Biomembrane reactor, waste water treating system and method for treating waste water

The invention provides a biomembrane reactor, which comprises an outer cylinder with a water inlet and a water outlet provided at the bottom part; an inner cylinder arranged in the outer cylinder, two ends of the inner cylinder are communicated with the outer cylinder, the top of the inner cylinder is lower than the top of the outer cylinder; a filling material used for filling a bio-contact oxidation tank of the inner cylinder; a filter material used for filling the biological filter tank between the inner cylinder and the outer cylinder; an aeration apparatus provided at the bottom of the outer cylinder, the aeration apparatus is communicated with the inner cylinder. The invention provides a waste water treating system and a method for treating waste water. The biomembrane reactor provided in the invention has the functions of the bio-contact oxidation tank and the biological filter tank, waste water forms a circulation between the inner cylinder and the outer cylinder under the promotion effect of the aeration apparatus, and waste water passes through the filling material used for bio-contact oxidation tank and the filter material used for biological filter tank for a purifyingprocess, thereby the effect of treating waste water can be improved.