PURPOSE: To perform continuous dephosphorization using a biomembrane technique by treating organic sewage using aerophobic bacteria, then supplying this phosphor-free sewage to a fixed layer filled with elastic particles of a three-dimensional mesh structure, and further treating the sewage using aerophilic bacterial and filtering it with SS with the introduction of at least, part of cleaned drain from said fixed filled layer through an aerophobic treatment process together with the organic sewage.

CONSTITUTION: The subject biological dephosphorization process system consists of an aerophobic tank 2 and an aerophilic tank 33. The aerophilic tank 3 is equipped with a liquid transport pipe 13 of water treated biologically using aerophobic bacteria from the aerophobic tank 2, a discharge pipe 6 of the treated water, an air dissipation device 15, a filtration bed 4 formed with a fixed layer filled with elastic particles of three-dimensional mesh structure, a pipe for washing back the filtration bed 4 by supplying a treated water from the bottom, and pipes 9, 14 for allowing water used for cleaning the filtration bed to flow out of the top and recycling part of said spent water to the aerophobic tank 2. That is, after the aerophobic biological treatment of organic sewage in the tank 2, the treated sewage is supplied to the filtration bed of the aerophilic tank 3 to allow it to receive an aerophilic biological treatment and an SS filtration process. After that, at least, part of water used for cleaning the fixed filled layer is sent to an aerophilic biological treatment process together with said organic sewage. Subsequently, continuous dephosphorization utilizing a biomembrane system is achieved.