WATER QUALITY CONTROLLER

PURPOSE:To always obtain stable water quality in the water quality controller which controls the residual salt control of prechlorine with a computer by sampling the raw water flowing into a water purification plant and predicting a chlorine consump tion from the water quality data of this raw water, then executing prechlorine residual salt control. CONSTITUTION:The control in the water purification place where chlorine is injected by a chlorine injector into the raw water taken in from rivers is executed by the computer is for controlling the chlorine injector, etc. This computer internally provided with a prechlorine residual salt control section 30, where the outputs of a chlorine demand meter, conductivity meter and residual salt meter and process data, such as present target value of the chlorine/injector, are read-in from an input section 31 and the chlorine consumption is predicted from the correction factor of the chlorine demand set in accordance with the value indicated by the chlorine demand meter and the value indicated by the chlorine demand meter at the present time. The actual value of the chlorine consumption is determined from the actual value of the residual chlorine and the chlorine injection rate and is compared with the predicted value of the chlorine consumption. The target value of the prechlorine injection rate is corrected in accordance with the deviation thereof, to control the chlorinator.