RECYCLING METHOD OF ACID BACKWASHING WASTEWATER

PROBLEM TO BE SOLVED: To provide a means for reducing the running cost of a membrane filter device by achieving the recycling of backwashing wastewater produced at the time of backwashing. SOLUTION: Raw water, loaded with an inorganic flocculant of an iron type, an aluminum type or the like, is filtered by a ceramic membrane 2 in a flocculation and mixing tank 1. Acid backwashing wastewater, which is produced when the ceramic membrane 2 is subjected to acid backwashing, is sedimented and separated in a backwashing wastewater tank 3 and the supernatant water from the backwashing wastewater tank 3 is returned to the raw water to utilize iron or aluminum contained in the acid backwashing wastewater as the flocculant. By this method, the load of the flocculant in the raw water can be reduced. The acid backwashing wastewater discharged heretofore can be recycled as a part of the raw water and the effective practical use of water resources becomes possible. COPYRIGHT: (C)2006,JPO&NCIPI