Removal of arsenic

Removal of arsenic in an automatic arsenic filter in a Danish waterworks.

Arsenic is a natural element and related to certain geochemical environments. Arsenic is found in two forms, As(III) and As(V), of which As(III) is more poisonous, harder to remove from the water, and more widespread.

WHO has assessed that arsenic forms a health risk when consumed and it is thought to be the reason for skin cancer, among other things.  

The increased authority demands (lowering of the threshold limiting value from 50 to 5 µg/l when leaving the waterworks) affect many water supplies for which it will be necessary to carry out a special water treatment in order to keep the quality
requirements.  

Possible solutions

If the limit value for arsenic in the drinking water is exceeded, a sensible and inexpensive solution is to optimize the water treatment. Arsenic is adhesive to iron and is filtered off with iron. In places without sufficient iron in the raw water for this process, the iron content of the water can be increased by adding iron chloride or iron sulphate and using iron oxide granulates as filter material. 

This is an inexpensive solution to the arsenic problem and the method is used when there are small exceedings of the permitted arsenic content. However, this calls for sufficient filter capacity for this extra iron content.   

Alternatively, arsenic can be reduced by adsorption filtration in a pressure filter with a special filter material based on iron hydroxide. Dosing with either iron chloride or iron sulphate and the use of iron oxide granulate as filter material are both water treatment solutions that is gaining a footing. EUROWATER offers both solutions and the choice depends on the actual conditions.

If you would like more information on removal of arsenic, references, installation and operational conditions, and prices, please contact your local office.

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