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31.
Several commercially available adsorbents were screened for their ability to remove Cu, Zn and organotin compounds from both artificial contaminated and real dockyard wastewater. An adsorption--flocculation process using a mixture of two adsorbents (a clay based adsorbent and a powdered activated carbon) was optimized for an optimal adsorbent and pollutant removal. At the optimal conditions the process was evaluated with both artificial and real shipyard wastewater, and the cost of the adsorption-flocculation process with relation to different influent concentrations and discharge limits was estimated. 相似文献
32.
In situ particle size spectra and density of particle aggregates in a dredging plume 总被引：11，自引：0，他引：11
An in situ laser particle sizer, the LISST-100, was used to describe the spatial variation of beam attenuation coefficient, in situ particle size spectra and aggregate densities in a dredging plume in the sound Øresund between Denmark and Sweden. The results proved that the above mentioned parameters varied significantly within the investigated length of the plume (approximately 2 km). It is shown how the small single primary particles aggregate and change the in situ particle size spectra into a slightly better sorted and coarser size distribution, and at the same time how the mean density of particles/aggregates decreases significantly. This shift in the state in which the particles exist in the water effectively changes the optical response of the mass of particles suspended in the water. It is shown that adequate correlations between mass concentrations and beam attenuation coefficients can only be obtained if parameters describing the in situ quality and state of the mass of particles, e.g. standard deviation of the size spectra and volume concentration, is included in the regression. From the spatial variation in mean density and in situ particle size, it was possible to calculate the spatial difference in settling velocity. It was found that the difference in settling velocity was only about a factor of 1.7, because increasing in situ particle size was counter-balanced by decreasing mean density. Furthermore, the time-scale of flocculation within the plume was found to be in the order of 50 min. 相似文献
33.
Jianhua Du Rada A. Pushkarova Roger St.C. Smart 《International Journal of Mineral Processing》2009,93(1):66-72
The destabilization of kaolinite suspension by anionic flocculant addition occurs in three zones; free settling, hindered settling and compression which usually includes a final bed raking process in mineral processing practice. This paper reports changes in the kaolinite aggregate and floc structures in the different settling and raking zones by cryo-vitrification/cryo-SEM techniques with image analysis combining micro- and macro-flocs. Cryo-SEM images indicate that, even during free settling, fine clay particles are bridged predominantly in edge–edge (E–E) with some face–face (F–F) configurations forming single, small flocs and some chain structures. When these small flocs and chains settle into the hindered settling zone, the collision between flocs and chains results in “honeycomb” network structures formed with lateral chain-like extension. The settled bed consists of these honeycomb structures with both inter-aggregate and intra-aggregate trapped water and has relatively low bed density (e.g. < 12 wt.% for a 2 wt.% slurry). The effect of the raking process in dramatically improving thickener underflow solids has been extensively studied but the structural changes in flocs and aggregates in this process are less well defined. Raking the compression zone for 1 h at 3 rpm can release some of the trapped water in the “honeycomb” structure and the bed density for 2 wt.% slurry improves dramatically to more than 36 wt.%. Cryo-SEM illustrates the extensive restructuring of flocs from predominantly E–E to predominantly F–F in many areas. The STructural IMage ANalysis (STIMAN) software is used to combine a series of images at magnifications from 1000× to 8000×, including both macro- and micro-flocs. This structural analysis comparing the un-raked and raked bed samples gives increases in total particle area of 30% and in relative particle area of 6%. The relatively low energy rake action of the shear stress results in the disruption of the E–E chains and the honeycomb structure, partly releasing the trapped water and inducing some E–E to F–F aggregate restructuring are clearly illustrated in these results. 相似文献
34.
Samples of surficial fine-grained laminae (SFGL) were collected in three south-western Ontario rivers. Each sediment sample was subjected to a sequential extraction procedure designed to partition particulate metals (Cd, Pb, Cu, Zn) into five operationally defined fractions: (1) exchangeable; (2) bound to carbonates; (3) bound to Fe-Mn oxides; (4) bound to organic matter; and (5) residual. Particulate phosphus was sequentially extracted from the sediment samples into three fractions: (1) non-apatite inorganic P; (2) apatite P; and (3) organic P. The major accumulate phases of trace metals in SFGL are carbonates, Fe-Mn oxides and organic matter. The content of NAIP in SFGL ranged from 17 to 38% of total particulate P. Compared with suspended and bed sediments, levels of P and trace metals in SFGL were lower at the study sites. A conceptual overview of physical, chemical and biological processes influencing formation of SFGL and the potential role of this fine-grained sediment for contaminant transport in fluvial systems is presented. 相似文献
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36.
长江口天然水流中细颗粒泥沙的絮凝作用 总被引：9，自引：0，他引：9
本文根据1978年水文测验资料,分析了长江口水流对细颗粒泥沙絮凝的影响。从中得出:(1)絮凝使长江口泥沙的竖向运动规律发生改变,出现竖向分层流。(2)存在一絮 凝临界流速,只有当流速小于该值时,絮凝泥沙的竖向运动规律才得以体现。(3)在小于絮凝临界流速的水流中,垂线不同高程处的絮凝条件受水流切应力制约。 相似文献
37.
本文对河口细颗粒泥沙絮凝作用的研究工作进行了综合评述．对盐度、有机物、水流切应力及悬浮颗粒的表面电荷等因素对河口细颗粒泥沙絮凝作用的影响规律及絮凝机理进行了总结和探讨． 相似文献
38.
Flocculation of colloidal size fraction for Cu, Zn, Pb, Ni and Mn was investigated on a series of mixtures with water salinities
ranging from 1.5 to 9.5‰ during mixing of Haraz River with the Caspian Sea water. The flocculation trend of Zn (85.5%) > Mn
(55.2%) > Cu (39.6%) > Pb (33.7%) > Ni (11.3%) indicates that Cu, Zn, Pb and Mn have non-conservative behavior and Ni has
relatively conservative behavior during estuarine mixing. Highest flocculation of heavy metals occurs between salinities of
1.5 and 4.5‰. Statistical analysis indicates that the flocculation of Cu, Zn and Ni is governed by pH and total nitrogen. 相似文献
39.
In order to improve the coagulation/flocculation efficiency of polyaluminum chloride (PAC), a composite flocculant of PAC and polydimethyldiallylammonium chloride (PDMDAAC), or PAC‐PDMDAAC, was prepared. The chemical species distribution of aluminum in PAC and PAC‐PDMDAAC, which has a close relationship with their coagulation/flocculation performance, was investigated by Al‐Ferron complexation timed spectrophotometry and 27Al‐NMR. The factors affecting the chemical species of aluminum in PAC‐PDMDAAC, such as the weight concentration of PDMDAAC (Wp), basicity (B) of PAC, and viscosity (η) of PDMDAAC, were studied. The flocculation efficiencies of PAC‐PDMDAAC, PAC and PDMDAAC were studied on a six‐spindle multiple stirrer unit. The results showed that the aluminum species distribution in PAC‐PDMDAAC depends on the Wp, B and η value. When the B value is 1.5 and η value is 1.22 dL/g, the composite flocculant with Wp = 15 % gives highest Alb and Al13 contents, and its flocculation efficiency is highest in the test flocculations. 相似文献
40.
An important element within the Defra funded Estuary Process Research project “EstProc” was the implementation of the new or refined algorithms, produced under EstProc, into cohesive sediment numerical models. The implementation stage was important as any extension in the understanding of estuarine processes from EstProc was required to be suitable for dissemination into the wider research community with a level of robustness for general applications demonstrated. This report describes work undertaken to implement the new Manning Floc Settling Velocity Model, developed during EstProc. All Manning component algorithms could be combined to provide estimates of mass settling flux. The algorithms are initially assessed in a number of 1-D scenarios, where the Manning model output is compared against both real observations and the output from alternative settling parameterisations. The Manning model is then implemented into a fully 3-D computational model (TELEMAC3D) of estuarine hydraulics and sediment transport of the Lower Thames estuary. The 3-D model results with the Manning algorithm included were compared to runs with a constant settling velocity of 0.5 mm s−1 and settling velocity based on a simple linear multiplier of concentration and with the above mentioned observations of suspended concentration. The findings of the 1-D case studies found the Manning empirical settling model could reproduce 93% of the total mass settling flux observed over a spring tidal cycle. The floc model fit was even better within the turbidity maximum (TM) zone. A constant 0.5 mm s−1 only estimated 15% of the TM mass flux, whereas the fixed 5 mm s−1 settling rate over-predicted the TM mass flux by 47%. Both settling velocity as a simple linear function of concentration, and van Leussen's method, did not fare much better estimating less than half the observed flux during the various tidal and sub-tidal cycle periods. When the Manning-settling model was applied to a layer with suspended concentrations approaching 6 g l−1, it calculated 96% of the observed mass flux. The main conclusions of the implementation exercise were that it was feasible to implement a complex relationship between settling velocity and concentration in a 3-D computational model of estuarine hydraulics, without producing any significant increase in model run times or reducing model stability. The use of the Manning algorithm greatly improved the reproduction of the observed distribution of suspended concentration both in the vertical and horizontal directions compared to the other simulations. During the 1-D assessments, the Manning-settling model demonstrated flexibility in adapting to a wide range of estuarine environmental conditions (i.e. shear stress and concentration), specifically for applied modelling purposes. 相似文献