From Event: SPIE Optical Engineering + Applications, 2016
Ultraviolet absorption spectroscopy is one of physical methods used for chemical oxygen demand (COD) measurements of water. The absorbances in ultraviolet band have a relationship to COD. However, turbidity in water could scatter emitting light and influence the absorbances. So it is very important to compensate for the impact of turbidity. In this study, the absorption spectra of standard COD solution (potassium acid phthalate), turbidity solution (Formazine) and their mixture are sampled in the wavelength range from 220 to 750 nm. The impacts of turbidity for COD measurement and compensation method are studied based on these data. The absorbance of mixture substract the absorbance of turbidity solution is less than the absorbance of standard COD solution. The result indicates that turbidity particles decrease the light absorption of organic molecules. Furthermore, we discover that the impact of turbidity is greater for the larger absorbance of the standard COD solution. Then attenuation coeffcient (AC()) is introduced and calculated based on exprimental results. In the process of turbidity compensation, the turbidity of solution is estimated using the absorbance of visible wavelength. The absorption spectra of the turbidity in the ultraviolet wavelength are simulated using normalization technique. The satisfactory prediction result of COD is achieved for the mixture after the turbidity compensation. In conclusion, the new turbidity compensation method could eliminate the influence of turbidity for COD measurements based on absorption spectroscopy.
Yizhang Wen, Yingtian Hu, and Xiaoping Wang, "The impacts of turbidity for COD measurements using UV-Vis spectrometry and compensation method
(Conference Presentation)," Proc. SPIE 9970, Optics and Photonics for Information Processing X, 997011 (Presented at SPIE Optical Engineering + Applications: August 30, 2016; Published: 2 November 2016); https://doi.org/10.1117/12.2236479.5178519693001.
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