Desalination Effect Research Articles

Self-sustained webs of polyvinylidene fluoride electrospun nano-fibers: Effects of polymer concentration and desalination by direct contact membrane distillation

The effects of the polymer polyvinylidene fluoride (PVDF) concentration on the characteristics and direct contact membrane distillation (DCMD) desalination performance of self-sustained electrospun nano-fibrous membranes (ENMs) have been studied. Different polymer concentrations ranging from 15 to 30wt% were considered in the solvent mixture N,N-dimethyl acetamide and acetone, while all other electrospinning parameters were maintained the same. Viscosity, electrical conductivity and surface tension of the polymer solutions were measured and the effects of the PVDF concentration on fiber diameter, thickness, water contact angle, inter-fiber space, void volume fraction, liquid entry pressure, mechanical and thermal properties of the ENMs were investigated. The minimum polymer concentration, critical chain entanglement concentration, required for electrospinning beaded fibers and the concentration needed for the formation of bead-free fibers were localized. Two groups of ENMs were identified based on the surface structure of the ENMs, their void volume fraction and inter-fiber space. Bead-free ENMs, prepared with PVDF concentration higher than 22.5wt%, exhibit higher DCMD permeate flux than the beaded ENMs. Beaded ENMs can be used in desalination by DCMD. Among the prepared ENMs, the optimized membrane exhibiting the highest DCMD performance was prepared with 25wt% PVDF concentration.

Development of a poultice for electrochemical desalination of porous building materials: desalination effect and pH changes

Salt induced deterioration of structures and stones are generally recognized as a frequent and serious problem. The deterioration is especially undesired in relation to cultural heritage as it is impossible to recreate original material (e.g. original murals). By presence of salts in decorated vaults two different techniques are applied: poultices or establishment of climate chambers. Both techniques can result in ion transport away from the valuable surfaces with murals, but satisfying desalination has not been obtained according to conservators from the Danish National Museums mural preservation section in consistence with the present available literature. In the present paper the possibility for salt removal by utilizing a well known and accepted transport process, electromigration, is investigated, i.e. movement of ions in a solution in an applied electric DC field. An experimental laboratory setup was designed to approximate real conditions in vaults and with ion contents corresponding to normal heavily polluted church vaults (1.0 wt% Chloride, added as NaCl). During the electromigration process acid and base is produced at the electrodes due to electrode reactions and in a clarifying experiment with a traditional poultice significant pH changes and an absence of satisfying high desalination effect was measured. The new idea in the present paper was to introduce a calculated amount of buffer components corresponding to the productions during the electrode processes to a poultice (a solid) to minimize the adverse effects and to optimize on the effects. The results showed good ability to retain neutral pH values in the substrate which is of major importance when the method should be applied on existing structures. Also the desalination process continued until a very low and harmless salt content was reached after introduction of the buffer components.

Application of the Enzymolysis and Membrane Technology in Glucan Extraction and Purification from <i>Grifola frondosa</i>

It has been investigated that the application of the enzymolysis and membrane technology in the extraction and purification of glucan from Grifola frondosa. The fruitbody of Grifola frondosa was been used to extract polysaccharides. Compared the yield, protein content and polysaccharide content in the extracts under 3 different process modes, it was found that the procedure processed by complex enzyme was better than the others. Microfiltrated with membrane of 0.2μm aperture and then ultrafiltrated with membrane with molecular weight cutoff of 1000 Dalton, it had glucan retained rate of 80.42% and protein removed rate of 88.27%. GCP experiment indicated that the glucan get from the procedure was a homogeneous polysaccharide with weight average molecular weight of 130355 Dalton. The index of molecular weight distribution was 1.1844. The desalination rate was increased by adding water to the concentrate while ultrafiltration was in progress. When the quantity of water added was 1.5 times of the concentrate volume, it had effective desalination effect with the ash content of 3.79% in final product.

Effectiveness of water desalination by membrane distillation process.

The membrane distillation process constitutes one of the possibilities for a new method for water desalination. Four kinds of polypropylene membranes with different diameters of capillaries and pores, as well as wall thicknesses were used in studied. The morphology of the membrane used and the operating parameters significantly influenced process efficiency. It was found that the membranes with lower wall thickness and a larger pore size resulted in the higher yields. Increasing both feed flow rate and temperature increases the permeate flux and simultaneously the process efficiency. However, the use of higher flow rates also enhanced heat losses by conduction, which decreases the thermal efficiency. This efficiency also decreases when the salt concentration in the feed was enhanced. The influence of fouling on the process efficiency was considered.

Effectiveness of desalination powered by a tracking solar array to treat saline bore water

A solar powered desalination unit was tested between October 2008 and February 2010 in the Brisbane Botanic Gardens, Mt. Coot-tha, Queensland, Australia to provide garden irrigation during drought conditions. Water was extracted from a saline bore, and the salt was removed with a 30kL/d brackish bore water desalination unit. The driving force was provided by a bore pump driven by a 1.44kW tracking solar array. This study demonstrated that solar powered desalination of saline bore water delivered fresh water to the rated flow rate of the RO membrane rack during periods of sunshine. During periods of overcast or rainy weather, the performance of desalination decreased. Consumption of permeate for flushing further reduced overall recovery rate during rainy weather. Solar desalination performance was inversely related to the El Niño Southern Oscillation Index (polynomial fitting R²>0.4). Analysis of performance in relation to satellite-derived daily horizontal solar radiation shows stronger correlation with permeate production.Wet seasons tended to hinder performance. Performance in terms of specific energy consumption is related to salinity. Other factors that contributed to the present finding of low specific energy consumption included tracking solar arrays, avoidance of batteries, and utilization of bore pump pressure to drive RO.

Seawater quality and microbial communities at a desalination plant marine outfall. A field study at the Israeli Mediterranean coast

Global desalination quadrupled in the last 15 years and the relative importance of seawater desalination by reverse osmosis (SWRO) increased as well. While the technological aspects of SWRO plants are extensively described, studies on the environmental impact of brine discharge are lacking, in particular in situ marine environmental studies. The Ashqelon SWRO plant (333,000 m 3 d −1 freshwater) discharges brine and backwash of the pre-treatment filters (containing ferric hydroxide coagulant) at the seashore, next to the cooling waters of a power plant. At the time of this study brine and cooling waters were discharged continuously and the backwash discharge was pulsed, with a frequency dependent on water quality at the intake. The effects of the discharges on water quality and neritic microbial community were identified, quantified and attributed to the different discharges. The mixed brine-cooling waters discharge increased salinity and temperature at the outfall, were positively buoyant, and dispersed at the surface up to 1340 m south of the outfall. Nutrient concentrations were higher at the outfall while phytoplankton densities were lower. Chlorophyll-a and picophytoplankton cell numbers were negatively correlated with salinity, but more significantly with temperature probably as a result of thermal pollution. The discharge of the pulsed backwash increased turbidity, suspended particulate matter and particulate iron and decreased phytoplankton growth efficiency at the outfall, effects that declined with distance from the outfall. The discharges clearly reduced primary production but we could not attribute the effect to a specific component of the discharge. Bacterial production was also affected but differently in the three surveys. The combined and possible synergistic effects of SWRO desalination along the Israeli shoreline should be taken into account when the three existing plants and additional ones are expected to produce 2 Mm 3 d −1 freshwater by 2020.

Effects of salinity and desalination on seed germination of six annual weed species

The effects of various salinities and desalination on seed germination of six annual glycophytes (Artemisia sieversiana, A. scoparia, Chloris virgata, Eragrostis pilosa, Chenopodium acuminatum and Chenopodium glaucum) were studied in Horqin Sandy Land, Inner Mongolia, China. NaCl solutions of five concentrations (0 mM, as the control, and 50, 100, 200 and 300 mM) were used for saline stress and desalination treatments. Increasing salinity significantly reduced germination percentages of A. sieversiana, A. scoparia, Ch.virgata and Ch. acuminatum, but had no effect on the germination percentages of E. pilosa. Lower salinity levels (50 mM) significantly increased germination percentage of Ch. glaucum. High salinity might be a precondition for germination after desalination for five of the six species, excepting E. pilosa at NaCl concentration of 300 mM in comparison with non-primed seeds. Higher salinity (>200 mM) led to some specific ion toxicity and reduced seed viability of A. sieversiana. No specific ion toxicity but an osmotic effect limited the germination of other five species was observed The final germination percentages (salinity stress and desalination) of the six species showed three variations in comparison with the controls, namely, indiscrimination, stimulation, and reduction. Germination responses to salinity and desalination suggested that the six species were separated into three categories. Three species (A. sieversiana, Ch. virgata and Ch. acuminatum) showed similar germination responses to salinity with those of halophyte, but also showed a lower tolerance limit than most halophytes, although this was not always the case. A. scoparia and Ch. glaucum exhibited some ‘salt stimulation’ in seed germination percentages after desalination, whereas E. pilosa did not show any obvious response to salinity. Therefore, salinity usually induces dormancy of seeds with strong germination capacity in fresh water, but has few, or even positive, effects on seeds with strong innate dormancy.

Study on Desalination Characteristics of Nanofiltration Separation

The study discussed the desalination effect of influence factors (operation pressure, salt concentration, pH, ionic valence and etc.) for two different types nanofiltration (NF) (DK and NF90), based on desalination NF characteristics of membrane. The results showed the same desalination characteristics of the two kinds NF that desalination performance decrease directly with NF operation pressure and salt concentration increasing. When pH value was controlled in an acidic range of 4 to 7, it could obtain both high salt removal and membrane flux in salt solution. The salt rejection sequence of two NF was NaCl <MgCl2 <Na2SO4 <MgSO4 <Na3PO4 in different valence salt neuter solution. The different desalination characteristics of two kinds NF showed that monovalent salt rejection of DK (over 35%) was lower than that of NF90 (above 85%). The multivalent salt rejection of two NF showed higher removal efficiency, with DK over 96% and NF90 over 99%.

Effects of water desalination on milk production and several blood constituents of Holstein cows in a hot arid climate

Summary Fourteen primiparous Holstein cows (180.0 ± 4.3 days in milk) with a mean (±SD) daily milk yield of 35.0 ± 1.3 kg and a body condition score of 3.2 ± 0.2 were allotted into two groups (n = 7), and were fed a ration consisting of (dry matter basis) 35% corn silage, 25% alfalfa hay and 40% concentrates. Salt was provided free choice. The experiment was performed during the period of heat stress, i.e., when the temperature-humidity index was greater than 72. One group was offered desalinated water containing 570 mg total dissolved solids (TDS) and another group was offered water containing 1400 mg TDS per L. Milk yield was measured weekly, and milk samples were taken on days 21 and 42 for determination of milk composition. Blood samples were taken on days 21 and 42 from the median caudal vein of the tail and the serum concentrations of Na + , K + , Ca 2+ , Mg 2+ , tri-iodothyronine (T3) and thyroxine (T4) were measured. Ruminal fluid was taken by rumenocentesis on day 42 for determination of volatile fatty acids (VFA) and pH. Milk yield, milk composition, serum concentrations of T3 and T4, Na + , Ca 2+ and Mg 2+ , ruminal fluid VFA concentration and pH were not significantly affected by water TDS (P>0.05); however, cows receiving desalinated water produced 2 kg more milk per cow per day. Serum K + concentration was significantly higher in cows consuming saline water (P<0.05). The present data indicated that water with a TDS of 1400 mg per L had no adverse effect on lactating cows; therefore, it is not necessary to desalinate water in the region under study. However, in light of the possible effects of saline water on thyroid hormones, further studies concerning the influence of saline water on the metabolism of high producing cows in hot climates are warranted.

Crystallization modifiers applied in granite desalination: The role of the stone pore structure

Soluble salts of marine origin are one of the main agents in the weathering of granitic rocks used in buildings and monuments; they cause a loss of cohesion between the mineral grains, which results in granular disintegration. This deterioration is produced by crystallization–dissolution processes of salts, mainly sodium chloride, in the interior of the rock. Desalination procedures (mainly immersion and application of adsorbent poultices) are the more usual intervention in this circumstance, but complete extraction of the salts is generally difficult to achieve. In this paper we present the results of a study of the effectiveness of two NaCl crystallization modifiers, potassium ferrocyanide and sodium ferrocyanide, in desalinating two types of granitic rock with significantly different pore structure. Evaluations have been made of how these modifiers influence, first, the transport of NaCl solution inside the rocks; second, the susceptibility of the granite to salt crystallization cycles; and third, the effectiveness of desalination by immersion in distilled water. The results obtained are that the effectiveness of the two modifiers is completely different in each of the two granites studied. In one type of rock studied, both ferrocyanides increase the evaporation rate of the saline solution inside the structure of the rock by permitting NaCl to crystallize on surfaces as efflorescences; consequently, first, the intensity of sand disaggregation during the salt crystallization test is reduced, and second, when either of the modifiers is added to distilled water, desalination is more effective than extraction with distilled water only. For the second type of granite evaluated, neither of the modifiers was found to be effective. Therefore, we conclude that the network of fissures in the rock has a significant effect on the behaviour of the solutions with modifiers, since the pore structure of the stone determines the dissolution/evaporation kinetics of the solutions of salts. Thus, generalizations about the effectiveness of specific modifiers in granites are not possible: their effectiveness must be studied for each specific stone.

활성 탄소 복합 전극을 이용한 Capacitive Deionization 공정의 제염 효과

<TEX>$TiO_2$</TEX>가 첨가된 탄소복합전극을 제조 Capacitive deionization(CDI)에서의 제염효과에 대하여 고찰하였다. 본 연구에서는 탄소전극과 탄소복합전극을 제조하여 순환전류전압법과 충전-방전 평가를 하였으며 이때의 이온제거율에 대하여 고찰하였다. 순환전류전압법으로 1 mV/s의 전위주사속도에서 측정한 결과 탄소전극은 125 F/g, 탄소복합전극의 축전용량은 243 F/g으로 2배 증가됨을 확인하였다. 탄소복합전극의 <TEX>$TiO_2$</TEX>의 함량은 10 wt.%로 고정하였으며 <TEX>$TiO_2$</TEX>가 첨가됨에 따라 전기이중층 흡착량이 증가되어 이온제거율이 탄소전극보다 25% 증가되었다. Desalination effects of Capacitive deionization(CDI) process using activated carbon <TEX>$TiO_2$</TEX> composite electrode. In this study, we made the activated carbon electrod and activated carbon <TEX>$TiO_2$</TEX> composite electrode, which analysed at cyclic voltammetry and charge-discharge. The results measured for discharge capacitance in cyclic voltammetry were 125 F/g in activated carbon electrode and capacitance of activatd carbon composite electrode was increased about two time, 243 F/g. The <TEX>$TiO_2$</TEX> content of activated carbon composite electrode was 10 wt.%. When it was added wtih TiO2, electric double layer adsorption content was increased, so it was increased 25% in ion removal ratio of activated carbon electrode.

Assessment of EU policy: Implications for the implementation of autonomous desalination units powered by renewable resources in the Mediterranean region

Small-scale autonomous desalination systems (ADS) powered by renewable energy are ideal for implementation in arid or semi-arid regions like the Mediterranean, especially in remote coastal or inland locations. The technology has made significant progress but wide scale implementation may face administrative barriers. This paper analyses the possible barriers imposed on ADS by the Water Framework Directive, the Drinking Water Directive, the EU Water Initiative, the European Mediterranean Partnership, and the European Neighbourhood Policy. It has been found that ADS developers have to comply with unnecessary strict regulations that apply to all drinking water supplies, while the consumers and the environment are not adequately protected from possible effects of desalination. A careful review of the relevant directives and standards has to be undertaken and adapt the documents to prepare for widespread use of ADS. On the other hand, there is widespread support for ADS within EU policy, mainly in the form of support for non-conventional water resources as well as for sustainable and rural development. The ADS community has to make use of this support and form a technology platform that will convince decision makers to improve policy and institutional framework conditions and will raise general awareness on the ADS benefits.

Economic Analysis of Environmental Issues Regarding Seawater Desalination

Desalination of seawater is becoming an important source of drinking water in many cities and towns, where the demand for water continues to increase, while the supply of fresh water is limited. We examine the economic aspects of several environmental issues that arise during consideration of desalination projects. We present a conceptual framework that demonstrates the differences between public and private objectives, and we use that framework to describe policies that can encourage firms and consumers to consider environmental impacts. Public policies can be implemented also to stimulate technological developments that will reduce the environmental impacts of desalination. We also examine the potential growth inducement effects of seawater desalination by describing the likely impacts of desalination on both the demand and supply components of the market for municipal water in a coastal area.

Calculating the environmental cost of seawater desalination in the Arabian marginal seas

Seawater desalination in the Arabian Gulf and the Red Sea is the reliable source of water supply to the population of Kuwait, Saudi Arabia, Bahrain, Qatar, and the United Arab Emirates. If desalination plants were to operate along the coasts of these arid climate semi-enclosed Arabian marginal seas, then the additional loss of water and returned brine waste due to the plant's water production would increase the salinity. A mathematical model is presented to calculate the impact of desalination plants on the salinity within a semi-enclosed sea of simple geometry. Due to the exponential sensitivity to the plant's location and its water production capacity, the effect of seawater desalination at the northern Arabian Gulf or Red Sea is found to be more severe.

Effects of Desalination and the Detergent Sodium Dodecylsulphate on the Early Development of the Sand Dollar Scaphechinus mirabilis

We studied the effects of reduced water salinity on early ontogenesis in the sea urchin Scapechinus mirabilis. It is shown that the lower limit of salinity tolerance for the embryos and larvae is the salinity of 28‰. Under the mutual effects of desalination and sodium dodecylsulphate (SDS), an addition of 0.1 mg/l of the detergent to water with a salinity of 28‰ caused disturbances in the development of the larvae, starting from the stage of blastula. Desalination of the water down to 22‰ with the presence of SDS exerts significant effects already at the stage of fertilization. The mass death of embryos (73%) was observed at the stage of the first cleavage. The increase in the concentration of SDS up to 1 mg/l in water with a salinity of 28 to 22‰ caused an increase in the percentage of abnormal embryos and larvae from 40 up to 100%.

Potential of nuclear desalination in the Arabian Gulf countries

Arabian Gulf countries are located in an arid area with limited water resources. Hydrological investigations point to large resources of underground water, but they are saline and need to be desalted. The best choice for providing fresh water in the Arabian Gulf countries is through seawater desalination with ground water as a back up. About 65% of desalination plants that are in operation worldwide are located in the Arabian Gulf countries, most of which are the dual-purpose multistage flash (MSF) plants, producing power and water. Reverse osmosis (RO) is used mainly for brackish water treatment and a limited number of multiple effect distillation (MED) plants are used in the Arabian Gulf countries. The use of nuclear desalination is practically essential in these countries where massive quantities of water are desalinated and there is a fast increase in power demand. These is no technical impediment to the use of nuclear reactors for supply of either heat or electricity or both to a desalination plant. However, the cost effectiveness of nuclear desalination is a site dependent matter. The type of desalination process and the size and type of the nuclear reactor have to be determined based on the specific site data. MSF plants are considered as energy intensive processes where energy cost is a major controlling parameter in the overall cost of desalination. Oil price fluctuations affect the cost of desalted water significantly, whereas nuclear power offers long term availability of indigenous fuel as well as long term fuel price stability. It has minimal environmental impact compared with other conventional desalination processes. This paper will discuss the potential of application of nuclear desalination in the Arabian Gulf countries. Various processes will be reviewed and most appropriate method selected.

Effect of desalination on the littoral tecturid gastropods in early development

The effect of decreased salinity on the limpetsCollisella dorsuosa, C. versicolor, C. radiata, andNotoacmea concinna (Mollusca, Gastropoda) is studied at early stages of development. It is shown that, for normal development from fertilization to the veliger stage, the salinity must be not less than 22–24‰. A decrease in salinity depressed the behavior of larvae. At earlier stages, the larvae were less sensitive to changes in salinity than at later stages. At the same time, veligers were better able to adapt to changes in salinity than trochophores. The vertical water distribution of larvae depended on their age. Two days after fertilization, the larvae sank down to start a benthic life. It is proposed that the narrow tolerance range of littoral limpet larvae to changes in salinity is connected with the fact that they spend a relatively small part of their life in plankton.

Desalinization of running waters: II. Benthic diatom communities: A comparative field study on responses to decreasing salinities

Desalinization effects on benthic diatom communities were investigated in two adjacent streams in Northern Thuringia, the creek Urbach and the river Helbe. Salt-saturated stockpile effluents had been introduced into the Urbach until 1996, resulting in fluctuating chloride concentrations with maximum values up to 25.4 g · 1 −1 (Helbe: max. 3.7 g · 1 −1). The diatom vegetation and hydrographical and chemical data of an Urbach site were compared to those of a sampling site further downstream. Monthly sampling in 1996 started at the end of salt influx in January. Reference samples from the years 1995, 1986 and 1963 were evaluated along with the 1996 samples. After termination of the introduction of salt-loaded effluents, relative abundances of brackish water species greatly decreased within three months. The Halobion Index ( Ziemann 1982 ), reflecting osmotic and ion composition effects on diatoms, decreased until May 1996, then stabilized. In summer 1996, several diatoms had a mass development, showing that salinization impacts had previously overruled effects of other environmental variables.

Water and salt movements in simultaneous flood-irrigation and well-drainage operations

This paper describes a new technology for solonchak soil reclamation in which surface flood irrigation of fresh water and pumped wells drainage of salty groundwater are combined. The comprehensive investigation of water and salt movement has been conducted through field test, laboratory simulation and numerical calculation. The dependence of desalination on irrigation water quantity, drainage quantity, leaching time and other parameters is obtained based on the field tests. The entire desalination process under the flood-irrigation and well-drainage operations was experimentally simulated in a vertical soil column. The water and salt movement has been numerically analyzed for both the field and laboratory conditions. The present work indicates that this new technology can greatly improve the effects of desalination.

Potential effects of electrochemical desalination of concrete on alkali – silica reaction

The recent development of an electrochemical method of chloride removal (desalination) for the treatment of corrosion of reinforcing steel in chloride-contaminated concrete offers the prospect of an effective repair strategy for certain types of structure that have been exposed to chloride ingress from the environment. As with any novel remedial technique, however, it is necessary to examine potentially detrimental side-effects. This Paper presents preliminary results of an investigation into one such phenomenon, namely cathodically stimulated alkali-silica reaction (ASR) in the concrete interfacial zone adjacent to the embedded steel. It is shown that for concrete specimens containing potentially reactive siliceous aggregates in cementitious matrices of bulk alkalinity below the threshold levels required to induce expansive ASR, local expansion and cracking in the vicinity of steel cathodes may be caused by the application of current densities in the range 1–8 A/m2 for periods of 4–12 weeks and subsequent moist storage. The relationship between the ultimate expansion of the concrete and the total charge passed through it during electrochemical treatment is complex and suggests a novel form of ‘pessimum’ behaviour. The discovery of this effect has important practical consequences, affecting the range of appropriate treatment conditions and testing regimes for diagnosis of ASR-susceptible concrete when electro-chemical desalination is being considered.