Coagulation-sedimentation method (gyoshu chinden ho)
凝集沈殿法ぎょうしゅうちんでんほうCoagulation-sedimentation is a method used mainly in water purification, and in particular to treat rice-washing wastewater. Coagulants such as polyaluminum chloride (PAC) and polyacrylamide (PAA) are used to gather suspended and dissolved substances in the wastewater into clumps (flocs), which are then allowed to settle, so that the water is purified efficiently. The technique is also important in the sake-making process, where it is used to secure water of high purity. This is said to improve the quality and flavor of the sake.