Biofouling
Encyclopedia
Biofouling or biological fouling is the undesirable accumulation of microorganism
s, plant
s, algae, or animal
s on wetted structures.
spiral wound membranes cooling water cycles of large industrial equipments and power station
s. Biofouling can also occur in oil pipelines carrying oils with entrained water especially those carrying used oils, cutting oils, soluble oil or hydraulic oils.
es, bio-dispersant
s can be used to control biofouling. In less controlled environments, anti-fouling coatings which contain biocides or non-toxic coatings which prevent organisms from attaching can be used.
. The biofilm creates a surface onto which successively larger microorganisms can attach. In marine environments this usually concludes with barnacle
attachment. The biocides often target the microorganisms which create the initial biofilm, typically bacteria
. Once dead, they are unable to spread and can detach. Other biocides are toxic to larger organisms in biofouling, such as the fungi and algae
. The most commonly used biocide, and anti-fouling agent, is the tributyltin
moiety (TBT). It is toxic to both microorganisms and larger aquatic organisms. It is estimated that TBT derived anti-fouling coatings cover 70% of the world's vessels.
The prevalence of TBT and other tin based anti-fouling coatings on marine vessels is a current environmental problem. TBT has been shown to cause harm to many marine organisms, specifically oysters and mollusks. Extremely low concentrations of tributyltin
moiety (TBT) causes defective shell growth in the oyster
Crassostrea gigas (at a concentration of 20 ng/l) and development of male characteristics in female genitalia in the dog whelk
Nucella lapillus (where gonocharacteristic change is initiated at 1 ng/l).
The international maritime community has recognized this problem and there is planned phase out of tin based coatings, including a ban on newly built vessels. This phase out of toxic biocide
s in marine coatings is a severe problem for the shipping industry; it presents a major challenge for the producers of coatings to develop alternative technologies. Safer methods of biofouling control are actively researched. Copper
compounds have successfully been used in paints and continue to be used as metal sheeting (for example Muntz metal
which was specifically made for this purpose), though there is still debate as to the safety of copper.
coatings.
There are two classes of non-toxic anti-fouling coatings. The most common class relies on low friction
and low surface energies
. This results in hydrophobic surfaces. These coatings create a smooth surface which can prevent attachment of larger microorganisms. For example, fluoropolymers and silicone coatings are commonly used. These coatings are ecologically inert but have problems with mechanical strength and long term stability. Specifically, after days biofilms (slime) can coat the surfaces which buries the chemical activity and allows microorganisms to attach.
The second class of non-toxic anti-fouling coatings are hydrophilic coatings. They rely on high amounts of hydration in order to increase the energetic penalty of removing water for proteins and microorganisms to attach. The most common example of these coatings are based on highly hydrated zwitterions, such as glycine betaine and sulfobetaine. These coatings are also low friction but are superior to hydrophobic surfaces because they prevent bacteria attachment, preventing biofilm formation. These coatings are not yet commercially available and are being designed as part of a larger effort by the Office of Naval Research
to develop environmentally safe biomimetic ship coatings.
formation and bacterial adhesion — and macrofouling — attachment of larger organisms, of which the main culprits are barnacle
s, mussel
s, polychaete
worms, bryozoans, and seaweed
. Together, these organisms form a fouling community
.
Individually small, accumulated biofoulers can form enormous masses that severely diminish ships' maneuverability and carrying capacity. Fouling causes huge material and economic costs in maintenance of mariculture
, shipping industries, naval vessels, and seawater pipelines. Governments and industry spend more than US$ 5.7 billion annually to prevent and control marine biofouling.
, Athenaeus
described the anti-fouling efforts taken in the construction of the great ship of Hieron of Syracuse (died 467 BCE). Before the 18th century various graving and paying techniques were used to try and prevent fouling using three main substances: White stuff, which was a mixture of train oil, rosin
and brimstone
; Black stuff, a mixture of tar
and pitch
; and Brown stuff, which was simply brimstone added to Black stuff.
Copper sheathing
was first suggested in 1708 by Charles Perry, as an anti-fouling device but the first experiments with copper sheathing were not made until the late 1750s, at which time the bottoms and sides of several ships' keels and false keels were sheathed with copper plates.
The copper performed very well in protecting the hull from invasion by worm, and in preventing the growth of weed, for when in contact with water, the copper produced a poisonous film, composed mainly of oxychloride, that deterred these marine creatures. Furthermore, as this film was slightly soluble it gradually washed away, leaving no way in which marine life could attach itself to the ship.
From about 1770, the Royal Navy
set about coppering the bottoms of the entire fleet and continued to the end of the use of wooden hulled ships. The process was so successful that the term copper bottomed came to mean something that was highly dependable or risk free.
Biofouling also occurs on the surfaces of living marine organisms, when it is known as epibiosis.
Microorganism
A microorganism or microbe is a microscopic organism that comprises either a single cell , cell clusters, or no cell at all...
s, plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...
s, algae, or animal
Animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...
s on wetted structures.
Impact
Biofouling is especially economically significant on ships' hulls where high levels of fouling can reduce the performance of the vessel and increase its fuel requirements. Biofouling is also found in almost all circumstances where water based liquids are in contact with other materials. Industrially important examples include membrane systems, such as membrane bioreactors and reverse osmosisReverse osmosis
Reverse osmosis is a membrane technical filtration method that removes many types of large molecules and ions from solutions by applying pressure to the solution when it is on one side of a selective membrane. The result is that the solute is retained on the pressurized side of the membrane and...
spiral wound membranes cooling water cycles of large industrial equipments and power station
Power station
A power station is an industrial facility for the generation of electric energy....
s. Biofouling can also occur in oil pipelines carrying oils with entrained water especially those carrying used oils, cutting oils, soluble oil or hydraulic oils.
Anti-fouling
Anti-fouling is the process of removing the accumulation, or preventing its accumulation. In industrial processIndustrial process
Industrial processes are procedures involving chemical or mechanical steps to aid in the manufacture of an item or items, usually carried out on a very large scale. Industrial processes are the key components of heavy industry....
es, bio-dispersant
Dispersant
A dispersant or a dispersing agent or a plasticizer or a superplasticizer is either a non-surface active polymer or a surface-active substance added to a suspension, usually a colloid, to improve the separation of particles and to prevent settling or clumping...
s can be used to control biofouling. In less controlled environments, anti-fouling coatings which contain biocides or non-toxic coatings which prevent organisms from attaching can be used.
Biocides
Biocides are chemical substances that can deter or kill the microorganisms responsible for biofouling. Biocides are incorporated into an anti-fouling surface coating, typically physical adsorption or through chemical modification of the surface. Biofouling occurs on surfaces after formation of a biofilmBiofilm
A biofilm is an aggregate of microorganisms in which cells adhere to each other on a surface. These adherent cells are frequently embedded within a self-produced matrix of extracellular polymeric substance...
. The biofilm creates a surface onto which successively larger microorganisms can attach. In marine environments this usually concludes with barnacle
Barnacle
A barnacle is a type of arthropod belonging to infraclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosive settings. They are sessile suspension feeders, and have...
attachment. The biocides often target the microorganisms which create the initial biofilm, typically bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
. Once dead, they are unable to spread and can detach. Other biocides are toxic to larger organisms in biofouling, such as the fungi and algae
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...
. The most commonly used biocide, and anti-fouling agent, is the tributyltin
Tributyltin
Tributyltin compounds are a group of compounds containing the 3Sn moiety, such as tributyltin hydride or tributyltin oxide. They are the main active ingredients in certain biocides used to control a broad spectrum of organisms...
moiety (TBT). It is toxic to both microorganisms and larger aquatic organisms. It is estimated that TBT derived anti-fouling coatings cover 70% of the world's vessels.
The prevalence of TBT and other tin based anti-fouling coatings on marine vessels is a current environmental problem. TBT has been shown to cause harm to many marine organisms, specifically oysters and mollusks. Extremely low concentrations of tributyltin
Tributyltin
Tributyltin compounds are a group of compounds containing the 3Sn moiety, such as tributyltin hydride or tributyltin oxide. They are the main active ingredients in certain biocides used to control a broad spectrum of organisms...
moiety (TBT) causes defective shell growth in the oyster
Oyster
The word oyster is used as a common name for a number of distinct groups of bivalve molluscs which live in marine or brackish habitats. The valves are highly calcified....
Crassostrea gigas (at a concentration of 20 ng/l) and development of male characteristics in female genitalia in the dog whelk
Dog Whelk
The dog whelk, dogwhelk, or Atlantic dogwinkle, scientific name Nucella lapillus, is a species of predatory sea snail, a carnivorous marine gastropod mollusc in the family Muricidae, the rock snails....
Nucella lapillus (where gonocharacteristic change is initiated at 1 ng/l).
The international maritime community has recognized this problem and there is planned phase out of tin based coatings, including a ban on newly built vessels. This phase out of toxic biocide
Biocide
A biocide is a chemical substance or microorganism which can deter, render harmless, or exert a controlling effect on any harmful organism by chemical or biological means. Biocides are commonly used in medicine, agriculture, forestry, and industry...
s in marine coatings is a severe problem for the shipping industry; it presents a major challenge for the producers of coatings to develop alternative technologies. Safer methods of biofouling control are actively researched. Copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
compounds have successfully been used in paints and continue to be used as metal sheeting (for example Muntz metal
Muntz metal
Muntz metal is a form of alpha-beta brass with about 60% copper, 40% zinc and a trace of iron. It is named after George Fredrick Muntz, a metal-roller of Birmingham, England who commercialised the alloy following his patent of 1832....
which was specifically made for this purpose), though there is still debate as to the safety of copper.
Non-toxic Coatings
Non-toxic anti-fouling coatings prevent any attachment of microorganisms thus negating the use of biocides. Further, these coatings are usually based on polymers and researchers are able to design self-healingSelf-healing material
Self-healing materials are a class of smart materials that have the structurally incorporated ability to repair damage caused by mechanical usage over time. The inspiration comes from biological systems, which have the ability to heal after being wounded...
coatings.
There are two classes of non-toxic anti-fouling coatings. The most common class relies on low friction
Friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and/or material elements sliding against each other. There are several types of friction:...
and low surface energies
Surface energy
Surface energy quantifies the disruption of intermolecular bonds that occur when a surface is created. In the physics of solids, surfaces must be intrinsically less energetically favorable than the bulk of a material, otherwise there would be a driving force for surfaces to be created, removing...
. This results in hydrophobic surfaces. These coatings create a smooth surface which can prevent attachment of larger microorganisms. For example, fluoropolymers and silicone coatings are commonly used. These coatings are ecologically inert but have problems with mechanical strength and long term stability. Specifically, after days biofilms (slime) can coat the surfaces which buries the chemical activity and allows microorganisms to attach.
The second class of non-toxic anti-fouling coatings are hydrophilic coatings. They rely on high amounts of hydration in order to increase the energetic penalty of removing water for proteins and microorganisms to attach. The most common example of these coatings are based on highly hydrated zwitterions, such as glycine betaine and sulfobetaine. These coatings are also low friction but are superior to hydrophobic surfaces because they prevent bacteria attachment, preventing biofilm formation. These coatings are not yet commercially available and are being designed as part of a larger effort by the Office of Naval Research
Office of Naval Research
The Office of Naval Research , headquartered in Arlington, Virginia , is the office within the United States Department of the Navy that coordinates, executes, and promotes the science and technology programs of the U.S...
to develop environmentally safe biomimetic ship coatings.
Types
Biofouling is divided into microfouling — biofilmBiofilm
A biofilm is an aggregate of microorganisms in which cells adhere to each other on a surface. These adherent cells are frequently embedded within a self-produced matrix of extracellular polymeric substance...
formation and bacterial adhesion — and macrofouling — attachment of larger organisms, of which the main culprits are barnacle
Barnacle
A barnacle is a type of arthropod belonging to infraclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosive settings. They are sessile suspension feeders, and have...
s, mussel
Mussel
The common name mussel is used for members of several families of clams or bivalvia mollusca, from saltwater and freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other edible clams, which are often more or less rounded or oval.The...
s, polychaete
Polychaete
The Polychaeta or polychaetes are a class of annelid worms, generally marine. Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made of chitin. Indeed, polychaetes are sometimes referred to as bristle worms. More than 10,000...
worms, bryozoans, and seaweed
Seaweed
Seaweed is a loose, colloquial term encompassing macroscopic, multicellular, benthic marine algae. The term includes some members of the red, brown and green algae...
. Together, these organisms form a fouling community
Fouling community
Fouling communities are communities of organisms found on the sides of docks, marinas, harbors, and boats throughout the world. These communities are characterized by the presence of a variety of sessile organisms including ascidians, bryozoans, mussels, tube building polychaetes, sea anemones,...
.
Individually small, accumulated biofoulers can form enormous masses that severely diminish ships' maneuverability and carrying capacity. Fouling causes huge material and economic costs in maintenance of mariculture
Mariculture
Mariculture is a specialized branch of aquaculture involving the cultivation of marine organisms for food and other products in the open ocean, an enclosed section of the ocean, or in tanks, ponds or raceways which are filled with seawater. An example of the latter is the farming of marine fish,...
, shipping industries, naval vessels, and seawater pipelines. Governments and industry spend more than US$ 5.7 billion annually to prevent and control marine biofouling.
History
Bio-fouling, especially of ships, has been a problem for many centuries and probably for as long as mankind has been sailing the oceans. In DeipnosophistaeDeipnosophistae
The Deipnosophistae may be translated as The Banquet of the Learned or Philosophers at Dinner or The Gastronomers...
, Athenaeus
Athenaeus
Athenaeus , of Naucratis in Egypt, Greek rhetorician and grammarian, flourished about the end of the 2nd and beginning of the 3rd century AD...
described the anti-fouling efforts taken in the construction of the great ship of Hieron of Syracuse (died 467 BCE). Before the 18th century various graving and paying techniques were used to try and prevent fouling using three main substances: White stuff, which was a mixture of train oil, rosin
Rosin
.Rosin, also called colophony or Greek pitch , is a solid form of resin obtained from pines and some other plants, mostly conifers, produced by heating fresh liquid resin to vaporize the volatile liquid terpene components. It is semi-transparent and varies in color from yellow to black...
and brimstone
Brimstone
Brimstone is an alternative name for sulfur. It may also refer to:* Fire and brimstone, an idiomatic expression of signs of God's wrath in the Bible* Brimstone , a DC Comics character...
; Black stuff, a mixture of tar
Tar
Tar is modified pitch produced primarily from the wood and roots of pine by destructive distillation under pyrolysis. Production and trade in tar was a major contributor in the economies of Northern Europe and Colonial America. Its main use was in preserving wooden vessels against rot. The largest...
and pitch
Resin
Resin in the most specific use of the term is a hydrocarbon secretion of many plants, particularly coniferous trees. Resins are valued for their chemical properties and associated uses, such as the production of varnishes, adhesives, and food glazing agents; as an important source of raw materials...
; and Brown stuff, which was simply brimstone added to Black stuff.
Copper sheathing
Copper sheathing
Copper sheathing was the practice of protecting the under-water hull of a ship or boat through the use of copper plates affixed to the outside of the hull. It was pioneered and developed by the Royal Navy during the 18th century.-Development:...
was first suggested in 1708 by Charles Perry, as an anti-fouling device but the first experiments with copper sheathing were not made until the late 1750s, at which time the bottoms and sides of several ships' keels and false keels were sheathed with copper plates.
The copper performed very well in protecting the hull from invasion by worm, and in preventing the growth of weed, for when in contact with water, the copper produced a poisonous film, composed mainly of oxychloride, that deterred these marine creatures. Furthermore, as this film was slightly soluble it gradually washed away, leaving no way in which marine life could attach itself to the ship.
From about 1770, the Royal Navy
Royal Navy
The Royal Navy is the naval warfare service branch of the British Armed Forces. Founded in the 16th century, it is the oldest service branch and is known as the Senior Service...
set about coppering the bottoms of the entire fleet and continued to the end of the use of wooden hulled ships. The process was so successful that the term copper bottomed came to mean something that was highly dependable or risk free.
Other areas of occurrence
Biofouling can also occur in groundwater wells where build-up can limit recovery flow rates, and in the exterior and interior of ocean-laying pipes. In the latter case it has been shown to retard the seawater flow through the pipe and has to be removed with the tube cleaning process.Biofouling also occurs on the surfaces of living marine organisms, when it is known as epibiosis.
See also
- FoulingFoulingFouling refers to the accumulation of unwanted material on solid surfaces, most often in an aquatic environment. The fouling material can consist of either living organisms or a non-living substance...
- Biomimetic Antifouling Coatings
- TributyltinTributyltinTributyltin compounds are a group of compounds containing the 3Sn moiety, such as tributyltin hydride or tributyltin oxide. They are the main active ingredients in certain biocides used to control a broad spectrum of organisms...
- Bottom paintBottom paintAnti-fouling paint or bottom paint is a specialized coating applied to the hull of a ship or boat in order to slow the growth of organisms that attach to the hull and can affect a vessel's performance and durability...
- ePaint
- KeelhaulingKeelhaulingKeelhauling is a form of punishment meted out to sailors at sea...
- Form of punishment at sea that involved 'hauling' an offender underneath the hull of a vessel, scraping them against the growths.