increased due to the presence of biocide. The presence of the biocide did not affect the number of bacteria and archaea attached to SAE 1010 carbon steel coupons. Corrosion rates revealed that THPS produced a decrease in corrosion initially, but the values were even high. The results suggested that the treatment with THPS produced the selection of a long-term resistant community with potential activity to induce corrosion of carbon steel.