METHOD FOR TREATING WATER BY FILTER CLOTH

PROBLEM TO BE SOLVED: To remove dissolved organic substances and colloidal and suspended organic substances which are main factors of water quality deterioration by adding a fine particle as an additive to raw water containing organic matters at the time when raw water is filtered by a filter cloth of a cloth material made of fibers while washing and back washing being carried out. SOLUTION: A filter cloth is attached to the circumference of a rotating drum 8 while keeping a filtration layer in the inside, raw water 2 is supplied to the inside of the drum from the center part of one side face, and the raw water is filtered from the inside to the outside by the head difference 9 between the water surfaces in the inside and the outside of the drum. The filter cloth 1 is led to an upper part simultaneously with the rotation of the drum and washed by jetting filtered water out of a nozzle. At that time, back washing 6 of the cloth is carried out in the outside of the drum and front washing 7 is carried out in the inside, the washing wastewater is collected in a center pipe by a hopper and recovered as a concentrated liquid. As a fine particle 10, a suspended solution produced by stirring diatomaceous earth in a purified water, diluting the resultant solution, and obtaining a supernatant solution after leaving the resultant diluted solution is added to the raw water while the concentration being controlled. Organic particles suspended in water can efficiently be removed at a low cost in compact facility by such a manner.