Study on Turbidity Compensation for COD Concentration Detection Based on Dual-wavelength Spectroscopy

Abstract:

Currently, water quality has become an important condition to guarantee the quality of people's daily life. Chemical oxygen demand (COD) is an important criterion for detecting the emission of pollutants and judging the quality of water. This paper improves the absorption spectrum compensation model for COD and turbidity mixed solution in the dual-wavelength spectral method based on the Lambert-Beer law additive principle. It compensates for the influence of turbidity on the absorption coefficient of the COD solution at 355nm by the absorption spectrum coefficient of the mixed solution at 623nm. This paper establishes a linear relationship model between the absorbance difference of the mixed solution at 355nm and 623nm and COD. The experimental determination coefficient R2 of the model is 0.98335, with a relative error of 3.5% and an average error of 0.7 mg/L. The design of the model is simple and easy to systematize, which is of strong significance for practical application.

Key words:COD concentration detection, Lambert-Beer law, dual wavelength spectroscopy, turbidity compensation