NIR Spectroscopy Analysis Of The Intracellular Polymers Content During The Enhanced Biological Phosphorus Removal Process

Enhanced biological phosphorus removal（EBPR）process of wastewater treatment is an important way to solve the Water Eutrophication,attracting widespread attention.Although the Biological phosphorus removal process is relatively mature,removal effect under the influence of nitrogen removal.In order to apply the biological phosphorus removal in the practical project more efficiently,Biological removal of phophous by“aerobic/anaerobic alternation process” was tested in this study.Study on content changes of EBPR sludge intracellular substances（PHA,glycogen）combining stoichiometric method and near infrared analytical technique.Moreover,the problem on the complexity of traditional chemical determination could be overcome.In addition,Sludge samples collected from five sewage plant and two phosphorus removal reactor.Extracting principal component of the near infrared spectrum by the method of principal component analysis（PCA）.Preliminary Study on the rapid classification of sludge samples combining the PAC method and near infrared spectral data.The main research contents and conclusions are as follows:Through comparing the near infrared spectrum of sludge samples and pure polymer,The position of the absorption peak resulted from special chemical bonds in polymer molecular was obtained.In order to have a further study on the correlation between the absorption bands and the chemical bonds,different proportions of standards were add into the sludge polymer.The experimental results show that the intensities of these bands at 110040cm^-1、8308cm^-1、6842cm^-1、5631cm^-1、4775cm^-1 increase when standard sample of glycogen was added in sludge samples.The spectrum band are closely related to the combination bands of O—H stretching vibration and C=O stretching vibration of glycogen molecular.when standard sample of PHB was added in sludge samples.the intensities of these bands at 8454 cm^-1、7174cm^-1、5909cm^-1、5808cm^-1、4659cm^-1、4350cm^-1 increase.The spectrum bands are closely related to the C-H、CH₂、CH₃、C-O and C=O bands.when standard sample of protein was added in sludge samples.the intensities of these bands at 9665 cm^-1、6649cm^-1、4867 cm^-1、4605 cm^-1、4296 cm^-1 increase.The spectrum bands are closely related to the frequency doubling of N-H bending vibration and C-H stretching vibration.Test of Savitzky-Golay smoothing（SG）and Multiplicative scatter correction（MSC）method were jointly used to preprocess the near infrared（NIR）spectra of the sludge samples,the quantitative analysis models between the NIR spectra and the PHA contentswere established with modified PLS methods such as interval partial least squares（i PLS）,backward interval partial least squares（bi PLS）and synergy interval partial least squares（si PLS）.SG-MSC pretreatment could effectively diminish the effect of spectrum interference factors.The optimal model was established by four sub-intervals [13,21,24,29]with si PLS method,divided the preprocessed spectrum into 30sub-intervals.The root mean square errors of cross validation（RMSECV）and the root mean square errors of prediction（RMSEP）were 0.2018 and 0.3120 respectively.The correlation coefficients of the calibration and prediction sets were 0.9925 and 0.9391 respectively.The best analysis spectrum band are closely related to the C — H bending vibration and C=O stretching vibration of PHA molecular.The modified PLS could not only optimize the spectra region,enhance the predictive ability of the models,but also realize the rapid and quantitative determination of intracellular PHA content in the granular sludge.The EBPR sludge is a Multi-Component Mixture,NIR absorption bands resulted from special chemical bonds in multiple polymer molecular.That would seriously interfere with the information extraction of single component.On the basis of the quantitative analysis of PHA contents,four Near-infrared spectral pre-processing methods were separately used to improve the performance of multivariate calibrations.The quantitative analysis models between the near-infrared（NIR）spectra and the glycogen contents were established based on synergy interval partial least squares（si PLS）method.Results showed that the optimal model was established by four sub-intervals [10 13 16 19] with si PLS method after the NIR spectra were treated with Savitzky-Golay smoothing and first derivative as pre-processing method,and the preprocessed spectra were devided into 20 sub-intervals.The root mean square errors（RMSEP）and the correlation coefficients（rp）of the prediction sets were 0.0048 and0.9105 respectively.The residual predictive deviation（RPD）values of cross-validation and prediction sets were all above 3.0.The NIR spectral model based on S-G smoothing and si PLS method can not only improve the predictive accuracy and reduce the variable numbers,but also realize the rapid and accurate determination of intracellular glycogen content in the sludge.Test of classifing sludge samples of five sewage plant and two SBR reactor with PCA.The results show that the first principal component（PC1）and the second principal component（PC2）almost contains the all information of sludge samples.The polymerization degree of classification with full spectrum by PCA is poor.when the spectra were devidedinto 20 sub-intervals,the optimal model was established at the wave band of6781cm^-17174cm^-1.the absorption bands resulted from X-H bonds in polymer molecular.The difference of sludge samples mainly due \to the different internal and external polymer in sludge.Combing effective selection of NIR spectra wave bands and PCA can realize the classification of the sludge samples.In summary.The key to established an optimization model with NIR spectra is the effectively selection for multivariate data analysis（MVA）and pretreatment method.The quantitative analysis models between the near-infrared（NIR）spectra and the sludge intracellular polymer content were established,that not only realize the rapid and quantitative determination of intracellular polymer content in the granular sludge but also has a great significance to the application of biological phosphorus removal in the actual engineering.