Service water quality monitor including hue and coloration grade

The authors introduce an index of coloration grade for evaluation of service water colour. The principle of the coloration grade measurement has been derived from authors' modification of the Tristimulus Filter Method of AWWA 1992 and JWWA 1993 Standard Method, and it has the advantage of applicability to all colours in the visible range. The characteristics of the hue and coloration grade measurement has been tested in the laboratory using various coloured samples obtained from water service pipes or an aqueduct. Compared with the “colour” measured by the platinum-cobalt method, the coloration grade is more sensitive to various water coloration and close to human senses. Applying the above stated device, a Service Water Quality Monitor was newly developed and successfully tested at several distinctive fields. It monitors three items, colour, turbidity and residual chlorine which are obligatory in Japan to be daily examined at appropriate house taps. For the field test of about six months without any manual calibration, the accuracy of the hue and the coloration grade has shown maximum deviation of only 2.5% FS compared with the measurement by means of the standard solutions once a month.