Partial Dewatering Research Articles

Iron ore tailings valorization through separate characterization and upgradation of different tailings streams of an Iranian iron ore processing plant.

In iron ore processing plants, different tailing streams are usually transferred to the tailings thickener for partial dewatering and finally transferred to the tailings dam as a single stream. Therefore, the mixing of different tailings streams happens. This way can challenge the process of reprocessing the tailings in the tailings dam since the mixing of different tailings streams causes more complexity in the mineralogical composition as well as the chemical composition of the tailings in the tailings dam. To solve this problem, the idea of separate characterization and separate upgradation of different tailings streams of an iron ore processing plant was carried out and a comparison was made between the results of magnetic upgradation of each tailings streams with the total tailings (i.e., the tailings in the tailings dam, which is a mixture of different tailings streams of the plant). Hence, the different tailings streams of an iron ore processing plant were sampled and characterize for total iron, FeO content, particle size distribution, mineralogical composition by X-ray diffraction (XRD), magnetic behavior by Davis tube tests, and dry solid tonnage rate. The characterization results showed that the iron grade and dominant iron ore mineral vary from one stream to another tailings stream of the iron ore processing plant. For instance, the total iron content of different tailings streams varies in the range of 18.46 to 64.68% and the dominate iron ore mineral in the Cobber tailings was hematite, but in the other tailings streams it was magnetite. The magnetic upgradation of the Cobber and Rougher tailings and also the total tailings were performed separately by the wet magnetic separation at different magnetic field intensities of 2000, 3500, 5000, and 15,000 Gauss. A concentrate with the highest iron grade of 61.79% and yield of 52.15% was produced from magnetic upgradation of the Rougher tailings, but magnetic upgradation of the total tailings produced a concentrate with the iron grade of 37% and yield of 15.2%. A comparison between the magnetic upgradation of the total tailings and the Cobber and Rougher tailings revealed that the upgradation of Rougher tailings results in a concentrate with higher iron grade and yield than the total tailings.

Harnessing the osmotic energy of cane molasses by forward osmosis: process studies and implications for a sugar mill

ABSTRACT The osmotic energy of cane molasses was used to drive the partial dewatering of sugarcane juice by Forward Osmosis. The studies were conducted at low molasses to juice ratio considering their relative abundances. Studies in recirculation mode provided insight into the maximum possible extent of dewatering and the variation of permeate flux () with bulk osmotic pressure difference. Operation in continuous single pass (CSP) mode helped maximise the throughput and . Data on permeation selectivity, back diffusion and osmotic energy use efficiency were additionally obtained for both modes of operation. The optimised CSP mode process was evaluated in a sugar mill employing commercial process streams. Energy saving – owing to reduced juice evaporation load – and freshwater saving – owing to simultaneous dilution of molasses – were the twin gains from the process considering sugar and ethanol as the final products. Areas of process improvement were identified.

Hydrogeochemical and microbiological effects of simulated recharge and drying within a 2D meso-scale aquifer.

Oscillating cycles of dewatering (termed drying) and rewetting during managed aquifer recharge (MAR) are used to maintain infiltration rates and could also exert an influence on subsurface microbial structure and respiratory processes. Despite this practice, little knowledge is available about changes to microbial community structure and trace organic chemical biodegradation potential in MAR systems under these conditions. A biologically active two-dimensional (2D) synthetic MAR system equipped with automated sensors (temperature, water pressure, conductivity, soil moisture, oxidation-reduction potential) and embedded water and soil sampling ports was used to test and model these important subsurface processes at the meso-scale. The fate and transport of the antiepileptic drug carbamazepine, the antibiotics sulfamethoxazole and trimethoprim, and the flame retardant tris (2-chloroethyl) phosphate were simulated using the finite element analysis model, FEFLOW. All of these compounds exhibit moderate to poor biodegradability in MAR systems. Within the operational MAR scenario tested, three episodic drying cycles spanning between 18 and 24 days were conducted over a period of 184 days. Notably, cessation of flow and partial dewatering of the 2D synthetic aquifer during dry cycles caused no measurable decrease in soil moisture content beyond the near-surface layer. The episodic flow introduction and dewatering cycles in turn had little impact on overall trace organic chemical biotransformation behavior and soil microbial community structure. However, spatial differences in oxidation-reduction potential and soil moisture were both identified as significant environmental predictors for microbial community structure in the 2D synthetic aquifer.

Investigation of the source of acidification in an aquifer in Northern Germany

Shallow groundwater in the Nethen well field, NW Germany, is affected by acidification, accompanied by elevated ferrous iron and sulphate concentrations. The acidity results in the mobilization of aluminum to groundwater which is subsequently re-precipitated in deeper, less acidic layers. This, in turn, caused the clogging of a water well by aluminum hydroxide phosphate. Analyses of the regional geological framework and both groundwater and sediment samples revealed that acid sulphate soils, although not uncommon in the region, and acid rain are not the cause of the acidification. The unconfined aquifer contains pyrite, which is exposed to oxygen during the partial dewatering of the aquifer during pumping, especially in the cone of depression. Nitrate, stemming from agricultural activities, may contribute to the pyrite oxidation but dewatering is the main cause. Both the oxidation of pyrite and the subsequent acid release influence the mobilization of trace elements.

Channelizing the osmotic energy of proximate sea bittern for concentration of seawater by forward osmosis under realistic conditions to conserve land requirement for solar sea salt production

The present investigation relates to partial dewatering of seawater or seawater-like feed solutions (π = 20–26 bar) by Forward Osmosis (FO) using concentrated brine/virgin sea bittern (π = 549–715 bar) available in proximity. An Aquaporin Inside™ hollow fibre FO membrane module (0.6 m2 active area) was used for the study. Initial studies with deionized water as feed and sea bittern as draw revealed that the reverse solute flux was 4560–6066 mg m−2 h−1, with salt rejection efficiency of 99.45–99.87%. Studies with ca. 36,000 mg L−1 NaCl feed and 24 °Bé [°Bé= 145(1–1/ρ), where ρ = specific gravity] concentrated sea brine draw resulted in 26.41%, 13.29% and 9.15% dewatering of feed (v/v) in continuous single pass (CSP) mode, with average flux (Jw) of 6.17, 6.48 and 6.73 L m−2 h−1, for feed to draw (F/D) ratios of 10:1, 20:1 and 30:1 v/v, respectively. Outlet feed concentrations estimated from density data were in good agreement with the values computed considering pure water permeation. FO experiments were subsequently undertaken with 2.84 °Bé natural seawater as feed and 29 °Bé virgin sea bittern as draw. The feed and draw flow rates were 45 and 1.5 L h−1, respectively, in the CSP mode in accordance with their relative abundance in a salt works. The extent of dewatering was 11% (v/v) and average Jw was 8.3 L m−2 h−1. When the same study was repeated in recirculation (RC) mode maintaining feed, draw and F/D ratio constant, the extent of dewatering was enhanced to 16.14% over 30 min of operation. A plot of Jw versus ∆π was also obtained, which exhibited deviation from linearity at large driving force. This was ascribed to dilutive internal concentration polarization and its effect was quantified. CSP mode was advantageous in terms of higher throughput, reduced contamination of feed with draw constituents, and lower circulation cost, while RC mode gave higher extent of dewatering over extended periods of operation. 10.17–19.22% of the pent-up osmotic energy in the draw amount taken was utilized for dewatering, all experiments considered. Partial dewatering of inlet stream by outlet stream through FO would help conserve 9–11% of land requirement for solar salt production from 3.5 to 2.8 °Bé seawater. It would also enable safer discharge of sea bittern owing to its ca. fourfold dilution.

Osmotic dehydration of fruit and berry raw materials in the food industry

Osmotic dehydration has recently received more attention as an effective method of preserving fruits and berries. Osmosis is a simple process that facilitates the processing of fruits and berries in order to preserve the original characteristics, namely nutritional value and organoleptic properties: color, aroma and texture. Osmotic dehydration has found wide application in the preservation of food products, as the activity of water in fruits and berries decreases, in some of them up to 90% of water is contained. The process of osmotic dehydration with the help of various agents is less energy-intensive than the process of drying or freezing, since it can be processed at ambient temperature. Osmotic dehydration has potential advantages in preserving the quality of food and in maintaining healthy food for the food industry. Treatment includes dehydration of fruits and berries by an osmotic agent followed by dehydration in dry or frozen apparatus where the moisture content decreases and the product becomes more stable. This process is a partial dewatering process to provide improved product quality compared to conventional drying processes or freezing. The purpose of studying osmotic dehydration is to identify the advantages and disadvantages in the treatment of osmotic agents. Various aspects of osmotic dehydration technology are considered, namely the solutions used, the characteristics of solutions, the effect of variable processes and the qualitative characteristics of osmo-dehydrated products. Factors of osmotic dehydration that depend on the osmotic agent, concentration of solute, temperature, time, size, shape and compactness of the material, mixing and the ratio of the solution to the samples.

Biodiesel production from wet microalgae feedstock using sequential wet extraction/transesterification and direct transesterification processes

Although producing biodiesel from microalgae seems promising, there is still a lack of technology for the quick and cost-effective conversion of biodiesel from wet microalgae. This study was aimed to develop a novel microalgal biodiesel producing method, consisting of an open system of microwave disruption, partial dewatering (via combination of methanol treatment and low-speed centrifugation), oil extraction, and transesterification without the pre-removal of the co-solvent, using Chlamydomonas sp. JSC4 with 68.7wt% water content as the feedstock. Direct transesterification with the disrupted wet microalgae was also conducted. The biomass content of the wet microalgae increased to 56.6 and 60.5wt%, respectively, after microwave disruption and partial dewatering. About 96.2% oil recovery was achieved under the conditions of: extraction temperature, 45°C; hexane/methanol ratio, 3:1; extraction time, 80min. Transesterification of the extracted oil reached 97.2% conversion within 15min at 45°C and 6:1 solvent/methanol ratio with simultaneous Chlorophyll removal during the process. Nearly 100% biodiesel conversion was also obtained while conducting direct transesterification of the disrupted oil-bearing microalgal biomass.

World's Largest In Situ Thermal Desorption Project: Challenges and Solutions

AbstractThis paper presents the largest In Situ Thermal Desorption (ISTD) project completed to date. The redevelopment of a former aerospace manufacturing facility adjacent to a commercial airport was the main driver, requiring relatively rapid reduction of several chlorinated volatile organic compounds (CVOC) in a 3.2‐acre source zone. The source zone was divided into four quadrants with differing treatment depths, heated simultaneously using a total of 907 thermal conduction heater wells. Five different depths were selected across the area, according to the depth of contaminant impact. Prior to implementation, a risk and optimization study led to placement of a vertical sheet‐pile wall around the treatment zone to minimize groundwater flow, and a pilot test of a novel direct‐drive method for installation of the heater casings. Because of a shallow water table, a layer of clean fill was placed over the treatment zone, and partial dewatering was necessary prior to heating. A network of vertical multiphase extraction wells and horizontal vapor extraction wells was used to establish hydraulic and pneumatic control and to capture the contaminants. The site was split into four decision units, each with a rigorous soil sampling program which included collecting a total of 270 confirmatory soil samples from locations with the highest pretreatment CVOC concentrations requiring reduction to below 1 mg/kg for each contaminant. Temperature monitoring and mass removal trends were used to trigger the sampling events. Eventually, a small area near the center of the site required the installation of four additional heaters before the soil goals were reached after 238 days of heating. The total energy usage for heating and treating the source area was 23 million kWh—slightly lower than the estimated 26.5 million kWh. Actual energy losses and the energy removal associated with the extracted steam were lower than anticipated. An estimated 13,400 kg (29,800 lbs) of CVOC mass was removed, and all soil goals were met. This paper presents the challenges associated with a project of this scale and describes the solutions to successfully complete the ISTD remedy.

The behavioural response of the invasive signal crayfish Pacifastacus leniusculus to experimental dewatering of burrows and its implications for eradication treatment and management of ponds with crayfish

Invasive non-indigenous crayfish threaten indigenous crayfish and aquatic communities. Biocide treatment to eradicate unwanted populations has been tried on small water bodies in the UK and a few other countries. It needs to be applied to the whole water body occupied by crayfish, so partial dewatering may reduce the cost of biocide. The whole population must be in the submerged dosed area, because if some individuals remain in exposed areas they may avoid treatment and hence eradication will not be achieved. This study looks at the response of signal crayfish Pacifastacus leniusculus to exposure of occupied burrows, in tanks and in the banks of a dewatered pond. Some crayfish emerged from exposed burrows by day (34% in tanks, 9% in field); the rest remained in burrows until after dark. In tanks, 96% of crayfish vacated exposed burrows on the first night when submerged burrows were available, but when all burrows were exposed, poorer-quality submerged refuges (open-ended tubes) and competition between crayfish kept subordinate individuals in the damp exposed burrows (32.5%). Subordinates did not vacate exposed burrows until dominant crayfish were removed. In the field, most crayfish emerged in 1–2 nights, but 0.5% remained alive in burrows six nights after exposure. In tank and field, about half of the crayfish climbed up onto dry exposed areas. In light of these findings, we recommend that if dewatering is a precursor to biocide treatment, exposed areas should be tested for presence of crayfish. If dewatering is for other management the potential for terrestrial roaming to other sites should be considered.

Facies Controlled Synaeresis Cracks in Mixed Siliciclastic-Carbonate Sediments of Middle Jurassic of Patcham Island, Kachchh, Western India

Abstract: Synaeresis cracks are observed at different stratigraphic levels in shallow marine mixed siliciclastic-carbonate sediments of the Middle Jurassic rocks of the Patcham Island, Kachchh, Western India. Cracks are preserved as cast or grooves in micritic sandstone of the Kuar bet member of Kaladongar Formation and sandy allochem limestone of the Raimalro Limestone member of Goradongar Formation. It bear distinct morphology of simple, straight to gently curved, spindle-shaped, irregular, unbranched to branched at acute angle; interconnected curlicue forms of non-orthogonal pattern. The X-radiography shows sharp margin and tapering twigs which support to nullify the possible biogenic origin. These cracks are developed at sediment-water interface and sediment-sediment interface in aqueous conditions, where partial dewatering of sediments causes reduction of sediment volume and loss of plasticity. Formation of cracks are also post-depositional phenomenon operated during initial phase of diagenesis where induced stress is generated due to compaction of sediments and neomorphism/recrystallisation of the susceptible carbonate grains.

Dewatering microalgae by forward osmosis

Microalgae are known to be an excellent source of biofuels, but many issues surrounding the scale and economics of their cultivation have yet to be resolved. In particular, dewatering methods, such as centrifugation and tangential flow filtration, are prohibitively energy intensive. In this study, forward osmosis (FO) is considered as a partial dewatering method for microalgae growing on wastewater in a marine environment. Using artificial seawater as the draw solution, average dewatering rates of 2l/m2membrane/h (range 1.8–2.4l/m2h) were observed and volumes decreased by 65–85%. For a single membrane, daily dewatering rates did not significantly change in 14 consecutive experiments. Hourly dewatering rates did not gradually decrease, as might be expected; instead the dewatering rate oscillated throughout each experiment. Exposing an FO membrane in the ocean for 45days caused significant biofouling on its surface, but its dewatering rate did not change. Exposing three FO membranes in the ocean for 52days also caused significant biofouling, but in this experiment all membranes developed leaks that allowed saltwater to pass. These experiments suggest that FO may be an energy-saving step in dewatering freshwater microalgae if an appropriate draw solution is available and if conditions are controlled to prevent leakage.

The change of the unit cell dimension of different zeolite types by heating and its influence on supported membrane layers

In comparison with the well-known swelling of organic polymer membranes, zeolite membranes have been considered for a long time as relatively stiff. The problem of the different thermal expansion coefficients of the α-Al 2O 3 support and the zeolite layer was usually reduced on a possible crack formation during the template removal of MFI membranes. However, the crack formation could be avoided by an extremely slow heating rate and by membrane layers formed of small and non-oriented zeolite crystallites. Several papers have shown that the isomorphous incorporation of Al into the MFI structure (silicalite → ZSM-5) results in an increase of the non-selective intercrystalline transport and – as a consequence – the separation selectivity drops. In accordance with this observation, no shape-selective gas separation is reported for the Al-rich zeolite membranes MOR, FAU and LTA. On the other hand, these membranes allow the highly selective separation of water from organic mixtures due to hydrophilic interactions. In the present paper the change of the unit cell dimension (UCD) for zeolites LTA, FAU, MOR and MFI was studied as a function of temperature and water content using Rietveld refinement. Parallel to the determination of the linear and volume expansion coefficients by in situ-heating XRD, the de-watering and de-templating was studied by thermogravimetry (TGA). A strong UCD-change was found for all Al-rich zeolite types as a result of the de-watering. In contrast, the smallest changes of the UCD in the temperature range 50–450 °C were found for MFI crystals. Nevertheless, also for MFI membrane layers with rising temperature an increasing tension between the expanding α-Al 2O 3 support and the slightly shrinking membrane layer takes place. Zeolite layers of small crystals with either a random or a preferential crystal orientation relative to the support and an only partial de-watering in the case of Al-rich zeolite layers can minimize the tension in the support-membrane system. Thus, the irreversible formation of macroscopic cracks can be avoided and the formation of small intercrystalline pores in the mesopore region becomes reversible.

A theoretical analysis of the flow stability in roll forming of paper

This paper deals with the fundamental mechanisms that control partial roll dewatering in papermaking. The flow around the forming cylinder is modelled in a cylindrical coordinate system and the wir ...

Fluid and Element Cycling in Subducted Serpentinite: a Trace-Element Study of the Erro-Tobbio High-Pressure Ultramafites (Western Alps, NW Italy)

cycling of exogenic components. Diopside and Ti-clinohumite are The oceanic serpentinization of peridotites and the influence of such the high-pressure minerals acting as repositories for REE and Sr, an alteration on element cycling during their subduction dewatering and for high field strength elements (HFSE), respectively. The are here investigated in a mantle slice (Erro–Tobbio peridotite), first aqueous fluid equilibrated with such an assemblage is enriched in exposed to oceanic serpentinization and later involved in alpine Cl and alkaline elements but strongly depleted in REE and subduction, partial dewatering and formation of a high-pressure HFSE (less than chondrite abundances). Sr is low [(0·2–1·6) olivine+ titanian-clinohumite+ diopside+ antigorite assemblage × chondrites], although selectively enriched relative to light REE. in the peridotites and in veins. Previous work indicates that highpressure veins include primary brines, representing a residue after crystallization of the vein assemblage and containing recycled oceanic Cl and alkalis. To reconstruct the main changes during oceanic

Thirty Years of Change in the Vegetation Communities of Three Valley Mires in Suffolk, England

Detailed floristic records from 12 mires on three Suffolk fens were gathered in 1959 and 1991. The data were analysed using tabulation and ordination to elucidate change at the plant community and individual species levels. Substantial changes at both levels were observed. The respective roles of three factors, namely lack of traditional management, changes in water regime and increased fertility, in accounting for these changes, have been explored. At community level, those mires which showed the greatest alteration were those subject to hydrological disturbance combined with dereliction. In terms of the British National Vegetation Classification they changed from short sedge mires allied to M13 Schoeno-Juncetum towards highly fertile tall herb fens with many ruderals and allied to S26 Phragmites australis-Urtica dioica fen. Partial dewatering led to M27 Filipendula ulmaria-Angelica sylvestris tall herb fen with few non-fen ruderals. Mires where ground water influx was reduced or eliminated but where traditional management was sustained showed less community change, with more of the principle community dominants being maintained. Here M13 Scheono-Juncetum mires developed into dry variants of M24 Molinia caerulea-Cirsium dissectum fen meadows. Mires with undisturbed hydrology but which became derelict were transformed from M13 Schoeno-Juncetum into hydrophytic Cladium-dominated communities of the S25 Phragmites australis-Eupatorium cannabinum tall herb fens. Many fen species were retained or recruited, while the colonization of ruderals, scrub and non-fen species that was noted in the dewatered mires did not occur. The dewatered mires showed the greatest alteration at species level. In unmanaged areas, all of the fen associates and bryophytes were lost and replaced by non-fen species and ruderal tall herbs. Where traditional management was maintained, most of the small species characteristic of wet fens and semi-aquatic conditions were still lost, although recruitment of ruderals and non-fen plants was less evident, being restricted to species of mesotrophic meadows. Retained species tended to be common fen plants or non-fen species. Mires which were derelict, but where the natural hydrology persisted, showed the least change in associated flora. Nevertheless, many of the smaller herbs were still eliminated by competition in the now dense tall-herb fen, indicating that traditional management was required as well as hydrological integrity for the survival of most wet-fen species. However, some wet-fen species were retained or recruited, indicating management to be subordinate to hydrology in their maintenance. They include Caltha palustris, Valeriana dioica, Lotus uliginosus and the bryophytes Campylium stellatum, Aneura pinguis, Sphagnum subnitens and Riccardia multifida. All mires showed a decline in conservation importance as measured by indices of botanical 'quality'. The mires which showed least decline (15-64% reduction in Rarity Weighted Principal Fen Species Score) were those which retained their hydrological integrity, regardless of management status. One mire, only partially dewatered but still managed, declined by nearly 70%. Although there were problems with the data, tentative comments are made on the relative importance of the three environmental factors to the maintenance of mire systems. It is concluded that maintenance of stable hydrologies is more important than extensive management in the long-term conservation of these sites.

A Field Study of Enhanced Recovery of DNAPL Pooled Below the Water Table

AbstractA large subsurface pool of waste solvent product, consisting primarily of 1,1,1‐tichloroethanc and carbon tetrachloride, was encountered during investigations at an industrial site in northern New Jersey. In the 1950s the product was discharged through a settling chamber directly below the shallow water table. Eventually the product accumulated within elongated depressions of erosional surface of varved clays at depths 10 to 15 feet below grade. The host sediment, line to medium sand, was overlain by line sand and silt. The delineated area of pooled DNAPLs covered 2750 feet2, and the maximum pool thickness exceeded 3 feel.The primary recovery involved pumping product from nine wells. Each recovery well was equipped with a sump extending into the clay, which enabled the system to keep the product pumping level below the bottom of the pool. A total of 3495 gallons of solvent product was recovered over two years. Nearly half of this volume was produced by two wells placed at the lowest points of the pools. Postpumping sampling of the former pools indicated that 43 to 94 percent of the pooled solvent mass was removed during the primary recovery. Average initial product salutation within the pool was estimated at 53.2 percent of the total porosity measured at 31 percent. Average residual saturation after the primary product recovery was 3.7 percent of the total pore volume.To test the feasibility of residual product recovery, an experimental secondary recovery was undertaken. Using sheet piling, a 506 feet2 lest cell was constructed inside the former DNAPL pool. The cell featured a central recovery well, six peripheral wells, and monitoring probes. I he selected sequence of secondary operations included partial dewatering. hot water injection, final dewatering, and thermally enhanced vapor extraction (TVE). During six weeks of the secondary recovery operations. 87.9 gallons of product were removed, of which 72 percent was from TVE. 25 percent from hydraulic mobilization effects. and 3 percent from dissolution of residuals. Confirmatory soil sampling showed an average reduction of residual contamination by 93.4 percent in comparison to the concentration of residuals prior to the secondary recovery. For the lest cell, a combined total solvent recovery of 99.6 percent was achieved. This high recovery exceeded DNAPL recoveries expected or achieved in other field‐scale attempts.

The effect of various processing methods on the physical and biochemical properties of shrimp head meals and their utilization by juvenile Penaeus monodon Fab.

Three meals were prepared from Penaeus monodon head waste by drying the raw material in a solar simulator, drying in an oven or blanching the raw material followed by partial de-watering under pressure and air drying. A further three meals were prepared by passing batches of raw or blanched shrimp head waste through a commercial meat/bone separator. The meat fraction was subsequently dried (MBDD) or ensiled. Separated meals contained around 6% less ash, 5% less chitin and 7.5% more protein than unseparated meals but the procedure failed to remove all the exoskeletal material. Separated meals also contained higher levels of astaxanthin and canthaxanthin than solar or oven-dried meals. The highest levels of n−3 polyunsaturated fatty acids (PUFAs) were found in separated meals. However, blanching the raw material prior to processing led to decreased PUFA content, higher free fatty acid levels and significantly higher ( P < 0.05) peroxide values. All the meals were found to be deficient in arginine and methionine plus cystine but separated meals contained greater quantities of the remaining essential amino acids and had essential amino acid indices greater than 0.70. Experimental rations were prepared incorporating either 54% fish meal or 31% of the solar-dried, oven-dried or MBDD shrimp head meals plus sufficient fish meal to generate isoproteinaceous diets. Each diet was fed to triplicate groups of 40, juvenile Penaeus monodon in a 50-day growth trial. Diets containing shrimp head meal performed significantly ( P < 0.05) better in terms of final individual weight, feed conversion ratio and production compared with the 54% fish meal based diet. The diet containing separated shrimp head meal produced the best response, followed by the diets containing oven-dried and solar-dried meal, but the differences were not statistically significant. Similar trends were noted for specific growth rate (SGR) and survival. Tests on the experimental diets indicated that the incorporation of shrimp head meals reduced water stability but increased diet palatability when compared to the fish meal based diet.

Modeling of dewatering and impregnation soaking process (osmotic dehydration)

Partial dewatering and simultaneous solute impregnation can be obtained by immersion of food pieces in concentrated solutions. Recently, further understanding of cross mass transfer was achieved by experimental study and modelling on agar model gel foods.

Simulation of groundwater flow in complex multiaquifer systems: Performance of a quasi three-dimensional technique in the steady-state case

The ability of the classical quasi three-dimensional formulation to describe steady-state groundwater flow problems in complex multiaquifer environments is examined. In the present formulation, discontinuities in the aquifer and aquitard units can be accommodated along with partial or complete aquifer dewatering and confined or unconfined flow conditions. Some of the main assumptions underlying classical quasi three-dimensional schemes are scrutinized, including the requirement of a two orders of magnitude permeability contrast between aquifers and aquitards. Performance of the numerical scheme is studied through a series of test problems by comparing with results obtained from a conventional finite element model. A high degree of accuracy and flexibility is achieved with the extended quasi three-dimensional technique, yet the numerical efficiency inherent in the classical formulation is maintained. By dividing an aquifer into a series of horizontal sublayers, vertical resolution of the flow field can be achieved without resorting to a numerically intensive fully three-dimensional scheme. Because it is possible to compute a three-dimensional representation of the hydraulic head distribution in individual aquifers with the quasi three-dimensional formulation, even in the absence of layers of contrasting hydraulic conductivity, the technique provides a viable alternative to the much more complex fully three-dimensional schemes for a wide variety of groundwater flow problems. Key words: groundwater flow, multiaquifer, complex stratigraphy, numerical analysis, quasi three-dimensional, steady state.

Highly concentrated ceramic bonding suspensions. Mechanism of structure formation and the kinetics of casting-up of the body with partial dewatering

The structure formation of highly concentrated ceramic bonding suspensions (VKVS) during their applications is attained by concentrating the system by means of removing the kinetically bonded liquid into the porous volume of the substratum (porous mold, filler, refractory).