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biofouling & biocorrosion

Corrosion in iron water pipe. It is now reported that up to 70% of all corrosion in water systems is caused or accelerated by microbes.
Corrosion

There is increasing recognition that microbes such as bacteria play an even larger role in all forms of corrosion than previously thought. [Refs here]

The widely-accepted model for bacterial fouling in water systems involves the following steps:

  1. Attachment of organisms to a surface.
  2. Absorption and metabolism of simple organic molecules that fuel further metabolic action (below left).
    Bacteria generating slime.Bacteria on a surface with simple organic molecules.
  3. Generation of the glycocalyx, a polysaccharide that serves to further anchor the organism and protect it from adverse environmental factors such as changes in temperature, flow, pH, or the action of biocides (above right).
Biofilm.

Through water channels in the glycocalyx the thriving bacterial colony is able to absorb nutrients and oxygen from the water. However, as growth continues and the depth of the slime layer increases, there is little penetration of oxygen in the layers against the pipe or vessel surface.

effects of biofouling

Anaerobic bacteria can propagate in the deeper layers of the biofilm where little oxygen reaches. Some of these anaerobes are capable of metabolizing carbon from stainless steel, and some produce nitric, sulfuric, or other organic acids that further accelerate corrosion.

The depletion of oxygen in the wetted surfaces under bacterial colonies can result in the formation of "differential aeration cells" that can lead to [more information] galvanic corrosion.

By interfering with the ability of microbes to attach to wetted surfaces, the Zeta Rod™ stops the microbial surface fouling at the source.

Heat transfer surfaces are maintained in a clean condition, sumps and tanks do not support the unchecked growth of biological colonies, and piping does not clog with biomass.


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