November 20, 2009

Muscling Out Mussels In The Water Process Industry

by Bob Murphy

In an earlier blog titled, We Are Being Invaded! – Mussels Muscling In On Our Water Process Structures, we discussed the impact and consequences of bio-fouling by indigenous and invasive mussels and barnacles on water processing equipment and structures.  In this blog, let’s talk about options to stop or eliminate fouling by these “critters”.

At a high level there are essentially two approaches to addressing fouling.  The first approach is to employ anti-fouling techniques.  With this approach there is some action that takes place to deter fouling attachment or cause the death of already attached organisms.  Three common anti-fouling techniques are:

1.      Chlorine injection – with this technique, a sufficient quantity of chlorine is injected into the water stream thereby killing the organisms.  While effective, there are signs of increasing concern of putting yet another chemical into the water supply and in some areas of the country even tighter regulatory controls are under consideration for this anti-fouling technique.

2.      Temperature variation – with this technique, the water temperature is raised or lowered above or below the tolerable limits of the fouling species either deterring them or causing their death.  A challenge with this technique is equipment of sufficient capacity to heat or cool the water to achieve the desired results.

3.      Anti-fouling coatings – with this technique, coatings applied to the substrates of the water processing equipment and structures are formulated to include biocides and/or heavy metals.  The fouling organisms absorb or ingest the toxins from the biocides and/or heavy metals, again causing their death.  Additionally, this technique has the potential to pollute our water resource.

While all three of these anti-fouling techniques successfully deter or cause the death of the mussels or barnacles, they also can and have caused the death of other living creatures in the environment.

The second approach to address fouling is known as fouling release.  Unlike the anti-fouling techniques which take some action, the techniques of fouling release are passive, providing a surface to which the fouling organisms are unable to attach.  Two common fouling release techniques are:

1.      Substrate materials – with this technique, process equipment and structures are made of materials that are extremely slick and, it is hoped, to which the barnacles and mussels are not able to attach.  One such family of materials is high density plastics.  However, they have experienced mixed results.  The below photograph shows trash racks made of high density polyethylene to which indigenous barnacles were able to attach.

2.      Fouling Release coatings – with this technique, coatings applied to the substrates of the water processing equipment and structures are formulated without biocides and/or heavy metals.  Rather they are formulated with silicones or fluoropolymers with highly effective, super slick attributes and to which the fouling species are unable to attach.

The below photographs show two identical test racks, one uncoated  andthe other coated with Sher-Release fouling release coating system.

Uncoated Steel Grate 7 months

Uncoated Test Rack

Sher-release Coated Test Rack

Fuji Grate 4 months

Both were exposed for approximately six months to the invasive quagga mussel.

Consequently, fouling release solutions, particularly the fouling release coatings, are highly effective at “muscling out mussels in the water process industry” and at the same time they are eco-sustainable.

For more on the Sher-Release fouling release system please feel free to contact the writer.

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