To prevent the generation of a residual buffering agent in waste water and the formation of a nitrogen compound by removing the sulfur pollution and the like in the desulfurization stage, and removing the nitrate pollution and the like and the buffering agent in the biological denitrification stage.
Desulfurization is carried out by adding a desulfurization agent containing lime or lime stone suspension and a buffering agent such as formic acid (desulfurization stage). Then biological denitrification is carried out by microbes grown by the residual buffering agent in the waste water after the desulfurization stage, and the waste water is cleaned (biological denitrification stage). In the desulfurization stage, the sulfur pollution such as SO2 and the like is turned into a calcium sulfate hydrate by the desulfurizing agent, precipitated and removed. The nitrate pollution and the residual buffering agent in the waste water are removed from the waste water by cleaning in the biological denitrification stage. The merit of desulfurization modified by adding the buffering agent in the above constitution is not offset by the continuation of presence of the buffering agent in the waste water, and utilized successively as a food source for the biological denitrification. Also the generation of residual buffering agent and the formation of a nitrogen compound in the waste water are prevented by cleaning and removing the buffering agent.
POTMA ANDREA AGATHA (NL)
ENOCH GERRIT DERK (NL)
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