Papers by Keyword: Nitrogen

Abstract: The primary objective of this research was to evaluate the effectiveness of a magnetic ion exchange process (MIEX) in removing inorganic anions from municipal secondary effluent. Municipal secondary effluent drew from Gaobeidian wastewater treatment plant treating about 800,000 m3/day domestic wastewater. In the pilot experiment, MIEX resin removed 37.01% phosphorus, 31.62% nitrate, 36.06% ammonium and 64.34% sulphate from municipal secondary effluent. Phosphorus concentration in resin influent influenced reclaimed water treatment efficiency. Phosphorus removal rate was positively correlated with the concentration in influent. If phosphorus concentration in influent was >0.82mg/L, phosphorus removal of >52% was achieved. Nitrate and sulphate removal had same variation laws. 18.92% average removal rate of nitrate in middle period was lower than 35.06% and 39.25% average removal rates in earlier and latter periods respectively. The average removal rates of ammonium in three periods were 83.03%, 43.51% and 84.29% respectively. Removed ammonium of each sample was about 0.250mg/L, average removal rate was 36.06%. Lower ammonium concentration in influent could cause higher removal rate. Otherwise, magnetic ion exchange process could increase turbidity and could not disinfect, the resin effluent will be treated with coagulation-sedimentation and ozonation for groundwater recharge research with reclaimed water.

Abstract: Determination of methylene blue concentrations of hydrogen sulfide in the air is sensitive and rapid ect. However, the standard curve tend to appear low line slope, leading to measurement errors. In the preparation of ZnS colloidal process, it is nitrogen as the carrier gas and protective gas. Its direct impact on the ventilation conditions colloidal particle size and uniformity of the precision for the calibration concentration have the significant impact, particles size appropriate uniform colloidal solution and the concentration can be more stable and accurate calibration by the standard curve. It was drawn to meet the requirement that is possible, too large or too small particles on the experimental results will lead to a greater impact. This article is related to the verification experiment of nitrogen ventilation conditions (uniform or not) with aeration velocity on the slope of the curve standard. The experiment we have come to: In this study, ZnS colloidal preparation on passing the nitrogen should be uniform, and the ventilation rate is smaller and needed to continuously bubbling one by one, in which the case of the experimental results, it is required by the standard curve that is drawn 0.1489, spiked recovery rate of 97.5% and 99.0%.

Abstract: Soil and water loss from sloped farmland is a mainly environmental and agricultural issue worldwide. Many management practices have been selected and are effective to reduce sediment and associated nutrient losses. Fallout ²¹⁰Pb_ex tracer technique was used to quantity the soil erosion in terrace cultivation and contour farming field. The soil erosion rate from up-and-down slope field was estimated by RUSLE2 model. The sediment yields from contouring and terraces were reduced 63% and 95%, respectively, by comparison with up-and-down tillage. Terraces could reduce soil erosion 74% and intercept runoff 45% than contouring tillage. However, the concentrations of nitrogen and phosphorus with runoff from terraces were greater than those from contouring field. Transport loads of TP, DTP, and phosphate (PO₄^3- -P) through water from terraces increased 4.54, 1.34, and 2.53 times than those from contouring tillage, respectively. It is concluded that no single mitigation option can reduce all pollutants. Terrace can achieve pollutants reduction target in tandem with other soil and water conservations.

Abstract: Effectiveness of combinations of seven different ecotypes of wetland plants including Thalia dealbata, Iris tectorum, Acorus calamus,Zizania aquatica, Nymphaea tetragona,Georgi, Myriophyllum aquaticum, Thalia dealbata purifying water was investigated by hydrostatic simulation experiment method. The research showed that combinations of various wetland plants had significant purification effects on eutrophic water body, plant community was stable, and plants grew well. Chemical Oxygen Demand (COD) removal efficiencies of various combinations were higher than 97%, and 25.9% higher than that of the blank control group; the average highest total phosphorus (TP) removal efficiency of plant combinations was 97.6%. Compared with COD and TP, Total nitrogen( TN)removal efficiency was lower, ranging from 90.4% to 83.1%.Different wetland plants had different purification effectiveness for different pollutant. The combination N+Z+A+ZI had the highest TNremoval efficiency, reaching 90.4%. Combinations N+Z+A+ZI and N+Z respectively won the first and second place in the disposal of TP,reaching 99.68%, 99.34%. For Chemical Oxygen Demand COD removal, the combination N+Z+C+T did the best and the highest removal efficiency reached 97.6%. Fuzzy comprehensive evaluation method is used to select the following combinations with stronger capacities of removing N and P in sewage: N+Z+A+ZI, N+Z, N+Z+C+T. They can be promoted and applied in purification of eutrophic water body in ecological projects.

Abstract: A field experiment was conducted to remove the potential eutrophication effect of N and P from rural wastewater (RW) during the whole rice growing season of 2010. Commercial fertilizer and RW were applied to furnish 40 kg P ha-1except CK. Results showed TN concentration of the floodwater in the paddy wetland system decreased quickly after transplanting, rosed significantly (P ≤ 0.05) after two N topdressings, and then decreased gradually as the following sequences: SW > GW > DW > BW > CK. Total P (TP) concentration had significantly declined after P application, from October 15 there were no significant increases in TP concentration in the floodwater. Meanwhile, the yield for CK was significantly less (P ≤0.05) than SW, GW, DW, and BW, with the yield of BW significantly greater (P ≤ 0.05) than other treatments. It is feasible to remove N and P from RW by the paddy wetland system and can be widely used to improve the yield of rice.

Abstract: The author measured TN, NH₄⁺-N, NO₂^--N, NO₃^--N, TP, PO₄^3--P and COD_Mn of the five aquaculture lakes that is, Liangzi Lake, Futou Lake, Chaipo Lake, Nanhu Lake and Yezhi Lake, in Wuhan in 2007, and had analyzed the results by means of Principal Component Analysis (PCA), Factor Analysis (FA) and Cluster Analysis (CA). The PCA result showed that the two principal components were nutrient factor (including TN, NO₂^--N, NO₃^--N, TP, PO₄^3--P and COD_Mn) and ammonium absorption factor (NH₄⁺-N), with their function expression integrated. The results of FA and PCA were in conformity, with their factor score function expression integrated. R-mode cluster result indicated that the seven hydrochemical indexes could be divided into four categories, i.e. NO₃ - -N, TP, TN and NO₂^--N make up of one category, and another three categories were PO₄^3--P, NH₄⁺-N and COD_Mn, respectively. Q-mode cluster result showed that the five lakes can be divided into two categories, Futou Lake and Liangzi Lake is one category, and Chaipo Lake, Yezhi Lake and Nanhu Lake is the other, which has been caused by urban waste water, domestic sewage and aquaculture production.

Abstract: With self-developed solubility determining unit, gas volume solubility of Daqing waxy crude oil saturated with nitrogen and natural gas was measured respectively at temperatures of 50°C, 55°C, 60°C and 65°C and under pressures from 2 to 20 MPa. The gas volume solubility in the crude oil is increased with the increasing of pressure for both nitrogen and natural gas at every temperature tested, which the increased extent of gas solubility of natural gas is much higher than that of nitrogen. Solubility of natural gas increases with the decreasing of temperature, but that of nitrogen increases with the increasing of temperature. Pressure has a main effect on gas volume solubility.

Abstract: This paper focuses on the formation of thin n+p junctions in p-type Silicon Carbide (SiC) epitaxial layers using two kinds of Nitrogen implantations. The standard beam ion implantations and PULSIONTM processes were performed at two distinct energies (700 eV and 7 keV), and the subsequent annealing was held at 1600°C in a resistive furnace specifically adapted to SiC material. No measurable electrical activity was obtained for both implantations performed at 700 eV, due to some outdiffusion of N dopants during the annealing despite a low surface roughness (rms ~ 1.4 nm) and no residual damage detected by RBS/C. A higher sheet resistance was measured in plasma-implanted samples at 7 keV (in comparison with beam-line implanted samples), which is partly related to N outdiffusion. The profiles of N atoms beam-implanted at 7 keV are not affected by the annealing. The corresponding electrical activation is fully completed.

Abstract: Oxygen precipitation (OP) behaviors were investigated for Czochralski (Cz) silicon wafers, which were coated with silicon nitride (SiNx) films or not, subjected to two-step anneal of 800C/4 h+1000°C/16 h following rapid thermal processing (RTP) at different temperatures ranging from 1150 to 1250C for 50 s. It was found that OP in the Cz silicon wafers coated with SiNx films was stronger in each case. This was because that nitrogen atoms diffused into bulk of Cz silicon wafer from the surface coated SiNx film during the high temperature RTP. Furthermore, it was proved that the RTP lamp irradiation facilitated the in-diffusion of nitrogen atoms, which was most likely due to that the ultraviolet light enhanced the breakage of silicon-nitrogen bonds.

Abstract: In order to explore the influence of the nitrogen concentrations on the impact toughness of the bearing steel GCr15，impact testing has been conducted on the steel samples with variant nitrogen contents (0.1-0.3 wt.%) on the tester JB－30B, and the fracture morphology of the samples after impact was investigated using scanning electron microscopy (SEM) and optical microscopy (OM). The results indicate that the impact toughness of the steel GCr15 with 0.1 wt.% nitrogen exhibits the lowest values with typical quasi-cleavage feature. The steel GCr15 with 0.2 wt.% nitrogen presents the maximum values in impact toughness associated with significant plastic deformation, suggesting ductile nature. The steel with 0.3 wt.% nitrogen presents a quasi-cleavage feature, and micro cracks observed beside the secondary precipitates. The impact toughness values of the steel with 0.3 wt.% nitrogen are higher than that with 0.1 wt.% nitrogen and lower than with 0.2 wt.% nitrogen. The results are valuable for a large-scale bench marked industrial manufacture of the bearing steel GCr15 with the optimized nitrogen concentrations.