[Spectral characteristics of soluble metabolites during endogenous respiration]

Endogenous respiration phase plays an important role in the sewage treatment process. In order to clearly understand the endogenous respiration process of the activated sludge process, three-dimensional fluorescence spectroscopy, ultraviolet spectroscopy and respirogram were employed for the analysis of endogenous respiration process. Results showed that the three-dimensional fluorescence spectroscopy and UV spectroscopy could identify all stages significantly. The following conclusions could be drawn: (1) Rapid decline phase of endogenous respiration:the excitation wavelength (EX) and emission wavelength (Em) of humic peak showed blue shift of 5 nm and 6 nm, respectively, the fluorescence index f450/500 and HIX (humification index) were reduced by 9. 3% and 0.2%, respectively, UV253/203 and UV254 increased by 37.5% and 200%, respectively. These results indicated the presence of bioavailable organics; (2)Slow decline phase of endogenous respiration: f450/500 was increased by 0. 5% , HIX was reduced by 0. 2% , UV253/203 was reduced by 20% , UV254 was increased by 16. 7%. These results indicated that hydrolysis or autolysis of cells might occur; (3)Stable phase of endogenous respiration: humic acid peak remained unchanged, indicating the adaption of microorganisms to starving environment. The analysis of the endogenous respiration process from the perspective of metabolites provides a new way for control of microbial wastewater treatment process.