The application of CO2-stripping system for calcium removal to upgrade organic matter removal and sludge granulation in a leachate-fed EGSB bioreactor was evaluated. Three-dimensional excitation-emission matrix (3D-EEM) spectroscopy combined with parallel factor (PARAFAC) analysis was used to characterize the transformation of the effluent dissolved organic matter (DOM) during the operation. X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) and scanning electronic microscopy (SEM) were used to assess the effects of a CO2-stripping unit on the microstructure of the granules. The introduction of the CO2-stripping system reduced the calcium concentration while upgrading methane evolution. The methane yield reached 0.33 L CH4 per g CODremoved in the bioreactor with the CO2-stripping unit compared with 0.31 L CH4 per g CODremoved without the unit as the control. The combined system produced 80% and 50-60% chemical oxygen demand (COD) and total nitrogen (TN) removal under steady-state conditions, which were 6.3% and 41.0% higher than those of the control, respectively. With 3D-EEM-PARAFAC analysis, three fluorescence components, associated as tryptophan protein-like (component 1, Ex/Em = 275-280/355-365 nm) and humic-like substances (component 2, Ex/Em = 240(295, 340)/450 nm and component 3, Ex/Em = 320/320 nm), were identified from the effluent samples. The componential characterizations confirmed the favorable influence of the CO2-stripping unit on the transformation of DOM. Further analysis through XRD, FT-IR and SEM demonstrated that the use of the unit alleviated inactivation of the granules through removing calcium, which might be the core reason for the enhancement of the EGSB performance.
ASJC Scopus subject areas
- Chemical Engineering(all)