The Study Of Online Monitoring Method About Water COD Using UV Photoelectron Spectroscopy

We know that COD is often used to measuring in water examination.Now,COD is also one of important index in the degree of water pollution.Its full name is Chemical Oxygen Demand,and is the quantity of reducing substance that is oxidized in the water.To know COD,we can make some of the measures to deal with wastewater.There are some useful methods to determine COD,like dichromate titration,potassium permanganate,spectrophotometry,fast digestion,etc.Dichromate titration and potassium permanganate are the most important method.The former is used for industrial wastewater and domestic sewage.The total amount of organic matter in water can be accurately obtained.But this method need many samples and take a long time(heating and reflux need two hours).And it spends a lot of money,while mercury is likely to cause secondary pollution.The latter,is namely that potassium permanganate,is used for measuring drinking water,raw water,and surface water.These two methods are unable to quickly measure in a great amount of samples.Based on the above advantages and disadvantages of the conventional method,we propose a new measurement method—COD determination in water by multiple linear regression.Every water samples has a particular ultraviolet absorption spectrum curve.Suggestion it is made of a lot of characteristic reference absorption spectra.We selected five characteristic curves.They are Dissolved Organic Compounds,Nitrate,Suspended Solids,Colloidal State Compounds,Anionic Surfactant.Water samples absorption spectrum at each wavelength can be computed as a linear combination of these five characteristic reference absorption spectra.Assume the contribution coefficient of reference spectra is constant along the wavelength range.The linear relation can be expressed as,S(?)=?i=1p?i?i(?i)±ri,here p is the number of reference spectra;Pi is the contribution coefficient of reference spectra;R is the absorbance of the reference spectra,ri is the deviation.We can obtain the contribution coefficient of reference spectra,?i,by multiple linear regression.And then we assume a water parameter R—such as COD,DOC—can be computed as the sum of contributions of five reference spectra,Ri=?i=1q?ivi±?i,here vi is the water parameter of five reference spectra.A number of water parameter can be measured in some samples.At last,we obtain index parameter vi and ?i while we know the mathematical model of some water sampleBased on the above analysis,a MFC-based COD determination system is designed for this experiment.MFC encapsulates many Windows API interface function.Programmers can easily call these functions to write code.We design this system for COD determination is because we can use control to operate and GUI is easily used for users.This system can save these datasheet.We can use these datasheet to do further analysis and to study.The COD determination is studied in this paper.Through experiments we find that this system has a good fit in COD determination.The results are satisfactory.We can also design a handheld device for COD determination for further future.