Enhanced Biocide Treatments with D-amino Acid Mixtures against a Biofilm Consortium from a Water Cooling Tower

Abstract

Different species of microbes form mixed-culture biofilms in cooling water systems. They cause microbiologically influenced corrosion (MIC) and biofouling, leading to increased operational and maintenance costs. In this work, two D-amino acid mixtures were found to enhance two non-oxidizing biocides [tetrakis hydroxymethyl phosphonium sulfate (THPS) and NALCO 7330 (isothiazoline derivatives)] and one oxidizing biocide [bleach (NaClO)] against a biofilm consortium from a water cooling tower in lab tests. Fifty ppm (w/w) of an equimass mixture of D-methionine, D-leucine, D-tyrosine, D-tryptophan, D-serine, D-threonine, D-phenylalanine, and D-valine (D8) enhanced 15 ppm THPS and 15 ppm NALCO 7330 with similar efficacies achieved by the 30 ppm THPS alone treatment and the 30 ppm NALCO 7330 alone treatment, respectively in the single-batch 3-h biofilm removal test. A sequential treatment method was used to enhance bleach because D-amino acids react with bleach. After a 4-h biofilm removal test, the sequential treatment of 5 ppm bleach followed by 50 ppm D8 achieved extra 1-log reduction in sessile cell counts of acid producing bacteria, sulfate reducing bacteria, and general heterotrophic bacteria compared with the 5 ppm bleach alone treatment. The 10 ppm bleach alone treatment showed a similar efficacy with the sequential treatment of 5 ppm bleach followed by 50 ppm D8. The efficacy of D8 was found better than that of D4 (an equimass mixture of D-methionine, D-leucine, D-tyrosine, and D-tryptophan) in the enhancement of the three individual biocides against the biofilm consortium.

Anaerobic Corrosion of 304 Stainless Steel Caused by the Pseudomonas aeruginosa Biofilm

“…The biofilm morphology on coupon surfaces was examined under SEM (Model JSM-6390 SEM, JEOL, Tokyo, Japan) and its energy-dispersive X-ray spectroscopy (EDS) accessary ( Jia et al, 2017e ). CLSM (Model LSM 510 microscopy, Carl Zeiss, Jena, Germany) was used to observe live and dead cells in biofilms and biofilm thickness ( Jia et al, 2017a ). The corrosion product layer was analyzed by XRD analysis performed on a Discover D8 machine with a Co K-alpha X-ray tube (Bruker, Karlsruhe, Germany).…”

“…More than 20% of metal corrosion damages was attributed to MIC ( Flemming, 1996 ). MIC is a serious problem in many settings, such as medical implants ( Jia et al, 2017g ), the oil and gas industry ( Liu et al, 2016 ), marine environments ( Ramírez et al, 2016 ), and water utilities ( Jia et al, 2017a ). Stainless steel is a commonly used metal in many industries due to their corrosion resistance ( Sedriks, 1996 ).…”

New Insights Into the Mechanisms and Biological Roles of D-Amino Acids in Complex Eco-Systems

“…However, the D -amino acid mix required for biofilm dispersal might vary depending on the species combinations. In addition, D -amino acids also enhanced the activity of the biocide NALCO7330 (active components: 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one) against biofilm on the steel coupons retrieved from a water cooling tower ( Jia et al, 2017 ).…”

Corrosion investigations of P235 carbon steel in deionized water

“…Različite vrste mikroba stvaraju biofilmove, pri čemu nastaju uvjeti za razvoj mikrobiološki poticane korozije (engl. microbiologically influenced corrosion -MIC) [14][15][16]. Naime, formirani biofilm značajno mijenja granicu faza između metala i okolne sredine koja ga okružuje.…”