METHOD FOR REGENERATING WASTE COOLANT, METHOD AND SYSTEM FOR TREATING WASTE COOLANT, AND METHOD FOR PRODUCING REGENERATED COOLANT

PROBLEM TO BE SOLVED: To provide a method for regenerating waste coolant, configured to exhibit sufficient coolant performance from waste coolant.SOLUTION: In a method for regenerating a waste coolant, a used coolant (waste coolant) used for cutting out a slice of a silicon ingot or the like, is housed in a waste coolant storage tank 1. A predetermined amount of waste coolant is supplied to a centrifuge 2 from the waste coolant storage tank 1. A separated liquid (supernatant liquid) to be obtained after centrifugal separation by the centrifuge 2 is supplied to a filtering machine 3, and the solid content such as silicon fine particles and bacteria included in the separated liquid is removed, to form filtrate and filtered concentrate. The filtrate obtained by the filter 3 is supplied to a recovery tank 4. In the recovery tank 4, the heated and sterilized filtrate, and if necessary, purified water and an unused coolant or the like are used, to adjust the concentration of the regenerated coolant to a predetermined value. The concentration of particles in the regenerated coolant is decreased, to obtain sufficient machining speed.