There are Calix offices and partners all across the globe.

To find one near you, and visit our regional websites - select your region below.

Magnesium hydroxide as a substitute for caustic soda and lime

Improving the Sustainability of Water Treatment

Ralph Lloyd-Smith \ June 27, 2020

Magnesium hydroxide is the least expensive and most powerful alkaline chemical treatment available on the market for pH control applications. At the same time, it is by far the safest and most gentle to use. By replacing the sodium in caustic soda or soda ash with the magnesium ion, the treated wastewater is transformed from having to deal with a detrimental form of salinity (Na+) to the benefit of a macronutrient (Mg2+). Mg2+ is the core element in chlorophyll that drives photosynthesis.

Controlling the pH of industrial wastewater is important to prevent harm to the wastewater collection/transmittance infrastructure by minimising the corrosive effect of gaseous acidic contaminants (such as H2S) or, if applied to farm land, to prevent harm to the irrigated crops. Once the wastewater enters a treatment plant, the control pf pH is essential to optimise aerobic and anaerobic microorganism activity. In this article, we explore three ways magnesium hydroxide has cost-effectively replaced caustic soda and lime in different wastewater treatment applications.

1) Safety is the driver

Caustic soda and lime are historically the two most industrially available choices for wastewater pH control, however, both have significant limitations. Caustic freezes at 15ºC to plug feed lines and is extremely hazardous to handle, causing severe chemical burns.

Lime is even better known for the plugging of feed lines, as well as wastewater transport lines due to the formation of calcium mineral scale, and over-exposure can also result in severe burns to operators’ hands.

2) Replacing caustic soda in a membrane bioreactor system

The membrane bioreactor (MBR) process allows for a much smaller footprint as compared to conventional wastewater treatment, due to the replacement of large clarifier basins with membranes. Recent innovations in membrane technology have reduced the cost of MBR systems, making them a more attractive choice in the market.

 

 

As the MBR process is microbiologically driven, the control of pH is critical, and there is no alkaline additive that is safer both for operators and microorganisms than magnesium hydroxide.

3) Improved solids settling

The wastewater stream for many industrial processes can be quite unpredictable and inconsistent. Dramatic changes in pH can have adverse effects on the settleability of suspended solids. To stabilise the pH, the wastewater is commonly neutralised with alkalis. The nature of the alkali selected can have a dramatic impact on the ability to settle suspended solids. Caustic soda typically provides no settling benefit and often results in gelatinous sludge that does not dewater easily. With lime (Ca(OH)2) there is typically a significant increase in sludge volume due to the formation of calcium minerals, like calcium carbonate (CaCO3).

In contrast, magnesium hydroxide assists with solids settling, providing a more compact sludge with a boost in alkaline pH to improve subsequent secondary treatment and anaerobic digestion performance.

ACTI-Mag for Caustic replacement

A safe and cost effective alternative to the use of sodium hydroxide (caustic soda) for wastewater alkalinity and pH adjustment.

Find out more about ACTI-Mag
Improving the Sustainability of Water Treatment \ Food & Beverage
Caustic soda replacement at a fruit processing plant

A food processing plant in the Pacific Northwest that manufactures fruit products was generating acidic wastewater and looking for a

Improving the Sustainability of Water Treatment \ Food & Beverage
Converting from caustic to magnesium hydroxide

Spokane County Regional Water Reclamation Facility, operated by Jacobs, processes 8 million gallons per day (mgd) of wastewater collected from

Improving the Sustainability of Water Treatment \ Food & Beverage
An innovative mixed-metal hydroxide for pH control and wastewater microorganism activity

An innovative mixed-metal hydroxide for pH control and wastewater microorganism activity at a meat processing facility in the United-States.

LATEST NEWS

December 20, 2020 \ Calix Global Challenges
News Issue December 2020

Welcome to Issue Number 37 of the Calix Newsletter. “In our last Newsletter for 2020, we reflect on our significant

December 20, 2020 \ Calix Global Challenges
Calix joins the United Nations Global Compact

The United Nations Global Compact is the world’s largest corporate sustainability initiative, driven by the realisation that companies play a

December 17, 2020 \ Calix Global Challenges
pH & Alkalinity – How are they related?

The relationship between pH & alkalinity is intimately connected with the chemistry of the aqueous bicarbonate equilibrium system. 

CALIX NEWSLETTER
Get the latest news, customer stories, and R&D updates delivered to your inbox.

  • This field is for validation purposes and should be left unchanged.

Join the conversation

#marsisforquitters

Calix supports @wateraid programs, to facilitate access to safe water, sanitation and hygiene in the world’s poorest and most marginalised communities.
This partnership aligns with our purpose “We Solve Global Challenges” and our core value of “positive impact”

Safe to work with, magnesium hydroxide is a slow-release #alkali which naturally buffers at pH 8.5 - 9, making it almost impossible to lose control of pH in the #wastewater treatment process, as can happen with caustic soda @FoodProcessAU
Find out more: https://buff.ly/3qfDeW5