METHOD FOR TREATING RAW SEWAGE BASED WASTE WATER

摘要

PPROBLEM TO BE SOLVED: To provide a method for treating raw sewage based waste water such as raw sewage and septic tank sludge. PSOLUTION: The method for treating raw sewage based waste water comprises: a first flocculation stage where waste water such as deslaged raw sewage and septic tank sludge is mixed with excess sludge produced in a biological treatment stage in the poststage, a flocculant is added thereto, and the obtained mixture is subjected to flocculation treatment; a first dewatering stage where the mixture subjected to the flocculation treatment in the first flocculation stage is separated into first dewatered sludge and first desorped water; a biological treatment stage where the separated water separated in the first dewatering stage is subjected to biological treatment; a solid-liquid separation stage where the mixed liquid subjected to the biological treatment in the biological treatment stage is separated into separated water and sludge returned to the first flocculation stage and the biological treatment stage; a second flocculation stage where a flocculant is added to the separated water separated in the solid-liquid separation stage, and flocculation treatment is performed thereto; a membrane separation stage where the mixed liquid subjected to the flocculation treatment in the second flocculation stage is separated into concentrated sludge and separated water; a second dewatering stage where the concentrated sludge separated in the membrane separation stage is subjected to dewatering treatment into second dewatered sludge and second desorped water; and a carrying stage where both the dewatered sludge from the first dewatering stage and the second dewatering stage is transferred to a dewatered sludge storage tank, and next, the mixture of the dewatered sludge is exhausted from the dewatered sludge storage tank to the outside of the treatment system. According to this method, the reelution of biological hard-to-decompose substance can be securely prevented. PCOPYRIGHT: (C)2007,JPO&INPIT