Struvite Precipitation and Struvite Formation in Wastewater

Struvite in pipe and bend

Struvite in heat exchanger

Struvite on outside of centrifuge before/after treatment

Struvite Precipitation and Formation

Struvite formation is written by the following chemical formula: Mg2+ + NH4+ PO4-3 + 6H2O → NH4MgPO4•6H2O (crystal form). The formula tells us that struvite crystals are created when magnesium, ammonia, and phosphate combine in water in a mole to mole to mole ratio of 1:1:1.   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. Struvite Remover STSR can remove the scale buildup if it has already formed, and Struvite Preventer STSP  prevents struvite precipitation and struvite formation thereafter.

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:

• Magnesium, a major ingredient and contributor of hard water
• 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. If left untreated, these crystals turn into rock like formations and heavily restrict flow through pipes and clogs equipment.

Depending upon the wastewater feedstock of the WWTP, struvite formation can be predicted, and pre-treatment with an effective chemical formula can help you remove, prevent and control struvite.

If you have questions about wastewater struvite formation, send us a message, and we’ll get back to you quickly!  We’ll help assess the severity of your issues and recommend either Struvite Preventer STSP or Struvite Remover STSR to remove and control struvite.

Where is Struvite Precipitation an Issue?

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
• Wastewater Sludge transfer line
• Plant Centrifuges
• Rollers of the Belt Press

Rough surface areas are one of the first areas to look for struvite formation. When struvite crystal rock is not 100% removed from the different surfaces, the remaining rough edges will form struvite more quickly.

What Are the Tell-Tale Signs of Struvite Formation?

• High pH is a warning for the potential struvite formation
• High conductivity increases the potential for struvite formation
• Low temperatures foster the environment for struvite formation
• Higher concentrations of ammonium, phosphate, and magnesium enable struvite precipitation

Effective Solutions for Struvite Removal and Prevention

We offer two effective struvite removal chemical formulas.

Struvite Remover STSR: Our typical recommendation is to use Struvite Remover STSR to clear the struvite and remove any potential growth sites. From there, many customers opt to do removal maintenance or removal/cleaning as needed.

Struvite Preventer STSP: The other option is to use the Struvite Remover STSR or Struvite Preventer STSP (added polymer) and dose between 30-90 ppm (on average). Dosing helps prevent struvite scale buildup by lowering the pH and dispersing/inhibiting the formation of struvite.

Ask us a question to learn more about struvite formation in wastewater and how to use our chemical formulas removal and prevention.

Struvite Removal Wastewater Videos and Studies:

Struvite Remover Egg Video Demo

Struvite Remover Centrifuge Case Study

Struvite Remover Foam Application