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Dosing AlkapHix® Magnesium Hydroxide Slurry

Now that you have an adequate storage tank for your AlkapHix® Magnesium Hydroxide Slurry, the next thing to consider is how it will be delivered to your system.

This is a follow up post to 'AlkapHix® Mg(OH)2 Storage Recommendation' entry. Quick access to the initial post can be found here:

Magnesium Hydroxide Dosing Location

Where you dose magnesium hydroxide slurry is dependent on a variety of factors.

These factors may include the following:

  • What is your overall goal for adding AlkapHix® Magnesium Hydroxide Slurry? Alkalinity, pH adjustment, odor control?

  • Do the above mentioned goals need to be accomplished throughout the entire plant or at a specific location?

Our recommended locations for dosing range based on individual plant needs, but are usually in areas containing agitated or moving water (wet wells, clarifiers, etc.). This helps move the magnesium hydroxide slurry as soon as it reaches your wastewater and prevents any unnecessary settling in your system.

Type of Pump For Dosing Magnesium Hydroxide Slurry

Garrison Minerals primarily uses peristaltic pumps to dose magnesium hydroxide slurry. The abrasive and viscous nature of Mg(OH)2 slurry makes peristaltic pumps an ideal candidate. Peristaltic pumps have a low maintenance cost and have efficient solids handling (Mg(OH)2 is typically 55-60% solids). Additionally, the rubber hose that allows slurry to be pushed through is abrasion resistant. Lastly, peristaltic pumps are very accurate and provide the same flow rate for each revolution.

Our preferred pumps for most applications are from Verderflex, part of the Verder Company. Verderflex manufactures peristaltic pumps, the ideal solution for difficult to pump liquids, abrasive, viscous or solids laden slurries, dosing chemicals and gently transferring fragile cell cultures. These range from small OEM tube pumps through precision dosing and dispensing pumps to the world’s largest high pressure hose pumps for very heavy duty applications.

Although other pumps can be used, peristaltic pumps have

shown most effective with magnesium hydroxide slurry.

Magnesium Hydroxide Pump Size

Depending on your plants desired goals, pumping rates can be achieved by sizing your system with the correct pump. Verderflex pumps offer a wide range of possible dosing volumes from 6 gallon per hour to over 4000 gallons per hour. Most of our clients are utilizing a Dura 5-7 pump (see data sheets below) which allow low volume dosing and an easy to maintain design.

Verderflex_Dura_D5 mkIV_INT_English_Datasheet
Download PDF • 261KB

Download PDF • 258KB

Other things to consider when choosing the correct pump size are length of dosing line and any elevation change from the storage tank to the dosing location. The amount of head pressure required to reach the dosing location needs to be considered when sizing a pump.

Turndown ratio should also be considered. Ideally, the desired dosing rate should be half of the maximum flow rate of the pump you choose. This gives you flexibility in the event you need to turn up/down the pump.

Magnesium Hydroxide Dosing Rate

Dosing rates of Mg(OH)2 slurry will vary depending upon the application. For example, if the application is pH and/or alkalinity control of wastewater, initial process conditions such as pH and influent flow rates need to be known. Additionally, the desired pH and/or alkalinity needs to be determined.

Additional Magnesium Hydroxide Slurry Dosing Considerations

  • Flushing Lines: Due to the viscous nature of magnesium hydroxide, lines are often clogged which can affect dosing accuracy. Garrison Minerals has automated flush cycles integrated into the dosing control systems which periodically clean the lines out. Also, Garrison Minerals has level telemetry which can provide feedback on actual dosing rates and notify our team in the event of rapid material loss due to hose ruptures or leaks.

  • Weather: Magnesium Hydroxide has a freezing point below 32°F and proper insulation of dosing lines should be considered.


As always, the Garrison Minerals' team is available for onsite or remote consultation on storage, dosing and use of our AlkapHix® Magnesium Hydroxide.

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