[Nitrogen Removal Characteristics and Metabolism Mechanism of High-Efficiency Cold-Tolerant Heterotrophic Nitrification-Aerobic Denitrification Bacterium Glutamicibacter sp. WS1 for Various Nitrogen Sources at Low Temperature].

For resolving the problems of poor nitrogen removal efficiency and substandard effluent quality in wastewater treatment plants during winter, a cold-tolerant strain Glutamicibacter sp. WS1, with heterotrophic nitrification-aerobic denitrification ability, was isolated from activated sludge. The functional genes for nitrogen conversion of strain WS1 were amplified by PCR, and the nitrogen removal characteristics of the strain were verified under different nitrogen sources at 15℃. In addition, the effects of environmental factors on the aerobic denitrification performance of the strain were explored at low temperature. Finally, a reasonable nitrogen metabolism pathway of strain WS1 was resolved based on functional genes and nitrogen balance analysis. The results showed that strain WS1 contained functional genes related to nitrogen conversion, including amoA, napA, nirS, and nirK genes. Notably, nirS and nirK genes coexisted in the strain. At the low temperature of 15℃, with NH4+-N, NO3--N, NO2--N+NO3--N, and NH4+-N+NO3--N as nitrogen sources, the corresponding removal efficiencies of strain WS1 were 100%, 98.10%, 99.87%+100%, and 100%+94.92%, respectively. The optimal denitrification performance of the strain was achieved with sodium citrate as the carbon source, C/N of 16, pH of 8, DO of 4.5-6.8 mg·L-1, and temperature of 30℃. In addition, the NO3--N removal efficiency of strain WS1 reached 92.50% under low temperature (15℃) and low C/N (10) conditions. Based on the results of PCR amplification and nitrogen balance analysis, heterotrophic nitrification-aerobic denitrification/aerobic denitrification and assimilation were the main pathways for nitrogen substrate removal by strain WS1, in which most of the inorganic nitrogen (47%-56%) was converted to gaseous nitrogen through heterotrophic nitrification-aerobic denitrification/aerobic denitrification. Strain WS1 has broad application prospects in the treatment of low-temperature nitrogenous wastewater.

[Analysis of the Performance and Mechanism of Phosphorus Removal in Water by Steel Slag].

In view of the significant differences in phosphorus removal processes by different steel slags, electric furnace slag was taken as the research object to discuss the effects of environmental factors, including the adsorption time and adsorption temperature, on phosphorus removal and to verify the phosphorus removal performances of steel slag for phosphate, pyrophosphate, and actual water bodies. With the help of spectral techniques including scanning electron microscopy(SEM), energy dispersive X-ray spectroscopy(EDS), X-ray fluorescence spectroscopy(XRF), and an X-ray diffractometer(XRD), the phosphorus removal mechanisms of steel slag were explored. Moreover, the phosphorus removal abilities of different absorptive media of steel slag, ceramsite, and zeolite were compared, and the safety performances of phosphorus removal by steel slag were evaluated. The results showed that the adsorption time significantly affected the phosphorus removal efficiency of steel slag. The phosphorus removal efficiencies of phosphate solutions with a concentration range of 1-20 mg·L-1 using steel slag could reach over 97% when the adsorption time was 30 min. The effect of temperature on phosphorus removal by steel slag was not significant. The pyrophosphate adsorption capacity of steel slag was weaker than that of orthophosphate, and the removal rate of pyrophosphate with an initial concentration of 3 mg·L-1 was 82.45%. Spectral analysis showed that the mechanisms of phosphorus removal by steel slag were chemical adsorption assisted by physical adsorption, and calcium-phosphorus was the main precipitate component. CaHPO4·2H2O was the main precipitate. Steel slag exhibited excellent phosphorus removal properties for removing phosphorus in the biological pond effluent and wetland system, achieving total phosphorus removal rates of 98.36% and 93.33%, respectively. In comparison, the phosphate removal performance of steel slag was better than that of ceramsite and zeolite, and the removal efficiencies of PO43- were 96%, 40%, and 10%, respectively. The contents of heavy metals in the leaching solution of steel slag met the requirements of the Class I standard of surface water; thus, the steel slag was safe and reliable.

[Community Characteristics of Cultivable Bacteria in Fine Particles(PM2.5) of Beijing and Baoding].

Fine particles(PM2.5) collected by two middle volume air samplers in the suburbs of Baoding and the urban area of Beijing during Jan 10th to 17th, 2015, were used to compare the community characteristics of cultivable bacteria in the two sites. In this study, we observed the particle morphology of PM2.5 using a field emission scanning electron microscope (FESEM), analyzed the air mass transportation source of the two sampling sites by the NOAA/ARL HYSPLIT-4 backward trajectory model, and measured the concentrations of the major water-soluble ions and heavy metal elements in the PM2.5 samples using ion chromatography, continuous flow analyzer and ICP-MS. The results indicated that, the cultivable bacteria of PM2.5 contained three phyla, which were Firmicutes, Actinobacteria and α-Proteobacteria. Nine genera and 17 species of cultivable airborne bacteria were isolated and identified. The most abundant phylum was Firmicutes. The Gram-positive bacteria accounted for more than 90%. The spore-forming Bacillus which was the dominant species contributed 68.15% and 75% to the total bacteria in urban Beijing and the suburbs of Baoding, respectively. The difference in the community structure of PM2.5's cultivable bacteria in the two sampling areas may be affected by PM2.5's physical and chemical properties and air mass transportation.