struvite

{{Infobox mineral

| name = Struvite

| category = Phosphate mineral

| boxwidth =

| boxbgcolor =

| image = Struvite crystals dog with scale 1.JPG

| imagesize =

| caption = Crystals of struvite from dog urine

| formula = {{chem2|NH4MgPO4*6H2O}}

| IMAsymbol = Suv{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616|doi-access=free}}

| molweight =

| strunz = 8.CH.40

| system = Orthorhombic

| class = Pyramidal (mm2)
H-M symbol: (mm2)

| symmetry = Pmn2₁

| color = Colorless, white (dehydrated), yellow or brownish, light gray

| habit = Euhedral to platy

| twinning = On {001}

| cleavage = {100} perfect

| fracture = Uneven

| mohs = 1.5–2

| luster = Vitreous to dull

| refractive = nα = 1.495 nβ = 1.496 nγ = 1.504

| opticalprop = Biaxial (+) 2V Measured: 37°

| birefringence = δ = 0.009

| pleochroism =

| streak = White

| gravity = 1.7

| density =

| melt =

| fusibility =

| diagnostic =

| solubility = Slightly soluble, dehydrates in dry, warm air

| diaphaneity = Transparent to translucent

| other = Pyroelectric and piezoelectric

| references = {{cite web | title = Struvite | url = http://rruff.geo.arizona.edu/doclib/hom/struvite.pdf | work = Handbook of mineralogy }}{{cite web | title = Struvite Mineral Data | url = http://webmineral.com/data/Struvite.shtml | work = Webmineral}}{{cite web | title = Struvite | url = http://www.mindat.org/min-3811.html | work = Mindat }}

}}

Struvite (magnesium ammonium phosphate) is a phosphate mineral with formula: NH₄MgPO₄·6H₂O. Struvite crystallizes in the orthorhombic system as white to yellowish or brownish-white pyramidal crystals or in platy mica-like forms. It is a soft mineral with Mohs hardness of 1.5 to 2 and has a low specific gravity of 1.7. It is sparingly soluble in neutral and alkaline conditions, but readily soluble in acid.

Struvite urinary stones and crystals form readily in the urine of animals and humans that are infected with ammonia-producing organisms. They are potentiated by alkaline urine and high magnesium excretion (high magnesium/plant-based diets). They also are potentiated by a specific urinary protein in domestic cats.

Name

Although struvite was briefly mentioned in Hooke's Micrographia,Witty, M (2016). Hooke’s Gravel was Struvite. Notes and Queries 63(4):569–570. https://doi.org/10.1093/notesj/gjw218

it was first described in detail in 1845 by the German chemist {{Interlanguage link multi|Georg Ludwig Ulex|de|lt=Georg Ludwig Ulex}} (1811–1883), who found crystals of struvite in what he surmised had once been a medieval midden in Hamburg, Germany; he named the new mineral after the geographer and geologist {{Interlanguage link multi|Heinrich von Struve|de|lt=Heinrich Christian Gottfried von Struve}} (1772–1851) of Hamburg.{{cite journal | vauthors = Ulex GL | date = 1845 | url = https://babel.hathitrust.org/cgi/pt?id=mdp.39015077853219;view=1up;seq=120 | title = On struvite, a new mineral | journal = Memoirs and Proceedings of the Chemical Society | volume = 3 | pages = 106–110 | doi = 10.1039/mp8450300106 }}

Occurrence

Struvite readily forms in alkaline conditions where its constituent ions are present. In nature, it forms primarily in areas associated with organic matter decomposition, including guano deposits, basaltic caves, and marshlands. Similar conditions are found when human bladders are infected by urease-producing bacteria, when wastewater is treated, etc.{{cite journal |last1=Zhao |first1=Tian-Lei |last2=Li |first2=Han |last3=Jiang |first3=Hao-Fan |last4=Yao |first4=Qi-Zhi |last5=Huang |first5=Ying |last6=Zhou |first6=Gen-Tao |title=Morphogenesis and evolution mechanisms of bacterially-induced struvite |journal=Scientific Reports |date=December 2021 |volume=11 |issue=1 |pages=170 |doi=10.1038/s41598-020-80718-y|pmid=33420384 |pmc=7794283 }}

Struvite is occasionally found in canned seafood, where its appearance is that of small glass slivers, objectionable to consumers for aesthetic reasons but of no health consequence.{{cite web | url=http://komonews.com/news/consumer/suspected-glass-in-canned-fish-actually-natural-crystal-11-28-2015 | first = Connie | last = Thompson | name-list-style = vanc | title=Suspected "glass" in canned fish actually natural crystal | publisher=Komo News | access-date=2016-07-21 | date=2011-03-10}} A simple test can differentiate struvite from glass.{{cite web | title = Struvite Crystals, the facts ... | date = 6 October 2023 | url = https://www.hambleton.gov.uk/download/downloads/id/1486/struvite_crystals_leaflet.pdf | publisher = Hambleton District Council }}

=Struvite kidney stones=

Struvite kidney stones are also known as triple phosphate stones (calcium magnesium ammonium phosphate), owing to the presence of carbonate apatite that precipitates to accompany struvite at high pH.{{cite journal|last1=Prywer|first1=Jolanta|last2=Kozanecki|first2=Marcin|last3=Mielniczek-Brzóska|first3=Ewa|last4=Torzewska|first4=Agnieszka|title=Solid Phases Precipitating in Artificial Urine in the Absence and Presence of Bacteria Proteus mirabilis—A Contribution to the Understanding of Infectious Urinary Stone Formation|journal=Crystals|volume=8|issue=4|year=2018|page=164 |id=Art. No. 164|doi=10.3390/cryst8040164|doi-access=free}}{{Citation |last1=Karki |first1=Niraj |title=Struvite and Triple Phosphate Renal Calculi |date=30 May 2023 |url=http://www.ncbi.nlm.nih.gov/books/NBK568783/ |work=StatPearls |access-date=21 June 2024|place=Treasure Island (FL) |publisher=StatPearls Publishing |pmid=33760542 |last2=Leslie |first2=Stephen W.}}{{Cite journal |last=Griffith |first=Donald P. |date=1978-05-01 |title=Struvite stones |journal=Kidney International |volume=13 |issue=5 |pages=372–382 |doi=10.1038/ki.1978.55 |issn=0085-2538|doi-access=free |pmid=351265 }} Struvite and carbonate apatite precipitate in alkaline urine, forming kidney stones. Struvite is the most common mineral found in urinary tract stones in dogs,{{cite web

|url=http://www.shilohshepherds.info/geneticTaskForce/Uroliths.htm

|title=Uroliths

|publisher=Shiloh Shepherd Genetic Task Force

|date=February 2014

|access-date=2014-02-07

|archive-date=2012-09-14

|archive-url=https://web.archive.org/web/20120914012227/http://www.shilohshepherds.info/geneticTaskForce/Uroliths.htm

|url-status=dead

}} and is found also in urinary tract stones of cats and humans. Struvite stones are potentiated by bacterial infection that hydrolyzes urea to ammonium and raises urine pH to neutral or alkaline values. Urea-splitting organisms include Proteus, Xanthomonas, Pseudomonas, Klebsiella, Staphylococcus, and Mycoplasma.{{citation needed|date=June 2024}}

Even in the absence of infection, accumulation of struvite crystals in the urinary bladder is a problem frequently seen in housecats, with symptoms including difficulty urinating (which may be mistaken for constipation) or blood in the urine (hematuria). The protein cauxin, a protein excreted in large amounts in cat urine that acts to produce a feline pheromone, has recently been found to cause nucleation of struvite crystals in a model system containing the ions necessary to form struvite. This may explain some of the excess struvite production in domestic cats.{{cite journal | vauthors = Matsumoto K, Funaba M | title = Factors affecting struvite (MgNH4PO4.6H2O) crystallization in feline urine | journal = Biochimica et Biophysica Acta | volume = 1780 | issue = 2 | pages = 233–9 | date = February 2008 | pmid = 17976920 | doi = 10.1016/j.bbagen.2007.09.013 }} In the past, surgery has been required to remove struvite uroliths in cats; today, special acidifying low magnesium diets may be used to dissolve sterile struvite stones.{{cite journal | vauthors = Smith BH, Stevenson AE, Markwell PJ | title = Urinary relative supersaturations of calcium oxalate and struvite in cats are influenced by diet | journal = The Journal of Nutrition | volume = 128 | issue = 12 Suppl | pages = 2763S–2764S | date = December 1998 | pmid = 9868260 | doi = 10.1093/jn/128.12.2763S | doi-access = free }}

Upper urinary tract stones that involve the renal pelvis and extend into at least two calyces are classified as staghorn calculi.{{citation needed|date=June 2024}} Although all types of urinary stones can potentially form staghorn calculi, approximately 75% are composed of a struvite-carbonate-apatite matrix.{{citation needed|date=June 2024}}

File:Struvite stones.JPG|Dog struvite bladder stones

File:Side view x-ray of large struvite stone in bladder of adult female bichon frise.jpg|X-ray showing large struvite in bladder (egg-shaped mass to left of femur)

File:Struvite crystals (urine) - Strüvit kristalleri (idrar) - 01.png|Struvite crystals in a human urine sample with a pH of 9. Abundant amorphous phosphate crystals, several squamous and non-squamous epithelial cells and a few leukocytes can also be observed.

File:Struvite crystals (urine) - Strüvit kristalleri (idrar) - 02.png|Another image from the same urine sample as with the image on the left.

File:Urine crystals comparison.png|Comparison of different types of urinary crystals.

=Struvite enteroliths=

Struvite is a common mineral found in enteroliths (intestinal concretions) in horses.{{cite journal | vauthors = Blue MG, Wittkopp RW | title = Clinical and structural features of equine enteroliths | journal = Journal of the American Veterinary Medical Association | volume = 179 | issue = 1 | pages = 79–82 | date = July 1981 | pmid = 7251465 }}

=Wastewater treatment=

Struvite can be a problem in sewage and waste water treatment, particularly after anaerobic digesters release ammonium and phosphate from waste material. Struvite can form a scale on lines and belts, in centrifuges and pumps, clog system pipes and other equipment including the anaerobic digester itself. Struvite, also referred to as MAP, forms when there is a mole to mole to mole ratio (1:1:1) of magnesium, ammonia and phosphate in the wastewater. The magnesium can be found in soil, seawater as well as drinking water. Ammonia is broken down from the urea in wastewater, and phosphate, which is found through food, soaps and detergents. These elements in place, struvite is more likely to form in a high pH environment, where there is higher conductivity, lower temperatures, and higher concentrations of magnesium, ammonia and phosphate. Recovery of phosphorus from wastestreams as struvite and recycling those nutrients into agriculture as fertilizer appears promising, particularly in agricultural manure and municipal waste water treatment plants.

File:Struvite. Clogged sewer pipes.jpg

Having struvite scale in a wastewater treatment system can lead to great inefficiency within the plant or operation due to clogging of the pipes, pumps and equipment. There have been a few options to solve this issue, including replacing the pipes, or using a hydro-jetter or a mechanical grinder to clear them. But many lines can be underground and either of these options implies considerable downtime and labor. Chemical cleaning is now predominately used to clear systems of struvite. Chemical cleaning products have been developed to remove and prevent struvite with minimal downtime. Even a chemical-free, electric method of removing and preventing struvite has been developed and tested successfully at wastewater treatment plants in the USA. The electronic sine wave it produces is sent through the water in the pipe and is therefore effective on underground piping as well.{{cite journal | vauthors = Burns RT, Moody LB, Walker FR | title = Laboratory and in-situ reductions of soluble phosphorus in swine waste slurries | journal = Environmental Technology | volume = 22 | issue = 11 | pages = 1273–8 | date = November 2001 | pmid = 11804348 | doi = 10.1080/09593332208618190 | bibcode = 2001EnvTe..22.1273B | s2cid = 25433506 | url = http://www.stormwater.ucf.edu/chemicaltreatment/documents/Burns%20et%20al.,%202001.pdf | archive-url = https://web.archive.org/web/20120327181220/http://www.stormwater.ucf.edu/chemicaltreatment/documents/Burns%20et%20al.,%202001.pdf | url-status = dead | archive-date = 2012-03-27 }}{{cite news |url=https://www.theglobeandmail.com/news/national/sewage-plant-carries-sweet-smell-of-phosphorus/article785525/ |title= Sewage plant carries sweet smell of phosphorus |first = Mark | last = Hume | name-list-style = vanc |newspaper=The Globe And Mail |access-date=2014-07-08}}{{cite news |url= https://vancouversun.com/news/metro/reclaiming-minerals-from-waste-water-to-make-fertilizer |title=Reclaiming minerals from waste water to make fertilizer |first = Brian | last = Morton | name-list-style = vanc |newspaper=The Vancouver Sun |access-date=2013-06-05}}

Uses

Use of struvite as an agricultural fertilizer was first described in 1857. It contains phosphorus and nitrogen, two of the three major plant macronutrients, with magnesium being a minor macronutrient as well. Struvite can be produced from urine by adjusting pH (often just by waiting for urease-producing bacteria to work) and adding magnesium.{{cite journal |last1=Wald |first1=Chelsea |title=The urine revolution: how recycling pee could help to save the world |journal=Nature |date=10 February 2022 |volume=602 |issue=7896 |pages=202–206 |doi=10.1038/d41586-022-00338-6|pmid=35140393 |bibcode=2022Natur.602..202W |s2cid=246700356 |doi-access= }} There is considerable interest in the utility of urine-derived struvite as a fertilizer in austere situations.{{cite thesis

|type=PhD

|last=Antonini

|first=Samantha

|date=2012

|title=Nutrient recovery from human urine: Treatment options and reuse potential

|publisher=University of Bonn, DE

|url=http://hss.ulb.uni-bonn.de/2013/3214/3214.pdf}}{{cite journal

|title=Nitrogen and Phosphorus Harvesting from Human Urine Using a Stripping, Absorption, and Precipitation Process.

|first1=Surendra K

|last1=Pradhan

|first2=Anna

|last2=Mikola