| 摘要 |
PURPOSE:To prevent the decrease in the rate of the water permeated through a membrane by flocculating of excess sludge and returning of a dehydrated filtrate to waste water treating stage and to execute an efficient treatment by introducing the filtrate of a dehydration treating device into a flocculation reaction chamber only when the permeated water of a 1st membrane separator is introduced into the flocculation reaction chamber. CONSTITUTION:The dehydrated filtrate in a filtrate storage tank 9 is returned into the flocculation reaction chamber 4 at the time of the operation of the 1st UF membrane separator 3, i.e., only when the permeated water from the 1st UF membrane separator 3 is introduced into the flocculation reaction chamber 4. The free polymers existing in the dehydrated filtrate, therefore, contribute preferentially to the flocculation reaction in the flocculation reaction chamber 4 and flocculate nearly completely. Consequently, the free polymers are hardly returned to the 2nd membrane separator 6 of the post stage. The degradation in the flux of the 2nd membrane separator 6 occurring in the adsorption of the polymers onto the membrane surfaces is, therefore, prevented and the effective treatment is executed. |
