To make it possible to easily epecify the cause of the degradation in membrane performance and to rapidly execute a procedure for restoring the membrane performance, by monitoring and mutually comparing the working states of main modules having large membrane areas of separating membranes and a sub-module having small membrane area of the separating membranes and detecting the working abnormality of the main modules.
This device is provided with the main modules 4A to 4C installed in juxtaposition and the sub-module 6 in juxtaposition therewith in order to separate solid from the flocculation treating liquid of waste water. At this time, the waste water is first subjected to a flocculation treatment by adding a flocculating agent and a pH control agent thereto in a flocculation reaction vessel 1 and thereafter, the water is fed to the main modules 4A to 4C and the sub-module 6 respectively under the same conditions by a circulating pump 3. The concd. water in the main modules 4A to 4C is returned to a circulating vessel 2 and the permeated water is discharged as the treated water to the outside of the system. On the other hand, the permeated water and concd. water of the sub-module 6 are returned to the circulating vessel 2. In such a case, the membrane performance of the main and sub-module is monitored and the cause for the degradation of the membrane performance is displayed from the results obtd. by mutually comparing the membrane performance.
TAKADOI TADASHI
SATO TAKESHI
CHIKASAWA KIYOHITO
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