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841.
Feasibility of a membrane-aerated biofilm reactor to achieve single-stage autotrophic nitrogen removal based on Anammox 总被引:11,自引:0,他引:11
A laboratory-scale membrane-aerated biofilm bioreactor (MABR) equipped with non-woven fabrics support around the gas-permeable carbon tube was developed for single-stage autotrophic nitrogen removal based on partial nitrification and anaerobic ammonium oxidization. This reactor allowed air to be supplied through the microporous carbon tube wall to the biofilm that was supported by non-woven fabrics. The partial nitrification and consumption of dissolved oxygen occurred in the inner layer and Anammox in the anoxic outer layer of the non-woven fabrics, thus realizing autotrophic nitrogen removal in a single reactor. After 116d of operation, the maximal nitrogen removal of 0.77kgNm(-3)d(-1) at a volumetric ammonium loading rate of 0.87kgNm(-3)d(-1) was achieved. The spatial profiles of the ammonia-oxidizing bacteria and Anammox bacteria were evaluated by fluorescence in situ hybridization. This study demonstrated that MABR was a very suitable experimental set-up for the operation of the single-stage autotrophic nitrogen removal process. 相似文献
842.
843.
Response of non-point source pollutant loads to climate change in the Shitoukoumen reservoir catchment 总被引:3,自引:0,他引:3
The impacts of climate change on streamflow and non-point source pollutant loads in the Shitoukoumen reservoir catchment are
predicted by combining a general circulation model (HadCM3) with the Soil and Water Assessment Tool (SWAT) hydrological model.
A statistical downscaling model was used to generate future local scenarios of meteorological variables such as temperature
and precipitation. Then, the downscaled meteorological variables were used as input to the SWAT hydrological model calibrated
and validated with observations, and the corresponding changes of future streamflow and non-point source pollutant loads in
Shitoukoumen reservoir catchment were simulated and analyzed. Results show that daily temperature increases in three future
periods (2010–2039, 2040–2069, and 2070–2099) relative to a baseline of 1961–1990, and the rate of increase is 0.63°C per
decade. Annual precipitation also shows an apparent increase of 11 mm per decade. The calibration and validation results showed
that the SWAT model was able to simulate well the streamflow and non-point source pollutant loads, with a coefficient of determination
of 0.7 and a Nash–Sutcliffe efficiency of about 0.7 for both the calibration and validation periods. The future climate change
has a significant impact on streamflow and non-point source pollutant loads. The annual streamflow shows a fluctuating upward
trend from 2010 to 2099, with an increase rate of 1.1 m3 s−1 per decade, and a significant upward trend in summer, with an increase rate of 1.32 m3 s−1 per decade. The increase in summer contributes the most to the increase of annual load compared with other seasons. The annual
NH4+-N load into Shitoukoumen reservoir shows a significant downward trend with a decrease rate of 40.6 t per decade. The annual
TP load shows an insignificant increasing trend, and its change rate is 3.77 t per decade. The results of this analysis provide
a scientific basis for effective support of decision makers and strategies of adaptation to climate change. 相似文献
844.
Total concentrations and speciation of heavy metals in soils of the Shenyang Zhangshi Irrigation Area, China 总被引:1,自引:0,他引:1
The Shenyang Zhangshi Irrigation Area (SZIA) was used for the spreading of municipal and industrial waste water, which is an economic way of irrigating crops, recycling nutrients and water treatment. Long-term irrigation resulted in a severe metal contamination of soils. To identify the soil phases implicated in retaining the metals, sequential extractions were performed. The most predominant metal was cadmium which was mainly associated with mobile, easily soluble and easily reducible fractions. Copper was mainly associated with the residual, EDTA extractable and moderately reducible fractions. Lead was bound to organic matter and poorly crystalline Fe-oxides. Nickel and zinc were mainly associated with the residual and strongly reducible fractions. Although copper, lead, nickel and zinc concentrations were of minor importance mobile metal concentrations of these metals as well as of cadmium exceeded German trigger values for plant production and plant growth. 相似文献
845.
Evaluating the effectiveness of routine water quality monitoring in Miyun reservoir based on geostatistical analysis 总被引:2,自引:0,他引:2
This study used geographic information system techniques and geostatistics methods to evaluate the effectiveness of routine water quality monitoring in the western segment of the Miyun reservoir in Beijing. Methodologies as well as the sampling design are evaluated. The single-layer evaluation and three integrated evaluation methods including principal component analysis (PCA), ordinary kriging (OK)_Mean, and Mean_Layers were used to validate the effectiveness of evaluation methods, and the effectiveness of each sampling design was validated by comparing their errors. Results indicated that, while a single-layer evaluation only shows the trophic state of water at a specific level, an integrated evaluation synthetically analyzes and evaluates the trophic state of the entire water body. Furthermore, results of the integrated analysis show that a PCA method is more accurate and can represent the trophic state of the entire water body. The OK_Mean and Mean_Layers methods are only able to represent the mean level for trophic state of the entire water body but cannot reflect local trophic state and distribution details. Although methods used in the routine monitoring of Miyun reservoir have some similarities to the OK_Mean and Mean_Layers methods, their range of errors and uncertainty are greater because of a lack of detailed spatial continuous information. The analysis on the number of sampling points shows that, within a certain range of error, minor changes of sampling points will have no obvious impact on the monitoring results. For the routine monitoring of western Miyun reservoir, using only three to five sampling points for monitoring is inadequate. According to our analysis, it is more appropriate to use at least ten sampling points for monitoring these areas. 相似文献
846.
This study first presents the spatial distribution, temporal variation, and sources of heavy metal pollution in groundwater of a nonferrous metal mine area in China. Unconfined groundwater was polluted by Pb, Zn, As, and Cu, in order, while confined karst water in the mines showed pollution in the following sequence: Zn, Cd, Cu, Pb, and As. Pollution by Pb was widespread, while Zn, As, Cu, and Cd were found to be high in the north–central industrial region and to decrease gradually with distance from smelters and tailings. Vertically, more Pb, Zn, Cu, and Cd have accumulated in shallow Quaternary groundwater, while more As have migrated into the deeper fracture groundwater in the local discharge area. Zn, Cd, and Cu concentrations in groundwater along the riverside diminished owing to reduced wastewater drainage since 1977, while samples in the confluence area were found to have increasing contents of Pb, Zn, As, Cu, and Cd since industrialization began in the 1990s. Sources of heavy metals in groundwater were of anthropogenic origin except for Cr. Pb originated primarily from airborne volatile particulates, wastewater, and waste residues and deposited continuously, while Zn, Cd, and Cu were derived from the wastewater of smelters and leakage of tailings, which corresponded to the related soil and surface residue researches. Elevated As values around factories might be the result of chemical reactions. Flow patterns in different hydrogeological units and adsorption capability of from Quaternary sediments restricted their cross-border diffusion. 相似文献
847.
动态网页是目前网站发展的趋势,也是网站设计的主流.动态网页设计的教学既是新型思维的训练又是综合技能的练习.本文结合现代高职教育的需求,针对动态网页设计教学课程的特点,从教学內容、教学方式、考核方式这三方面阐述了如何改进该课程的教学效果. 相似文献
848.
849.
Pot experiment was conducted to evaluate the phytoremediation of pyrene-contaminated soil using alfalfa (Medicago sativa L.). Alfalfa biomasses, microbial viable counts, dehydrogenase activity, residual pyrene concentration and pyrene removal percentage were determined after 60 days of alfalfa growth. The results indicated that pyrene had an inhibitive effect on alfalfa growth, and higher pyrene concentration seriously affected alfalfa growth. In addition, the inhibitive effect on the root was more severe than that on the shoot. When pyrene concentration reached 492 mg kg(-1) in soil, the shoot and root biomasses were only 34% and 22% of those of alfalfa growing in non-spiked soil, respectively. The rhizospheric bacterial and fungi counts were 5.0-7.5 and 1.8-2.3 times higher than those in non-rhizosphere soil, respectively. The residual concentrations of pyrene in the rhizosphere soil were lower than those in the non-rhizosphere soil. After 60 days, 69-85% and 59-80% of spiked pyrene disappeared from the rhizosphere and non-rhizosphere soils, respectively. The removal percentage decreased with increasing pyrene concentration. However, the average removal of pyrene in the rhizosphere soil was 6% higher than that in the non-rhizosphere soil. Therefore, the presence of alfalfa roots was effective in promoting the phytoremediation of freshly added pyrene into the soil. 相似文献
850.