Struvite 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 platey 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. They also are potentiated by a specific urinary
protein, in domestic cats. Name
Struvite was first described from medieval sewer systems in Hamburg
Germany in 1845 and named for geographer and geologist Heinrich Christian
Gottfried von Struve. Occurrence
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. Use of struvite as an agricultural
fertilizer was in fact first described in 1857.
= Struvite kidney stones= Struvite precipitates in alkaline urine,
forming stones. Struvite is the most common mineral found in urinary tract
stones in dogs, 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, Pseudomonas, Klebsiella,
Staphylococcus, and Mycoplasma. 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 or blood
in the urine. 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. 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.
Upper urinary tract stones that involve the renal pelvis and extend into at
least 2 calyces are classified as staghorn calculi. Although all types of
urinary stones can potentially form staghorn calculi, approximately 75% are
composed of a struvite-carbonate-apatite matrix.
= Struvite enteroliths= Struvite is a common mineral found in
enteroliths in horses. = 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 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.
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.
Replacing the pipes, using a hydro-jetter or a mechanical grinder,
but many lines can be underground and have to consider the great amount of
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. References
External links Website of the European Phosphorus
Platform about Phosphorus Recovery