Research On The Standard Method Of Water Color Determination And COD Measurement Method Based On UV-Visible Spectrum

In this paper, the standard method of water color determination and aCOD measurement method based on UV-visible spectrum have been studied. Inorder to apply the methods to automated measurement of water quality, a broadbandspectrum water quality detection system is designed, which is mainly composed oflight source, sensor, the collimating and beam splitting system, the optoelectronicdetection and photoelectric conversion system, the data acquisition and processingsystem. The detection system can directly measure the color and COD value of waterby optical detection method. Compared to the traditional water quality detection withmanual sampling and laboratory analysis, this system achieves the real-time onlinedetermination of water quality without any chemical reagents, and has many otheradvantages, such as portability, easy operation, low cost, fast response, highreliability, and so on.The main content of this paper includes the following aspects:1、A transmission type fiber optic sensor has been designed. The sensor adopts afour-way structural design, machining with titanium alloy （TC4）. The incident andemergent optical fiber are connected to the transverse ends of the sensor with opticalfiber collimating lens, and the sensing part of the sensor lies in the transverse regionbetween the two optical fiber collimating lens. The water can freely flow across thelongitudinal area of the sensor, and both ends are placed a nut structure to fix thefilter, preventing interferences from the suspended materials in water. When it works,we shoud just put the sensor into water.2、The spectral properties analysis and calculation method of water color hasbeen studied. By analyzing the spectral characteristics of the colourimetric standardsolutions （platinum-cobalt standard solutions）, and utilizing the color differenceformulas recommended by the Chinese national standards, a new spectrum analysismethod for water color determination is proposed based on three-wavelength luminous transmittance.3、The spectral properties analysis and calculation method of COD in water hasbeen studied. We have analyzed the spectral characteristics of potassium biphthalate（C₆H₄COOHCOOK）, and measured the COD values of water samples by using areaintegration method and multiple linear regression. Meanwhile, we have also studiedsimultaneous determination of benzene （C₆H₆）, dimethylbenzene （CH₃C₆H₄CH₃）,chlorobenzene （C₆H₅Cl） and nirtrobenzene （C₆H₅NO₂） in mixed organiccompounds solutions.4、The design and assembly of a micro USB fiber spectrometer. The collimatingand beam splitting module, optoelectronic detection and photoelectric conversionmodule, and A/D conversion module have been integrated and assembled into amircro fiber spectrometer. The wavelength accuracy of the spectrometer is within0.3nm, and spectral bandwidth is less than2nm, which can satisfy the requirementsfor spectral measurement of solutions.5、System test. The sewage detection system in broadband spectrum has been setup, that used to measure the color and COD values in waste wate. Also the standardcalibration curves have been established for determination of actual water samples.