Abstract
The efficiency of biocides can be improved by optimizing treatment programs and including the inhibiting effect of other production chemicals. Here, the efficiency of batch versus continuous treatment with a biocide formulation of tetrakis(hydroxymethyl)phosphonium sulfate (THPS) was investigated in a setup with flow-through bioreactors containing biofilm derived from the Danish Sector of the North Sea. The experiments were performed with injection seawater (ISW), produced water (PW), and amended with spent H2S scavenger (SS) and scale inhibitor (SI). In 100% ISW, 60 ppm continuous THPS treatment had a similar biocide effect on sulfate-reducing Bacteria (SRB) activity as after 800 ppm batch THPS treatment. Further, the presence of SS and SI had a significant antimicrobial effect in 100% ISW, reducing SRB activity by 97%. This beneficial effect of SS and SI with continuous biocide dosing was counteracted when the PW fraction was increased to 70% and lost in 100% PW. However, in 100% PW batch biocide dosing reduced microbial activity significantly. These studies show how biocide treatments can be optimized depending on the water source and water chemistry and the impact these have on biofilm formation.
