Sodium Sulphate Use in Water Treatment

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Sodium metabisulphite and other oxygen scavengers are also used in the ultrapure water industry to remove dissolved oxygen, chlorine and other oxidizing agents.

Are you referring to a municipal water treatment plant or a bottled water plant?

Probably a municipal water treatment plant or in waste water treatment. I understand the above chemicals but it is sodium sulfate that has been used and I don't understand how or why.

What country are you in?

Canada

Where did you get the information that this was being added to your water. You do realize that this is naturally occurring, and may just be present in the raw water supply.

You are misunderstanding me. We are natural producer of sodium sulphate and have sold product to water treatment plants although small quantities. I wanted to know what it is used for.

Surely a telephone call to the Customer would be quicker than waiting around on CR4?

I would assume they use it in their labs, not in the actual treatment of the potable water.

I too live in Ontario, Canada and have worked on and inspected water treatment plants. Sodium is one of those things you don't really want to add to a water supply. It has implications for people with renal or hypertension problems. Warnings for users are given when the level exceeds 22 mg/L and usually involves sophisticated removal over 200 mg/L . At that level it may impart a salty taste. Google sodium in water supplies or check drinking water criteria for Ontario, Canada, EPA, or WHO and you will find they are all saying the same thing. Sulphate at levels greater than 500 mg/L will impart a cathartic effect on users (Montezuma's revenge). Why would anyone want to add sodium sulphate?

Aluminum sulphate (alum) is used as a coagulant agent in surface water plants. It is precipitated along with fine particles in the early stage of treatment before/during filtration. Lime softening can result in sodium sulphate as a byproduct but is not added to the water. This occurs when the hardness is considered non carbonate or permanent hardness. I know of no process that adds sodium sulphate. I would ask the operators of the plant to explain.

If you are shipping the mineral, I must assume you are correct in the naming of the product. It may have side uses in the manufacture of another product such as soda ash. Or maybe someone has discovered how to make laundry soap with sodium percarbonate and sodium sulphate as the filler. Just a wild guess.

I am wondering if it might be used to regenerate ion exchange media, instead of sodium chloride?

I have never heard of sodium sulphate being used in water to regenerate softeners. I think it may be because of residual sulphate ion may be adverse to taste and its cathartic affect. Also sodium sulphate has a low solubility at temperatures less than 20 degrees C. Sodium chloride has a more uniform solubility over wide temperature changes. You would have to use a considerable more amount of sodium sulphate than sodium chloride salts. I am guessing a bit.

I suppose you know the compound that you sell ... but sodium sulphite has been used in boiler feedwater to eliminate oxygen and carbon dioxide...?