抄録
An experiment on domestic sewage treatment was made through activated sludge treatment system with membrane separation using tank-submerged type ceramic membrane. Treatment scale was 10 m3/day and flux was fixed to 0.43 m3/ (m2·day) and 0.54 m3/ (m2·day). Membrane was washed once an hour by back-washing with filtrate and every four times of back-washing, sodium hydrochlorite (NaClO) solution was added to the filtrate. The result of this experiment revealed that transmembrane pressure drop was fairly stable and less than 15 kPa for one year and three months operation without chemical cleaning of ceramic membrane module.
The ceramic membrane used in this experiment was inspected using Scanning Electron Microscope (SEM). No fouling formed on inner surface of the membrane owing to the back-washing with NaClO solution, but mainly microorganic fouling materials formed on outer surface. Therefore, to remove these fouling materials, the membrane had better be cleaned by chemicals periodically at about one year's intervals.
Chemical cleaning test of the used ceramic membranes was conducted. The microorganic fouling materials were removed by dipping the membranes into the 1, 000 mg-Cl/l NaClO solution, but the temperature of the NaCIO solution had influence on the effect of cleaning. Therefore, the membrane had better be cleaned on warm condition.
