BIOLOGICAL NITROGEN REMOVAL METHOD AND NITROGEN-CONTAINING WASTE WATER TREATMENT APPARATUS

PROBLEM TO BE SOLVED: To provide a treatment method which, even if an environmental change such as decrease in water temperature occurs, can maintain stable nitrogen removal treatment and perform biological nitrogen removal in ammonia nitrogen-containing waste water in a continuous state with small fluctuation of nitrogen removal efficiency by a simple configuration in spite of nitrogen removal treatment using anammox bacteria.MEANS FOR SOLVING THE PROBLEM: A biological nitrogen removal method comprises a nitrogen removal process where waste water containing ammonia nitrogen and nitrite nitrogen is contacted with anammox bacteria so as to remove nitrogen by an anaerobic ammonia oxidation reaction. In addition, the nitrogen removal process is provided with means for further contacting the waste water with autotrophic sulfur oxidizing bacteria using a reducing sulfur compound as an electron donor. The waste water containing ammonia nitrogen and nitrite nitrogen is made to flow into the nitrogen removal process, and decrease in the ratio of nitrogen removal by denitrification due to the anaerobic ammonia oxidation reaction caused by an environmental change is suppressed by removing the nitrogen in the waste water by the sulfur oxidizing bacteria.SELECTED DRAWING: Figure 1 【課題】アナモックス細菌を利用した脱窒処理でありながら、水温の低下等の環境変化があったとしても、簡便な構成で、安定した脱窒処理が維持できる、脱窒効率の変動が少なく、連続した状態でアンモニア性窒素含有廃水の生物学的窒素除去が可能な処理方法の提供。【解決方法】アンモニア性窒素と亜硝酸性窒素とを含有する廃水をアナモックス細菌に接触させて、嫌気的アンモニア酸化反応による脱窒を行う脱窒工程に、更に、還元性硫黄化合物を電子供与体として用いる独立栄養性の硫黄酸化菌に廃水を接触させる手段を設け、該脱窒工程に、アンモニア性窒素と亜硝酸性窒素とを含有する廃水を流入させるようにして、環境変化によって生じる嫌気的アンモニア酸化反応による脱窒による窒素の除去率の低減を、前記硫黄酸化菌で廃水中の窒素の除去を行うように構成して、窒素の除去率の低減を抑制する生物学的窒素除去方法。【選択図】図１