MIC is acronym for microbiologically influenced corrosion. It is a mode of corrosion incorporating microbes that react and cause the corrosion or influence other corrosion process of metallic materials.
MIC is caused by specific bacteria which feed on nutrients and other elements found in fresh, salt and brackish waters. IN presence of the nutrients (Metals), water and oxygen, these microbes are capable of forming slime or biofilm on the surface of metals. These biofilms provide the environment for bacterial growth activity to form corrosive products/byproducts causing corrosion of surfaces.
Several types of micro-organisms involved are:
Aerobes (GAB) – Oxygen consuming
Anaerobes (GAnB)- Non-oxygen consuming
Groups of bacteria are categorized based on byproducts like acid producing, Sulphate reducing (SRB), Nitrate & Iron reducing biofilms Ex. Gallionella, Sphaerotilus, Pseudomonas, Klebsiella, Eneterobacter, Acinetobactor, Bacillus, Aeromonas & Legionella.
Over a period of time Biofilms are capable of colonizing virtually any surface and they are extremely difficult to kill. In industries, biofilms can be found adhering to surfaces in most aqueous environments, such as those of a pipeline wall or the tubes of a heat exchanger.
Biofilm formationbeginswhen asingle planktonicbacteriumattachestoasurface by weak Van derWaals forces As the new sessile bacterium growsand multiplies, it secretes a polysaccharide matrix that anchors it firmly tothe substrate leadingtoa more attractive adhesion site to passing bacteria and begins to engage in what is referred to as “quorumsensing”.
Established biofilmsconsistofmillions ofcellsin mats, many thousands of layers deep, completely encased in adense polysaccharide complex that renders them virtually impervious toantibiotics and chemical poisons (viz. … biocides). They also contain exo-proteins, fats and nucleic acids.
Polysaccharides arepolymericcarbohydratemoleculescomposed of long chains of monosaccharide units bound together by glycoside linkages and on hydrolysis give the constituent monosaccharide or oligosaccharides.They range in the structure from linear to highly branched.Examples of linear are starch and glycogen, and branched cellulose and chitin.
Five stages of biofilm development:
(1) Initial attachment
(2) Irreversible attachment
(3) Maturation I
(4) Maturation II
(5) Dispersion
Dispersal of cells from the biofilm colony is an essential stage of the biofilm life cycle. Dispersal enables biofilms to spread and colonize new surfaces. Nitric oxide has also been shown to trigger the dispersal of biofilms of several bacterial species.
Mature biofilm formations behave like a single living organism and they also may move collectively across the surface or detach themselves in clumps as a mean to spread, colonize and damage new surfaces.
A base metal, such as iron (Fe) goes into aqueous solution as positively charged cation, Fe2+.As the metal is oxidized under anaerobic condition by the protons of water, H+ ions are reduced to form molecularH2. This can be written in the following ways under acidic and neutral conditions respectively:
Fe + 2 H+ → Fe2+ + H2
Fe + 2 H2O → Fe(OH)2 + H2
Usually, a thin film of molecular hydrogen forms on the metal. Sulfate-reducing bacteria, oxidize the molecularhydrogen to produce hydrogen sulfide ions (HS−) and water:
4 H2 + SO2−→ HS−+ 3 H2O + OH−
The iron ions partly precipitate to from iron (II) sulfide.
A reaction with water also occurs, producing iron hydroxide.
Fe2+ + HS− →FeS + H+
3 Fe2+ + 6 H2O → 3 Fe(OH)2 + 6 H+
The net equation comes to:
4 Fe + SO42− + H+ + 3 H2O → FeS + 3 Fe(OH)2 + OH−
This form of corrosion by sulfate-reducing bacteria can, in this way, be far more harmful than anaerobic corrosion.
This metabolic process breaks down the iron and steel of even heavy-walled pipes, resulting in leaks and catastrophic pipeline failure. Other classes of bio film can form thick plaques capable of plugging exchangers and valve bodies in industries.
CoryoZyme an innovation product thatenzymaticallymanipulatesbacterial behavior to deliver numerous benefits. It controls and removes MIC Biofilms &contains no live bacteria.
How it works:
Exogenous Polysacceride degrading Enzymes consisting of : Xylanase, Carboxy-methylcellulase, Amylase, Ligno-cellulases, Alpha/Beta-Glucosidases and various other proprietary developed Cellulases from specially bread microorganisms target the Biofilm’s primary matrix.
Presence of these enzymes help prevent Planktonic bacteria from forming Biofilms, thereby, reducing the number of sessile bacteria plaques in the water downstream of the dousing.The enzymes will also help destroy existing biofilm plaques on the couponsthereby increasing the life of the coupons.
CoryoZyme consists of the following:
Urease: Converts Urea to Ammonia
Exogenous Polysacceride degrading Enzymes consisting of Xylanase, Carboxymethylcellulase, Amylase, Lignocellulases, Alpha/Beta-Glucosidases includes cellulases : enzymes used by bacterial, fungi and Protozoa to digest/breakdown starches and cellulose into sugar units.
Ammonia monooxygenase : converts ammonia to Nitrate
Anammox reaction : converts ammonia and nitrate to nitrogen gas
Acid Phosphatase : frees attached phosphate groups from other molecules
Lipases : catalyses the hydrolysis of fats, they are a subclass of esterases.
Proteases : Enzymes that perform proteolysis, that is begins protein catabolism, by hydrolysis of the peptide bonds that link amino acids together in the polypeptide chain forming the protein.
Ammonia monooxygenase : converts ammonia to Nitrate
Anammox reaction : converts ammonia and nitrate to nitrogen gas
The presence of this enzyme promotes an alternative source of electrons from Nitrogen cycle, thereby reducing the dependency of reducing Sulphate to Sulphide by SRB’s
Arrests… Clears.. Inhibits..
They digests the polysaccharidesthus dislodging and exposing the bacteria thereby allowing Biocides to penetrate, accomplish and deliver the required results.
Dousing is done UPSTREAM
• of all trouble spotswhere BRW, RCW, PDW and EFW have largepopulations of Sessile GAnB’s.
Dosing measure is determined by effluent flow-rates and achieved through sustained release durable packs&liquid dousing form