| 摘要 |
PROBLEM TO BE SOLVED: To increase the rate at which the quantity of a permeated water is recovered by arranging a larger filtration particle than the pore diameter of a membrane, on the permeated water side of the membrane and filtering the water to be treated with the help of the membrane after filtering the water to be treated through the filtration particle. SOLUTION: An untreated water RW ducted in from a river reaches a sand sedimentation pond 1 to have a sand of large grain size removed and then is guided to an untreated water tank 2. A treatment tank 3 is arranged on the downstream side of the untreated water tank 2 and the untreated water RW to be water to be treated is supplied to the treatment tank 3 by a water suction pump 4. A strainer 5 is arranged on the suction side of the water suction pump 4 to have impurities present in the water to be treated removed. A filtration particle 6 is stored in the treatment tank 3 and is of a grain diameter which is about 1 mm and larger than the pore diameter of a membrane 9. In addition, the filtration particle 6 is selected so that it is substantially equal to the specific gravity of the water to be treated which is supplied into the treatment tank 3. Further, the filtration particle 6 is arranged on the permeated water side of the membrane 9 which constitutes a membrane filtration device 7. Thus it is possible to improve the efficiency at which the quantity of a permeated water is recovered and reduce a membrane cleaning cost. |
