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1.
A pilot scale study was set up to investigate the principle design parameters of up flow anaerobic sludge blanket (UASB) reactors for treating wastewater of small communities in the tropical regions of Iran. A steel pipe with a diameter of 600 mm and a height of 3.6 m was used as the reactor in which a digestion and a 3-phase separator element had a volume of 0.848 and 0.17 m3 respectively. During this study, which lasted for 203 days, two distinct phases were carried out according to the ambient temperature. The temperature of the wastewater entering the reactor was naturally ranged from 22 to 26 °C and no heat exchanger was used. The hydraulic retention times including 2, 4, 6, 8, and 10 hours with various loading rates of 0.95 to 5.70 kg COD/m3/day for colder period and from 1.35 to 6.40 kg COD/m3/day for warmer period were examined. On the basis of the results the optimal hydraulic retention time for warmer period with a 2.20 kg COD/m3/day organic loading rate was 6 hours which BOD5, COD and TSS removal efficiency were 71, 63 and 65 percent respectively. During the colder period the removal ratio of BOD5, COD and TSS with an optimal hydraulic retention time of 8 hours and organic loading rate of 1.22 kg COD/m3/day were 54, 46 and 53 percent respectively.  相似文献   

2.
滑体渗透系数是决定滑坡对降水入渗或库水位波动响应的关键参数。当滑坡区有较丰富的地下水位监测数据时,基于监测数据反演滑体渗透系数是公认的最有效途径之一。然而,反演参数的准确性受制于监测数据的采集频率和时长。确定反演滑体渗透系数的相对最优监测频率和监测时长是获取准确反演结果的前提。本文以三峡库区典型的碎石土滑坡——李家坡滑坡为例,通过渗流场反演模拟和反演结果与监测数据拟合途径,以反演结果的稳定性和离散性为评价指标,分析地下水位监测频率和监测时长对滑体渗透系数反演结果的影响,进而提出水库环境中反演碎石土滑坡滑体渗透系数的相对最佳监测频率和监测时长。研究发现:(1)监测时长不大于810 d、监测频率高于15 d/次时,可以获得水位误差相对最小、且基本稳定的反演结果;(2)监测频率1 d/次和5 d/次、监测时长同为270 d时,或监测频率10 d/次、监测时长540 d时,反演所得渗透系数的稳定性较好、离散性较小;(3) 监测频率15 d/次和30 d/次时,即使监测时长长达1 170 d,反演所得渗透系数的稳定性、离散性依然较差。综合反演水位误差大小、反演渗透系数的稳定性和离散性以及监测成本,认为监测频率5 d/次、监测时长270 d为三峡库区碎石土滑坡相对最佳的监测频率和监测时长。  相似文献   

3.
The analysis of the liquid silicate density model recently proposed in Bottingaet al. (1982) by Ghiorso and Carmichael (1984) is shown to be based on a combination of unwarranted mathematical assumptions, refusal to recognize experimental and theoretical evidence for the non-linear effect of composition on liquid silicate density, and a totally unrealistic view of the accuracy with which the thermal expansion of silicate liquids can be measured. As a consequence, none of the general or specific points raised by Ghiorso and Carmichael are relevant to the issue of which of the existing calculation models (Bottinga and Weill, 1970; Nelson and Carmichael, 1979; Moet al., 1982; or Bottingaet al., 1982, 1983) should be used. As stated in Bottinga, Richet and Weill (1983), there is a problem in using a combination of the molar volume parameters from the first three of these models because they are not mutually independent. However, the set of partial molar volumes and thermal expansion constants given in Bottingaet al. (1982, 1983) are internally consistent and mutually compatible. We remain firmly of the opinion that our latest model is an improvement over previous attempts because it conforms to a much wider set of observations, it incorporates a larger set of melt components, it calculates density and thermal expansion more accurately, and it points the way to one possible method of accommodating a non-linear phenomenon into a nonlinear model.  相似文献   

4.
Sago industry is one of the major small-scale sectors in India and over 800 units are located in the southern State of Tamilnadu. Processing of sago generates enormous quantities of high strength wastewater requiring systematic treatment prior to disposal. The present study is an attempt to treat the sago wastewater using Hybrid Upflow Anaerobic Sludge Blanket (HUASB) reactor, which offers the advantages of both fixed film and up flow anaerobic sludge blanket treatment. HUASB reactor with a volume of 5.6 L was operated at Organic Loading Rates varying from 10.7 to 24.7 kg COD/m3.day. After 130 days of startup, the reactor produced appreciable decrease in COD of wastewater and removed solids efficiently. The COD removal varied from 91–87%. While the removal of Total Solids was in the range of 61–57%, that of volatile solids varied from 70–67%. The ideal OLR for the reactor was 23.5 kg COD/m3.day. The findings of the study open up newer possibilities of design low cost and compact onsite treatment systems with very short retention periods.  相似文献   

5.
The factors which control concentrations of soluble inorganic phosphorus in the Amazon estuary are described and the efflux of phosphorus through the estuary is estimated using estuarine data collected on three field excursions (two in December, 1982 and one in May, 1983), and various laboratory mixing experiments. There is evidence to suggest that suspended sediments release significant quantities of inorganic phosphate to the estuarine waters. Bottom sediments collected from the estuary released soluble inorganic phosphorus at rates of approximately 0.2 μM day−1, when suspended in mixtures of seawater and deionized water. Release rates depended on salinity but were independent of sediment concentrations. Inputs of phosphate persisted for approximately 3 days in suspensions with sediment concentrations of 0.5 g l−1, but the duration of release increased to greater than 8 days at concentrations greater than 10 gl−1. A one-dimensional dispersion model was developed incorporating input rates derived from the laboratory mixing experiments. The model predicts phosphate concentrations which are consistent with field observations, and it provides quantitative estimates for total fluxes of soluble inorganic phosphorus to the high salinity fringes of the estuary (~25 ppt) of approximately 15 × 106molesday−1 and 27 × 106molesday−1 during December, 1982 and May, 1983 respectively. The data indicate a significant phosphate loss from estuarine waters at salinities from 0–4 ppt, possibly associated with iron and humate removal. More than 50% of the predicted flux could be contributed by phosphate released from suspended sediments within the turbid part of the estuary.  相似文献   

6.
Under stagnant conditions, the ability of 15 earth materials (non-lime) including various inorganic 2:1 and 1:1 layer silicates, an amorphous oxide, and two 'whole' soils were tested for their pH-buffering efficiency in an acid mine drainage (AMD) water. The purpose was to decrease AMD acidity to a level where sulfate-reducing bacteria (SRB) placed in it may be activated. Of all materials, a whole soil (a high cation-exchange capacity clayey mollisol containing 40% clay, and 4% soil organic matter) caused the greatest pH increases from 2.5 up to 5.5 units after 10 days in the AMD water. Influent AMD was then ameliorated at various speeds through an SRB driven bioreactor using a 50/50 weight over weight (w/w) combination of the mollisol and ryegrass (MR) as the pH buffer substrate. This substrate combination decreased the SRB acclimatisation period (from 50 days in a previous experiment utilising sludge + ryegrass) to <10 days in the present experiment. After causing pH increases from 2.8 to >6 units in 5 days, the buffer reduced the hydraulic retention time (HRT) of the constant-flow reactor from 12 days at flow speeds of 100 ml/day to 2 days at 25 ml/day, respectively. After 10 days, soluble Fe, Al and sulfate were all decreased >1,800-, >40- and 3-fold, respectively. This was a more efficient performance than the no-flow bioreactor of a previous experiment using sludge + ryegrass. This method of AMD rehabilitation is an alternative for localities that lack cheap sources of calcium compounds for chemical treatment, but have a similar soil type and copious quantities of fresh decomposable plant wastes.  相似文献   

7.
Iran is a developing country, and nowadays, a demand to establish a time transfer system can be sensed more than anytime. On the other hand, global positioning system (GPS) is one of the most efficient and accurate systems in precise time estimation and dissemination domain. This study aims to investigate the different accuracy limiting effects of a time transfer system in a geodetic point of view. For this purpose, a simulation study is performed in which pseudo-range and carrier phase observations are simulated for some GPS stations in Iran. The baselines for time transfer have been chosen in a way that the maximum effect of each bias source can be analyzed. Therefore, the results of this study can be used in order to design the absolute and relative locations of the GPS stations equipped with external atomic frequencies in Iran considering a specific application. As a result, the most prominent bias source is the site-specific troposphere parameters which produce a variation of more than 1 ns in the time transfer results. Other bias sources including bias in the coordinate components and orbital information have a considerable impact only for time keeping purposes. Additionally, the influence of noise of the carrier phase and pseudo-range observations is analyzed. Variations of clock estimations between consecutive epochs up to 70 ps and day boundary discontinuities up to 0.6 ns, respectively, are the results of measurement errors. On the other hand, a time transfer between H-masers located at US Naval Observatory and National Resources Canada has been conducted to pursue a standard and efficient algorithm to deal with the problem of day boundary jumps. The method of overlapping batches with 12 h coverage of each of the involved days is applied to overcome this problem. The results of this method show a considerable decrease in the magnitude of the day boundary jumps.  相似文献   

8.
Coastal flooding induced by storm surges associated with tropical cyclones is one of the greatest natural hazards sometimes even surpassing earthquakes. Although the frequency of tropical cyclones in the Indian seas is not high, the coastal region of India, Bangladesh and Myanmar suffer most in terms of life and property caused by the surges. Therefore, a location-specific storm surge prediction model for the coastal regions of Myanmar has been developed to carry out simulations of the 1975 Pathein, 1982 Gwa, 1992 Sandoway and 1994 Sittwe cyclones. The analysis area of the model covers from 8° N to 23° N and 90° E to 100° E. A uniform grid distance of about 9 km is taken along latitudinal and longitudinal directions. The coastal boundaries in the model are represented by orthogonal straight line segments. Using this model, numerical experiments are performed to simulate the storm surge heights associated with past severe cyclonic storms which struck the coastal regions of Myanmar. The model results are in agreement with the limited available surge estimates and observations.  相似文献   

9.
Mountain range specific analog weather forecast model is developed utilizing surface weather observations of reference stations in each mountain range in northwest Himalaya (NW-Himalaya). The model searches past similar cases from historical dataset of reference observatory in each mountain range based on current situation. The searched past similar cases of each mountain range are used to draw weather forecast for that mountain range in operational weather forecasting mode, three days in advance. The developed analog weather forecast model is tested with the independent dataset of more than 717 days (542 days for Pir Panjal range in HP) of the past 4 winters (2003–2004 to 2006–2007). Independent test results are reasonably good and suggest that there is some possibility of forecasting weather in operational weather forecasting mode employing analog method over different mountain ranges in NW-Himalaya. Significant difference in overall accuracy of the model is found for prediction of snow day and no-snow day over different mountain ranges, when weather is predicted under snow day and no-snow day weather forecast categories respectively. In the same mountain range, significant difference is also found in overall accuracy of the model for prediction of snow day and no-snow day for different areas. This can be attributed to their geographical position and topographical differences. The analog weather forecast model performs better than persistence and climatological forecast for day-1 predictions for all the mountain ranges except Karakoram range in NW-Himalaya. The developed analog weather forecast model may help as a guidance tool for forecasting weather in operational weather forecasting mode in different mountain ranges in NW-Himalaya.  相似文献   

10.
The mineral water at Borjomi has been bottled since the 19th century. Currently, the production comes from the regulated artesian flow of 11 boreholes. The total yield is about 540 m3/day. The mineral water is of sodium, hydrogen carbonate and CO2 type with mineralization up to 7.5 g/l and a temperature up to 40°C. Long-term observation has enabled the history of the structure of the Borjomi mineral water to be reconstructed from the beginning of its exploitation until the present. The hydrogeological structure of the Borjomi locality is very complex, but on the regional scale it occupies a relatively small area. The hydraulically well-defined and closed structure allows a simple conceptual model for each of the three main sectors to be designed. These are, namely, the Central, the Vaschlovani and the Likani sectors. The long-term extraction limits are about 190 m3/day in the Central sector, 300 m3/day in the Vashlovani sector and 77 m3/ day in the Likani sector.  相似文献   

11.
Anomalous sea level, anomalous observed dynamic height (0/400 db) and anomalous model dynamic height are examined at the locations of 13 island sea level stations in the tropical Pacific for each bimonth of the four year period 1979 to 1982. Starting in 1981, the anomalous dynamic height data show off-equatorial Rossby waves propagated toward the W boundary of the Pacific basin. At the W boundary, the model Rossby wave activity was found to have excited coastally trapped Kelvin-Munk waves which transmitted the anomalous dynamic height equatorward. At the equator, coastally trapped wave activity excited eastward propagating equatorial Kelvin waves, yielding a pair of anomalous peaks in dynamic height variability in the E equatorial Pacific associated with the 1982–1983 ENSO event. The evolution of the peaks in dynamic height associated with the Rossby and Kelvin wave activity reflects the redistribution of observed upper-ocean heat content in the W tropical Pacific, providing a qualitative hindcast for the 1982–1983 ENSO event. In consequence of these results, and the results of a related study (Inoue et al. 1985), the redistribution of both observed and model heat content, as evidenced in dynamic height in the W Pacific during the 23-year period 1964–1985, is examined for its ability to hindcast and forecast ENSO events in this period. Complex EOF analysis is applied to the Onset Phase of ENSO events occurring in 1968–69, 1972–73, 1976–77, and 1982–83; it is used to determine the characteristic redistribution of heat content (dynamic height) prior to the Mature Phase of ENSO events. This analysis found both model and observed dynamic height in the N hemisphere to be characterized by wind-driven, westward propagating, baroclinic Rossby wave activity, having a remarkably stable period of 3 years over the 23-year period. The complex time series associated with these first spatial eigen-functions are used to construct observed and model hindcast indices that yield high values one year prior to the Mature Phase of ENSO events of the period. These indices achieve these values due to the incidence upon the Philippine coast in fall/winter of a positive anomaly in dynamic height propagating from the east at nondispersive Rossby long wave speeds.  相似文献   

12.
Kubo  Syozo  Akimoto  Hiromichi  Moriwake  Takumi 《Natural Hazards》2003,29(3):553-566
Transportation is one of the most important and urgent tasks in a disaster, e.g., earthquake or flood. Trains, trucks and cars are very restricted by destruction of rail and road, bridges and buildings fall down, flood waters and thick mud, landslides, cracks, level differences, severe traffic jam etc. Sunken objects in the water and damages of quays prevent ships from reaching harbors. The situation remains days, weeks and even months.Hovercraft can run on almost every surface: ground, water surface, mud, sands, grits, weeds etc. The performance is very favorable in the first-aid transportation in a disaster.A middle size hovercraft with payload of 2–3 tons is suitable for first-aid work in a disaster. The amount of load is appropriate for loading and unloading by manpower without using a special loading machine. Small loads with frequent return trip are desirable to fulfill needs that are changing from time to time. A system of first-aid transportation by a number of hovercraft of middle size is proposed in this paper as an additional system of transportation to existing ones. The system is very useful for first-aid transportation in a disaster.A simulation of hovercraft transportation was carried out after the Kobe Earthquake in 1995 as an example. We assume that 20 hovercraft of middle size are operated from 6 bases just outside of the disaster area to 12 destinations in the area. The result shows that they can transport up to 1,200 tons goods in a day in addition to those of conventional transportation means without disturbing them.  相似文献   

13.
Heat wave has become a severe problem over China in recent year. Based on daily air temperature data from 719 meteorological stations in China in the period of 1961-2012, the heat wave events were classified into three levels by duration: weak HW, medium heat wave and strong heat wave. This paper describes the spatial and temporal characteristics among three levels of heat wave over China during the period 1961-2013. The results showed that the number of hot days displayed a weakening trend from the 1960s to the early 1990s, followed by a strengthening trend from the late 1990s up to now. Long-term linear trends in hot days had significant regional differences, for instance, the number of hot days in southwest and southern China growing sharply than other regions; three levels heat wave occurred in different regions that weak heat wave usually occurred in the northwest and middle part of China while strong heat wave mainly happened in the southern part of China. When it came to the first day of heat wave, weak heat wave occurred earliest in China, and it happened around July 3rd while medium heat wave and strong heat wave always started on July 13th and July 14th, respectively. In general, the earliest heat wave was always found in southwest China while the last ones usually occurred in southern part and southwest China. Increasing trend of three levels heat wave were found in the entire country, except for southwest China. The trend of the last day of heat waves showed significant difference between northern and southern part of China. The last day of weak and medium heat wave occurred later in the south China, while strong heat wave happened earlier in north China.  相似文献   

14.
城市扩张下的北京平原区降雨入渗补给量变化   总被引:1,自引:0,他引:1  
朱琳  刘畅  李小娟  郭高轩  潘云 《地球科学》2013,38(5):1065-1072
结合WetSpass模型与地理信息系统(geographic information system,GIS)、遥感(remote sense,RS)技术分析了城市扩张引起的土地利用类型变化对北京平原区降水入渗补给量的影响.在估算出1982年和2007年降水入渗补给量的基础上,将2007年土地利用类型还原成1982年的情景重新估算,利用转移矩阵分析两年土地利用类型的相互转化关系,同时,基于GIS空间数据统计功能,计算出不同土地利用类型下的地下水补给量.结果表明,1982年至2007年,研究区内水浇地减少874 km2,其中517 km2转变为城镇建设用地.相对于1982年,2007年城镇建设用地扩张了831 km2,区内降水入渗补给量减少约3 000万m3.研究成果可以为北京平原区的地下水资源保护及土地资源配置提供较为科学的参考.   相似文献   

15.
闽北是地质灾害的易发区。通过分析闽北地质灾害与降水的关系, 建立了闽北地质灾害与降水的关系模型(有效雨量) , 并应用GIS技术开发了闽北地质灾害气象预警系统。分析结果表明: 闽北地质灾害的发生与近10天的降水均有关系, 与当天大暴雨和近3天降水的关系最为密切, 群发性地质灾害大多在近3天合计雨量≥180 mm或近3天雨量≥100 mm且中4天(或远3天) 有连续性暴雨的情况下出现。降水量(有效雨量) 大小与地质灾害的发生呈指数关系, 出现地质灾害的有效雨量为: 在中南部高易发区为60 mm, 在中北部中易发区为75~80 mm, 在北部低易发区为100 mm。  相似文献   

16.
This study demonstrates the application of a stochastic procedure to enhance confidence in the predictions of numerical groundwater flow models. The objective was to assess the hydrogeological conditions and groundwater potential of a semi-confined aquifer system in Legon, Accra. The study applied the parameter randomization procedure in the Groundwater Modelling System (GMS) to evaluate model uncertainties arising from uncertainties in the data of model input parameters. A total of 2500 equally likely solutions of the numerical model were simulated through the Latin hypercube stochastic option. Regarding the size of the terrain and the number of parameters used for calibrating the model, the 2500 model realizations were adjudged to be largely sufficient to represent the possible solutions that could arise from the various permutations of the parameter data. High variances would suggest significant differences in the realizations, indicating high levels of non-uniqueness in the solutions. The 2500 solutions were compared using standard deviations computed from the differences in the estimated horizontal hydraulic conductivity, specific yield and specific storage estimates. The transient model calibrated for this domain suggests very close similarities in the model-computed aquifer parameters for all the 2500 solutions. This suggests that any of the solutions could be used to represent the conditions prevailing in the domain. Risk analyses were then performed on abstractions through all the 2500 solutions. The study shows that the domain is sustained largely by lateral subsurface inflows from adjoining areas amounting to 399,278 m3/day, with direct vertical infiltration and percolation of precipitation accounting for an average of 2450 m3/day. The analysis suggests that at this rate of input, the domain can sustain groundwater abstraction to meet all water needs in the area. In addition, the domain has demonstrated resilience against annual increment in abstraction rates by 5 % over a 20-year period at the current recharge conditions. However, increasing abstraction rates by up to 200 % of the current abstraction rates over the 20-year period (2015–2035) but with a gradual decrease in groundwater recharge by up to 10 % over the period will result in drastic lowering of the hydraulic head especially in the south-central portions of the domain. This situation might induce reversal of the current flow and potentially lead to contamination and/or aquifer dewatering in the domain.  相似文献   

17.
Mount Erebus is an active volcano in Antarctica located on Ross Island. A convecting lava lake occupies the summit crater of Mt. Erebus. Since December 1980 the seismic activity of Mt. Erebus has been continuously monitored using a radio-telemetered network of six seismic stations. The seismic activity observed by the Ross Island network during the 1982–1983 field season shows that: (1)Strombolian eruptions occur frequently at the Erebus summit lava lake at rates of 2–5 per day; (2)centrally located earthquakes map out a nearly vertical, narrow conduit system beneath the lava lake; (3)there are other source regions of seismicity on Ross Island, well removed from Mt. Erebus proper. An intense earthquake swarm recorded in October 1982 near Abbott Peak, 10 km northwest of the summit of Mt. Erebus, and volcanic tremor accompanying the swarm, may have been associated with new dike emplacement at depth.  相似文献   

18.
Gypsum Induced Strength Behaviour of Fly Ash-Lime Stabilized Expansive Soil   总被引:1,自引:1,他引:0  
Physical and engineering properties of soil are improved with various binders and binder combinations. Fly ash and lime are commonly used to improve the properties of expansive soils. An attempt has been made, in this paper, to examine the role of gypsum on the physical and strength behaviour of fly ash-lime stabilized soil. The change in strength behaviour is studied at different curing periods up to 90 days, and the mechanism is elucidated through pH, mineralogical, microstructural and chemical composition study. The strength of soil-fly ash mixture has improved marginally with the addition of lime up to 4 % lime and with curing period for 28 day. Significant increase in strength has been observed with 6 % lime and enhanced significantly after curing for 90 days. The variations in the strength of soil with curing period is due to cation exchange and flocculation initially, and binding of particles with cementitious compounds formed after curing. With addition of 1 % gypsum to soil-fly ash-lime, the strength gain is accelerated as seen at 14 day curing. The accelerated strength early is due to formation of compacted structure with growth of ettringite needles within voids. However, strength at curing for 28 day has been declined due to annoyance of clay matrix with the increase in size of ettringite needle; and again increased after curing for 90 days. The rearrangement of clay matrix and suppression of sulphate effects with formation of cementitious compounds are observed and found to be the main responsible factors for strength recovered.  相似文献   

19.
At the India Meteorological Department (IMD), New Delhi, a 12-level limited area model with 100 km horizontal resolution has been in use for weather forecasting. The present study uses this model together with a higher horizontal resolution (50 km) and vertical resolution (16-levels) model to examine the impact of increased resolution to simulate mesoscale features of rainfall during monsoon disturbances. The model was run for 22 days in the month of August 1997 and one week in September 1997 during three monsoon depressions and one cyclonic storm in the Bay of Bengal. The model results are compared with observations. The study shows that the model can capture mesoscale convective organization associated with monsoon depression.  相似文献   

20.
Since the 1980s, high-nitrate concentration in one of the groundwater sampling wells at the Nankou site, northwest of the Beijing Plain, has become a major concern for the local water authority. In a previous study (Sun et?al. in Environ Earth Sci 64(5):1323?C1333, 2011), a hydrogeological structural model was developed based on the borehole logs of this area and the steady, as well as transient groundwater-flow models, were calibrated using the measured hydraulic heads. In this paper, the potential pollution sources in this area are investigated. The chemical analysis of the groundwater is also presented. The results demonstrate that the most likely pollution source is the untreated wastewater discharge from a nearby fertilizer factory. Furthermore, a mass transport model is developed to reproduce the nitrate transport process in the aquifer at the Nankou site under different pollution sources, i.e., a fertilizer factory, river with wastewater and an agriculture field. The combined effects of the river and agriculture fields present a better understanding of the nitrate transport in the local aquifer. In addition, a pumping scenario is designed to clean up the current nitrate concentration. The pumping rate and the well location are first estimated with 2-D analytical solutions of the type curves method. Then a 3-D numerical model is used to calculate the nitrate-concentration changes after the pumping activities start. In the downstream direction of the regional groundwater flow, three pumping wells are set up for the clean-up strategy. The calculated pumping rate in each well is about 1,500 m3/day. After 1?year, the nitrate concentration in the observation well recedes to 68?mg/l from the initial value of 72.9?mg/l, and it will be lower than the limitation value (20?mg/l) after 5,400 days of groundwater extraction. The data assessment and clean-up scenarios reported in this paper are fundamental for the contaminated aquifer management in the future.  相似文献   

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