Effect of sludge anaerobic digestion on enhanced release of phosphorus and organic matter under the control of free ammonia
For the purpose of sludge resource utilization and energy utilization,free ammonia was adopted to control the organic matter in the system to increase the volume fraction of methane in biogas while analyzing the changes of phosphorus concentration and form in the system.The experimental results showed that,compared with the blank stage,the mass concentration of soluble protein and polysaccharide in the system increased by 16.34％and 26.43％respectively,and the average volume fraction of methane in biogas increased from 73.61％to 85.04％.Through three-dimensional fluorescence spectroscopy(3D-EEM)and parallel factor method(PARAFAC)analysis of the two reaction stages of anaerobic sludge supernatant,the proportion of aromatic protein Ⅰ decreased from 35％and 47％to 29％and 40％,respectively,indicating that the utilization of aromatic protein Ⅰ was slightly improved after free ammonia regulation.In the aspect of phosphorus speciation analysis,the free ammonia regulation increased the total phosphorus and phosphate concentration in the water inlet and outlet by 948.64％,1219.35％,2254.55％and 2280％respectively,and the phosphorus release effect was obvious.According to the analysis results of X-ray energy dispersion spectroscopy(EDS),Fourier transform infrared spectroscopy(FTIR)and X-ray photoelectron spectroscopy(XPS),it was found that P mainly existed in the form of complex salt with Fe,Al and other metal elements in the sludge,and a certain proportion of phosphorus transformation occurred in the process of anaerobic digestion.However,furhter study was still needed to investigate the mechanism of phosphorus transformation induced by free ammonia.The results further showed that the regulation of free ammonia enhanced the utilization of organic matter and promoted the release and morphological change of phosphorus in the process of anaerobic digestion.The results of this study can provide a reference for the release of organic matter and phosphorus under the regulation of free ammonia.
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