| 摘要 |
PROBLEM TO BE SOLVED: To reduce the number of times of the backwashing work of the adsorbent of the fixed bed of an adsorption tower by adding a sterilizing agent to membrane permeated water between a biological treatment tank and the adsorption tower. SOLUTION: A sodium hypochlorite aq. soln. is stored in a sterilizing agent storage tank 1 2. Sodium hypochlorite is added to the membrane permeated water within an intermediate tank 30 by a sterilizing agent supply pump 13 so that the concn. of effective chlorine in the membrane permeated water to which biological treatment and membrane separation treatment are applied becomes about 10 mg/l to be mixed therewith by a stirrer 15 to perform sterilizing treatment. When the pressure loss of an adsorption tower 5 exceeds about 0.5 kg/cm<2> by this treatment, the adsorbent of the fixed bed 10 of the adsorption tower 5 is backwashed. By this constitution, bacteria permeated through the flat membranes of a filter membrane unit 3 are killed and the generation frequency of the clogging of the fixed bed 10 is reduced and backwashing can be dispensed with until about 90 days are elapsed. |
