Magnesium Oxide Media

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Granular Magnesium Oxide Mineral

Utilized to raise pH of acidic water (pH 4.0 to 5.5).  A granular magnesium oxide mineral, specifically designed for potable and non-potable water treatment and certified to NSF Standard 60 for Drinking Water Chemicals.


  • CAS Number: 1309-48-4
  • Molecular Formula: MgO
  • Molecular Weight: 40.3044 g/mol

Physical and Chemical Properties:

  • Color: Grayish White
  • Density: 75 lbs./cu. ft.
  • Effective Size: 1.27 mm
  • Uniformity Coefficient: 1.48
  • Active Material: 84-90%
  • Composition: MgO 97% minimum
  • NSF Certified


50 lb. bag

pH Adjustment  at Chlorinated Sites

Bacteria are very sensitive to low pH.  The optimal pH for bioremediation is between 6 and 8.5.  Most microbial processes associated with the breakdown of electron donors tend to lower pH by the production of acidic fermentation products such as carbon dioxide and volatile fatty acids.  Conversely, some microbial processes such as the reduction of sulfur stimulated by an electron donor can increase pH.

Sites with a groundwater pH below 6.0 prior to electron donor injection are likely to produce pH values well below 6.0 after the addition of any electron donor.  Magnesium oxide is the oxide salt of magnesium.  It is commonly used as an antacid or, laxative and to raise pH of acidic waters with a pH 4.0 to 5.5.  Solid magnesium oxide reacts with water to form solid magnesium hydroxide, Mg(OH)2, which reacts chemically to neutralize or buffer acids.

Reaction with water:

Mg(OH)2(s) ⇌ Mg2+(aq) + 2OH(aq)

Reaction with acids:


The chemistry of Mg(OH)2 (Milk of Magnesia) has advantages as a pH adjustment agent with its two hydroxides that include:

  • Long-term pH adjustment
  • Minimized risk of overshooting pH

If you need assistance in estimating the dosage to adjust the pH, we suggestion performing an acidity titration on groundwater and soil slurries to evaluate the amount of alkalinity needed to reach the optimal pH range.    Often clients only want to perform this titration on groundwater only.  Most of the buffer capacity is in the solids and we would not recommend a titration on groundwater only.  SiREM is a company that can assist with titration testing.