How+do+we+avoid+it?

=Solutions to Biological Fouling =

The Use of Copper
The toxicity of copper makes it an effective method for preventing biological fouling. It has been found that alloys containing 60-70% copper content will not support marine growth. Copper is not ideal for many heat exchangers. It is not as resistent to high temperatures and corrosion as a metals such as Titanium. To counter this, paints have been infused with copper ions to benefit from its toxic effects. The most commonly used being cuprous oxide. It has been found that introducting cuprous oxide in paints increase the period of protection of the surface 1.5 to 2 years.

Copper can be used in anoidic production. Acting as the anode, copper will be oxidized to produce copper ions As said before, copper ions are very toxic and thereofor very effective at removing organisms. A study using Copper-sulphate solution showed that the copper ions reduced both macro and micro biological fouling. It should be noted that other toxic metals ions such as mercury, lead, and cadium could be used in place of the commonly used copper.





**Chlorination **
Chlorine is in wide use for cleaning. It is well know for it use in water treatment and sanitation. These cleaning properties can be applied in preventing biofouling as well. Chlorine reacts with water to produce both hypochlorous and hydrochloric acid. Both of these acids are known to kill bacteria and other organisms.



A common type of chlorination is electrochemical chlorination. An electric current is passed through sea water. This causes hydrogen and chlorine to be produced through electrochemical reactions. Chlorine can then react with the water to produce hypochlorous and hydrochloric acid.





Unfortunately, chlorine has been known to be problematic. Chlorine reacts with organic compounds to form chloro-organic substances otherwise known as disinfection byproducts (DBP’s). These substances are strong carcinogens.To avoid these harmful by products, ozonation is used instead. Ozone is a very a strong oxidation agent as show by the half reaction below: 

 This allows ozone to react with elements such as bromide to form by products that are effective in removing bacteria and organisms. Ozone is such a strong oxidizing agent that it if it reacts in the fatty tissues of an organic compound, it will oxidize the membrane to the point of the membrane being ruptured. This will prevent the membrane from adhering to the surface of the heat exchanger. Ozonation can be much more effective then chlorination. A sample size of Ecoli was exposed to chlorine for 4 hours before it was eliminated. The same sample size of Ecoli was eliminated in 5 seconds by ozone.



 

A disadvantage of ozone is that it is not a readily available element. Because of this limitation, ozone has to be produced by passing an electric charge through oxygen. This makes ozone very expensive.

<span style="font-family: Arial,Helvetica,sans-serif;">Other Notable Solutions
<span style="font-family: Arial,Helvetica,sans-serif;">Methods have been used previously to prevent biofouling, while other techniques are being investigated and researched. These methods include:


 * <span style="font-family: Arial,Helvetica,sans-serif;">The use of radioactive isotopes. A test with isotope technetium-99, which produces beta nuclides, showed that this isotope could provide protection for biofouling for up to 2 years. This technology is expensive and very environmentally hazardous, making it very impractical.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Biomimicry has found its way into preventing biofouling. Research has went into marine species that do not suffer from biological growth. Sharklet is a type of technology trying to pattern sharkskin. Adhesion to sharkskin is difficult, and nanotechnology has provided society will the tools to try mimic this trait. Improvements in genetic engineering are also being used. A molecule from Australian seaweed has been proven to prevent biofouling. Both of these technologies are ineffective though due to lack of resources and cost. Another example of biomimicry is the use of the lotus effect. Researchers are trying to mimic the effect leaves have on adhesion. The waxy layer on leaves makes adhesion nearly impossible. However, this technology has only proven effective for solid-gas boundaries. The above methods are much more environmentally friendly than the use of toxic metals (copper or mercury) or chlorine, the problem is making them cost effective and as readily available as other conventional methods.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Poisonous compounds called tributyltins (TBT) have been used in industy. An example of this is self polishing copolymers, which is a paint that releases the highly toxic TBT. While this method has been proven effective at eliminating biofouling, it is highly toxic and dangerous to the environment. An example of this is the effect TBT has had on an invertebrate called Nucella Lapyllus. TBT has caused the female invertebrates to have male sex traits, making it impossible for the invertebrate to reproduce. An effect like this has made the use of TBT banned in many countries.

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