Patent ID: 8303893

Claim:
An apparatus for determining an amount of coagulant to be injected to an amount of water to be treated (coagulant injection rate) in a coagulation-sedimentation water treatment in which coagulant is injected into water to be treated, the apparatus comprising: plural sample water tanks that each has a mixer and that collects a predetermined same amount of the water to be treated; coagulant injection means for injecting a predetermined different amount of a coagulant to each water sample collected in the plural sample water tanks to prepare plural water samples each having a different coagulant injection rate, injection of the coagulant causing flocs to form in each of the plural water samples; a detector that detects a size and number of the flocs in each of the plural water samples, the detector including a light beam radiation unit that radiates light toward the respective plural water samples, a photoelectric converter that receives the light scattered by flocs in the respective plural water samples or the light transmitted through the respective plural water samples and converts the received light into an electrical signal, and an electric circuit that measures the size and the number of the flocs in each of the plural water samples based on the electrical signal; an agglomeration start time measuring unit for measuring for each of the plural water samples an agglomeration start time at which agglomeration of particles starts after the coagulant is injected and dispersed by mixing, based on an output from the detector; and an arithmetic unit for computing a correlation between the agglomeration start time and the coagulant injection rate for each of the plural water samples as a fitting line and computing a coagulant injection rate for a water treatment plant based on the fitting line and an agglomeration start time of the water treatment plant.