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1.
为阐明强潮河口最大浑浊带的形成机制及其运动规律,通过瓯江和椒（灵）江实测资料分析,系统分析了强潮河口最大浑浊带形成的影响因素及其与河口地貌的响应关系。考虑黏性细颗粒泥沙运动特性和盐度的影响,开发了强潮河口最大浑浊带数学模型,对椒（灵）江枯季大潮最大浑浊带运移过程进行了模拟。结果表明:①强潮河口最大浑浊带是潮波变形、咸淡水混合、泥沙再悬浮等复杂因素在一定河口边界和泥沙条件下相互作用的产物,潮波变形和泥沙供给是影响最大浑浊带形成的关键因素。②强潮河口最大浑浊带模拟必须充分考虑潮流、盐淡水混合、泥沙周期性起动、絮凝和沉积密实等因素,所建立的数学模型可用于强潮河口最大浑浊带研究。  相似文献   

2.
The laboratory tests for the use of sapogenic amphiphilic glycosides as a coagulation–flocculation aid are presented in this paper. These amphiphilic glycosides were obtained, through a natural fermentation process, of the juice, of fique (Furcraea sp.) leaves. Decantation allows for the separation of a supernatant denominated “supernatant fique juice” and a decanted fraction denominated “decanted fique juice.” The latter contains most of the sapogenic amphiphilic glycosides and was mixed with the chemical coagulant ferric chloride hexahydrate, at varying doses. Ferric chloride hexahydrate was also used as a control to ascertain the removal efficiency of persistent contaminants from samples of a textile industry effluent. The parameters of interest were typical indicators of water quality such as color, turbidity, chemical oxygen demand, pH and conductivity. The results indicate that the decanted fique juice, when used as a coagulation–flocculation aid, and upon comparison with the chemical coagulant alone, causes an additional color and turbidity reduction of 31 and 17 %, respectively. No significant differences were noted in the chemical oxygen demand values (α = 0.05; P < 0.001). Thus, there is a scope for further research about the commercial feasibility of DFJ as an industrial water treatment agent, which reduces the toxicity of raw fique juice and its detrimental environmental effects.  相似文献   

3.
We discuss various strategies for parallelizing streamline simulators and present a single-phase shared memory implementation. The choice of a shared memory programming model is motivated by its suitability for streamline simulation, as well as the rapid advance of multicore processors, which are readily available at low-cost. We show that streamline-based methods are easily parallelizable on shared memory architectures through their decomposition of the multidimensional transport equations into a large set of independent 1D transport solves. We tested both a specialized explicit load balancing algorithm that optimizes the streamline load distribution across threads to minimize the time that any of the threads are idle, and the dynamic load balancing algorithms provided by OpenMP on the shared memory machines. Our results clearly indicate that built-in schedulers are competitive with specialized load balancing strategies as long as the number of streamlines per thread is sufficiently high, which is the case in field applications. The average workload per thread is nominally insensitive to workload variations between individual streamlines, and any load balancing advantage offered by explicit strategies is not sufficient to overcome associated computational and parallel overhead. In terms of the allocation of streamlines or streamline segments to threads, we investigated both the distributed approach, in which threads are assigned streamline segments, and the owner approach, in which threads own complete streamlines. We found that the owner approach is most suitable. The slight advantage that the distributed approach has in terms of load balancing is not enough to compensate for the additional overheads. Moreover, the owner approach allows straightforward re-use of existing sequential codes, which is not the case for the distributed approach in case of implicit or adaptive implicit solution strategies. The tracing and mapping stages in streamline simulation have low parallel efficiency. However, in real-field models, the computational burden of the streamline solves is significantly heavier than that of the tracing and mapping stages, and therefore, the impact of these stages is limited. We tested the parallelization on three shared memory systems: a 24 dual-core processor Sun SPARC server; an eight-way Sun Opteron server, representative of the state-of-the-art shared memory systems in use in the industry; and the very recently released Sun Niagara II multicore machine that has eight floating point compute units on the chip. We test a single-phase flow problem on three heterogeneous reservoirs with varying well placements (this system gives the worst case scenario as the tracing and mapping costs are not negligible compared to the transport costs). For the SPARC and Opteron system, we find parallel efficiencies ranging between 60 and 75 for the tracer flow problems. The sublinear speedup is mostly due to communication overheads in the tracing and mapping stages. In applications with more complex physics, the relative contributions of these stages will decrease significantly, and we predict the parallel performance to be nearly linear. On the Niagara II, we obtain almost perfect linear scalability even for the single-phase flow problem thanks to the lowered communication costs on these architectures that have a shared cache. This result is all the more satisfactory considering that future server designs will be akin to this system.  相似文献   

4.
Surfactants are among the most widely disseminated xenobiotics that contribute significantly to the pollution profile of sewage and wastewaters of all kinds. Among the currently employed chemical unit processes in the treatment of wastewaters, coagulation-flocculation has received considerable attention for yielding high pollutant removal efficiency. Jar-test experiments are employed in order to determine the optimum conditions for the removal of surfactants, COD and turbidity in terms of effective dosage, and pH control. Treatment with FeCl3 proved to be effective in a pH range between 7 and 9. The process is very effective in the reduction of surfactants and COD, the removals are 99 and 88 % respectively, and increased BOD5/COD index from 0.17 to 0.41. In addition to precipitation coagulation process, adsorptive micellar flocculation mechanism seems contribute to the removal of surfactants and organic matters from this rejection.  相似文献   

5.
Estuarine systems are complex environments where seasonal and spatial variations occur in concentrations of suspended particulate matter, in primary constituents, and in organic matter content. This study investigated in the laboratory the flocculation potential of estuarine-suspended particulate matter throughout the year in order to better identify the controlling factors and their hierarchy. Kinetic experiments were performed in the lab with a “video in lab” device, based on a jar test technique, using suspended sediments sampled every 2 months over a 14-month period at three stations in the Seine estuary (France). These sampling stations are representative of (1) the upper estuary, dominated by freshwater, and (2) the middle estuary, characterized by a strong salinity gradient and the presence of an estuarine turbidity maximum. Experiments were performed at a constant low turbulent shear stress characteristic of slack water periods (i.e., a Kolmogorov microscale >1,000 μm). Flocculation processes were estimated using three parameters: flocculation efficiency, flocculation speed, and flocculation time. Results showed that the flocculation that occurred at the three stations was mainly influenced by the concentration of the suspended particulate matter: maximum floc size was observed for concentrations above 0.1 g l−1 while no flocculation was observed for concentrations below 0.004 g l−1. Diatom blooms strongly enhanced flocculation speed and, to a lesser extent, flocculation efficiency. During this period, the maximum flocculation speed of 6 μm min−1 corresponded to a flocculation time of less than 20 min. Salinity did not appear to automatically enhance flocculation, which depended on the constituents of suspended sediments and on the content and concentration of organic matter. Examination of the variability of 2D fractal dimension during flocculation experiments revealed restructuring of flocs during aggregation. This was observed as a rapid decrease in the floc fractal dimension from 2 to 1.4 during the first minutes of the flocculation stage, followed by a slight increase up to 1.8. Deflocculation experiments enabled determination of the influence of turbulent structures on flocculation processes and confirmed that turbulent intensity is one of the main determining factors of maximum floc size.  相似文献   

6.
A single fracture is usually idealized theoretically as smooth parallel plates, but the real fractures are rough-walled with points of contact. Though relative roughness is considered in quantifying the flow through a single rough fracture (SRF) previously, additional factors such as the distribution of rough elements and bending degree of streamlines should be considered in order to obtain more accurate results. Semiempirical friction factor (f) and discharge per unit width (q) equations are first deduced taking relative roughness, roughness elements distribution and streamline reattachment length into consideration. A horizontal SRF model was then set up and a series of experiments and simulations were performed. Main conclusions are drawn: Recirculation of streamlines arises in the rough element and the intensity of the recirculation increases with the angle from which the streamlines enter into the rough elements and Reynolds number (Re); streamlines are discontinuously distributed when asperity height is large and nonlinear flow occurs; the nonlinearity of the flow increases with the increasing the asperity height and Re; the critical value of related roughness used to judge whether the influence of roughness on water flow through a SRF can be ignored or not should be much lower than 0.033; the revised f and q equations under laminar flow through a SRF are proved to be better when calculating the f and q values.  相似文献   

7.
The study of low-cost techniques for the tertiary treatment of wastewater is of global interest; above all low-energy techniques that do not require the use of chemicals. In this study, a wastewater treatment technology based on the filtration by a zooplanktonic population (Daphnia magna) is studied in controlled laboratory and mesocosm experiments for different hydraulic retention times (HRT). The efficiency of the treatment is evaluated in terms of particle removal efficiency. From laboratory experiments, HRT over 12 h and Daphnia concentrations above 50 individuals l?1 guarantee a particle removal efficiency greater than 30 %. However, low HRT of 6 h would require Daphnia concentrations above 70 individuals l?1 in order to obtain a particle removal efficiency of 20 %. The minimum removal efficiency of 2 % was for HRT = 3 h, independent of the Daphnia concentration. In the mesocosm, the growth of Daphnia individuals enhanced Daphnia magna filtering rates and higher removal efficiencies than those in the laboratory for the same HRT range. In the mesocosm experiments E. coli concentrations were reduced to a maximum of 2 logarithmic units. A balance equation model is proposed to predict particle removal efficiencies for varying HRT.  相似文献   

8.
In this study, a naturally available crab shell chitosan of low molecular weight (20?kDa) has been used as adsorbent to evaluate the pollution load in vegetable oil mill effluent. A series of batch experiment was conducted by varying chitosan dosage (100?C400?mg), pH (2?C9), stirring time (15?C90)?min and agitation speed (25?C150?rpm) to study their effects on adsorption and flocculation processes. The parameters considered for adsorption study are chemical oxygen demand, total suspended solids, electrical conductivity and turbidity. The maximum reduction in chemical oxygen demand, total suspended solids, electrical conductivity and turbidity is 74, 70, 56 and 92?% , respectively. The observed experimental result showed that crab shell chitosan could able to reduce significantly the chemical oxygen demand, turbidity, electrical conductivity and suspended matter. The optimum conditions were estimated as 400?mg/l chitosan, pH 4 and 45?min of mixing time with mixing speed of 50?rpm. Chitosan showed very good pollution removal efficiency and can be used for the effective treatment of vegetable oil mill effluent.  相似文献   

9.
KATE KRANCK 《Sedimentology》1981,28(1):107-114
The concentration and grain size of the natural and deflocculated inorganic suspended particulate matter were measured along the length of the Miramichi Estuary and interpreted with respect to flocculation and transport properties. Changes in particulate matter concentration are associated with regular changes in grain-size characteristics. In the turbidity maximum region of the estuary the suspended matter occurs mostly as large flocculated particles whereas, in the waters with lower particle concentrations, a larger proportion of the material occurs as fine material. At higher concentrations natural floc modes and inorganic grain modes vary simultaneously but at low concentrations the two modes vary inversely. This modal relationship and the variation in organic matter within the estuary is proposed to result from variation in inorganic—organic composition of flocs. Increase in settling rates due to flocculation is believed to increase the trapping effect of the estuarine circulation that produces the turbidity maximum.  相似文献   

10.
Summary ¶This paper deals with the mineralogical features of the most important and widespread pyroclastic formation of Southern Italy: the Campanian Ignimbrite. This formation is characterized by four stratigraphic units, different in colour and mineralogical composition. The lowermost unit (USAF) is constituted by an incoherent, thin (few tens of cm) sequence of glass or feldspar-rich layers. The middle part of the succession is formed by two main units: a lower grey, welded unit (WGI) capped by a yellow and lithified unit (LYT) that differ in both volcanological features and mineralogical composition. Locally these units are found separately. An incoherent unit (max thickness about 2m) mainly represented by fresh glass, forms the upper part of the succession. A detailed analysis has been carried out on six sections representative of the entire succession. The WGI is feldspathized by authigenic mineralization processes, and the feldspar content ranges between 30 and 90%. The LYT has been deeply affected by zeolitization processes and the total zeolite content often reaches 60%. Based on a comparative examination of both volcanological and mineralogical data, it is hypothesized that these two units were involved in different secondary mineralization processes. The portion of the succession characterized by the highest emplacement temperatures suffered welding and feldspathization and the result of these processes gave rise to the WGI unit. In contrast, the overlying lower-temperature and incoherent portion of the deposit was affected by circulation of meteoric water, thus enhancing zeolitization and lithification. The product of this process gave rise to the LYT unit.Received July 4, 2002; revised version accepted April 23, 2003  相似文献   

11.
In recent years, concerns about the occurrence and fate of active pharmaceutical ingredients, solvents, intermediates and raw materials that could be present in pharmaceutical industry effluents have gained increasing attention. Conventional treatment methods, such as activated sludge, are not sufficient enough to remove active pharmaceutical ingredients completely. As a result, complementary treatment methods like coagulation and flocculation are often used and play a critical role in industrial and municipal wastewater treatment. The primary goal of these methods is to destabilize and remove colloidal particles along with other organic/inorganic contaminants. Recently empirical works have considered ozone as the most promising oxidant for the removal of micro-pollutants. The current study examined the effectiveness of coagulation/flocculation process using ferric chloride, polyaluminum chloride, and aluminum sulfate as a reasonable approach to tackle the issue of treating pharmaceutical wastewater. In addition, the results were compared with the process using only ferric chloride that was the coagulant of an actual treatment plant. Then, improvement of the process performance was investigated using ozone as an oxidant. In conclusion, it was found out that polyaluminum chloride presented better performance among two other coagulants and also adding 200 mg/L of polyaluminum chloride can lead to 97–98 % turbidity removal efficiency. Moreover, polyaluminum chloride was capable of reducing most of the environmental parameters such as chemical oxygen demand and total dissolved solid with the removal efficiency of 70 and 68 %, respectively. Additionally, ozonation improved the coagulation process, especially iron ion removal, and dramatically decreased the concentration from 5.68 to 0.19 mg/L.  相似文献   

12.
Backwater tidal sloughs are commonly found at the landward boundary of estuaries. The Cache Slough complex is a backwater tidal region within the Upper Sacramento–San Joaquin Delta that includes two features that are relevant for resource managers: (1) relatively high abundance of the endangered fish, delta smelt (Hypomesus transpacificus), which prefers turbid water and (2) a recently flooded shallow island, Liberty Island, that is a prototype for habitat restoration. We characterized the turbidity around Liberty Island by measuring suspended-sediment flux at four locations from July 2008 through December 2010. An estuarine turbidity maximum in the backwater Cache Slough complex is created by tidal asymmetry, a limited tidal excursion, and wind-wave resuspension. During the study, there was a net export of sediment, though sediment accumulates within the region from landward tidal transport during the dry season. Sediment is continually resuspended by both wind waves and flood tide currents. The suspended-sediment mass oscillates within the region until winter freshwater flow pulses flush it seaward. The hydrodynamic characteristics within the backwater region such as low freshwater flow during the dry season, flood tide dominance, and a limited tidal excursion favor sediment retention.  相似文献   

13.
Exploitation of coalbed methane (CBM) involves groundwater extraction to depressurize coal reservoirs. This can involve groundwater extraction from multiple coal seams (commingled drainage). Interlayer interferences, caused by heterogeneity of hydrodynamic fields of the different coal gas reservoirs, can restrain CBM production. Understanding of the hydrogeological characteristics of each reservoir, inseparable from characteristics of the sequence stratigraphic framework, is critical for CBM exploration. Analysis of Zhuzang syncline in Guizhou province, China, found gas- and water-blocking strata near the maximum flooding surface in the upper part of each third-order stratigraphic sequence; thus, the hydrogeological units were divided vertically (SQ4, SQ3, SQ2 and SQ1) by the boundaries of the third-order sequence. The commingled-drainage CBM wells were analyzed by numerical simulation and Extenics theory, on the basis of characteristics of the hydrogeological units. Gas content, reservoir pressure and hydrodynamic parameters were found to vary between the hydrogeological units. The interlayer interference was not obvious where there was commingled drainage within single hydrogeological units with similar hydrodynamic force; this was validated by observing the consistent pressure decrease within each reservoir using historical matching. Since the source of drainage water varied from stratum SQ3 to SQ4 (containing lower hydrodynamic force compared to SQ3), it was obvious that groundwater extraction from SQ4 was restrained by SQ3, by showing obvious interlayer interference and restrained CBM production during commingled drainage across the different hydrogeological units. Reservoirs within each single hydrogeological unit tend to obtain higher CBM yield, thus take priority for commingled drainage.  相似文献   

14.
Several media have been used in treatment plants, however, their efficiency for turbidity removal, which is determined by qualitative indices, has been considered. Current qualitative indices such as turbidity and escaping particle number could not completely measure the efficiency of the filtration system; therefore defining new qualitative indices is essential. In this study, the efficiency of two different dual media filters in turbidity removal was compared in different operating condition using qualitative indices. The pilot consisted of a filter column (1-m depth) in which the filter-1 was consisted of a layer of anthracite (450-mm depth) and a layer of silica sand (350-mm depth); and filter-2 had the same media characteristics except for the first layer that was light expanded clay aggregates (LECA). Turbidities of 10, 20, and 30 NTU, coagulant concentrations of 4, 8, and 12?ppm and filtration rates of 10, 15, and 20?m/h were considered as variables. Results showed that the media of filter-2 is a suitable substitute for the media of filter-1 (P value?<?0.05). Turbidity removal efficiencies in different condition were 79.97?±?1.79 to 91.37?±?1.23% for the filter-2 and 75.12?±?2.75 to 86.82?±?1.3% for the filter-1. The LECA layer efficiency in turbidity removal was independent of filtration rates and due to its low head loss; LECA can be used as a proper medium. Results also showed that the particle index was a suitable index as a substitute for turbidity and escaping particle number as indices.  相似文献   

15.
The thickness and lateral distribution of sand and mud beds and bedsets on channel bars from the tidally influenced Fraser River, British Columbia, Canada, are quantitatively assessed. Fifty‐six vibracores totalling ca 114 m of vertical section are used to tabulate bed thicknesses. Statistical calculations are undertaken for nine channel bars ranging from the freshwater and tidal zone, to the sustained brackish water and tidal zone. The data reveal that thickness trends can be organized into three groups that broadly correspond to time‐averaged hydrodynamic and salinity conditions in the various distributary channels. Thick sand beds (up to 30 cm) and thin mud beds (up to 5 cm) characterize the freshwater tidal zone. The tidal and freshwater to brackish‐water transition zone comprises thin sands (up to 10 cm) and thicker muds (up to 19 cm), and the sustained brackish water tidal zone consists of thin muds (up to 6 cm) with relatively thicker sands (up to 25 cm). The results suggest that the locus of mud deposition occurs in the tidal freshwater to brackish‐water zone, probably reflecting mud flocculation and deposition at the turbidity maximum. Landward of the turbidity maximum, mud deposition is linked to tidal influence (tidal backwater effect and reverse eddy currents on channel margins) as mud beds thin in the landward direction. These results support the hypothesis that mud deposition is greatest at the turbidity maximum and decreases in both the seaward and landward direction. This study also showcases that mud‐bed thicknesses are greatest towards the turbidity maximum and thin in both the landward and seaward direction. In the rock record, the apex of mud deposition probably marks the position of the palaeo‐turbidity maximum.  相似文献   

16.
Stratigraphical-structural units separated by regional unconformities in the Andes of Peru and Chile, display a pattern of low grade burial metamorphism. Each stratigraphical-structural unit shows a particular facies series covering part or all the range between the zeolite and the greenschist facies. These facies series were episodically generated as part of the geological evolution of each unit prior to its own folding. Mineralogical breaks are found to coincide with the regional unconformities and often cases of higher grade assemblages on top of lower grade ones occur. This pattern may be explained by a process of sealing of each unit after its particular metamorphic episode took place. Porosity and permeability conditioning P f, as demonstrated for individual lava flows, are the significant controlling factors in the production of the metamorphic assemblages.  相似文献   

17.
A comparative study was performed between cactus (Opuntia spp.) and alum as coagulants. Monthly samples of raw water, delivered from (Al-Mashroo Canal), were studied and analyzed for turbidity removal during the period from August 29, 2014, to July 23, 2015. The analysis was conducted to decide the optimum dose, optimum velocity gradient, and optimum flocculation time for both coagulants. The results of the study indicate the efficiency of alum over cactus and that the optimum dose of alum was larger than that of cactus. The pH level of raw water was in the range of 7.734–8.203, while the temperature of raw water was in the range of 13–35 °C during the period of the study. The reliable velocity gradient for both coagulants was 25 1/s, and the reliable flocculation time for both coagulants was 20 min. The residual turbidity for cactus was in the range of 0.0–296 NTU, while that of alum was in the range of 0.0–5.81 NTU.  相似文献   

18.
Based on previous research, muriatic modification parameters (including the volume of hydrochloric acid, modification temperature and reaction time) were optimized by L9 (33) orthogonal design using the removal efficiency of unicellular M. aeruginosa as an index. The results showed that the optimized modification conditions consisted of a hydrochloric acid volume of 4 mL, a modification temperature of 200 °C and a reaction time of 3 h. Under the above conditions, the removal rate for unicellular and colonial M. aeruginosa was 89.26 and 75.53%, respectively. In addition, the flocculation process caused no cell damage, and the cells remained intact after use of the modified water treatment residuals (WTRs) flocculant. TP and TN in water were reduced by 63.37 and 19.03%, respectively. Therefore, the modified WTR flocculant was a technically viable method to remove unicellular and colonial M. aeruginosa.  相似文献   

19.
An approximate solution for the effects of high strain rates, and gradual strength degradation, on the penetration resistance of penetrometers can be obtained by combining the strain‐path method with the classical upper bound theorem. The stream path calculations require the integration of the material constitutive equation along the streamlines. Unless the geometry is simple so that the integration can be evaluated analytically, numerical procedures are required to backtrack streamlines. The strain at any location is calculated by finding the streamline that passes through the given point and integrating the strain rate along that streamline from its inlet boundary. Thus, the calculations can be complicated, and errors can be accumulated during the calculation procedure. This paper presents an efficient approach for evaluating cumulative strains around penetrometers without the need to backtrack individual streamlines. In this approach, the strain components are treated as field variables. The global solution is obtained using the streamline upwind Petrov–Galerkin method. The new method together with an Eulerian‐based finite element formulation was used to study the cone penetration test and evaluate the effect of strain softening on the cone resistance. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

20.
An analysis is presented of the maximum thickness of a stationary buoyant oil-mass, trapped under an angled incline, when subjected to hydrodynamic, surface tension and buoyancy forces. For high water-flow speeds down the aquifer, with upward buoyancy forces dominantly combating hydrodynamic pressure, it is shown that the maximum oil thickness occurs at about 60% of the length of the oil stringer measured from the upward end. The length of the oil stringer then is roughly proportional to the square root of the oil-mass contained, as is the maximum thickness. For low water-flow speeds, in which buoyancy and surface tension are dominantly balanced (with only lesser contributions from hydrodynamic pressure), the oil length is effectively constant, whereas the maximum thickness grows proportionately to the 3/4 power of the contained oil mass at low oil masses, and proportionately to the oil mass at high mass values. As the water-flow velocity increases, the shaping of the oil stringer shifts from the small bubble form to the long oil stringer form. Analytic formulae are given to provide approximate methods from which to estimate oil and gas accumulations under more complex conditions.  相似文献   

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