• Resources Recycling
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• v.25 no.3
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• pp.63-73
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• 2016

With the purpose of concentrating the magnesium from seawater, in this study, we have conducted experiments to precipitate the magnesium using three precipitants (NaOH, cement kiln dust, and paper sludge ash), and then extract it using sulfuric acid. Results show that the precipitation and extraction performance does not depend so significantly on the kind of precipitant: for all the precipitants used, the precipitation efficiency is measured almost 100% and the extraction efficiency is in the short range of 77 - 89%. The magnesium concentration in the extract is measured 4975 - 5775 mg/L, implying that the magnesium in seawater should be 3.8 - 4.4 times concentrated through the precipitation and extraction reactions. The reaction efficiency of the industrial by-product used as a precipitant in this study is almost 100% similar to those of the other existing expensive precipitants.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.5
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• pp.407-412
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• 2014

A new apparatus for seawater desalination, based on the principle of gas hydrates, is suggested. The equipment continuously produces and pelletizes gas hydrates by a squeezing operation in a dual cylinder unit, which is able to extract pure hydrate pellets from the seawater-containing reactor. Desalination efficiency for each dissolved ion from seawater samples was tested by inductively coupled plasma atomic emission spectroscopy (ICP-AES) and ion chromatography (IC) analysis. This study demonstrates that the suggested method and the stated apparatus may solve the difficulty of separating hydrate crystals from concentrated brine solutions, and therefore may be applied to improve the efficiency of existing desalination processes.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.3
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• pp.334-343
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• 2019

The Al-Zour coastal area, located in southern Kuwait, is a region of concentrated industrial water use, seawater intake, and the outfall of existing power plants. The Al-Zour LNG import facility project is ongoing and there are two issues regarding the seawater temperature in this area that must be considered: variations in water temperature under local meteorology and an increase in water temperature due to the expansion of the thermal discharge of expanded power plant. MIKE 3 model was applied to simulate the water temperature from June to July, based on re-analysis data from the European Centre for Medium-Range Weather Forecasts (ECMWF) and the thermal discharge input from adjacent power plants. The annual water temperatures of two candidate locations of the seawater intake for the Al-Zour LNG re-gasification facility were measured in 2017 and compared to the numerical results. It was determined that the daily seawater temperature is mainly affected by thermal plume dispersion oscillating with the phase of the tidal currents. The regional meteorological conditions such as air temperature and tidal currents, also contributed a great deal to the prediction of seawater temperature.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.38 no.1
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• pp.65-69
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• 2005

We have developed a new method of manufacturing salts by horizontal spray drying technique, using the concentrated deep ocean water after desalination processes. We studied the chemical characteristics of the spray-dried salts. Sodium content in the spray salts is $28.4\%$, which is $10-30\%$ lower than that of bay salts, bamboo salts and boiling salts $(32-38.2\%)$. However, the contents of magnesium, potassium and calcium of the spray salts are 2.5 times, 3 times and 4.5 times higher relative to those of bay salts, respectively. On the one hand, sulfur content in spray salts is 14 times lower than those of bay salts, which is caused by their volatilization during spray and vaporization of the concentrated seawater. Enrichment factors of Mg (0.8), K (0.9) and Ca (1.0) in the spray salts are relatively higher than those in bay salt (0.2-0.3), bamboo salt (0.15-0.4) and boiled salt (0.4-0.7), respectively. On the contrary, enrichment factor of sulfur in spray salts is observed to be 0.07, which is considerably lower than those in other salts (0.3-0.7). It means that the minerals like Mg, K and Ca can be well conserved from seawater to salts through spray drying techniques, while volatile elements like sulfur, lead, mercury and organic compounds can be easily removed from seawater via spray and heating processes.

• Journal of Korean Society of Water and Wastewater
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• v.27 no.6
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• pp.771-778
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• 2013

Gas hydrate (GH) process is a new desalination technology, where GH is a non- stoichiometric crystalline inclusion compounds formed by water and a number of gas molecules. Seawater GH is produced in a low temperature and a high pressure condition and they are separated from the concentrated seawater. The drawback of the GH process so far is that salt contents contained in its product does not meet the fresh water quality standard. This means that the GH process is not a standalone process for seawater desalination and it needs the help of other desalting process like reverse osmosis (RO). The objective of this study is to investigate the effect of GH process on energy saving for RO process in seawater desalination. The GH product water quality data, which were obtained from a literature, were used as input data for RO process simulation. The simulation results show that the energy saving effect by the GH process is in a range of 68 % to 81 %, which increases as the salt removal efficiency of the GH process increases. Boron (B) and total dissolved solids (TDS) concentrations of the final product of the hybrid process of GH and RO were also investigated through the RO process simulation to find relavant salt rejection efficiency of the GH process. In conclusion, the salt rejection efficiency of the GH process should exceed at least 78% in order to meet the product water quality standards and to increase the energy saving effect.

• Membrane and Water Treatment
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• v.8 no.5
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• pp.449-462
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• 2017

Direct treatment of municipal wastewater by forward osmosis (FO) process was evaluated in terms of water flux decline, reverse salt diffusion, pollutants rejection and concentration efficiency by using synthetic seawater as the draw solution. It was found that when operating in PRO mode (active layer facing the draw solution), although the FO membrane exhibited higher osmotic water flux, more severe flux decline and reverse salt diffusion was also observed due to the more severe fouling of pollutants in the membrane support layer and accompanied fouling enhanced concentration polarization. In addition, although the water flux decline was shown to be lower for the FO mode (active layer facing the feed solution), irreversible membrane fouling was identified in both PRO and FO modes as the water flux cannot be restored to the initial value by physical flushing, highlighting the necessity of chemical cleaning in long-term operation. During the 7 cycles of filtration conducted in the experiments, the FO membrane exhibited considerably high rejection for TOC, COD, TP and $NH_4{^+}-N$ present in the wastewater. By optimizing the volume ratio of seawater draw solution/wastewater feed solution, a concentration factor of 3.1 and 3.7 was obtained for the FO and PRO modes, respectively. The results demonstrated the validity of the FO process for direct treatment of municipal wastewater by using seawater as the draw solution, while facilitating the subsequent utilization of concentrated wastewater for bioenergy production, which may have special implications for the coastline areas.

• Corrosion Science and Technology
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• v.19 no.5
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• pp.239-249
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• 2020

The characteristics of cavitation-erosion damage with changes in the amplitude of 5052-O aluminum alloy for ships were investigated in a seawater environment. In the cavitation-erosion experiment, the cavitation environment was created using a vibration-generating device with a piezo-electric effect. The amplitudes of 5 ㎛, 10 ㎛, and 30 ㎛ were created by changing the geometric shape of the cavitation horn. The resistance characteristics of cavitation-erosion damage were evaluated by weight loss and pitting area. The damaged surface was analyzed using scanning electron microscopy (SEM) and 3D optical microscopy. As the amplitude increased, the amount of damage and the area of the damaged surface increased, and the damage was concentrated at the center and edge of the specimen. The pit was created after the initial incubation period with increasing experimental time, and then the pits were merged to grow and propagate into craters, and eventually, the surface was detached and damaged. The cavitation-erosion damage after 30 minutes with amplitude of 10 ㎛ and 30 ㎛ was 1.48 and 2.21 times compared to 5 ㎛, respectively.

• Journal of Korean Society of Water and Wastewater
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• v.25 no.3
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• pp.399-405
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• 2011

In a desalination technology using RO membranes, chemical cleaning makes damage for membrane surface and membrane life be shortened. In this research cleaning technology using direct osmosis (DO) was introduced to apply it under the condition of high pH and high concentration of feed. When the high concentration of feed is injected to the concentrate side after release of operating pressure, then backward flow occurred from treated water toward concentrated for osmotic pressure. This flow reduces fouling on the membrane surface. Namely, flux of DO was monitored under pH 3, 5, 10 and 12 conditions at feed concentrations of NaCl 40,000 mg/L, 120,000 mg/L and 160,000 mg/L. As a result, DO flux in pH 12 increased about 21% than pH 3. DO cleaning was performed under the concentrate NaCl 160,000 mg/L of pH 12 during 20 minutes. Three kinds of synthetic feed water were used as concentrates. They consisted of organic, inorganic and seawater; chemicals of SiO2 (200 mg/L), humic acid (50 mg/L) sodium alginate (50 mg/L) and seawater. As a result, fluxes were recovered to 17% in organic fouling, 15% in inorganic fouling and 14% of seawater fouling after cleaning using DO under the condition of concentrate NaCl 160,000 mg/L of pH 12.

• Journal of Energy Engineering
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• v.25 no.4
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• pp.1-6
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• 2016

Seawater desalination plants generally have two inherent problems which stem from energy inefficiency and desalination concentrate management. The former has been somewhat resolved thanks to the innovative methods in utilizing new and renewable energy resources whereas the latter still has much issues to be dealt with. This paper introduces the application of a desalting process for the disposal of desalination concentrate (especially, Mg) and to improve its cost effectiveness of a MVR seawater desalination plant built in Jeju. Principal component analysis on the desalination concentrate has revealed a steady reduction of Mg with the application of the desalting process verifying its functional reliability. Also, it was found that our MVR seawater desalination plant is not only energy efficient but also could be effectively applied for the dual purpose of fresh water production and concentrate management.

• Journal of the Korean Applied Science and Technology
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• v.32 no.2
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• pp.188-193
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• 2015

Blast Furnace Slag is good for enhancing the qualities of concrete such as reducing hydration heat increasing fluidity, long-term strength and durability, but it has some problems: construction time is increased or the rotation rate of form is decreased due to low development of early strength. In this study, an aqueous alkali solution for alkali activated reaction was obtained by the electrolysis using concentrated water discharged from seawater desalination process. Prepared aqueous alkali solution was applied to produce mortars using blast furnace slag. The results can be summarized as follows : For the mortar, compressive strength was decreased below 2% of NaOH and increased below 6% of NaOH. And compressive strength was increased gradually with increasing NaOCl contents. However, NaCl contents of mortars caused a decrease of 28days strength above early strength.