Characterization Of The Protein Content In The Excess Sludge With Near Infrared Spectroscopy And The Spectral Analysis During The Anaerobic Fermentation Process

In this paper, the protein in the excess sludge was analyzed qualitatively and quantitatively using near infrared spectroscopy and chemometrics. Wet chemical analysis and spectroscopy were used to characterize the anaerobic fermentation process of the excess sludge. The transformation of the cellular substance and the production of the liquid phase product were analyzed. It would provide the research basis for the utilization of the excess sludge.?1?Different sludge samples were characterized by using near infrared?NIR?spectroscopy and the cluster analysis was realized using principal components projection method. Based on the difference of NIR spectra, and combining with the analysis results of the protein contents in the sludge samples determined by Kjeldahl method, the modeling spectral region of 4382 cm^-1- 3996 cm^-1 was chosen to establish the correlation models between NIR spectra and protein contents with interval partial least squares?i PLS? method.The correlation coefficient is 0.973, the root mean stand errors of cross-validation?RMSECV? is 1.321, and the relative errors between the predicted and the real values in the range of-10.0% 8.52%, which implicated that NIR spectroscopy could be used to identify the origin of the sludge sample and quantitate the protein contents in the sludge samples rapidly.?2?Anaerobic fermentation of excess sludge under natural conditions and the extent of the whole fermentation was studied by wet chemical analysis method and fluorescence spectroscopy.In fermentation broth, the values of ammonia nitrogen, phosphate and COD increased in the first phase and then levelled off. The fluorescence intensity of coenzyme F₄₂₀ showed the same variation profile, which implicated that the intensity of methane production increased at first and then decreased.?3?The removal of ammonia nitrogen, phosphate and organic matter in the sludge anaerobic fermentation broth was carried out by chemical methods and biological treatment methods.The results showed that the phosphate removal rate reached 95% by adding iron and phosphorus chemical method when n(Fe²⁺:Fe³⁺=1:1): n(PO+₄^3--P) was above 1.8,The SBR aerobic biological treatment method was used to remove Ammonia nitrogen and COD. In the first 3h aeration, COD concentration decreased gradually and tended to be stable?about 20mg/L?, ammonia nitrogen, nitrate nitrogen remained basically unchanged, which implicated that the heterotrophic bacteria gave priority to the use anddegradation of COD at the beginning.After 3h aeration, the ammonia nitrogen gradually decreased, the nitrate nitrogen content increased gradually, and the ammonia nitrogen and nitrate nitrogen showed a decreasing trend, which may be due to the result of aerobic denitrification.?4?The aerobic biological treatment process of sludge fermentation liquid was characterized by three-dimensional fluorescence spectroscopy, and the linear relationship between the fluorescence score of the fermentation broth and the change of COD concentration was established, the correlation coefficient R²=0.908 was obtained, which showed that there was a good linear relationship between the fluorescence score and COD value of the protein, and it could reflect the change of COD concentration in the fermentation process by three dimensional fluorescence spectroscopy.