Editing Filtration (section)

==Biological filtration==
Biological filtration may take place inside an organism, or the biological component may be grown on a medium in the material being filtered. Removal of solids, emulsified components, organic chemicals and ions may be achieved by ingestion and digestion, adsorption or absorption. Because of the complexity of biological interactions, especially in multi-organism communities, it is often not possible to determine which processes are achieving the filtration result. At the molecular level, it may often be by individual catalytic enzyme actions within an individual organism. The waste products of some organisms may subsequently broken down by other organisms to extract as much energy as possible and in so doing reduce complex organic molecules to very simple inorganic species such as water, carbon dioxide and nitrogen.

===Excretion===
{{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.

===Biofilms===
{{main|Biofilm}}
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=Chapter 3 - Biofilms, filtration, microbial kinetics and mechanism of degradation: a revolutionary approach |date=18 June 2021|pages=25–43 |doi=10.1016/b978-0-12-823804-2.00018-5 |url=https://doi.org/10.1016/B978-0-12-823804-2.00018-5|isbn=9780128238042 |s2cid=237996887 |language=en}}</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|editor1-first=Dharumadurai|editor1-last=Dhanasekaran|editor2-first=Nooruddin|editor2-last=Thajuddin|title=Microbial Biofilms - Importance and Applications |date=13 July 2016 |doi=10.5772/63499|isbn=978-953-51-2435-1 |s2cid=5035829 |doi-access=free }}</ref>

===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|cillia]] 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.