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Safety of common alkalis for wastewater treatment
Wastewater treatment presents a multitude of hazards, such as drowning; confined spaces; and exposure to hazardous chemicals or gases.
↑ Caustic skin burn caused by sodium hydroxide (caustic soda)
Hazardous chemicals can pose a significant risk to health and safety if not managed correctly. Municipal and industrial plant managers have specific duties under
increasingly stringent health and safety regulations to manage risks associated with using, handling and storing hazardous chemicals.
Being a plant manager at a wastewater treatment plant is an enormous responsibility with the need to answer to many high authorities such as the Environmental Protection Agency (EPA) or Occupational Health and Safety Administration (OSHA).
In this article, we have compared three common alkalis for wastewater treatment, and explained why IER magnesium hydroxide products are the safest and most-cost-effective options.
- Ca(OH)2 -> calcium hydroxide, lime slurry, hydrated lime
- NaOH -> sodium hydroxide, caustic soda
- Mg(OH)2 -> magnesium hydroxide, milk of magnesia
There are laws in each state or territory that set out the requirements for handling and transporting dangerous goods. Switching to safer chemical products means you are not only protecting the health and safety of your people, but you are also making cost savings for years to come.
Lime slurry
Ca(OH)₂
Lime slurry is an odorless, low viscosity suspension of calcium hydroxide in water. It is commonly used for municipal water treatment, pH adjustment, metals precipitation and odor control.
Lime slurry is not combustible or flammable but it can react violently with acids and combustible materials.
Prolonged and repeated skin contact with lime slurry can cause irritant dermatitis or alkaline burns.
If a large volume of lime dust (or slurry) is splashed into the eye, alkaline burns can cause permanent damage.
HAZARD(S) IDENTIFICATION
Classification of the substance or mixture:
Irritant
• Skin irritation, category 2
• Specific target organ toxicity following single exposure, category 3
Corrosive
• Serious eye damage, category 1
Signal word: Danger
Caustic soda
NaOH
Caustic soda (sodium hydroxide) is one of the most common alkalis used to provide alkalinity in wastewater treatment.
Caustic soda is very corrosive. At high concentrations, it is extremely hazardous to handle and several precautious must be in place to safely use it in the treatment process.
It can cause irritation to the eyes, skin, and mucous membrane, allergic reactions, eye and skin burns and temporary loss of hair.
Workers may be significantly harmed from exposure to sodium hydroxide.
HAZARD(S) IDENTIFICATION
Classification of the substance or mixture:
Irritant
• Skin irritation, , category 1B
Corrosive
• Serious eye damage, category 1
• Corrosive to metals, category 1
Signal word: Danger
Magnesium hydroxide
Mg(OH)2
Magnesium hydroxide is increasingly used as a substitute for caustic soda and lime. Not only is it less expensive but it is also the safest and most gentle-to-use alkaline chemical treatment available on the market for pH control applications.
Though magnesium hydroxide is much stronger for supplying OH- buffering, it is dramatically safer for operators to handle and for treating wastewater microorganisms. Magnesium hydroxide dissolves only when it encounters acidity, unlike NaOH which immediately releases OH- to burn operator’s skin and eyes. As a result no extra PPE or secondary containment is needed to handle magnesium hydroxide, thus reducing operating cost.
Not only is it safe, but magnesium hydroxide is also recognized as a skin-care essential.
HAZARD(S) IDENTIFICATION
Classification of the substance or mixture:
Not classified under GHS.
• Non-hazardous
• Non-corrosive
Magnesium hydroxide success stories
September 11, 2020 \ ACTI-Mag \ 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
October 07, 2020 \ ACTI-Mag \ Improving the Sustainability of Water Treatment \ Food & Beverage
Replacing caustic soda with magnesium hydroxide for metal ion precipitation
A microelectronics manufacturer in the Pacific Northwest was using a complex system of chemical additions in order to effectively remove
November 10, 2020 \ 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
AMALGAM 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 moreMagnesium Hydroxide – safe and cost effective alternative to sodium hydroxide / caustic soda
Disclaimer: This experiment was not performed in a controlled lab environment and is routinely performed safely as a benchtop demonstration to show that magnesium hydroxide provides more CaCO3 equivalent alkalinity on an equal weight basis when compared to caustic soda, which means less chemical consumption and can result in significant cost savings. Magnesium hydroxide is non-hazardous and non-corrosive which makes handling safer and easier.
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