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Staying Neutral: A Case for Magnesium Hydroxide in Wastewater

Many industries, such as pulp/paper, metal and petrochemical, have several processes that result in the production of wastewater that must be treated prior to its release into the local sewage collection system. This treatment neutralizes the acidic wastewater byproduct and any dangerous materials contained therein.

Magnesium Hydroxide as an Alternative to Caustic Soda and Lime

Magnesium Hydroxide is a safe and cost efficient alternative in wastewater treatment
Wastewater Treatment

In the case of wastewater neutralization and containment, magnesium hydroxide has proven to be a safer and more cost-effective solution as compared to caustic soda (sodium hydroxide) and lime (calcium hydroxide). Though less commonly used as an alkalinity source, numerous studies indicate that magnesium hydroxide has consistently improved the performance of process-based equipment, and its use results in a superior end-product.

Safer Use

Wastewater Treatment Plant
Wastewater Treatment Plant

Magnesium hydroxide is classified as a non-hazardous chemical and requires minimal precautionary containment and handling protocol. While caustic soda and lime can cause chemical burns, poisoning and other harmful side effects, magnesium hydroxide is included in numerous over-the-counter pharmaceutical products fit for human consumption.

Due to its non-corrosive nature, magnesium hydroxide can be cleaned and disposed of quickly and easily in the event of excess or spillage without impacting the surrounding environment. Magnesium hydroxide has a lower heat of reaction, allowing it to be stored safely in most industrial areas, and does not have a negative reaction when combined with water as a rinsing agent on hands, floors or other surfaces. Overall, the use of magnesium hydroxide as an alternative to sodium hydroxide and lime limits hazardous chemicals on site and can improve workplace and employee safety.

Lower Cost

Historically, magnesium hydroxide has had a lower pound-for-pound cost in the chemical marketplace than sodium hydroxide with greater overall price stability, allowing for more accurate allocation of financial resources for large projects and industrial initiatives. Magnesium hydroxide also functions more effectively than caustic soda and lime in alkalinity adjustment, requiring less of the ingredient to accomplish the same neutralization.

This table shows the comparisons between magnesium hydroxide vs caustic soda and lime.

Experts estimate thousands of dollars of savings stemming both from the lower raw material cost and smaller amounts required for each application as well as the reduced need for supplementary components such as polymers and acids for additional pH adjustment post-treatment.

Improved End-Product and Equipment Performance

Even in slurry form, magnesium hydroxide has a lower solubility in water than caustic soda and lime, reducing instances of overdosing in wastewater treatment while still consistently producing better water quality prior to dispersal into municipal water systems. In addition to greater pH control, magnesium hydroxide can significantly reduce sludge volume compared to other alkalis.

This image shows the resulting sludge created after acidic water from a wastewater treatment plant was treated with 20% solutions of caustic soda, magnesium hydroxide, and lime.
Sludge comparisons

In field tests, the use of magnesium hydroxide instead of caustic soda and lime results in increased sludge density and optimized filtration. Thicker, heavier sludge is easier to dewater and less expensive to remove and haul. When coupled with improved pH control and reduced processing time, this can extend the lifetime of the filtration, treatment and logistics equipment.


One of the more innovative applications of industrial magnesium hydroxide is its use in acid mine mitigation
Acid Mine Drainage

One of the more innovative applications of industrial magnesium hydroxide is its use in acid mine mitigation. Hard-rock mining sites are often left abandoned, and without proper maintenance, they begin to freely discharge highly acidic wastewater. There are many sites both globally and in the United States that leak wastewater containing dangerous levels of dissolved minerals. Though lime is traditionally used to mitigate these minerals, magnesium hydroxide can treat the wastewater, raising pH and encouraging precipitation of the metals it contains.


Contact Garrison Minerals to discuss your unique wastewater treatment requirements or to receive a sample of magnesium hydroxide.



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