Filtration: Difference between revisions
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'''Filtration''' is a physical [[separation process]] that separates [[solid]] matter and [[fluid]] from a mixture using a ''filter medium'' that has a complex structure through which only the fluid can pass. Solid particles that cannot pass through the filter medium are described as ''oversize'' and the fluid that passes through is called the ''filtrate''.<ref>{{cite web | title=Filtration |publisher=Lenntech BV| url=https://www.lenntech.com/chemistry/filtration.htm |date=2009}}</ref> Oversize particles may form a [[filter cake]] on top of the filter and may also block the filter lattice, preventing the fluid phase from crossing the filter, known as ''blinding''. The size of the largest particles that can successfully pass through a filter is called the effective ''pore size'' of that filter. The separation of solid and fluid is imperfect; solids will be contaminated with some fluid and filtrate will contain fine particles (depending on the pore size, filter thickness and biological activity). Filtration occurs both in nature and in [[engineering|engineered]] systems; there are [[biology|biological]], [[geology|geological]], and [[Industry (manufacturing)|industrial]] forms.<ref>{{cite book |last1=Sparks |first1=Trevor |last2=Chase |first2=George |title=Filters and Filtration Handbook |date=2015 |publisher=Butterworth-Heinemann |edition=6th |isbn=9780080993966}}</ref> In everyday usage the verb "strain" is more often used; for example, using a [[colander]] to drain cooking water from cooked [[pasta]]. | '''Filtration''' is a physical [[separation process]] that separates [[solid]] matter and [[fluid]] from a mixture using a ''filter medium'' that has a complex structure through which only the fluid can pass. Solid particles that cannot pass through the filter medium are described as ''oversize'' and the fluid that passes through is called the ''filtrate''.<ref>{{cite web | title=Filtration |publisher=Lenntech BV| url=https://www.lenntech.com/chemistry/filtration.htm |date=2009}}</ref> Oversize particles may form a [[filter cake]] on top of the filter and may also block the filter lattice, preventing the fluid phase from crossing the filter, known as ''blinding''. The size of the largest particles that can successfully pass through a filter is called the effective ''pore size'' of that filter. The separation of solid and fluid is imperfect; solids will be contaminated with some fluid and filtrate will contain fine particles (depending on the pore size, filter thickness and biological activity). Filtration occurs both in nature and in [[engineering|engineered]] systems; there are [[biology|biological]], [[geology|geological]], and [[Industry (manufacturing)|industrial]] forms.<ref>{{cite book |last1=Sparks |first1=Trevor |last2=Chase |first2=George |title=Filters and Filtration Handbook |date=2015 |publisher=Butterworth-Heinemann |edition=6th |isbn=9780080993966}}</ref> In everyday usage the verb "strain" is more often used; for example, using a [[colander]] to drain cooking water from cooked [[pasta]]. | ||
Oil filtration refers to the method of purifying oil by removing impurities that can degrade its quality. Contaminants can enter the oil through various means, including wear and tear of machinery components, environmental factors, and improper handling during oil changes. The primary goal of oil filtration is to enhance the oil’s performance, thereby protecting the machinery and extending its service life.<ref name="Minimac Systems">{{cite web |last1=Systems |first1=Minimac |title=What is Oil Filtration? Importance, Types, and Benefits Explained. |url=https://www.minimacsystems.com/what-is-oil-filtration-understanding-its-importance-types-and-benefits |website | Oil filtration refers to the method of purifying oil by removing impurities that can degrade its quality. Contaminants can enter the oil through various means, including wear and tear of machinery components, environmental factors, and improper handling during oil changes. The primary goal of oil filtration is to enhance the oil’s performance, thereby protecting the machinery and extending its service life.<ref name="Minimac Systems">{{cite web |last1=Systems |first1=Minimac |title=What is Oil Filtration? Importance, Types, and Benefits Explained. |url=https://www.minimacsystems.com/what-is-oil-filtration-understanding-its-importance-types-and-benefits |website=Minimac Systems |access-date=2024-12-28}}</ref> | ||
Filtration is also used to describe biological and physical systems that not only separate solids from a fluid stream but also remove chemical species and biological organisms by [[Entrainment (engineering)|entrainment]], [[phagocytosis]], [[adsorption]] and [[Absorption (chemistry)|absorption]]. Examples include [[slow sand filter]]s and [[trickling filter]]s. It is also used as a general term for macrophage in which organisms use a variety of means to filter small food particles from their environment. Examples range from the microscopic ''[[Vorticella]]'' up to the [[basking shark]], one of the largest fishes, and the [[baleen whale]]s, all of which are described as [[filter feeder]]s. | Filtration is also used to describe biological and physical systems that not only separate solids from a fluid stream but also remove chemical species and biological organisms by [[Entrainment (engineering)|entrainment]], [[phagocytosis]], [[adsorption]] and [[Absorption (chemistry)|absorption]]. Examples include [[slow sand filter]]s and [[trickling filter]]s. It is also used as a general term for macrophage in which organisms use a variety of means to filter small food particles from their environment. Examples range from the microscopic ''[[Vorticella]]'' up to the [[basking shark]], one of the largest fishes, and the [[baleen whale]]s, all of which are described as [[filter feeder]]s. | ||
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There are several laboratory filtration techniques depending on the desired outcome namely, hot, cold and [[Suction filtration|vacuum filtration]]. Some of the major purposes of obtaining the desired outcome are, for the removal of impurities from a mixture or, for the isolation of solids from a mixture. | There are several laboratory filtration techniques depending on the desired outcome namely, hot, cold and [[Suction filtration|vacuum filtration]]. Some of the major purposes of obtaining the desired outcome are, for the removal of impurities from a mixture or, for the isolation of solids from a mixture. | ||
[[File: Hot FIltration.jpg|thumb|left|Hot filtration for the separation of solids from a hot solution]] | [[File: Hot FIltration.jpg|thumb|left|Hot filtration for the separation of solids from a hot solution]] | ||
'''Hot filtration''' method is mainly used to separate solids from a hot solution. This is done to prevent crystal formation in the filter funnel and other apparatus that come in contact with the solution. As a result, the apparatus and the solution used are heated to prevent the rapid decrease in temperature which in turn, would lead to the crystallisation of the solids in the funnel and hinder the filtration process.<ref>{{cite web|title=ORGANIC LABORATORY TECHNIQUES 3: Filtration Methods|url=http://www.chem.ucalgary.ca/courses/351/laboratory/filtration.pdf|publisher=[[University of Calgary]]|date=19 September 2013<!--from PDF source-->|archive-date=13 February 2015|archive-url=https://web.archive.org/web/20150213060129/http://www.chem.ucalgary.ca/courses/351/laboratory/filtration.pdf|url-status=live}}</ref> | '''Hot filtration''' method is mainly used to separate solids from a hot solution. This is done to prevent crystal formation in the filter funnel and other apparatus that come in contact with the solution. As a result, the apparatus and the solution used are heated to prevent the rapid decrease in temperature which in turn, would lead to the crystallisation of the solids in the funnel and hinder the filtration process.<ref>{{cite web|title=ORGANIC LABORATORY TECHNIQUES 3: Filtration Methods|url=http://www.chem.ucalgary.ca/courses/351/laboratory/filtration.pdf|publisher=[[University of Calgary]]|date=19 September 2013<!--from PDF source-->|archive-date=13 February 2015|archive-url=https://web.archive.org/web/20150213060129/http://www.chem.ucalgary.ca/courses/351/laboratory/filtration.pdf|url-status=live}}</ref> One of the most important measures to prevent the formation of crystals in the funnel and to undergo effective hot filtration is the use stemless filter funnel. Due to the absence of a stem in the filter funnel, there is a decrease in the surface area of contact between the solution and the stem of the filter funnel, hence preventing re-crystallization of solid in the funnel, and adversely affecting the filtration process. | ||
One of the most important measures to prevent the formation of crystals in the funnel and to undergo effective hot filtration is the use stemless filter funnel. Due to the absence of a stem in the filter funnel, there is a decrease in the surface area of contact between the solution and the stem of the filter funnel, hence preventing re-crystallization of solid in the funnel, and adversely affecting the filtration process. | |||
[[File: Cold Filtration.jpg|thumb|Cold filtration, the ice bath is used to cool down the temperature of the solution before undergoing the filtration process]] | [[File: Cold Filtration.jpg|thumb|Cold filtration, the ice bath is used to cool down the temperature of the solution before undergoing the filtration process]] | ||
'''Cold filtration''' method is the use of an ice bath to rapidly cool the solution to be crystallized rather than leaving it to cool slowly in the room atmosphere. This technique results in the formation of very small crystals as opposed to getting large crystals by cooling the solution at room temperature. | '''Cold filtration''' method is the use of an ice bath to rapidly cool the solution to be crystallized rather than leaving it to cool slowly in the room atmosphere. This technique results in the formation of very small crystals as opposed to getting large crystals by cooling the solution at room temperature. | ||
'''[[Suction filtration|Vacuum filtration]]''' technique is mostly preferred for small batches of solution to dry small crystals quickly. This method requires a [[Büchner funnel]], filter paper of a smaller diameter than the funnel, [[Büchner flask]], and rubber tubing to connect to a vacuum source. | '''[[Suction filtration|Vacuum filtration]]''' technique is mostly preferred for small batches of solution to dry small crystals quickly. This method requires a [[Büchner funnel]], filter paper of a smaller diameter than the funnel, [[Büchner flask]], and rubber tubing to connect to a vacuum source.<ref>{{Cite web |last=chemtalk |date=2023-08-13 |title=What is Vacuum Filtration? |url=https://chemistrytalk.org/what-is-vacuum-filtration/ |access-date=2025-08-23 |website=ChemTalk |language=en-US}}</ref> | ||
'''Centrifugal filtration''' is carried out by rapidly rotating the substance to be filtered. The more dense material is separated from the less dense matter by the horizontal rotation.<ref name="Filtration">{{cite web |title=Filtration - Definition, Types, Functions & Quiz |url=https://biologydictionary.net/filtration/ |website=Biology Dictionary |date=3 March 2017}}</ref> | '''Centrifugal filtration''' is carried out by rapidly rotating the substance to be filtered. The more dense material is separated from the less dense matter by the horizontal rotation.<ref name="Filtration">{{cite web |title=Filtration - Definition, Types, Functions & Quiz |url=https://biologydictionary.net/filtration/ |website=Biology Dictionary |date=3 March 2017}}</ref> | ||
'''Gravity filtration''' is the process of pouring the mixture from a higher location to a lower one. It is frequently accomplished via simple filtration, which involves placing filter paper in a glass funnel with the liquid passing through by gravity while the insoluble solid particles are caught by the filter paper. Filter cones, fluted filters, or filtering pipets can all be employed, depending on the amount of the substance at hand.<ref name="Filtration"/> Gravity filtration is in widespread everyday use, for example for straining cooking water from food, or removing contaminants from a liquid. | '''[[Gravity filtration]]''' is the process of pouring the mixture from a higher location to a lower one. It is frequently accomplished via simple filtration, which involves placing filter paper in a glass funnel with the liquid passing through by gravity while the insoluble solid particles are caught by the filter paper. Filter cones, fluted filters, or filtering pipets can all be employed, depending on the amount of the substance at hand.<ref name="Filtration"/> Gravity filtration is in widespread everyday use, for example for straining cooking water from food, or removing contaminants from a liquid. | ||
===Filtering force=== | ===Filtering force=== | ||
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Two main types of filter media are employed in laboratories: | Two main types of filter media are employed in laboratories: | ||
*''Surface filters'' are solid sieves with a [[mesh]] to trap solid particles, sometimes with the aid of [[filter paper]] (e.g. [[Büchner funnel]], [[belt filter]], [[rotary vacuum-drum filter]], [[cross-flow filtration|cross-flow filters]], [[screen filter]]). | *''Surface filters'' are solid sieves with a [[mesh]] to trap solid particles, sometimes with the aid of [[filter paper]] (e.g. [[Büchner funnel]], [[belt filter]], [[rotary vacuum-drum filter]], [[cross-flow filtration|cross-flow filters]], [[screen filter]]).<ref>{{cite book |last1=Zobel |first1=S. |last2=Gries |first2=T. |title=Applications of Nonwovens in Technical Textiles |chapter=The use of nonwovens as filtration materials |date=2010 |pages=160–183 |doi=10.1533/9781845699741.2.160 |isbn=978-1-84569-437-1 }}</ref> | ||
* ''[[Depth filter]]s'', beds of granular material which retain the solid particles as they pass (e.g. [[sand filter]]). | * ''[[Depth filter]]s'', beds of granular material which retain the solid particles as they pass (e.g. [[sand filter]]).<ref>{{Cite web |title=MULTI-MEDIA WATER FILTERS (Depth Filters) |url=https://www.apecwater.com/blogs/water-health/814-multi-media-filters |access-date=2025-08-23 |website=APEC WATER |language=en}}</ref> | ||
Surface filters allow the solid particles, i.e. the residue, to be collected intact; depth filters do not. However, the depth filter is less prone to clogging due to the greater surface area where the particles can be trapped. Also, when the solid particles are very fine, it is often cheaper and easier to discard the contaminated granules than to clean the solid sieve.<ref>{{ | Surface filters allow the solid particles, i.e. the residue, to be collected intact; depth filters do not. However, the depth filter is less prone to clogging due to the greater surface area where the particles can be trapped. Also, when the solid particles are very fine, it is often cheaper and easier to discard the contaminated granules than to clean the solid sieve.<ref>{{cite book |title=Coulson and Richardson's Chemical Engineering |chapter=Liquid Filtration |date=2019 |pages=555–625 |doi=10.1016/B978-0-08-101098-3.00011-1 |isbn=978-0-08-101098-3 }}</ref> | ||
Filter media can be cleaned by rinsing with solvents or detergents or backwashing. Alternatively, in engineering applications, such as [[swimming pool]] water treatment plants, they may be cleaned by [[Backwashing (water treatment)|backwashing]]. Self-cleaning [[screen filter]]s utilize point-of-suction backwashing to clean the screen without interrupting system flow. | Filter media can be cleaned by rinsing with solvents or detergents or backwashing. Alternatively, in engineering applications, such as [[swimming pool]] water treatment plants, they may be cleaned by [[Backwashing (water treatment)|backwashing]]. Self-cleaning [[screen filter]]s utilize point-of-suction backwashing to clean the screen without interrupting system flow. | ||
====Achieving flow through the filter==== | ====Achieving flow through the filter==== | ||
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Filtration is a more efficient method for the [[separation of mixtures]] than [[decantation]] but is much more time-consuming. If very small amounts of solution are involved, most of the solution may be soaked up by the filter medium. | Filtration is a more efficient method for the [[separation of mixtures]] than [[decantation]] but is much more time-consuming. If very small amounts of solution are involved, most of the solution may be soaked up by the filter medium. | ||
An alternative to filtration is [[centrifugation]]. Instead of filtering the mixture of solid and liquid particles, the mixture is centrifuged to force the (usually) denser solid to the bottom, where it often forms a firm [[Filter cake|cake]]. The liquid above can then be decanted. This method is especially useful for separating solids that do not filter well, such as gelatinous or fine particles. These solids can clog or pass through the filter, respectively. | An alternative to filtration is [[centrifugation]]. Instead of filtering the mixture of solid and liquid particles, the mixture is centrifuged to force the (usually) denser solid to the bottom, where it often forms a firm [[Filter cake|cake]]. The liquid above can then be decanted. This method is especially useful for separating solids that do not filter well, such as gelatinous or fine particles. These solids can clog or pass through the filter, respectively.<ref>{{cite journal |last1=Mkpuma |first1=Victor Okorie |last2=Moheimani |first2=Navid Reza |last3=Ennaceri |first3=Houda |title=Microalgal dewatering with focus on filtration and antifouling strategies: A review |journal=Algal Research |date=2022 |volume=61 |article-number=102588 |doi=10.1016/j.algal.2021.102588 |bibcode=2022AlgRe..6102588M }}</ref> | ||
==Biological filtration== | ==Biological filtration== | ||
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{{main|Renal physiology#Filtration}} | {{main|Renal physiology#Filtration}} | ||
In mammals, reptiles, and birds, the [[kidney]]s function by renal filtration whereby the [[Glomerulus (kidney)|glomerulus]] selectively removes undesirable constituents such as [[urea]], followed by selective reabsorption of many substances essential for the body to maintain homeostasis. The complete process is termed [[excretion]] by [[urination]]. Similar but often less complex solutions are deployed in all animals, even the [[protozoa]], where the [[contractile vacuole]] provides a similar function. | In mammals, reptiles, and birds, the [[kidney]]s function by renal filtration whereby the [[Glomerulus (kidney)|glomerulus]] selectively removes undesirable constituents such as [[urea]], followed by selective reabsorption of many substances essential for the body to maintain homeostasis. The complete process is termed [[excretion]] by [[urination]]. Similar but often less complex solutions are deployed in all animals, even the [[protozoa]], where the [[contractile vacuole]] provides a similar function.<ref>{{cite book |last1=Ogobuiro |first1=Ifeanyichukwu |last2=Tuma |first2=Faiz |title=StatPearls |date=2025 |publisher=StatPearls Publishing |chapter-url=http://www.ncbi.nlm.nih.gov/books/NBK538339/ |chapter=Physiology, Renal |pmid=30855923 }}</ref> | ||
===Biofilms=== | ===Biofilms=== | ||
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Biofilms are often complex communities of bacteria, phages, yeasts and often more complex organisms including [[protozoa]], [[rotifer]]s and [[annelid]]s which form dynamic and complex, frequently gelatinous films on wet substrates. Such biofilms coat the rocks of most rivers and the sea and they provide the key filtration capability of the [[Schmutzdecke]] on the surface of [[slow sand filter]]s and the film on the filter media of [[trickling filter]]s which are used to create potable water and treat sewage respectively. | Biofilms are often complex communities of bacteria, phages, yeasts and often more complex organisms including [[protozoa]], [[rotifer]]s and [[annelid]]s which form dynamic and complex, frequently gelatinous films on wet substrates. Such biofilms coat the rocks of most rivers and the sea and they provide the key filtration capability of the [[Schmutzdecke]] on the surface of [[slow sand filter]]s and the film on the filter media of [[trickling filter]]s which are used to create potable water and treat sewage respectively. | ||
An example of a biofilm is a biological slime, which may be found in lakes, rivers, rocks, etc. The utilization of single- or dual-species biofilms is a novel technology since natural biofilms are sluggishly developing. The use of biofilms in the biofiltration process allows for the attachment of desirable biomass and critical nutrients to immobilized support. So that water may be reused for various processes, advances in [[biofiltration]] methods assist in removing significant volumes of effluents from [[wastewater]].<ref name="Biofilms">{{cite book|last1=Dave |first1=Sushma |last2=Churi |first2=Hardik |last3=Litoria |first3=Pratiksha |last4=David |first4=Preethi |last5=Das |first5=Jayashankar|title=Membrane-Based Hybrid Processes for Wastewater Treatment|chapter= | An example of a biofilm is a biological slime, which may be found in lakes, rivers, rocks, etc. The utilization of single- or dual-species biofilms is a novel technology since natural biofilms are sluggishly developing. The use of biofilms in the biofiltration process allows for the attachment of desirable biomass and critical nutrients to immobilized support. So that water may be reused for various processes, advances in [[biofiltration]] methods assist in removing significant volumes of effluents from [[wastewater]].<ref name="Biofilms">{{cite book |last1=Dave |first1=Sushma |last2=Churi |first2=Hardik |last3=Litoria |first3=Pratiksha |last4=David |first4=Preethi |last5=Das |first5=Jayashankar |title=Membrane-Based Hybrid Processes for Wastewater Treatment |chapter=Biofilms, filtration, microbial kinetics and mechanism of degradation: A revolutionary approach |date=2021 |pages=25–43 |doi=10.1016/b978-0-12-823804-2.00018-5 |isbn=978-0-12-823804-2 }}</ref> | ||
Systems for biologically treating wastewater are crucial for enhancing both human health and [[water quality]]. Biofilm technology, the formation of biofilms on various filter media, and other factors have an impact on the growth structure and function of these biofilms. To conduct a thorough investigation of the composition, diversity, and dynamics of biofilms, it also takes on a variety of traditional and contemporary molecular approaches.<ref>{{cite book|last1=Sehar |first1=Shama |last2=Naz |first2=Iffat |chapter=Role of the Biofilms in Wastewater Treatment | Systems for biologically treating wastewater are crucial for enhancing both human health and [[water quality]]. Biofilm technology, the formation of biofilms on various filter media, and other factors have an impact on the growth structure and function of these biofilms. To conduct a thorough investigation of the composition, diversity, and dynamics of biofilms, it also takes on a variety of traditional and contemporary molecular approaches.<ref>{{cite book |last1=Sehar |first1=Shama |last2=Naz |first2=Iffat |title=Microbial Biofilms - Importance and Applications |chapter=Role of the Biofilms in Wastewater Treatment |date=2016 |doi=10.5772/63499 |isbn=978-953-51-2435-1 |url=https://openresearchlibrary.org/viewer/a2f9b258-c5ad-460b-8143-19497f0750fc }}</ref> | ||
===Filter feeders=== | ===Filter feeders=== | ||
{{main|Filter feeders}} | {{main|Filter feeders}} | ||
Filter feeders are organisms that obtain their food by filtering their, generally aquatic, environment. Many of the protozoa are filter feeders using a range of adaptations including rigid spikes of [[protoplasm]] held in the water flow as in the [[suctoria]] to various arrangements of beating [[Cilium| | Filter feeders are organisms that obtain their food by filtering their, generally aquatic, environment. Many of the protozoa are filter feeders using a range of adaptations including rigid spikes of [[protoplasm]] held in the water flow as in the [[suctoria]] to various arrangements of beating [[Cilium|cilia]] to direct particles to the mouth including organisms such as ''Vorticella'' which have a complex ring of cilia which create a vortex in the flow drafting particles into the oral cavity. Similar feeding techniques are used by the [[Rotifera]] and the [[Ectoprocta]]. Many aquatic [[arthropods]] are filter feeders. Some use rhythmical beating of abdominal limbs to create a water current to the mouth whilst the hairs on the legs trap any particle. Others such as some [[Caddisfly#Ecology|caddis flies]] spin fine webs in the water flow to trap particles.<ref>{{Cite web |date=2025-08-14 |title=Protozoan - Ingestion, Digestion, Nutrition {{!}} Britannica |url=https://www.britannica.com/science/protozoan/Mechanisms-of-food-ingestion |access-date=2025-08-23 |website=www.britannica.com |language=en}}</ref> | ||
==Examples== | ==Examples== | ||