Editing Biofouling (section)

==Prevention==

=== Antifouling ===
'''Antifouling''' is the process of preventing accumulations from forming. In [[industrial process]]es, [[dispersant|biodispersant]]s can be used to control biofouling. In less controlled environments, organisms are killed or repelled with coatings using biocides, thermal treatments, or pulses of energy. Nontoxic mechanical strategies that prevent organisms from attaching include choosing a material or coating with a slippery surface, creating an [[ultra-low fouling]] surface with the use of [[zwitterion]]s, or creating [[Nanoscopic scale|nanoscale]] surface topologies similar to the skin of sharks and dolphins, which only offer poor anchor points.<ref name="antifouling_review" />

====Coatings====
===== Non-toxic coatings =====
[[File:ProteinAdsorptionPrevention.png|thumb|upright=1.3|A general idea of non-toxic coatings. (Coating represented here as light pea green layer.) They prevent [[proteins]] and microorganisms from attaching, which prevents large organisms such as [[barnacles]] from attaching. Larger organisms require a [[biofilm]] to attach, which is composed of [[proteins]], [[polysaccharides]], and [[microorganisms]].]]
Non-toxic anti-sticking coatings prevent attachment of microorganisms thus negating the use of biocides. These coatings are usually based on organic polymers.<ref>{{citation|title=Integrated Antimicrobial and Nonfouling Hydrogels to Inhibit the Growth of Planktonic Bacterial Cells and Keep the Surface Clean|author=Gang Cheng|display-authors=et al|journal=[[Langmuir (journal)|Langmuir]]|date=2 June 2010|volume=26|pages=10425–10428|doi=10.1021/la101542m|pmid=20518560|issue=13}}</ref>

There are two classes of non-toxic anti-fouling coatings. The most common class relies on low [[friction]] and low [[Surface energy|surface energies]]. Low surface energies result 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.<ref>{{citation|title=Clean Hulls Without Poisons: Devising and Testing Nontoxic Marine Coatings|first=R.F.|last=Brady|journal=Journal of Coatings Technology|volume=72|number=900|pages=44–56|date=1 January 2000|doi=10.1007/BF02698394|s2cid=137350868|url=http://www.highbeam.com/doc/1G1-59245245.html|archive-url=https://web.archive.org/web/20140611030850/http://www.highbeam.com/doc/1G1-59245245.html|url-status=dead|archive-date=11 June 2014|access-date=22 May 2012}}</ref> 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.<ref name=antifouling_review/> The current standard for these coatings is [[polydimethylsiloxane]], or PDMS, which consists of a non-polar backbone made of repeating units of silicon and oxygen atoms.<ref>{{Citation|last1=Krishnan|first1=S|title=Advances in polymers for anti-biofouling surfaces|journal=Journal of Materials Chemistry|year=2008|volume=12|issue=29|pages=3405–3413|doi=10.1039/B801491D|last2=Weinman|first2=Craig J.|last3=Ober|first3=Christopher K.}}</ref> The non-polarity of PDMS allows for biomolecules to readily adsorb to its surface in order to lower interfacial energy. However, PDMS also has a low modulus of elasticity that allows for the release of fouling organisms at speeds of greater than 20 knots. The dependence of effectiveness on vessel speed prevents use of PDMS on slow-moving ships or those that spend significant amounts of time in port.<ref name="Vladkova"/>

The second class of non-toxic antifouling 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 examples of these coatings are based on highly hydrated [[zwitterion]]s, such as [[glycine betaine]] and [[Polysulfobetaine|sulfobetaine]]. These coatings are also low-friction, but are considered by some to be superior to hydrophobic surfaces because they prevent bacteria attachment, preventing biofilm formation.<ref>{{citation|first1=S.|last1=Jiang|first2=Z.|last2=Cao|title=Ultralow-Fouling, Functionalizable, and Hydrolyzable Zwitterionic Materials and Their Derivatives for Biological Applications|journal=Advanced Materials|year=2010|volume=22|pages=920–932|doi=10.1002/adma.200901407|issue=9|pmid=20217815|bibcode=2010AdM....22..920J |s2cid=205233845 }}</ref> 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.<ref name=V1/>

===== Biocides =====
{{main|Biocide|Biomimetic antifouling coating}}
Biocides are chemical substances that kill or deter microorganisms responsible for biofouling. The biocide is typically applied as a paint, i.e. through [[physical adsorption]]. The biocides prevent the formation of [[biofilm]]s.<ref name="antifouling_review" /> Other biocides are toxic to larger organisms in biofouling, such as [[algae]]. Formerly, the so-called [[tributyltin]] (TBT) compounds were used as biocides (and thus anti-fouling agents).  TBTs are toxic to both microorganisms and larger aquatic organisms.<ref name="TBT_review">{{cite journal |last1=Evans |first1=S.M. |last2=Leksono |first2=T. |last3=McKinnell |first3=P.D. |title=Tributyltin pollution: A diminishing problem following legislation limiting the use of TBT-based anti-fouling paints |journal=Marine Pollution Bulletin |date=January 1995 |volume=30 |issue=1 |pages=14–21 |doi=10.1016/0025-326X(94)00181-8 |bibcode=1995MarPB..30...14E }}</ref> The international maritime community has phased out the use of organotin-based coatings.<ref>{{Cite web|url=http://www.imo.org/en/OurWork/Environment/Anti-foulingSystems/Pages/Default.aspx|title=Anti-fouling Systems|access-date=10 June 2017|archive-date=11 June 2017|archive-url=https://web.archive.org/web/20170611064311/http://www.imo.org/en/OurWork/Environment/Anti-foulingSystems/Pages/Default.aspx|url-status=dead}}</ref> Replacing organotin compounds is [[dichlorooctylisothiazolinone]]. This compound, however, also suffers from broad toxicity to marine organisms.

==== Ultrasonic antifouling ====
{{main|Ultrasonic antifouling}}
Ultrasonic transducers may be mounted in or around the hull of small to medium-sized boats. Research has shown these systems can help reduce fouling, by initiating bursts of ultrasonic waves through the hull medium to the surrounding water, killing or denaturing the algae and other microorganisms that form the beginning of the fouling sequence. The systems cannot work on wooden-hulled boats, or boats with a soft-cored composite material, such as wood or foam. The systems have been loosely based on technology proven to control algae blooms.<ref>{{cite journal|last1=Lee|first1=TJ|last2=Nakano|first2=K|last3=Matsumara|first3=M|year=2001|title=Ultrasonic irradiation for blue-green algae bloom control|journal=Environ Technol|volume=22|issue=4|pages=383–90|doi=10.1080/09593332208618270|pmid=11329801|bibcode=2001EnvTe..22..383L |s2cid=22704787}}</ref>

====Energy methods====
Pulsed laser irradiation is commonly used against [[diatoms]]. Plasma pulse technology is effective against zebra mussels and works by stunning or killing the organisms with microsecond-duration energizing of the water with high-voltage electricity.<ref name=stanczak/>

Similarly, another method shown to be effective against algae buildups bounces brief high-energy acoustic pulses down pipes.<ref>{{citation|last1=Walch|first1=M.|last2=Mazzola|first2=M.|last3=Grothaus|first3=M.|year=2000|title=Feasibility Demonstration of a Pulsed Acoustic Device for Inhibition of Biofouling in Seawater Piping|publisher=Naval Surface Warfare Center Carderock Div.|location=Bethesda, MD|id=NSWCCD-TR-2000/04|url=http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA376166|archive-url=https://web.archive.org/web/20130408130814/http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA376166|url-status=dead|archive-date=8 April 2013|format=pdf|access-date=21 May 2012}}</ref>

====Other methods====
Regimens to periodically use heat to treat exchanger equipment and pipes have been successfully used to remove mussels from power plant cooling systems using water at 105&nbsp;°F (40&nbsp;°C) for 30 minutes.<ref>{{citation|title=Oceans 86 Proceedings|contribution=Development of a Site Specific Biofouling Control Program for the Diablo Canyon Power Plant|first=David C.|last=Sommerville|pages=227–231|doi=10.1109/OCEANS.1986.1160543|date=September 1986|publisher=IEEE Conference Publications|s2cid=110171493}}</ref>

The medical industry utilizes a variety of energy methods to address [[bioburden]] issues associated with biofouling. [[Autoclave|Autoclaving]] typically involves heating a medical device to 121&nbsp;°C (249&nbsp;°F) for 15–20 minutes. Ultrasonic cleaning, UV light, and chemical wipe-down or immersion can also be used for different types of devices.

Medical devices used in operating rooms, ICUs, isolation rooms, biological analysis labs, and other high-contamination-risk areas have negative pressure (constant exhaust) in the rooms, maintain strict cleaning protocols, require equipment with no fans, and often drape equipment in protective plastic.<ref>{{cite book |doi=10.1007/978-3-319-99921-0_35 |chapter=Operation Department: Infection Control |title=Prevention and Control of Infections in Hospitals |year=2019 |last1=Andersen |first1=Bjørg Marit |pages=453–489 |isbn=978-3-319-99920-3 |s2cid=86654083 }}</ref>

[[Ultraviolet#Subtypes|UVC]] irradiation is a noncontact, nonchemical solution that can be used across a range of instruments. Radiation in the UVC range prevents biofilm formation by deactivating the [[DNA]] in bacteria, viruses, and other microbes. Preventing biofilm formation prevents larger organisms from attaching themselves to the instrument and eventually rendering it inoperable.<ref>Hari Venugopalan, ''Photonic Frontiers: LEDs - UVC LEDs reduce marine biofouling'', Laser Focus World (July 2016) pp.&nbsp;28–31 [http://www.laserfocusworld.com/articles/print/volume-52/issue-07/features/photonic-frontiers-leds-uvc-leds-reduce-marine-biofouling.html StackPath]</ref>