Techniques for treating waste water by adding a valent ion, such as CaO/CaCO3,
which depends on the pH value of the waste water, to reduce the chemical oxygen
demand (COD) are provided. Organic acid intermediates formed from the oxidization
of organics with ozone will chelate with valent ions dissolved in water and precipitate
from the waste water, so as to reduce the amount of ozone consumed and save cost.
The method of the present invention is preferably conducted by adjusting the pH
value of the reaction and/or adding hydrogen peroxide.
