PROBLEM TO BE SOLVED: To provide a water treatment apparatus capable of reducing the risk of nitrite nitrogen or ammonia nitrogen flowing into a breeding water tank and preventing water with a low dissolved oxygen concentration from flowing into the breeding water tank, even when the nitrite nitrogen or ammonia nitrogen is generated by a denitrification unit.SOLUTION: A water treatment apparatus A includes nitrification unit 1 for performing nitrification treatment by nitrifying bacteria, and a denitrification unit 4 for performing denitrification treatment by denitrifying bacteria. The denitrification unit 4 receives supply of breeding water W0 in the breeding water tank T, and the nitrification unit 1 receives supply of breeding water W0 in the breeding water tank T as well as supply of breeding water W4 denitrified by denitrifying bacteria, so that breeding water W1 nitrified by nitrifying bacteria circulates into the breeding water tank T.COPYRIGHT: (C)2013,JPO&INPIT【課題】脱窒手段で亜硝酸態窒素やアンモニア態窒素が発生した場合であっても、これらが飼育水槽に流入するリスクを下げることができ、かつ、溶存酸素濃度の低い水が飼育水槽に流入することを防ぐことができる水処理装置を提供すること。【解決手段】硝化菌による硝化処理が行われる硝化手段1と、脱窒菌による脱窒処理が行われる脱窒手段4とを具備する水処理装置Aであって、脱窒手段4は、飼育水槽T中の飼育水W0の供給を受け、硝化手段1は、飼育水槽T中の飼育水W0の供給を受けるとともに、脱窒菌により脱窒処理された飼育水W4の供給を受け、硝化菌により硝化処理された飼育水W1が飼育水槽Tに環流する。【選択図】図1
