Patent ID: 7540959

Claim:
Equipment for treating an ammonium containing liquid by biologically denitrifying ammonium in the ammonium containing liquid, the equipment comprising: a nitrification tank of primarily separating the ammonium containing liquid into two separated ammonium containing liquids, and nitrifying ammonium in one of the separated ammonium containing liquids to nitrate by nitrifying bacteria; a denitrification tank of further secondarily separating the nitrified liquid obtained in the nitrification tank into two separated nitrified liquids, mixing one of the separated nitrified liquids with the other primarily separated ammonium containing liquid, and carrying out denitrification treatment of nitrate in the separated nitrified liquid by denitrifying bacteria using an organic substance in the separated ammonium containing liquid as a hydrogen donor; and an anaerobic ammonium oxidation tank of mixing the other secondarily separated nitrified liquid with the denitrified liquid from the denitrification tank and carrying out nitrate reduction treatment of reducing nitrate contained in the separated nitrified liquid to nitrite by heterotrophic denitrifying bacteria using an organic substance in the denitrified liquid as a hydrogen donor, and of simultaneously denitrifying nitrite produced by the nitrate reduction treatment and ammonium in the denitrified liquid by anaerobic ammonium oxidizing bacteria.