Hui Du,Dong Liu,Hua Liu,Peng Gao,Renqing Lv,Ming Li,Bin Lou,Yuanxi Yang
The composition, structure, and colloidal stability of hydrocracked products at various hydrogen pressures were analyzed to investigate the role of hydrogen pressure in slurry-phase hydrocracking of Venezuela heavy oil. Experimental data showed that the formation of gas, naphtha, and coke was suppressed by a high hydrogen pressure during the slurry-phase hydrocracking. In addition, the maximum of light oil per coke ratio was observed at 8 MPa of hydrogen. The desulfurization and denitrogenation were promoted by the increase of hydrogen pressure. However, the influence of hydrogen pressure on the desulfurization rate was reduced at higher pressure, while the influence on the denitrogenation rate was still obvious. With the increase of hydrogen pressure, the Conradson carbon residue (CCR) of the vacuum residue (VR) product decreased. Meanwhile, the coking inducing period of the atmospheric residue (AR) product prolonged, which means that the colloidal stability of the AR product was enhanced by a high hydrogen pressure. Structural parameters of asphaltene were studied according to the reference of the Fourier transform infrared (FTIR) spectroscopy method of kerogen structure studying. The cracking and hydrogenation saturation of asphaltene were promoted by a high hydrogen pressure, which lead to the increase of the A factor (infrared absorption intensity ratio of saturated aliphatic carbon and aromatic carbon) and nCH2/nCH3 of asphaltene products as well as the decrease of the Y factor (condensation index of asphaltene) and Z factor (discriminative index of the side-chain fracture situation of asphaltene).
Subsurface wastewater infiltration system (SWIS) is an ecological wastewater treatment technology that has the advantages such as low operating costs, satisfactory pollutant removal effects and ecological service functions. However, emerging compounds in wastewater has increased uncertainties in its treatment performance. In this study, antibiotics were added to the raw water with stepwise increasing concentrations, and the content of pollutants and structure of microbial populations were analyzed, aiming to qualitatively and quantitatively reveal the effect of sulfamethoxazole (SMX), oxytetracycline (OTC) and levofloxacin hydrochloride (HCl-Lev) antibiotics on denitrification rate of SWIS and explore the responses of microbial community. The results showed that the SMX, OTC and HCl-Lev removal rates ranged 34.4–48.7%, negatively correlating with the influent loads in SWIS. Under the stress of compound antibiotic (30.90 ± 0.39–32.49 ± 0.37 mg L −1 ), N removal rate decreased from 89.8 ± 1.4 (control) to 43.6 ± 2.0% and 38.9 ± 5.0% with increasing the concentrations of antibiotics. As a result, the effluent NH 4 + -N, NO 3 − -N, NO 2 − –N and TN hardly meet the discharge standards in China. Proteobacteria , Acidobacteria , Bacillus , Firmicute s and Bacteroidetes dominated in SWIS, accounting for about 70–90% of all microorganisms, independent of the antibiotics additions. RDA analysis showed that the activities of urease and catalase were negatively correlated with the concentrations of COD, NH 4 + –N, NO 3 − –N, TN, SMX, OTC, and HCl-Lev, further indicating that in SWIS, nitrogen and organic compounds are mainly removed by microbial degradation.
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