Patent ID: 7611638

Claim:
A method to purify polluted water containing a first concentration of at least one difficultly biodegradable or non-biodegradable organic compound, in which method the above mentioned organic compound is oxidized by bringing the polluted water into contact with at least one ozone containing gas, characterized in that in a first treatment step part of the above mentioned organic compound present in the polluted water is oxidized by bringing said polluted water into contact with the above mentioned ozone containing gas in such a way that the first concentration of said organic compound is reduced to a second concentration, the entire amount of said organic compound present in the polluted water being reacted with ozone for a total of at least 20 minutes in said first treatment step, after the first treatment step the second concentration of said organic compound is reduced by dilution with an aqueous liquid to a third concentration which is at most two thirds of the second concentration, and in a second treatment step a further part of the above mentioned organic compound present in the polluted water is oxidized by bringing the diluted polluted water into contact with the above mentioned ozone containing gas in such a way that the third concentration of said organic compound is reduced to a fourth concentration, the entire amount of said organic compound present in the diluted polluted water being reacted with ozone for a total of at least 20 minutes in said second treatment step.