In this study, 6 strains of microbial agents were investigated as environment-friendly scale and corrosion inhibitors for industrial cooling water applications. The static jar tests along with characterization methods were applied to evaluate the scale inhibition performance. Results showed that under a concentration of 240 mg/L, the Nitrobacteria, Denitrobacteria and Lactobacillus agents reached high CaCO3 scale inhibition efficiencies of 83, 82, and 86% respectively. Characterization methods indicated the deposited crystals morphologies were modified and the crystals peak intensities were lowered. In addition, weight loss measurements, electrochemical measurements, surface characterization analyses were conducted to study the corrosion inhibition performances and mechanisms. It was found that at 40 °C, Bacillus cereus agent with 200 mg/L possessed the highest corrosion inhibition efficiency of 60.11% at 3 d, together with the second-lowest current density of 13.0 μA cm−2 at 12 d. The corrosion inhibition mechanisms were attributed to biofilm accumulation and biomineralization on Q235 CS surfaces to form protective film. The results suggested microbial agents have promising potential as environment-friendly scale and corrosion inhibitors for industrial cooling water applications.

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During the operation of the circulating cooling water system, the inorganic scale deposition may cause technical problems, such as reduction of heat transfer efficiency in cooling systems and obstruction of pipes. In the industry, chemicals are often used as scale inhibitors in scale deposition control, antiscalants popular in industry are generally phosphorus and nitrogen containing chemicals, which may lead to eutrophication. However, increasing environmental concern and discharge limitations have guided antiscalants to move toward biodegradable, nontoxicity and cost-effectiveness. This paper reviews current researches on application of using bio-materials as scale inhibitors, including proteins and amino acids, polysaccharides, plant extracts, microbial reagents, and microbiological product. The non-bioaccumulation, low cost, readily biodegradability and sustainably available characters promote the development of green scale inhibitor chemistry.

In this study, corrosion behavior of Q235 carbon steel (CS) under Bacillus cereus (B. cereus) inoculum in simulated cooling water was evaluated. Weight loss study proved B. cereus inoculum possessed anticorrosion e ciencies of 92.84% and 73.88% for 3 d and 14 d rotation tests respectively. The electrochemical measurements indicated added B. cereus inoculum increased the charge transfer resistance and reduced corrosion current density. The B. cereus cells with strong bio lm-forming capacity were able to adhere onto Q235 CS surface to form compact bio lms and cause biomineralization.Surface characterization analysis demonstrated the presence of B. cereus inoculum reduced the amount of Fe 2 O 3 and simultaneously increased the amount of CaCO 3 in corrosion products. The corrosion inhibition mechanisms of B. cereus inoculum involve forming bio lm, generating biomineralized layer, and consuming dissolved oxygen. Thus, B. cereus inoculum provides a biological strategy for the industrial cooling water anti-corrosion application.

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