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The mystery of how Struvite is formed: How does it accumulate so quickly in urine?
Struvite (magnesium ammonium phosphate) is a phosphate mineral with the chemical formula: NH4MgPO4·6H2O. This mineral crystallizes in the orthorhombic crystal system. Its color ranges from white to light yellow or brown-white, and the crystal form is mostly pyramidal or flake-shaped. It is a softer mineral, with a Moss hardness of 1.5 to 2, and has a low specific gravity, about 1.7. Struvite has low solubility under neutral and alkaline conditions, but is easily soluble in acidic environments.
The formation of Struvite crystals is closely related to the types of ammonia-producing bacteria in urine.
Struvite forms in urine primarily because the urine is infected with ammonia-producing microorganisms. These bacteria hydrolyze urea into ammonia, which in turn increases the pH of the urine, making it more alkaline. In such an environment, struvite and its associated precipitated calcium carbonate phosphate can easily form kidney stones.
Causes of Struvite kidney stones
Struvite kidney stones are also called triple phosphate stones, so named because they contain calcium carbonate phosphate. These stones are primarily found in the urethra of dogs, but are occasionally found in cats and humans. When the pH in urine rises, precipitation of struvite and calcium carbonate phosphate can lead to the formation of kidney stones. Relevant urea-hydrolyzing microorganisms include proteases, Xanthomonas, Pseudomonas aeruginosa, Klebsiella and Staphylococcus aureus.
Cauxin, a protein found in cat urine, was found to possibly promote the formation of struvite crystals.
Even in the absence of bacterial infection, cats can accumulate struvite crystals in their urine, which can cause symptoms such as difficulty urinating or blood in the urine. In the past, struvite stones in cats often required surgical removal, but now a specialized acidified low-magnesium diet can effectively dissolve sterile struvite stones.
Struvite’s presence in other environments
Struvite is mainly formed in nature in environments where organic matter decomposes, such as guano deposits, basalt caves and swamps. This situation also occurs in the gall bladders of people infected with urease-producing bacteria and in wastewater treatment.
During the wastewater treatment process, struvite will form scale and affect the operating efficiency of the system.
In sewage treatment, struvite will cause equipment blockage and affect treatment efficiency. To solve this problem, operators can choose to replace the pipes or use a hydrocleaner or mechanical grinder to clean them. Several chemical cleaning products have been developed to remove and prevent struvite formation, reducing system downtime. Additionally, there are chemical-free, electrokinetic methods that have been successfully tested in wastewater treatment plants in the United States.
Agricultural applications of Struvite
The use of struvite as an agricultural fertilizer dates back to 1857. Struvite contains phosphorus and nitrogen, two major plant essential nutrients, and magnesium is also a trace element. This gives struvite good potential for use in agriculture, especially in situations of scarce resources.
Struvite can be produced from urine after adjusting the urine pH and adding magnesium.
Due to its rich nutritional content, the recycling of struvite looks quite promising in agriculture. This not only reduces waste emissions but also helps improve soil quality. However, further research and testing are still needed to fully understand the effectiveness of struvite in actual agricultural operations.
Overall, the formation and aggregation of struvite is driven by the interaction of multiple environmental factors and biological factors. This raises a thought-provoking question: How should we effectively manage and utilize this micro-mineral in contemporary society to cope with increasingly severe environmental challenges?
