Struvite precipitation causes crystal formation issues in several areas of a wastewater treatment plant, including:
- Anaerobic digesters
- Places where there is high kinetic energy (high turbulence)
- Pipe connections – especially elbows
- Pumps are a prime location
- Valves
- Aeration assembly
- Internal pumping components
- Plant overflow box of the anaerobic digester
- Plant Centrifuges
How does struvite form in wastewater?
How Does Struvite Form in Wastewater? Struvite formation most frequently occurs in wastewater treatment plants that have anaerobic digesters, but can other form in other operations and industries. Three things contribute to struvite precipitation and crystal formation:
What factors affect struvite precipitation in wastewater treatment plants?
WWTP’s wastewater temperature and its pH are also contributing factors to struvite precipitation. The higher the wastewater pH, the more likely the mole to mole to mole balance will be affected, and the formation of struvite crystals will occur. Utilizing a struvite control product interrupts this 1:1:1 mole to mole ratio.
What causes struvite crystals to form?
Ammonia, a byproduct of urea and urine Phosphate, which is a major element in the organic matter processed at the plant When magnesium, ammonia, and phosphate come together in the plant’s piping system, it precipitates and causes struvite crystals to form.
What are the impurities that can inhibit the growth of struvite?
This reaction can be inhibited by impurities that may precipitate in solution. Due to dissolved species, the net effect of other species in solution is a reduction in the precipitation potential of struvite (calcium ions) ( Le Corre et al., 2009 ). This compound can affect the growth rate of struvite crystals ( Jones, 2002a,b ).
How do you get rid of struvite?
Struvite removal products work by injecting a specific concentration of the solution into a wastewater system and using a pump to circulate the struvite remover through the system. Other uses for struvite removal chemicals include soaks, low-pressure spray or foaming applications.
What is struvite precipitation?
Struvite precipitation is a technology that is used mainly for P recovery. Struvite is a crystalline mineral composed of equimolar concentrations of magnesium (Mg), ammonium (NH4) and phosphate (PO4) with the chemical formula MgNH4PO4*6H2O.
What are the chemical constituents of struvite?
The scientific community defines struvite as a phosphate mineral crystal, struvite composition is of magnesium, ammonia and phosphate forms in water. The struvite chemical formula or struvite formula is chemically written as NH4MgPO4•6H2O.
Is struvite soluble in water?
Struvite has low solubility in water, with a solubility constant of 10−13.26 (Ohlinger et al., 1998). In contrast, it is readily soluble in acidic environments: 0.033 g 100−1 mL−1 in 0.001 M HCl and 0.178 g 100−1 mL−1 in 0.01 M HCl at 25°C (Le Corre et al., 2009).
What causes struvite?
Struvite stones are caused by an upper urinary tract infection (UTI) from bacteria. Ammonia produced as a waste product by the bacteria can make the urine less acidic (or more alkaline). Struvite stones form when the urine becomes more alkaline.
What pH does struvite form in?
The ideal pH range for struvite precipitation could occur at a wide pH range of 7.0 to 11.5. However, the suitable pH range for struvite formation is 8 to 9.5 [30]; this is consistent with many other reports [17, 29]. Interfering ions in solution also affect the pH range for struvite precipitation and nutrient removal.
What bacteria causes struvite stones?
Struvite stones are formed by urinary tract infection with urease producing bacteria that splits urea to ammonium, and increases urine pH to neutral or alkaline values. Organisms splitting urea are Proteus, Pseudomonas, Klebsiella, Staphylococcus, and Mycoplasma.
Is triple phosphate the same as struvite?
Struvite stones are also known as triple-phosphate (3 cations associated with 1 anion), infection (or infection-induced), phosphatic, and urease stones. Other, less common staghorn calculi can be composed of mixtures of calcium oxalate and calcium phosphate.
What is struvite fertilizer?
Struvite is a phosphate fertilizer, although it contains a significant amount of nitrogen and magnesium, and it is an effective alternative source of rock phosphate to maintain the agricultural production system.
How fast do struvite crystals form?
Struvite stones are one of the most common causes of staghorn calculi, which are known to potentially form rapidly, in the order of 4–6 weeks.
What is the solubility of struvite?
The solubility of struvite determined in deionized water was found to be 169.2 (+/-4.3) mg l(-1) at 25 degrees C, with the maximum value of 212.7 (+/-3.8) mg l(-1) at 35 degrees C.
What is the meaning of struvite?
Struvite is a mineral that's produced by bacteria in your urinary tract. About 10 to 15 percent of all kidney stones are made from struvite. This type of stone is more common in women than in men. Struvite stones can grow very quickly. Eventually, they can block your kidney, ureter, or bladder and damage your kidney.
What is struvite in wastewater treatment?
Struvite and Wastewater Treatment Plants. Struvite is a mineral precipitate that causes major problems in Waste Water Treatment Plants (WWTP) in the United States, as well as WWTP’s throughout the world. Struvite initially precipitates in crystalline form. When Struvite is left untreated, its initial brittle crystal precipitate turns ...
What is struvite in centrifuges?
Struvite is known to cause problems in the areas of anaerobic digesters and centrifuges. Struvite formation can cause problems for the pumps pumping digested biosolids through the dewatering and Struvite scale has been known to form on WWTP centrifuges, again interfering with the dewatering process.
What happens when you leave struvite untreated?
When Struvite is left untreated, its initial brittle crystal precipitate turns to a solid scale and ultimately to a concrete-like hard rock formation. When Struvite forms its rock formation in pipes, pumps, centrifuges, anaerobic digesters and other parts of a waste water treatment plant, it significantly slows the process plant down ...
What are the three components of struvite?
The three chemical components of Struvite are magnesium, ammonia, and phosphorus, also known as MAP for short. The chemical formula for the formation of struvite is Mg 2 + NH 4 + PO 4-3 + 6H 2 O -> NH 4 MgPO 4 - 6H 2 O, which tells us that when magnesium, ammonia, and phosphate combine in water in a mole to mole to mole ratio of 1:1:1 ...
What is activated sludge?
The majority of wastewater treatment plants in the United States use an activated sludge process to treat their wastewater. Their primary sludge and activated waste sludges are combined and gravity thickened before they are sent to the WWTP’s anaerobic digester for processing.
What is struvite in water?
The scientific community defines struvite as a phosphate mineral crystal, struvite composition is of magnesium, ammonia and phosphate forms in water.
What is the composition of struvite?
Struvite is also referred to as MAP by the wastewater industry, which stands for the nutrients of struvite composition: magnesium, ammonia, phosphate compound, it forms when there is a mole to mole to mole ratio (1:1:1). The ammonia is from the urea in wastewater, phosphate is found through food, soaps, and detergents.
What is the color of struvite?
Struvite Formation Issues. Struvite can also be known as a form of scale or rock crystal formations and will be found in varying colors from white to yellow to brown, depending upon the MAP content in the water.
What are the factors that affect the formation of struvite crystals?
The other important factors, besides pH, which affect the formation of this crystal, are (1) molar ratios of each reactant, (2) temperature, and (3) the presence of spectator ions ( Liu et al., 2013 ). Precipitating struvite crystal should be done in a dedicated reactor, instead of allowing its instantaneous formation.
What ions affect the precipitation of struvite?
Similar to Ca ions, the presence of F ions affects the precipitation of struvite as well. Fluoride ions will compete with NH 4 +, inhibiting the struvite crystal precipitation. Moreover, fluoride ions will compete with HPO 4 2 − to form MgF 2.
What ions can intervene in struvite formation?
Calcium ions can intervene struvite formation by competing for phosphate ions or by blocking the active growth site ( Le Corre et al., 2005 ). The formation of struvite crystals consists of two stages: nucleation (crystal birth) and crystal growth until equilibrium ( Jones, 2002a,b ).
What is struvite powder?
Pure struvite is generally a white or transparent fine powder, but the morphology of struvite particles differs under various formation conditions and includes a needle-like shape ( Fig. 26.1 ), a cube-like shape, and irregular shapes ( Zhang et al., 2009 ).
What are the physical and chemical properties of K-struvite?
The physical and chemical properties of K-struvite are similar to those of struvite, including the needle-like crystal shape and transparent to whitish appearance ( Graeser et al., 2008 ).
When was Phase IV of the Waste Management System built?
The Phase IV landfill was constructed in late 2000, just for a landfill with 4900 t/d. Phase V was used in 2010, including a refuse landfill, an incineration plant with 3000 and 6000 t/d together, a hazardous wastes landfill, and a dewatered sewage sludge landfill.
Is struvite a phosphate fertilizer?
Alternatively, struvite can be used as a phosphate fertilizer to provide sustainable phosphor us usage. Struvite is a crystalline substance consisting of magnesium, ammonium, and phosphorus in equal molar concentrations (MgNH4 PO 4) ( Munir et al., 2017 ). Struvite forms orthorhombic (straight prisms with a rectangular base) crystals in the ratio of 1:1:1 among the magnesium, ammonium, and phosphate (Eq. 1 ).