Filtration of Activated Sludge Using a Rotary Membrane Separator with a Micro Strainer
Takao Fujii*, Akiyoshi Sakoda* and Motoyuki Suzuki**Abstract
We showed that the use of a rotary membrane separator for activated sludge filtration is superior in terms of energy-saving efficacy and endurance. By using a micro strainer with a diameter of approximately 45microm, the separator let plugging substances, which disturb the separation efficiency, pass through the membrane easily. The system was capable of controlling the degree of the formation of the cake layer. As a result, the resistance of filtration was remarkably low and the separation could stand for a long period.
Basically, this system is a sludge separat or utilizing cake separation. However, it can avoid sludge consolidation by controlling the differences in the separation pressure between 1 and 2kPa. Furthermore, the use of a rotary membrane separator could limit or prevent the build-up of cake layers by increasing the shee stress due to the rotation of the micro strainer. The result of the experiments with a stainless steel screen(pore size 45microm)which is for hydrophobic treatment on its surface showed that we can maintain the sludge separation process stability with a simple brush washing twice every three months and the water treated by this method is clean enough(SS and TOC concentration is about 10 mg/L).
Key words: activated sludge process, membrane separation, plugging substance, cake layer filtration, surface treatment