Experimental Studies for the characterization of the mixing processes in negative buoyant jets

Hybrid membrane system for desalination and wastewater treatment : Integrating forward osmosis and low pressure reverse osmosis

Research progress of sodium super ionic conductor electrode materials for capacitive deionization

Integrated production of fresh water, sea salt and magnesium from sea water

Laboratory experiments are performed to understand the controlling parameters of the electrical field associated with the seepage of water through a porous material. We use seven glass bead packs with varying mean grain size in an effort to obtain a standard material for the investigation of these electrical potentials. The mean grain size of these samples is in the range 56–3000 μm. We use pure NaCl electrolytes with conductivity in the range 10−4 to 10−1 S m−1 at 25°C. The flow conditions cover viscous and inertial laminar flow conditions but not turbulent flow. In the relationship between the streaming potential coupling coefficient and the grain size, three distinct domains are defined by the values of two dimensionless numbers, the Dukhin and the Reynolds numbers. The Dukhin number represents the ratio between the surface conductivity of the grains (due to conduction in the electrical double layer coating the surface of the grains) and the pore water electrical conductivity. At high Dukhin numbers (≫1) and low Reynolds numbers (≪1), the magnitude of the streaming potential coupling coefficient decreases with the increase of the Dukhin number and depends on the mean grain diameter (and therefore permeability) of the medium. At low Dukhin and Reynolds numbers (≪1), the streaming potential coupling coefficient becomes independent of the microstructure and is given by the well‐known Helmholtz‐Smoluchowski equation widely used in the literature. At high Reynolds numbers, the magnitude of the streaming potential coupling coefficient decreases with the increase of the Reynolds number in agreement with a new model developed in this paper. A numerical application is made illustrating the relation between the self‐potential signal and the intensity of seepage through a leakage in an embankment.

This work is concerned with the characteristics of very low frequency sound propagation (VLF, ≤100 Hz) in the shallow marine environment. Under these conditions, the classical hypothesis of considering the sea bottom as a fluid environment is no longer appropriate, and the sound propagation characteristics at the sea bottom should be also considered. Hence, based on the finite element method (FEM), and setting the sea bottom as an elastic medium, a proposed model which unifies the sea water and sea bottom is established, and the propagation characteristics in full waveguides of shallow water can be synchronously discussed. Using this model, the effects of the sea bottom topography and the various geoacoustic parameters on VLF sound propagation and its corresponding mechanisms are investigated through numerical examples and acoustic theory. The simulation results demonstrate the adaptability of the proposed model to complex shallow water waveguides and the accuracy of the calculated acoustic field. For the sea bottom topography, the greater the inclination angle of an up-sloping sea bottom, the stronger the leak of acoustic energy to the sea bottom, and the more rapid the attenuation of the acoustic energy in sea water. The effect of a down-sloping sea bottom on acoustic energy is the opposite. Moreover, the greater the pressure wave (P-wave) speed in the sea bottom, the more acoustic energy remains in the water rather than leaking into the bottom; the influence laws of the density and the shear wave (S-wave) speed in the sea bottom are opposite.

Conservative desalination technology including distillation requires high energy and cost to operate. Hence, pretreatment process can be done prior to desalination to overcome energy demand and cost reduction. The objective of this investigation is to study the effect of calcination temperature of hybrid catalyst in photocatalytic reactor system in the seawater desalination i.e salt removal in the seawater. The catalyst was synthesized via wet impregnation method with 1:1 weight ratio of TiO 2 and activated oil palm fiber ash (Ti:Ash). The catalyst was calcined at different temperature, i.e. 500 o C and 800 o C. The study was carried out in a one litre Borosilicate photoreactor equipped with mercury light of 365 nanometers for two hours with 400 rpm mixing and catalyst to seawater sample weight ratio of 1:400. The Chemical Oxygen Demand (COD), pH, dissolved oxygen (DO), turbidity and conductivity of the seawater were analyzed prior and after the testing. The fresh and spent catalysts were characterized via X-Ray Diffractogram (XRD and Nitrogen physisorption analysis. The calcination temperature significantly influenced the adsorption behaviour and photocatalytic activity. However, Ti:Ash which calcined at 800 o C has less photocatalytic activity. It might be because the surface of fiber ash was sintered after calcined at high temperature. The Ti:Ash catalyst that calcined at 500 o C was found to be the most effective catalyst in the desalination of seawater by reducing the salt concentration of more than 9 % compared to Ti:Ash calcined at 800 o C. It can be concluded that catalyst calcination at 500 °C has better character, performance and economically feasible catalyst for seawater desalination.

This study was performed to understand the chemical properties of coastal groundwaters of Korea and to evaluate salinization and desalinization using the chemical compositions of groundwaters, ionic ratios and base cation exchange. Salinization and desalinization frequently occurs in coastal and reclaimed regions, respectively. The reclaimed regions are mainly distributed in western coastal areas, but those are hardly distributed in southern coastal area. Thus, in the western coastal areas, the chemical compositions of groundwaters were mainly affected by salinization by seawater encroachment and desalinization by recharge of fresh water. 33 ~ 37% of the total groundwater samples were affected by seawater, and 6 ~ 15% of the total brackish and saline groundwater samples observed desalinization. However, in the southern coastal areas, the chemical compositions of groundwaters were mainly influenced by salinization (approximately 30 ~ 34%). Also, desalinization processes were observed in some southern groundwater samples (approximately 2 ~ 4%). While the desalinization in the western coastal groundwater was mainly observed in reclaimed regions, desalinization in the southern coastal groundwater was not observed in only reclaimed region. This study shows that desalinization can be one of main factors controlling the chemical compositions of groundwaters in the coastal areas including reclaimed regions and base cation exchange is good tool to identify desalinization.

Thermal and membrane based desalination plants are being operated all over the world to address the demand of fresh water required by industries and large cities in water scarce coastal areas. The desalination and energy are very much interlinked, as plants are energy intensive. The energy consumption of desalination plants varies from 5 to 15 kWh m-3 of product water depending on the technology. In addition, the percentage of reject seawater/brine exiting the plants varies from 60% to 80% depending on the desalination technique. The concentrated reject brine is a source of valuable trace elements/metals, which is an untapped source that is wasted. With advances in Desalination technologies, it has been established that recovery of critical metals and elements and their selective recovery from reject brine of desalination plants gives an added advantage of energy credits to desalination plants as well as reduce cost of desalinated water [1, 2]. Research and technological developments are required for brine mining from desalination plants, i.e., by the recovery of nuclear fuel and other valuable materials (e.g. U, Li, Rb), from reject brine streams. This is being achieved by adsorption of these elements/ions onto a selective sorbent that is dipped either in reject brine/inlet seawater or in the open sea [1]. The major factor determining the practical utilization of the technology and lifetime of the adsorbent is fouling of the adsorbent by suspended particles or due to biological growth. The paper presents the status review on a recovery of important trace metals and other alkali metals from seawater and highlights the potential of Indian desalination plants for the recovery of trace metals. The adsorption studies carried out using radiation grafted polymeric adsorbents along with fouling studies are discussed in this paper. The studies involve determination fouling tendency of the adsorbents in a different environment, and recovery of uranium and vanadium from the reject brine. The paper also gives the schematic diagram and major unit operations involved in process flow scheme.

A bacteriological survey has been made of the waters and bottom sediments in the Gulf of Maine and Georges Bank. The samples of water, plankton tow, and sedimentary material were taken under sterile conditions and subjected immediately to bacteriological analysis as soon as brought on board the "Atlantis."The agar-plate method was used for the enumeration of the numbers of bacteria. This was supplemented to a limited extent by the dilution method. Various specific media were used to determine the distribution and relative abundance of certain groups of bacteria which are believed to take part in important marine processes.The results obtained demonstrated the fact that the bacterial population of the sea can be divided into three groups on the basis of their habitat: (1) those forms which live in the sea bottom, especially in the surface layers; (2) those bacteria which live in the free water, this being possible only when the water contains in solution organic and inorganic substances which can serve as ...

Alternative approach for assessment and limitation of environmental impacts from desalination plant water discharges by substitution of the „mixing zone” by a „minimum dilution volume”

Negatively buoyant jets develop when fluids are released upwards into a lighter fluid or, vice versa, downwards into a heavier fluid. There are many engineering applications, such as the discharge, via submerged outfalls, of brine from desalination plants into the sea. Some concerns are raised about the potential negative environmental impacts of this discharge. The increase in salinity is the major cause for environmental impact, as it is very harmful to many marine species. The diffusers for brine discharge are typically inclined upwards, to increase the path before the brine reaches the sea bottom, as it tends to fall downwards driven by negative buoyancy. The negatively buoyant jet that develops conserves axisymmetry only when released vertically, so that it is not possible to use the well-known equations for axisymmetric jets. The main target of this paper is to investigate on a laboratory model the effects of different stratifications on the features of negatively buoyant jets. This has been done via a LIF (Light Induced Fluorescence) technique, testing various release angles on the horizontal and densimetric Froude numbers. Except for the initial stage, a different widening rate for the upper boundary and the lower boundary has been highlighted.

The objective of this chapter is to perform laboratory and direct numerical modeling of turbulent wind over water surface under stable stratification conditions. Laboratory and numerical experiments are performed under the same bulk Reynolds and Richardson numbers which allow a direct comparison between the measurements and calculations. The laboratory experiments are performed in a wind-wave flume on the basis of a thermostratified tank facility at IAP RAS. A sufficiently strong stable stratification (with the air–water temperature difference of up to 18 K) and a comparatively large bulk Richardson number (up to Ri ≈ 0.04) in the experiment are created by heating the incoming air flow while maintaining a relatively low wind speed (up to 3 m/s) and the corresponding bulk Reynolds number up to Re ≈ 60000. The air velocity field is retrieved by employing both contact (Pitot tube) and PIV methods, and the air temperature profile is measured simultaneously by a set of contact probes. The same bulk Ri and Re are prescribed in direct numerical simulation where turbulent Couette flow is considered as a model of the near water constant stress atmospheric boundary layer. The mean velocity and temperature profiles obtained in our laboratory and numerical experiments agree well and also are well predicted by the Monin–Obukhov similarity theory. The results show that sufficiently strong stratification, although allowing a statistically stationary turbulent regime, leads to a drastic reduction of both turbulent momentum and heat fluxes. Under this regime, the flow turbulent Reynolds number (based on the Obukhov length scale and friction velocity) is found to be in agreement with known criteria characterizing stationary strongly stratified turbulence.

The primordial method to prevent, avoid and/or mitigate the deterioration of desalination plants (DP) materials is the selection of chemical and mechanical resistant materials to the DP operation conditions. Three different types of saline waters (SW) are treated in DPs: sea water, brackish water (BW) and brines, a byproduct that showed be disposed to avoid ecological problems. A DP is a complex, organized structure managing physicochemical processes: compression, filtration, evaporation, condensation, and circulation, involve diverse equipment, e.g. pumps, pipelines, turbines, heat exchangers, deaerators, storage tanks, valves, control and flow instruments. Metallic, plastic and composite materials are applied for the manufacture of these equipments. The surface of DP equipment should be kept clean and smooth applying sanitation regulation to prevent sealing and fouling difficulties. It is convenient to attach a corrosion technician at a DP to manage a corrosion laboratory, to expose corrosion test specimens of new materials and to control the corrosive factors of the DP fluids, to avoid expensive damaging corrosion occurrences. Modern DPs are built from correctly selected CRA and CRM. Application of recognized and approved technology of corrosion protection and control should provide prolonged equipment service life and freedom form corrosion. Correct operation and maintenance of a DP will assure the efficiency and economic profitability of the desalination industry (DI) rand provide prolonged equipment service life and freedom from corrosion.

Mixing of wastewater effluent in rivers and coastal areas is a primary research area in environmental hydraulics. Mixing is important with respect to both short-term immediate toxicity of the disposed materials as well as their long term effect on aquatic life and the ecosystem. Mixing studies are also carried out with the purpose of assessing the fulfillment of environmental regulations. The main goal of all of these studies is to determine the current environmental situation and to develop a general, accurate and applicable controlling method. Mixing studies fall within this category and are conducted to improve the understanding about the mixing pattern of different outfalls systems in the receiving environment which can be river, sea or ocean. Mixing study results can greatly help environmental authorities to prepare development plans and to make decisions in critical situations. Ras Laffan Industrial City is the largest industrial compound of Qatar. Sea water is used to cool petrochemical, gas and fuel refinery in the industrial city. Part of the heated water from the plants is transferred to the Ras Laffan desalination plant. Desalination plants usually use sea water and discharge their hypersaline outfall into the sea. The Ras Laffan desalination plant uses a Multi Stage Flash (MSF) process. Due to the added heat, MSF desalination plant effluent is normally neutral or positively buoyant, which causes the plume to rise. In the Ras Laffan compound the effluent of the desalination plant is mixed with the cooling water which comes from other plants before being discharged into the sea. The productivity of the desalination plant is 10%, so the effluent salinity is expected to be 10% higher than the sea water. As this effluent is mixed with the mentioned cooling water before discharging into the port, the final effluent density is lower than the receiving water. Figure 1 Ras Laffan Industrial City Port. The photo was adopted from the Google Earth RLIC has a surface outfall located at 25° 53.480' North (latitude) and 51° 34.483' East (longitude), discharging about 222 m/s into the sea. The very high discharge value and shallow depth at the outfall generate a wall-jet-like flow regime. The outfall is located inside the Ras Laffan port, and therefore the generated plume is a confined jet. The water level in the port varies during the tidal cycle; however, due to the low tidal current velocity in the port, the ambient water can be considered as stagnant. Extensive field measurements were carried on the outfall of RLIC March and May 2014. The near field and far field temperature and salinity of the RLIC effluent plume were also surveyed using a CTD. Figure 2: Measured temperature fields from CTD. a)March 19,2014; b)March 24, 2014; c)May 15, 2014; 31

Experience with plate-and-frame ultrafiltration and hyperfiltration systems for desalination of water and purification of waste water