共查询到20条相似文献，搜索用时 453 毫秒
1.
微曝气垂直流湿地处理城郊低浓度生活污水模拟实验 总被引：1，自引：0，他引：1
本文提出微曝气垂直流湿地的概念,并通过柱状模型实验模拟研究了其对云南滇池流域城郊低浓度生活污水的处理效果.测定了模型的氧利用效率,最高为14.04%.在高水力负荷15.29m3/(m2·d)、气水比1:2的条件下,BOD5和NI4-N去除率分别为74.4%和63.5%,出水平均含量分别为4.96mg/L和272mg/L.结果说明,微曝气垂直流湿地工艺能满足低浓度生活污水高水力负荷的处理要求,微曝气耗能折价O.04-0.05元/m3. 相似文献
2.
本文研究了分级进水对阶梯垂直流人工湿地处理生活污水效果的影响.在保持总水力负荷为100 mm/d的情况下,分别将总进水量的0%、10%、20%和30%用于湿地第2级阶梯的进水,分析了系统对化学需氧量(COD)和氮、磷的总去除率和沿程变化.结果表明,不同分级进水比例条件下人工湿地对COD和总磷(TP)的去除率差异不明显,COD和TP的最高去除率分别为87.80%和81.17%,COD的去除主要集中在第1级,其贡献率平均为82.18%,TP的去除主要集中在第3级,贡献率平均为54.37%.分级进水对总氮(TN)去除率影响显著(P0.05),当2级进水比例为20%时,TN去除率最高,为61.70%±4.48%,且3个梯级对TN的去除贡献率分别为36.52%、42.11%和21.37%.相同组合形式的垂直流人工湿地处理生活污水的工程应用中,可根据需求设置20%左右的2级进水比例,以提高人工湿地对污染物的去除效果. 相似文献
3.
基于植物昼夜释氧变化规律的复合垂直流人工湿地氮形态 总被引：1，自引：1，他引：0
为了研究植物根系释氧规律对人工湿地中硝化与反硝化作用的影响,采用传统连续运行方式及根据释氧规律调节的新型运行方式(白天连续进水、夜间停水),在复合垂直流人工湿地小试系统中进行实验,采用代表性的挺水植物香蒲作为湿地植物,水力负荷为0.71 m3/(m2.d).结果表明:系统内白天以好氧的硝化作用为主,夜间以厌氧、缺氧的反硝化作用为主,且在新型运行方式下,系统内白天亚硝酸盐氮累积量为传统运行方式的5倍,硝酸盐氮累积量为其2倍,夜间亚硝酸盐氮和硝酸盐氮减少量又分别比传统运行方式高64%和26%.这说明在新型运行方式下,人工湿地脱氮效果优于传统运行方式. 相似文献
4.
云南抚仙湖窑泥沟复合湿地的除氮效果 总被引：11，自引：3，他引：8
为了延缓抚仙湖局部湖湾水体富营养化趋势,在北岸建设了净化面积1hm2.的复合人工湿地.综合利用生物氧化塘、水平潜流湿地和表面流湿地治理技术,对入湖河道窑泥沟污水中氮的去除效果进行了试验研究.试验结果表明,湿地系统的除氮效果十分明显,水力负荷年平均为437mm／d,氮负荷年平均为3.315 g／(m2·d),湿地系统氮滞留量年平均为1.91g／(m2·d).其中,通过植物吸收同化作用除氮量为0.142g／(m2·d),占总氮滞留量的7.5％左右.湿地系统对污水中硝酸盐及亚硝酸盐氮(NOX-)、氨氮(NH4+)、有机氮(TON)和总氮(TN)的去除率年平均分别为62.7％、53.8％、62.4％和57.5％.在湿地系统各功能区中,表面流人工湿地除氮效果最佳,氮去除率年平均为39.4％,硝化和反硝化作用均较强;生物净化塘除氮效果次之,氮去除率年平均为18.5％;潜流人工湿地氮去除率年平均为10.6％;沉淀池中氮去除率年平均只有3.6％. 相似文献
5.
垂直流人工湿地对尾水的净化效果及最佳水力负荷 总被引：1，自引：1，他引：0
以污水厂尾水为处理对象,研究垂直流人工湿地在4种水力负荷(125、250、375和500 mm/d)条件下的周年净化效果,结果表明:秋季时系统的总氮去除率最高,冬季则显著降低;温度为10℃、溶解氧浓度为1.1 mg/L是反硝化强度显著降低的关键拐点;总磷在冬季较其他季节净化效果高;125 mm/d水力负荷下CODCr去除率显著高于其他水力负荷,冬季CODCr去除率显著降低,而其他水力负荷及季节下的去除效果没有显著差异;当湿地以高去除率为目标时,最佳水力负荷为125 mm/d;当湿地以地表水水环境质量Ⅴ类标准为目标时,最佳水力负荷为375 mm/d;当湿地以污染物去除量为目标时,最佳水力负荷为500 mm/d.综合推荐375 mm/d为最佳水力负荷. 相似文献
6.
垂直流人工湿地填料的淤堵机理初探 总被引：12，自引：1，他引：11
应用人工湿地技术处理污水时,填料的淤堵往往是制约其处理功效和使用寿命的主要因素.本研究采用垂直流人工湿地单元模型,通过测定填料有效孔隙率与截留SS总量、COD降解量、生物膜的增长量之间的关系,初步探讨填料淤堵机理.结果表明:进水中悬浮颗粒全部为无机颗粒的系统较进水中全部为溶解态污染物质的系统更易造成淤堵,进水中全部为溶解态污染物的系统至实验结束时未出现淤堵现象.淤堵发生后,填料上层的渗透系数明显低于中下层,表明淤堵主要发生在填料上层部分;截留的不可生物降解无机SS、被截留但未被降解的有机SS、生物膜的生长及老化脱落、以及被上述物质吸附的水是导致淤堵的主要原因.淤堵发生后,湿地日污染物去除总量降低,湿地功效受到影响. 相似文献
7.
利用生物膜强化表流湿地处理农村生活污水的试验 总被引：1，自引：0，他引：1
针对农村生活污水难以集中处理的问题,提出了采用生物膜强化表流湿地工艺就地进行农村生活污水处理的方法,并对其进行试验研究.结果表明:在表流湿地表面设置生物膜载体后,系统的水质净化能力提高,处理负荷较高的条件下(CODCr:657.27 mg/L、TN:26.27 mg/L、TP:8.66 mg/L和SS:276 mg/L),处理效果显著提高.在效果明显的试验组中,生物膜设置后系统对TN、TP、CODCr的去除率分别提高了21.64%、16.24%、19.12%.另外,通过对系统中微生物的检测发现,生物膜载体的引入对湿地系统本身影响不大,系统水质净化能力的提高主要源于载体上微生物的增加.该方法在未增加系统占地面积的情况下提高了水质净化能力,为解决农村生活污水处理难的问题提供了新的思路. 相似文献
8.
微曝气生态浮床净化入湖河口污染河水原位模型实验 总被引：5，自引：1，他引：4
针对污染河水黑臭缺氧、NH_4~+-N含量高等问题,研发了一种"漂浮载体悬挂弹性生物膜填料+水生植物并辅以人工微曝气系统"的微曝气生态浮床系统.通过原位模型实验,研究了其在大清河入湖河口对污染河水的净化效果,当水力负荷为1500mm/d时,对TN和NH_4~+-N的平均去除率分别为81.1%、91.3%,对TP的平均去除率为72.7%,对PO_4~(3-)-p的平均去除率为92.5%,对有机物亦有较强的去除能力;处理1m~3水需要的曝气费用约为0.007元.微曝气生态浮床系统整体运行稳定、去除效率高、能耗低,适合流水环境,可直接在污染河道和人湖河口区对污染河水进行自流净化. 相似文献
9.
不同水生植物对湿地无机氮素去除效果的模拟 总被引：7，自引：1，他引：6
分别以芦苇、花叶水葱和苦草构建成小规模人工湿地模拟系统,开展不同类型水生植物湿地中无机氮（硝态氮和铵态氮）去除效果的试验。试验结果表明：在分别以芦苇、花叶水葱和苦草构成的模拟湿地单元中,虽然氧化还原等环境条件呈现较大差异,但不同类型水生植物湿地单元的铵态氮和硝态氮的去除率并没有显著差别,这与以往关于不同类型水生植物对氮素去除贡献的认识有所不同;水生植物对模拟湿地体系中氮素的去除具有重要作用,在相对较低的氮负荷（NH4^＋-N约为2.85mg／L,NO3^-N约为1.07mg／L,相当于一般城市污染河流）条件下,有水生植物湿地单元中铵态氮和硝态氮的10d去除率分别在39.32％和21.91％以上,而无水生植物的空白湿地单元对铵态氮和硝态氮的10d去除率分别只有34.68％和13.86％;在提高模拟湿地体系水体氮（NH4^＋-N约为5.50mg／L,NO3^-N约为3.37mg／L,是一般城市污染程度的2倍）负荷条件下,有水生植物湿地单元中铵态氮和硝态氮的10d去除率分别大于或等于66.87％和78.92％以上,而无水生植物的空白湿地单元对铵态氮和硝态氮的10d去除率仅为40.62％和31.77％,为人工湿地对原污水或初沉池出水的处理提供了有力依据。试验结果还表明,水生植物能有效促进湿地的氮素转化过程,显著缩短无机氮素在湿地中的寄宿时间。 相似文献
10.
滇池流域点源污染控制与存在问题解析 总被引：14，自引：4，他引：10
滇池是我国著名的高原淡水湖泊,是国家"三河三湖"治理重点之一.对2007年滇池流域点源污染现状和近20年变化趋势进行了分析,并在此基础上解析了滇池流域点源污染存在问题.结果表明,2007年滇池流域点污染源COD.TN和TP产生量分别为55913t、11222t和1008t,生活污水为主要的点污染源,COD、TN、TP所占比例分别达89%、96%、98%;1988-2007年,流域点源污染负荷产生量持续增长,但由于1991年以来污水处理能力的大幅度提升,其后点源污染负荷总体上呈现下降的趋势,尤以COD和TP下降趋势最为明显,TN保持波动状态.滇池点源污染存在四方面问题,一是未来城市的扩张和人口的持续增长,势必给滇池水环境带来巨大压力;二是老城区合流制排水系统无法改变、新城区雨污管网混接、部分污水处理厂河道取水,导致雨季合流污水溢流污染问题长期存在;三是局部区域污水产生量与污水处理厂处理能力不匹配,且污水处理厂雨季处理能力不足;四是点源污染末端处理已不能满足滇池保护的要求,亟待加大污染全过程控制. 相似文献
11.
Praveen Galav N. Dashora S. Sharma R. Pandey 《Journal of Atmospheric and Solar》2010,72(17):1309-1317
We present the mean diurnal, seasonal and annual variations in TEC during the lowest solar activity phase from low latitude Indian zone recorded at Udaipur (Geog. Lat. 24.6°N, Geog. Long.73.7°E, Geomag. Lat. 15.6°N) using a GPS receiver. Seasonal variations in daytime TEC show a semiannual periodicity, with a minimum in winter. Results of seasonal variations have been compared with that of the IRI-2007 model. Model calculations reveal significant seasonal as well as longitudinal differences in TEC. Seasonal variations in the nighttime TEC reveal an annual periodicity. Near the crest of the EIA, TEC shows a very good correlation with the solar flux. The results also point to weakening of the anomaly crest as well as its spatial and temporal contraction with declining solar activity. 相似文献
12.
13.
Scaling properties of Canadian low flows, namely annual minimum mean 1-, 5- and 7-day flows, are evaluated across Canada and in its sub-climatic regions. Across the entire country, the log relationship between the kth product moments (PMs, E[Qik]) of low flows and drainage area (Ai) can be represented by: ln(E[Qik])=ak+bkln(Ai)and bk=k, with = 0.86, 0.94 and 0.93 for annual minimum mean 1-, 5- and 7-day flows, respectively. The log linear relationships between the kth probability weighted moments (PWMs, ) and Ai are ln()=ck+Hln(Ai), in which H is constant and is independent of k. The values of H are 0.87, 0.97, and 0.96 for annual minimum mean 1-, 5- and 7-day flows, respectively, which are almost the same as the values. The coefficients of variation (Cv) are almost independent of drainage area. These results demonstrate that Canadian low flows generally exhibit simple scaling and drainage area alone describes most of the variability in the moments of the low flows. Low flows in each of the sub-climatic regions also obey a simple scaling law. The values of , H and Cv are different in each region, which may stem from physiographical and climatological differences among these regions. The finding lays a basis for applying the index flood method to conduct regional low flow frequency analysis as simple scaling is equivalent to the index flood method.Acknowledgements The authors thank Prof. Thian Yew Gan of University of Alberta, Canada for providing additional pristine data sites for regions 4 and 10. A constructive comments provided by an anonymous reviewer improved the quality of the paper. 相似文献
14.
Recent measurements have shown that the magnetic coercive forces of some Apollo lunar samples show an un-expected decrease with decreasing temperature at cryogenic temperatures. This behavior can be explained quantitatively in terms of a model which considers additive contributions from a soft, reversible magnetic phase and from a harder, hysteretic magnetic phase. 相似文献
15.
Interference effects of aircraft on earth's electromagnetic response at very low frequency and low frequency 
下载免费PDF全文
下载免费PDF全文 Over the last few decades, very low frequency electromagnetics has been widely and successfully applied in mineral exploration and groundwater exploration. Many radio transmitters with strong signal‐to‐noise ratios are scattered in the very low frequency band and low frequency band. Based on experiences gained from ground measurements with the radio‐magnetotelluric technique operating in the frequency interval 1–250 kHz, broadband magnetometers have been used to cover both very low frequency (3–30 kHz) and low frequency (30–300 kHz) bands to increase the resolution of the near‐surface structure. The metallic aircraft as a conductive body will distort the magnetic signal to some extent, and thus it is important to investigate aircraft interference on the electromagnetic signal. We studied noise caused by rotation of an aircraft and the aircraft itself as a metallic conductive body with three methods: 3D wave polarization, determination of transmitter direction and full tipper estimation. Both very low frequency and low frequency bands were investigated. The results show that the magnetic field is independent of the aircraft at low frequencies in the very low frequency band and part of the low frequency band (below 100 kHz). At high frequencies (above 100 kHz), the signals are more greatly influenced by the aircraft, and the wave polarization directions are more scattered, as observed when the aircraft turned. Some aircraft generated noise mixed with radio transmitter signals, detected as ‘dummy’ signals by the 3D wave polarization method. The estimated scalar magnetic transfer functions are dependent on the aircraft flight directions at high frequencies, because of aircraft interference. The aircraft eigenresponse in the transfer functions (tippers) between vertical and horizontal magnetic field components was compensated for in the real part of the estimated tippers, but some unknown effect was still observed in the imaginary parts. 相似文献
16.
S. A. Lawal W. E. Watt D. G. Watts 《Stochastic Environmental Research and Risk Assessment (SERRA)》1997,11(4):303-321
A model is developed for annual low flow hydrographs. Its two primary components reflect the fact that hydrologic processes
during streamflow rise (function of water input) and recession (function of basin storage) are different. Durations of periods
of rise (wet intervals) and recession (dry intervals) are modelled by discrete probability distributions — negative binomial
for dry intervals and negative binomial or modified logarithmic series for wet intervals depending on goodness of fit. During
wet intervals, the total inflow is modelled by the lognormal distribution and daily amounts are allocated according to a pattern-averaged
model. During dry intervals, the flow recedes according to a deterministic-stochastic recession model.
The model was applied to three Canadian basins with drainage area ranging from 2210 to 22000 km2 to generate 50 realizations of low flow hydrographs. The resulting two standard-error confidence band for the simulated probability
distribution of annual minimum 7-day flows enclosed the probability distribution estimated from the observed record. A sensitivity
analysis for the three basins revealed that in addition to the recession submodel, the most important submodel is that describing
seasonality. The state of the basin at the beginning of the low flow period is of marginal importance and the daily distribution
of input is unimportant. 相似文献
17.
A model is developed for annual low flow hydrographs. Its two primary components reflect the fact that hydrologic processes
during streamflow rise (function of water input) and recession (function of basin storage) are different. Durations of periods
of rise (wet intervals) and recession (dry intervals) are modelled by discrete probability distributions — negative binomial
for dry intervals and negative binomial or modified logarithmic series for wet intervals depending on goodness of fit. During
wet intervals, the total inflow is modelled by the lognormal distribution and daily amounts are allocated according to a pattern-averaged
model. During dry intervals, the flow recedes according to a deterministic-stochastic recession model.
The model was applied to three Canadian basins with drainage area ranging from 2210 to 22000 km2 to generate 50 realizations of low flow hydrographs. The resulting two standard-error confidence band for the simulated probability
distribution of annual minimum 7-day flows enclosed the probability distribution estimated from the observed record. A sensitivity
analysis for the three basins revealed that in addition to the recession submodel, the most important submodel is that describing
seasonality. The state of the basin at the beginning of the low flow period is of marginal importance and the daily distribution
of input is unimportant. 相似文献
18.
Seasonality indices for regionalizing low flows 总被引：2，自引：0，他引：2
In this study we examine three seasonality indices for their potential in regionalizing low flows. The indices are seasonality histograms (SHs) that represent the monthly distribution of low flows, a cyclic seasonality index (SI) that represents the average timing of low flows within a year, and the seasonality ratio (SR), which is the ratio of summer and winter low flows. The rationale of examining these indices is the recognition that summer and winter low flows are subject to important differences in the underlying hydrological processes. We analyse specific low flow discharges q95, i.e. the specific discharge that is exceeded on 95% of all days at a particular site. Data from 325 subcatchments in Austria, ranging in catchment area from 7 to 963 km2, are used in the analysis. In a first step, three seasonality indices are compared. Their spatial patterns can be interpreted well on hydrological grounds. In a second step, the indices are used to classify the catchments into two, three, and eight regions based on different combinations of the indices. In a third step, the value of the seasonality indices for low flow regionalization is examined by comparing the cross‐validation performance of multiple regressions between low flows and catchment characteristics. The regressions make use of the three seasonality‐based classifications. The results indicate that grouping the study area into two regions and three regions and separate regressions in each region gives the best performance. A global regression model yields the lowest performance and a global regression model that uses different calibration coefficients in each of the eight regions only performs slightly better. This suggests that separate regression models in each of the regions are to be preferred over a global model in order to represent differences in the way catchment characteristics are related to low flows. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
19.
Geomagnetic storm effects at low latitudes 总被引：1，自引：0，他引：1
R. G. Rastogi 《Annales Geophysicae》1999,17(3):438-441
The geomagnetic horizontal (H) field from the chain of nine observatories in India are used to study the storm-time and disturbance daily variations. The peak decrease in storm-time variation in H showed significant enhancements at the equatorial electrojet stations over and above the normally expected decrease due to the ring current effects corrected for geomagnetic latitudes. The disturbance daily variation of H at equatorial stations showed a large decrease around midday hours over and above the usual dawn-maximum and dusk-minimum seen at any mid-latitude stations around the world. These slow and persistent additional decreases of H of disturbance daily variation at equatorial latitudes could be the effect of a westward electric field due to the Disturbance Ionospheric dynamo coupled with abnormally large electrical conductivities in the E region over the equator. 相似文献