Method for purifying aqueous suspension

A method for purifying an aqueous suspension comprising:

• feeding the aqueous suspension containing fine particles comprising an inorganic component from outer surfaces to inner surfaces of wavy hollow fiber membranes, each having an outer diameter from 0.5 to 3.1 mm, to filter said aqueous suspension wherein filtration time is controlled so an amount of suspended solids accumulating is from 0.005 to 10, the hollow fiber membranes having a bulkiness and being mounted or packed so as to substantially prevent rubbing of the membranes against each other during physical washing, wherein the amount of suspended solids accumulating is defined by the following formula:
• amount of suspended solids accumulating=(raw water turbidity {degree})×(total amount of filtrate permeating membrane in filtration time {m3})/(membrane surface area {m2}),
• the raw water turbidity {degree} meaning an average turbidity of raw water, which can be obtained by measuring turbidity for plural days according to JIS K 0101 9.2 and averaging the obtained value;
• and
• physically washing the hollow fiber membranes.