| Water is the origin of life，and it plays a very significant role on people’s lives andproduction. However, with Chinese rapid economic development and urbanization，water pollution problems are becoming more and more serious，and water pollutionincidents happen frequently, highlighting the quality of our water environment is notoptimistic.Water quality is closely related to industrial and agricultural production safety andhuman health, which depends on water quality testing techniques to judge, forecast andmonitor of the pros and cons of water quality. While traditional instruments and testingequipment can detect water quality parameters, but generally only for single parametermeasured. For example, in order to detect of water COD, TOC, TURB and NO3-N andother parameters, it usually requires COD analyzers, TOC analyzer, turbidity meter,NO3-N analyzers and other equipment individually, which is not conducive to theintegration of data, but also increases the cost of testing. In recent years, UV-VISabsorption spectroscopy, as one spectral analysis of water quality testing techniques, hasattracted more worldwide attention, with abandoning many shortcomings of thechemical analysis, electrochemical analysis and chromatographic analysis of waterquality testing technology, such as complex water samples pretreatment technology,long period measurement, and a large number of chemical reagents requirement, andacquiring the advantage of quick detection, low cost, online and in-situ measurements,etc. Nevertheless, UV-VIS absorption spectroscopy, general a single parameterinstrument, still can not achieve simultaneous detection of multiple parameters such aswater quality COD, TOC, TURB, NO3-N.This paper is rooted in Sichuan Province Science and Technology Agency supportProgram(2012SZ0111)，Sihuan Belam Technology Co. horizontal cooperation researchproject (1042012920140453) and the National Natural Science Foundation of China(61201346) jointly funding, Launched theory, instrumentation, methods, technologyand application research of UV–VIS spectroscopy multi-parameter water qualitytesting. A set of multi-parameter water quality testing instrument systems， based onUV-VIS spectroscopy， has been developed, Which is a complete process includingdata collection of water quality, water quality spectral processing, water qualityparameters solver, laboratory analysis to verify, and the actual water quality multi-parameter detection, what is more, the system is completely independentintellectual property rights. The main contents in this paper are as follows:①Describes the domestic and foreign status and development trend ofspectroscopy and spectroscopy to detect water quality parameters. Based on a detailedcomparative analysis of existing water quality detection technology at home and abroad,this paper presents the UV-VIS spectroscopy multi-parameter water quality principlesand methods of detection technologies and applications, and Systematically studys theUV-VIS spectroscopy multi-parameter water quality testing key technical issues, suchas water quality spectral processing, water quality parameters solver.②Developed a UV-VIS spectroscopy multi-parameter water quality testinginstrument systems. By analyzing the principle of UV-VIS spectroscopy water qualitytesting, studying the multi-parameter water quality detection principle, and analyzingthe feasibility of multi-parameter spectral detection, on this foundation, we built theimplementation of water quality multi-parameter detection system, and designed,emulated, manufactured and tested water immersion optical path difference detectionprobe. On the processing of the probe is conducting water quality spectral dataacquisition, this system can effectively reduce noise, improve system sensitivity, andquickly and accurately identify the sensitive wavelength range of tested water. By usingminiature fiber optic spectrometers as the core of the spectrum measurement unit, whichcombined with the UV-VIS absorption spectroscopy, we can finish water samples COD,TOC, TURB and NO3-N multi-parameter detection. Meanwhile, based on LabVIEWdevelopment platform, with system software design and debugging, we achieve a flowpath for cleaning, processing, display, storage, printing and master function. Thisprovides a hardware and software conditions or platform for achieving multi-parameterwater quality spectrometry detection.③This paper studied the water spectrum processing method based onwavelet-packet de-noising and Water spectrum treatment technology of multiplicativescatter correction. For the needs of surface water, municipal wastewater in linedetection and control of major pollutants, taking the UV-VIS spectroscopy water COD,TOC, TURBO and NO3-N multi-parameter detection as the specific research object,and based on the analysis of water quality characteristics of spectral information, weproposed the water quality spectrum processing method on wavelet-packet de-noising inorder to improve the SNR of the water quality spectrum. The results show that the noiseof the spectra of the raw water samples, processed by UV-VIS absorption spectrum after de-noising via wavelet packet, has been significantly suppressed, and thecharacteristic has been remained. Suspended solids in water, scattering spectra of watersamples, on the effective of UV-VIS absorption spectra, would generated baseline drift,translation and other issues, which will seriously affect the stability and the detectionaccuracy of the system, and then have a direct impact on water quality detectionspectroscopy of COD. Because of this, we studied the water quality of spectralprocessing method based on the multiplicative scatter correction. By the multiplescattering correction method, without affecting the water samples by UV-VISabsorption spectra under the premise of features, suspended solids in water can causewater turbidity caused by scattering interference or baseline shift of the absorptionspectrum curve effectively corrected by multiplicative scatter correction methods. Thisnot only improves detection signal to noise ratio of water quality spectrometry COD,but also established an accurate and effective analytical model for water quality testingCOD stoichiometry, which were effective data preprocessing.④Studied the technology of principal component analysis dimensionalityreduction for water quality and least squares support vector machines for soft sensormodeling of water quality parameters of water quality spectrum processing method.After wavelet packet de-noising and multiplicative scatter correction processing, thereare still problems redundancy and multiple collinear water quality spectrum acquisitionin water quality UV-VIS spectroscopy. We applied the principal component analysismethod to reduce the dimension of water quality spectral signal, and then used the leastsquares support vector machines for water quality parameters COD to build soft sensormodel. The results showed that, after the primary element analysis method of waterquality spectral data dimensionality reduction, it removed redundant information,retained the effective features. On this basis, the application of least squares supportvector machine for soft sensor modeling of water quality parameters, can improve waterquality modeling accuracy and COD parameters of the system solver accuracy.⑤Launched a performance test research of the UV-VIS spectroscopymulti-parameter water quality testing instrument prototype. To ensure that the UV-VISspectroscopy multi-parameter water quality testing instrument systems effective, stableoperation, in accordance with the relevant standards, we tested the performance of theprototype. The results show that the test instrument prototype for the accuracy of thechemical oxygen demand COD standard solution is less than4.70%and repeatability ofless than1.43%; namely for TOC measurement accuracy,which is less than2.69%and repeatability of less than1.98%; for TURB turbidity test, which is less than4.78%andrepeatability of less than1.55%; for right nitrate NO3-N, which is less than4.67%oftest accuracy and repeatability of less than2.92%. In summary, the performance of thedeveloped instrument prototype not only met the design requirements of the missionstatement, through the Chinese Research Institute of Chemical Technology Institute testreport, it also met the relevant standards and industry of our country.This article combined disciplinary expertise organically, such as spectroscopy,optical technology, environmental science, chemistry measurement methods, signalanalysis and processing and so on, with being the first in the country to study and buildmulti-parameter water quality testing instrument systems based on UV-VISspectroscopy. The research results-the instrument prototype has been identified bythe experts of Sichuan Province Science and Technology Department, which hasimportant theoretical and practical significance on further theory of instrumentation,methods, techniques and applied research work of UV-VIS spectroscopy detection ofmulti-parameter water quality. |
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