Quality monitoring of flowing water using colorimetric method based on a semiconductor optical wavelength sensor

Chroma and turbidity of flowing water were measured by using a colorimetric method that requires no conventional spectrophotometer, colorimeter or turbidimeter. A dual-wavelength light-source and a BDJ (buried double p–n junction) optical wavelength sensor were employed in the measurement. The intensity–insensitive photocurrent ratio of the two p–n junctions in the sensor is monotonously related to chroma and turbidity of water. The potential applications of this method of monitoring water chroma and turbidity, two important physics indexes to describe the quality of water, have been demonstrated. The results show that this simple method is sensitive and accurate, and not affected by fluctuation of flowing water.