Desalination

Published by Elsevier
Online ISSN: 0011-9164
Publications
Article
An oxygen transport ceramic membrane was prepared with La0.6Sr0.4TixFe1−xO3−δ (x = 0.2 and 0.3) oxides which was synthesized by polymerized complex method. In order to investigate the effects of Ti substitutions into lanthanum–strontium ferrites, material property, thermal expansion coefficient, oxygen permeation, electrical conductivity and phase stability were examined according to Ti contents. The thermal expansion coefficients of LSTF6428 and LSTF6437 were 25.76 × 10−6 K−1 and 21.32 × 10−6 K−1 in the temperature range of 973−1273 K, respectively. The oxygen permeation fluxes through a disk type dense membrane of LSTF6428 and LSTF6437 with 1.6 mm thickness increased exponentially with increasing temperature and were 0.17 mL min−1cm–2 and 0.13 mL min−1cm−2 with Ph = 0.21 atm (O2 rich side) and Pl = 10−5 atm (lean side) at 1223 K, respectively. In the result of phase stability test with various conditions such as He, H2/N2 and CO2 atmosphere, La0.6Sr0.4TixFe1−xO3−δ was confirmed to be more stable than La0.6Sr0.4Ti0.2Fe0.8O3−δ through XRD and SEM analysis.
 
Article
Special care must be taken when designing pre-treatment systems for iron-rich feed waters at high temperature. The essential need for a cooling tower introduces a potential source of algal, bacterial and suspended solids contamination not usually encountered in standard closed, low temperature systems.Membrane fouling with mineral salts is easily prevented, but the simplistic use of chlorine will generally still allow some degree of biological fouling.This paper looks at modifications made to the pre-treatment system as a result of practical experience and increased water demand.
 
Article
Electrodialysis (ED) was employed to remove the organic and inorganic salts from actual 1,3-propanediol (PDO) fermentation broth. These salts cause many problems during the purification of PDO if not removed. Suitable operation parameters such as applied potential and the flow rate of streams were selected to ensure a stable and durative desalination process for PDO fermentation broth. Under these conditions, the membrane fouling can be alleviated effectively by changing pole and cleaning membranes so that further industrial production is possible. The experiment results show that about 90% of organic acid salts in PDO broth are removed by the ED process. In addition, a simulated diffusion PDO experiment proved that the diffusion of PDO results in its loss from fermentation broth and the loss ratio is less than 6% under the chosen operating conditions.
 
Article
Poly(1,4-phenylene sulfide) was sulfonated with fuming sulfuric acid to different degrees. The products were ground and sieved (mesh size 50 μm) to obtain small particles. The particles and linear polyethylene were mixed in various ratios and the resulting blends were press-molded at 150°C to obtain the membranes. Membranes containing up to 66 wt.% of sulfonated particles could be prepared without any problem with the required mechanical strength. The membranes with high concentrations of highly sulfonated particles were as conductive as Nafion 117 membranes and had high values of permselectivity in HCl solutions.
 
Article
The mechanical vapour compression process and its application to seawater desalination is presented. As an example the largest unit so far constructed by Sidem using this process is described: a 1,500 m3/d unit installed in the Nuclear Power Plant of Flamanville in France which supplies a high quality water to that plant.The advantages of this process are outlined, compared to other distillation processes: multiflash and ejectocompression, and the series of mechanical vapour compression units that Sidem has developed in a size range between 25 and 2,500 m3/d is also presented.
 
Article
This compilation of test methods applies to both reverse osmosis and electrodialysis membranes currently available in the commercial market place. The techniques described can be used for quality control of manufactured products, newly purchased materials and those membrane products which have been in service. The procedures for the physical and chemical properties have been presented separately; however, in actual fact these properties are interrelated.The physical properties apply to equipment design and in addition they impact on the application to some extent. Some chemical methods have been included to provide an overall treatment.For those familiar with membrane technology, it will be apparent that many of the procedures described can be modified to reflect or nearly duplicate a particular application. In most cases this can be accomplished by the prudent choice of electrolyte, concentration, time or temperature used.These methods cannot be applied to those reverse osmosis devices supplied as hollow fiber modules. Operating characteristics of these devices have been addressed by ASTM. In general, however, this type of equipment must be tested as a complete installation by following the supplier's instructions. This type of detailed operation is outside the scope of this presentation.
 
Article
This chapter discusses some of the fundamental characteristics of those flow phenomena that are encountered in multistage flash (MSF) and vertical-tube evaporator (VTE) desalination plants, and how they affect plant control and stability. Many of the factors affecting economic plant operation, such as stability, controllability, efficiency at reduced-load conditions, and nonequilibrium losses, are often not directly or easily observable, but should nonetheless be understood by the plant designer and operator.From both the modeling and the control standpoints, MSF processes are the more challenging. Descriptions of both single-phase and two-phase open-channel flow MSF models are presented, as are confirmatory data derived from a variety of experimental studies. Some of the problems to be encountered on the receiving end of the MSF process, i.e. in the control of condensation in horizontal tube bundles, especially during part-load and transient operation, are also noted briefly.VTE processes and their control characteristics and problems (or lack of problems) are outlined, along with results of some dynamics tests on VTE test beds.Finally, some research done on desalination plant process dynamics is described, including studies of various plants tied to different types of heat sources. Some control problems peculiar to MSF dual-purpose (electrical plus water) plants are also noted.
 
Article
The quality of the drinking water supply has become more important with Hungary's entry into the European Community. In some regions of the country, similar to many parts of the world, arsenic removal from drinking water is an urgent task to supply water with an arsenic content under 10 μg/l. We have worked out a new technology for arsenic removal using a membrane technique. Measurements on site were performed in a pilot plant with equipped with a pre-treatment system and a ZW-1000 (Zenon) membrane module. Before expanding the technological process, experiments on laboratory scale were done to find out which kind of pre-treatment and membrane configuration are needed. These experiments were performed with water from deep wells, among them with a high arsenic concentration (200–300 μg/l). The steps of the pre-treatment process were: oxidation with potassium permanganate (KMnO4), coagulation with ferrous(III) sulphate (Fe2(SO4)3), fast mixing of chemicals with a mixer, coagulation with slow mixing and settlement. Following membrane separation, the arsenic concentration was under the permitted value (10 μg/l). Results of experiments on site proved that the new technology was successful and is suitable to produce drinking water at the required quality from raw water with a high arsenic content in a pilot plant.
 
Article
The corrosion performance of 66-30-2-2 and 70/30 Cupro-nickels in sea water is influenced both by surface condiions and operating parameters. Corrosion tests performed in corrosion potentials of these alloys and their corrosion performance. The grwoth of cathodic oxide films is always a cause of intiation of localised corrosion. In this regard, the trend fo the corrosion potential during the first days of sea water exposure is of paramount importance.The effect of different pretreatments to keep corrosion potentials within the safe region and prevent the occurrence of pitting and under-deposit attack, was also studied.
 
Article
This paper sets the foundation of the optimal design of most systems that use or produce heat and/or power including desalination. The separation process of the desalination technologies by membranes and by distillation is considered as an example for the purpose of clarity and for the special importance to desalination. Both the energetics and the economics of the separation process are based on a quantitative formulation of the second law of thermodynamics in terms of the concept of exergy and its destruction. The separation process is considered for five main desalination systems: reverse osmosis, electrodialysis, vapor compression, boiling evaporation and flash evaporation. The results of the energetic analysis show a close competition between reverse osmosis and distillation for seawater desalination. The electrodialysis process is justified for the treatment of more dilute brackish water. It is shown that the determination of the driving force associated with exergy destruction occupies a central position in this comparison. The optimal design of the separation surface for minimum cost of energy and surface requirements takes off smoothly from the energetic analysis and sets the basis of a general and powerful approach to optimal system design. A second paper [1] is devoted to the general approach and its extension to cover almost all kinds of industrial processes and their combinations to produce one or more products.
 
Article
This paper outlines the operational experience with 2 × 11,500 m3 p.d. Multi Stage Flash desalination plants which were introduced to Bahrain in 1976. It attempts to place in perspective the problems which this technology presented, as it was new to Bahrain. The particular difficulties which resulted from use of bare carbon steel are identified. The corrective measures which were taken to minimise the rate of corrosion are stated. The paper concludes that careful specifications of materials for such plants is essential, and that the necessary expertise must be available at start up to achieve stable operation and to minimise down time.
 
Article
A Pb2+-selective sensor was fabricated from polyvinyl chloride (PVC) matrix membranes containing the ionophore 3,7,11-tris (2-pyridylmethyl)-3,7,11,17-tetraazabicyclo [11.3.1] heptadeca-1(17),13,15-triene (I). The effects of anion excluders (KTpClPB, NaTPB) and plasticizers (o-NPOE, DBP, DOP) on the performance of the membrane sensor were studied. The membrane with the composition of I:PVC:o-NPOE:KTpClPB in the percentage ratio (wt.%) of 2:32:60:6 exhibited the best performance, having a slope of 28.5 ± 0.2 mV/decade in the concentration range 10− 6–10− 1 M, a response time of 20 s and a lifetime longer than four months. The sensor was selective for Pb2+ ions over other monovalent, divalent and trivalent interfering cations and could be used in the pH range of 5–8. The high selectivity in the presence of Cd2+ may be important for further studies. The efficiency of the proposed sensor was demonstrated by its application in Pb2+ ions determination in water samples.
 
Article
The sorption kinetic and equilibrium data obtained at different water activities allowed us to determine the water sorption isotherms and mean diffusion coefficient in the Nafion® membrane. The water sorption isotherm is reminiscent of systems in which there is water clustering at high water activities, with a marked Langmuir sorption at low water activity for the acid form of the membrane. The variation of the diffusion coefficient with the water activity showed a maximum value whose coordinates depend on the counter-cation nature. The smaller the counter-cation, i.e. the larger the counter-cation hydration energy, the higher the diffusion coefficient and the lower the water activity at the maximum point.
 
Article
The Saline Water Conversion Corporation, Research and Development Center (SWCC-RDC) carried out exploratory research study to evaluate the adaptability of the brackish water softening nanofiltration technique as a permeation pretreatment of feed to seawater reverse osmosis (SWRO) and as make-up to MSF. This exploratory work was designated as part I of an applied research project that was carried out from March 1997 to May 1998. Based on initial remarkable results, SWCC applied for a patent on the process during 1997. This paper reports on the pretreatment approach and its application to thermal desalination using MSF. The work carried out in part I of this project is reported where make-up to a 20 kiloliter/d MSF pilot plant distiller was either fresh nanofiltration permeate (NFP) or SWRO reject (while SWRO was fed with NFP). This paper also addresses the plan of elevating MSF top brine temperature (TBT) to as high as 160°C since operation at TBT of 120°C with very little or no scale control treatment gave excellent results.
 
Article
Two case studies are described that explain the role, value, limitations and policy requirements for storing reclaimed water in aquifers for indirect reuse. The first case involves aquifer storage and recovery of water, the product of tertiary treated municipal sewage effluent, via a single injection and recovery well at Bolivar, South Australia. The recovered water, like the source water for injection, is used for unrestricted irrigation of horticulture. A limestone aquifer at a depth of 100 to 160 m confined by clay and containing brackish groundwater provides the storage zone. In the second case, located at Alice Springs, trials are proceeding to assist in the design and establishment of a soil–aquifer treatment system which will allow water derived from secondary treatment of municipal sewage effluent to be stored in an unconfined alluvial aquifer for irrigation of horticulture. Intermittent infiltration from basins provides supplementary water treatment. In each case, the motivations, choice of methods, required investigations, public consultation processes, and economics of subsurface storage are presented. The lessons learned that may assist with development of policies to facilitate environmentally sustainable subsurface storage of water in water reuse projects are discussed.
 
Article
This study investigated the feasibility of applying ozone (O3) to reduce the color content of wastewater caused by two commercial reactive dyes (Blue-19 and Orange-13). In the bench-scale experiment, experimental parameters including pH, ozone dosage, and reaction time were evaluated in a 14-L reactor to obtain the optimal operating conditions. Results show that ozone dosage and pH dominated the effectiveness of the decolorization process. The color content could be reduced from 2000 to 200 ADMI (American Dye Manufacture Institute) values within a reaction time of 30 min with the ozone input rate of 2.66 g/h. The pH values of 3 and 10 favored decolorization of Blue-19 and Orange-13, respectively. This was due to the effects that reactive and oxidizing species of molecular ozone and hydroxyl radicals were predominant at low and high pH, respectively. Moreover, molecular ozone was more selective to certain dye structures during the oxidation process. Kinetic analyses show that decolorization of Orange-13 and Blue-19 followed first-order kinetics. The degree of decolorization was primarily proportional to the ozone dosage. Results from this study provide insights into the characteristics and mechanisms of decolorization by the O3 technique. Results will also aid in designing a system for practical application.
 
Article
This paper presents the major design criteria and features for the 13.3 million gallons per day (MGD) seawater reverse osmosis (RO) desalination plant that is currently under construction in Madinat Yanbu Al-Sinaiyah, Yanbu Industrial City, in the Kingdom of Saudi Arabia. The seawater RO plant is made up of six trains of about 2.2 MGD capacity each. The plant consists of five major systems: seawater supply, seawater pretreatment, high pressure pumping, RO modules, and permeate posttreatment. The paper also discusses technical issues and parameters associated with the plant design, and advances made in the seawater reverse osmosis desalination technology.
 
Article
The initial eighteen month period of operation of the 15,000 m3/day municipal plant on the Island of Corfu, Greece, is described.The 15,000 m3/day desalting plant employing the electrodialysis reversal process (EDR) produces potable water (500 ppm) from a blend of brackish sources with salinities up to 2000 ppm TDS. The paper describes the plant and integration of the plant into the municipal system. The unique system employed to segregate the treatment of the different brackish waters employing only the highest salinity water for blowdown water is also described.The plant was started up in the fall of 1977 and provided water to the municipal system during the 1978 season.The paper presents operating cost data for this period and compares these costs with projected costs which form part of the contractual agreement, with the Municipality.
 
Article
The potential of industrial wastewater reuse in Jordan is discussed. Industrial water requirements, wastewater production, types of pollutants in industrial wastewater and the technologies for wastewater treatment have been evaluated. A total of thirty industries have been reviewed. The total effluent from the thirty industries reviewed estimated at approximately 10,200 m3/d. Of this amount, approximately 4,400 m3/d are discharged to public sewerage system, which is about 3% of the total flow. The amounts of metals to be controlled are: 6800 kg/y, 3000 kg/y, 45 kg/y, 65 kg/y, 20 kg/y, 2 kg/y, 25 kg/y, 60 t/y and 8 t/y of Cr, Zn, Cu, Pb, Ni, Cd, Sn, Fe and Al, respectively. Nineteen industries, which discharge mainly organic polluted process wastewater, are food industries. Approximately 5.3 t of BOD/d is discharged from these industries. Of these, approximately 2.2 t BOD/d are discharged to the public sewerage system and about 3.1 t BOD are used for irrigation. It has been shown that most of the selected industries require some treatment of their wastewater. It is recommended to carry out further studies to establish the type of wastewater pretreatment strategies and their estimated capital cost. There is a need for the introduction of a cleaner technology in the selected industries. This could include substitution of raw and auxiliary materials, water and energy saving, recirculation of water, recovery of chemicals, improved process control, waste minimization, and good housekeeping.
 
Article
A powdered activated carbon/submerged microfiltration (PAC/SMF) system was investigated to examine the removal efficiency of 17β-estradiol (E2) as well as the membrane filterability in the presence of natural organic matter (NOM). The removal of E2 was approximately 92%, but the presence of NOM did not significantly affect the adsorption efficiency of E2 on PAC. When E2 was spiked in the raw water containing NOM, the coupling phenomena did not occur in the rejection of E2 and NOM, but took place in the membrane fouling. Although the reduction of filterability by E2 itself was not so significant, membrane fouling by the river water in the presence of E2 significantly deteriorated in comparison to that generated by filtrating only the river water without E2. This was because E2 induced the additional adsorption of weakly-adsorptive NOM. This coupling phenomenon was related to the initial contact concentration of E2 with the membrane surface. The higher the initial contact concentration, the worse the fouling by NOM.
 
Article
In this biological nitrate removal study, the performance of the bacterial strain Acidovorax avenae subsp. avenae LMG 17238 using different carbon sources such as ethanol, methanol, sodium acetate, glucose and poly(ε-caprolactone) was investigated. Additionally the parameters such as an increase of nitrate concentration, carbon source amount (C/N) and dilution of a synthetic medium were studied. In laboratory conditions LMG 17238 and a mixed bacterial culture (soil suspension, wastewater treatment and macro algae Gracilaria verrucosa) have been immobilized as a comparative study to determine their efficiency in the biological denitrification of drinking water. For the continuous system as a carbon source, G. verrucosa was studied in fixed-bed columns. Various variables such as hydraulic retention time (HRT), mass amount of the substrate, and the initial nitrate concentration were investigated. A comparative study was achieved by using biodegradable poly(ε-caprolactone) as a carbon source using a mixed bacterial culture (LMG 17238 and G. verrucosa) in a fixed-bed column. Also Monod type equations were used to model the denitrification kinetics. The study proves that, LMG 17238 can be successfully used with different carbon sources. G. verrucosa can be considered as a promising alternative to poly(ε-caprolactone) with a maximum denitrification rate of 13.83 and 0.94 mg NO3−N/L d respectively.Research highlights► Investigating LMG 17238 using different carbon sources in a batch system. ► Promising results with carbon sources ethanol, methanol, sodium acetate and glucose. ► A comparative study for PCL in a fixed bed column with mixed culture. ► Monod type equations to model the denitrification kinetics.
 
Article
Global concern about the persistence of endocrine disrupting chemicals (EDC) in the freshwater environment is more evident due to their possible disruptive effects. Even at nanogram levels these compounds increase the risk of cancer, decrease egg and sperm production, reduce gamete quality and tend complete feminization of the male fish. The present study demonstrated the potential of activated charcoal as adsorbent in removing synthetic estrogen 17α-ethynylestradiol (EE2) from aqueous phase by sorption process employing both agitated batch and column adsorption experiments. Batch sorption studies showed good removal of EE2 and dependent on the concentration loaded. Equilibrium data of EE2-charcoal sorption system showed a reasonably good fit with pseudo first-order kinetic plot. Intra-particle diffusion plot indicated the complex nature of EE2-charcoal sorption system involving both boundary layer and intra-particle diffusions. Experimental data confirmed to linear Langmuir's isotherm model. Highest EE2 sorption capacity of activated charcoal was observed at neutral conditions. Fixed bed column studies were performed with EE2 spiked untreated domestic sewage. Based on the data derived by fixed bed column studies, rapid small-scale column test (RSSCT) methodology was used to design full-scale GAC system. Total EE2 concentration was quantitatively estimated by direct competitive immuno-enzymatic colorimetric method.Research Highlights► Removal of synthetic estrogen (17-α ethynylestradiol (EE2)) was studied by adsorption. ► Batch sorption data showed good fit with linear Langmuir’s isotherm model. ► Fixed bed column studies for EE2 removal from domestic sewage was carried out. ► Rapid small-scale column test was employed for designing full scale GAC system.
 
Article
The presented studies have focused on application of photocatalysis in degradation of azo-dye Acid Red 18 (C20 H11 N2 Na3 O10 S3) under UV irradiation. The effect of parameters such as initial dye concentration and catalyst dosage on the photocatalytic degradation of model dye was investigated. Another important factor affecting the photodegradation process performance was the temperature of the reaction mixture. The reaction temperatures were equal to 293, 323, 333 and 343 K. The initial dye concentrations amounted to 10 and 30 mg/dm3 and the photocatalyst (TiO2 Aeroxide® P25, Degussa, Germany) dosage was in the range of 0.1–0.5 g/dm3. The effectiveness of model dye photodecomposition was evaluated on the basis of changes of Acid Red 18 and total organic carbon (TOC) concentration and total dissolved substances (TDS) content. The effectiveness of photodecomposition of Acid Red 18 increased with increasing the catalyst concentration. However, an unfavourable effect of light scattering and reduction of light penetration through the solution in case of photocatalyst loading of 0.5 g/dm3 was observed. It was found that a linear correlation between the apparent rate constant and the reaction temperature exists in the range of 293–333 K. At the temperature of 343 K a decrease in the reaction rate was observed.
 
Article
Whereas a very adequate inventory of desalting plants in operation around the world has been available for many years, there is no compilation of capital and operating costs for these plants. Yet for any agency or municipality considering desalination, such cost data is vital to making a decision on whether or not to build the plant, and if the decision is to build, what process to employ. The reasons for the unavailability of this information is due either to the reluctance of the owmers to release the information, or more likely, no standard format has been accepted by which costs can be compared.Accordingly the current needs must be met by periodic cost analyses, projections, and updates. It is with this objective this paper has been prepared. Available capital cost information on some past constructions is correlated. Current capital and operating costs are predicted for three commercially available processes, using a format similar to that used in the U.S. Office of Water Research and Technology Reports. (The most recent O.W.R.T. update was issued in 1981.)Looking beyond the present the author lists some factors which are likely to influence what type of plants will be built in the next ten years.
 
Article
Photochemical degradation and relative toxicity reduction of agricultural wastewater contaminated with methyl 1-[(butylamino)carbonyl]-1H-benzimidazol-2-ylcarbamate (benomyl) by the sonophotocatalytic system was compared with that of the photocatalytic system. Under the optimal conditions, i.e., initial benomyl concentration was 3.2 mg/L, the concentration of TiO2 was 2 g/L and H2O2 concentration was 1.5 mM, the degradation rates with a sonication/UV/TiO2 system was about 1.5 times higher than with a UV/TiO2 system and sonication/UV/TiO2/H2O2 system was about 1.3 times higher than with a UV/TiO2/H2O2 system, respectively. Furthermore, the relative toxicity with a sonophotocatalysis was about 18% lower than with a photocatalysis within a reaction time of 120 min.
 
Article
The purpose of this study was to determine the treatability of 2,4 dichlorophenol (DCP) in an anaerobic/aerobic sequential reactor system when molasses was used as carbon source. Laboratory scale upflow anaerobic sludge blanket (UASB) reactor/completely stirred tank reactor (CSTR) were operated at different 2,4 DCP loading rates and constant hydraulic retention times (HRTs) to investigate the COD removal efficiencies, accumulation of volatile fatty acid (VFA), total, methane gas productions and methane percentages. Studies were carried out in continuous mode and the effluent of the UASB reactor was used as feed of the CSTR reactor. 2,4 DCP removal efficiency decreased from 99 to 78.7% when the initial 2,4 DCP concentration and 2,4 DCP loading rates were increased from 5 to 120 mg/l and from 0.006 to 0.144 g/l.d, respectively. The maximum COD removal efficiency was achieved as 77% at a 2,4 DCP loading rate of 0.042 g/l.d. When the 2,4 DCP loading rate was increased to 0.12 g/l.d, the maximum measured VFA concentration was 1000 mg CH3COOH l–1 in UASB reactor. In the aerobic reactor, the COD removal efficiencies varied between 60 and 90% depending on UASB reactor treatment efficiencies and to COD concentration coming from the UASB reactor. The effects of sludge retention time (SRT) on the 2,4 DCP and COD removal efficiencies were also investigated in the aerobic reactor. The 2,4 DCP and COD removal efficiencies were observed as 90 and 85%, respectively, at a SRT of 25 d. 86.67% 2,4 DCP removal efficiency was obtained in the whole sequential anaerobic/aerobic (CSTR) reactor system at an initial 2,4 DCP concentration of 120 mg/l.
 
A. EC 50 (%) values obtained in Microtox of samples taken at the beginning and the end of the adsorption process for both activated carbon and date seeds at 2,4-DNP initial concentration of 100 mg/L. B. EC 50 (%) values obtained in Microtox of samples taken at the beginning and the end of the adsorption process for both activated carbon and date seeds at 2,4-DNP initial concentration of 500 mg/L. C. EC 50 (%) values obtained in Microtox of samples taken at the beginning and the end of the adsorption process for both activated carbon and date seeds at 2,4-DNP initial concentration of 1000 mg/L.
Composition of synthetic medium.
Full 2 4 factorial design with levels to optimize activated carbon and date seed adsorption.
Central composite surface design to continue the optimization process.
Adsorption capacities (K) and the adsorption intensity (n) for phenolic wastes.
Article
The main goal of this research was to evaluate the adsorption capability of non-conventional, low-cost adsorbents at elevated 2,4-dinitrophenol (DNP) concentrations. Commercial activated carbon was also evaluated in an attempt to identify the sorption mechanism. Isotherms for adsorption of 2,4-dinitrophenol from water and basal salt medium onto date seeds and activated carbon were determined. These isotherms were modeled by the Freundlich isotherm. The experimental results showed that only 0.5 g of date seeds , with a 125 ml salt medium, were a suitable adsorbent for the removal of DNP from samples. The studies showed date seeds to be an efficient sorbent material for DNP removal from solutions. Of the parameters investigated, pH was determined to be most crucial, with an optimum pH range of 4.0 to 5.0 for good DNP removal. The DNP adsorption capacity of both adsorbents exceeded the original value of the raw material when regenerated by microwave irradiation. The regeneration efficiency of date seeds was 96% compared to 85% of activated carbon. In addition, the use of basal salt medium solution does not appear to play a significant role in DNP adsorption by activated carbon compared to water medium. However, the basal salt medium was associated with a higher adsorption capacity when used with date seeds. Finally, the treatment of a high DNP concentration with date seeds and activated carbon significantly reduced the toxicity of the DNP effluent.
 
Article
In order to determine the interactions between anaerobic bacteria and the performance of the upflow anaerobic sludge blanket, UASB, chemical oxygen demand, COD, volatile fatty acid, VFA, and methane gas productions were determined. The variations of anaerobic microorganisms in the anaerobic granular sludge were counted under different operational conditions. The study was composed of two parts. In the first part, the numbers of methanogens and acedogens in the anaerobic granular sludge were counted at different COD removal efficiencies. The relationships between the numbers of methanogens, the methane gas production and VFA production were investigated. Most probable number (MPN) results showed that the mean number of total methanogens were between 15×104 and 29×1049 MPN/g at COD removal efficiencies of 33% and 82% in an UASB reactor treating 2,4 DCP at loading rates of 0.024–0.116 g/l.day, respectively. Decreases in methane gas percentage could be attributed to lowering in number of methanogens. The results showed that the COD removal efficiencies elevated from 33% to 82% while the number of total acedogens decreased from 120 cfu/ml to 8 cfu/ml as the 2,4 DCP loading rates lowered from 0.116 g/l.day to 0.024 g/l.day. There is a strong correlation between acedogen, methanogen bacteria numbers and reactor performances. In the second part, Methanobacterium bryantii, Methanobacterium formicicum, Methanobrevibacter smithii, Methanococcus voltae, Methanosarcina mazei, Methanosarcina acetivorans, Methanogenium bourgense, and Methanospirillum hungatei were identified in the reactor treating 2,4 DCP.
 
Article
Mn-modified activated carbon (PLAC-Mn) was prepared by impregnating Polygonum orientale Linn activated carbon (PLAC) with a MnNO3 solution. The feasibility of both PLAC and PLAC-Mn to remove 2,4-dichlorophenol (2,4-DCP) from an aqueous solution was examined. The absorbents were characterized by BET, XRD, FTIR and Boehm titration analysis. The influence of different parameters such as contact time, temperature, pH and ionic strength has been carried out. Property studies showed that impregnation with MnNO3 altered the structure of PLAC and Mn oxide was formed on the surface of PLAC-Mn. The 2,4-DCP adsorption capacity of PLAC-Mn was higher as compared to plain PLAC. The adsorption kinetic followed the pseudo-second-order equation for both adsorbents. The equilibrium data of PLAC was found to best fit to the Langmuir model, while PLAC-Mn was best explained by the Freundlich model. The adsorption of 2,4-DCP on both adsorbents decreased with an increase in pH. The ionic strength and desorption studies confirmed a chemical sorption mechanism.
 
Article
2,4,6-trichlorophenol is an important water pollutant owing to the severity of its toxicity. The aqueous phase photocatalytic oxidation of 2,4,6-trichlorophenol over ZnO was investigated as a potential method for the abatement of this pollutant. The effects of operating parameters such as initial ZnO doses and substrate concentration on the removal of 2,4,6-trichlorophenol were studied and optimised at 0.75 g L− 1 and 50 mg L− 1, respectively. The photocatalytic system afforded the highest degradation efficiency at neutral pH. The decomposition of 2,4,6-trichlorophenol by the photoprocess agreed satisfactorily with pseudo zero-order kinetic model. The effect of the presence of SO42−, S2O82−, HPO42− and Cl− on the 2,4,6-trichlorophenol removal rate was for the first time revealed. Some hitherto unreported pathway intermediates of ZnO-assisted 2,4,6-trichlorophenol degradation were recorded using gas chromatography–mass spectrometry (GC–MS) and high performance liquid chromatography (HPLC). A tentative reaction mechanism for the formation of these intermediates was proposed.
 
Article
An activated carbon was prepared from the stalk of the scrap aquatic plant loosestrife, by H3PO4 activation and then was evaluated for its ability to adsorb 2,4,6-trichlorophenol (TCP). The effects of solution pH, agitation time, TCP initial concentration, and temperature on TCP adsorption were investigated. The equilibrium adsorption data of TCP on activated carbon were analyzed by Langmuir, Freundlich and Temkin isotherm models. The Temkin model gave the best correlation with the experimental data. The adsorption was found to follow the pseudo-second-order kinetics. The intraparticle diffusion model was used to determine the mechanism of the adsorption process. Thermodynamic parameters such as standard enthalpy (ΔHo), standard entropy (ΔSo), and standard free energy (ΔGo) were obtained. Adsorption of TCP is exothermic with ΔHo at −12.87 kJ/mol.Research highlights► An inexpensive activated carbon was prepared from the renewable source loosestrife. ► The inner structure of loosestrife can be an advantage to produce quality adsorbent. ► The LAC is a high quality adsorbent with surface area as high as 1255.75 m2/g. ► The adsorption potential of 2,4,6-TCP adsorbed on LAC was favorable.
 
Article
In the preparation of the title polymer by interfacial polycondensation the two reaction routes were studied and compared with respect to yield and polymer viscosity. The reaction conditions of the more readily accessible route involving the reaction of 2,5-pyridinedicarboxylic acid chloride with hydrazine was investigated in some detail. The polycondensate was fabricated into a reverse osmosis membrane by crosslinking reinforcement. Two attempts were made to improve water permeability: blending a more hydrophilic polymer, poly(4-vinylpyridine) and addition of an inorganic salt to the casting solution. Addition of the proper amount of lithium nitrate or a small amount of magnesium perchlorate was most effective for the improvement without considerable decrease in the membrane strength. The effect of the kind of the salt and addition ratio on the performance was discussed on the difference in the structure of polyhydrazides.
 
Article
Multi-stage flash (MSF) desalinators are, in general, ruggedly engineered plants with no moving parts and are designed so that the fluids, in passing through the plants, are constrained to behave in accord with fixed physical laws. So, theoretically, once initially adjusted they should be able to operate steadily with no operator interference and without any controlling instrumentation. The paper first discusses factors which militate against such an ideal situation and identifies needs for specific controls and instruments in differing circumstances in practice. The functions requiring control are then examined individually, methods of control are described and interactions with other parameters identified.Because the MSF process works at relatively low temperatures, it is not fuel efficient by itself but combines well with other mechanical processes which reject low-grade heat, e.g. electric power generation. In such cases some integration of the control systems becomes necessary and is discussed.Reliability of the control systems is briefly dealt with and the merits of various methods of signal transmission are compared, including electronic computer-based systems.
 
Article
A high pressure system, using Danfoss APP pumps both as high pressure pumps and also as reverse running water hydraulic motors for energy recovery has been tested. The pumps were built together on a transmission, built by Balder Water Technology A/S. So that the speed of the pumps, waterhydraulic motors and the electrical motor was linked together in a fixed relation. Four different configurations/combinations of pumps/waterhydraulic motors were tested to get results of production rate, recovery and energy consumption per m3 of water produced. The combinations tested covered the area from 8 to 23 m3/day with recoveries from 31 to 46%. However all possible combinations of the smaller range of the Danfoss APP pumps on such a transmission can cover the area from 8 to 60 m3/day. The result shows that energy consumptions between 3 and 4 kWh/m3 is very well achievable with pressure units using APP2.2 and 1.8, also in combination with APP1.0. For some combinations an energy consumption between 3.0 and 3.5 kWh/m3 is achievable. For pressure units using APP1.0 and 0.6 the energy consumption will be from 4.4–4.8 kWh/m3. The results show that the energy consumption is reduced with 6–9% after a run-in period of 12–16 h. For combinations with APP2.2/1.8 and 1.0 the results show that the energy consumption is reduced with reduced speed. For the combination with APP1.0/0.6 the energy consumption had a minimum point at 3100 rpm. It is believed that the other combinations also have minimum points, but at lower speed than 2500 rpm. There is an indication that lower recovery leads to higher energy consumption with this system. However, for small plants like this it is very unpractical to have very high recovery. The operation of the system is very smooth and stable and the result shows that this system can be an interesting alternative for small desalination plants, especially where low energy consumption is important.
 
Article
Solar distillation devices for the production of pure water operate at highly variable rates, with zero production just before sunrise and maximum production about mid-day. Furthermore, the diurnal production of pure water by a solar plant varies seasonally, from a maximum in mid-summer to a minimum in winter. This is in contrast to other types of water desalination plants, which use heat energy from fuels or electric power, and can operate at essentially constant production rates throughout the day and year. Thus, the instrumentation and control devices of solar plants are completely different from those used in other desalination plants. This chapter describes schemes for determining daily quantities, rather than rates, and discusses some of the operational problems encountered in solar distillation devices.
 
Article
This chapter discusses the constraints of reverse osmosis desalination and the techniques and controls generally recommended in the design and operation of reverse osmosis systems. Adequate quality of feedwater to reverse osmosis systems is vital to obtain satisfactory service between cleanings and to obtain maximum membrane life. The controls employed to assure this quality are discussed. Reverse osmosis membranes have constraints in pH, temperature, pressure, flow and oxidation resistance which are important in the selection and operation. The reverse osmosis system and its design must take account the analysis of the saline water, the service requirements, and the operability of the system. The process engineering of a reverse osmosis system achieves these goals within the guidelines of the membrane manufacturer. This is done to safeguard the warranties which are extended by the membrane manufacturer on the performance and life of the membranes.Biological constraints of reverse osmosis systems are frequently satisfied by chlorination. However, as some membranes are sensitive even to very low concentrations of oxidant, effective dechlorination and measurement of residual oxidant is necessary.The measurements, instrumentation and controls employed to assist the operator in meeting the constraints of reverse osmosis desalination are discussed in considerable detail. The objective is to provide general guidance to the user of reverse osmosis systems.
 
Article
The 200 MWt nuclear heating reactor (NHR-200) is designed with a number of advanced and innovative features, including integrated arrangement, natural circulation, self-pressurized performance, hydraulic control rod drive and passive safety systems. The NHR-200 can serve as a safe and economic energy source for seawater desalination. This paper will cover the development status, main design and safety features of the NHR-200 as well as the solutions for coupling the NHR-200 with the seawater desalination process.
 
Article
(A Fellow of the Institution of Chemical Engineers, Dr Kharbanda is a visiting prof, an author of repute and consults worldwide including to UNIDO)
 
Article
Belgard EV-2000 was used as an anti-scale agent in the operation of two MSF distillers at Umm Al Nar station (U.A.E.) for 700 days. The following parameters were measured on a regular basis: seawater inlet and outlet temperatures to and from the heat rejection section, brine heater inlet and outlet temperatures, condensate temperature, brine recirculation flow rate and distillate production. The gain output ratio and the heat transfer coefficient of the heat input section were computer. The top temperature of the distillers varied between 90 and 95°C. The results obtained were compared with those of a similar study using polyphosphate at a top temperature of 90°C.On the whole Belgard EV-2000 ensures a steady distsillers performance, an improvement of the gain output ratio, steadiness of the heat transfer coefficient and an increase in distillate production. Other benefits of Belgard EV-2000 at higher top temperatures are also outlined.
 
Article
The performance of MSF distiller depends on scale formation inside the condenser tubes since scale impairs heat transfer and adversely affects the production of the main utility. In the past three decades a great deal of research activity has focussed on the development and testing of anti-scale agents. Three basic methods are commonly applied in inhibition of scale formation. The first method involves the prevention of scale deposition through pH adjustment by acid addition. The second method controls scale precipitation through the addition of special chemicals either alone or coupled with sponge ball cleaning. The third method is a combination of additive and acid addition.In 1988, a comparative performance study was carried out using two polymer-based chemicals as anti-scale agents in the two identical units of Doha East desalination plants. Both units were multi-stage flash, low temperature, cross-tubed and brine recirculation with a nominal capacity of 6.0 migdp (27,276 m3/d). The test period was 92 days. Both distillers exhibited excellent performance and demonstrated a steady successful operation. The results of the comparative study show that Belgard EV 2000 and Belgard EVN are effective in controlling alkaline scale deposition on critical heat transfer surfaces of the evaporators.The results show a remarkable improvement in heater overall heat transfer coefficient, reducing significantly the heater fouling factor, increasing the Gained Output Ratio (GOR) and Performance Ratio (PR) values, maintaining the distillate production and steam consumption. Belgard EV 2000 showed better performance and was slightly more effective than Belgard EVN. The results of Belgard EV 2000 show an insignificant difference in the values of Overall H.T. coefficient and fouling factor of heat gain section.
 
Article
Scale formation on heat transfer surfaces, which is one of the basic problems in the distillation of seawater, can be effectively controlled or minimized by the addition of chemical additives.The most popular additives polyphosphate and Belgard EVN have extensively been used as scale control additives in Multi Stage Flash (MSF) plants in Kuwait. In 1988, a new product was introduced by Ciba-Geigy known as Belgard EV 2000. Belgard EV 2000 is an aqueous solution of an organic acid which acts either as threshold inhibitor or increases the adsorption of scale so as to reduce adhesion to metal surface.Ciba-Geigy collaborated with MEW in conducting a trial which is designed to show whether Belgard EV 2000 is a more cost-effective alternative than the currently used products Belgard EVN and polyphosphate.The present paper speculates the evaluation of Belgard EV 2000 as antiscaling agent in MSF plants. This additive was tested by the Ministry of Electricity and Water (ME&W) on unit A4 of Doha East Power & Water Production Station. The duration of the trial was from 18th April to 28th August, 1988, on a 130-day trial using low brine temperature (90°C), with a unit capacity of 6.0 migd.This additive exhibited satisfactory performance during the test period and successfully controlled the deposition of alkaline scale. No significant changes were observed in heater fouling when the dose level of Belgard EV 2000 was reduced from 2.5 ppm and maintained at 1.5 ppm.The brine heater and heat gain sections were inspected at the end of the trial period and the condenser tubes were found to be clean, which confirmed the capability of Belgard EV 2000 in controlling alkaline scale formation, in spite of the fact that the evaporator was not fitted with a sponge ball cleaning system.
 
Article
The two anti-scale agents BELGARD EV (BELEV) and BELGARD EV 2000 (BELEV 2) are titrated against standard NaOH solution. Both the potentiometric (pH metric) and the conductometric titration techniques are used. For the sake of comparison the reaction of the monomer (maleic acid, H2M) is also investigated. The two titration techniques reveal that H2M neutralizes along two equal steps. The pK1 and pK2 of the acid are calculated as 2.9 and 6.1, in good agreement with the values quoted in the literature. The potentiometric titration curves of BELEV and BELEV 2 solutions are similar and show a single drawn-out inflexion. Computer analysis of the curves reveal four acid species in case of BELEV and two in case of BELEV 2. The pK values, the percentage composition and the mean average molecular weights of all species are computed. The consumption of NaOH till any one and the same pH value varies linearly with the additives content in solution. This offers a simple method for analysis of BELEV and BELEV 2 preparations. The conductometric titration curves of the two agents indicate the presence of three acid species. Correlation with the pH curves is made in every case. Not all the inflexions in conductometric curves have correspondence in pH curves. The effect of addition of increasing concentrations of H2M to BELEV (BELEV 2) solutions and of increasing BELEV (BELEV 2) concentrations to H2M on the pH-metric curves is examined in detail. The two materials affect the neutralization pattern of one another. The results suggest the masking of the free-acid protons through hydrogen bonding with the polymers.
 
Article
In a Sino-German research project, a joined developed sustainable water reclamation concept was developed for different applications of municipal water reuse at the Olympic Green 2008. The concept combines advanced technological processes like membrane bioreactors, specific phosphorus (P) adsorption columns and ultrafiltration (UF) with nature-based treatment processes like wetland and bank filtration mechanisms. The project’s approach is not only to comply with the reclamation requests of the Olympic Green 2008, but also to give an example for better, adapted and energy efficient reuse applications throughout China. The study shows that fixed-bed granular ferric hydroxide (GFH) adsorbers after a membrane bioreactor (MBR) can maintain a total phosphorus (TP) concentration of <0.03 mg L−1. A low P concentration will be necessary to control eutrophication in the artificial Olympic Lake filled with treated wastewater. With an adsorption capacity of approx. 20 mg g−1 d.m. at a corresponding equilibrium concentration of 1 mg L−1 P, GFH reaches long operation times and can be repeatedly regenerated by caustic solutions with an efficiency of 50%. Apart from scenic impoundments, treated wastewater will be used for irrigation and toilet flushing. The latter requires a superior quality that will be delivered by low pressure UF treatment after lake (bank) filtration. A crucial reduction of fouling potential for dead-end UF is expected.
 
Article
Distillation/dehydration represents the largest fraction of the energy used in the production of ethanol. The Siftek™ technology introduced in this paper carries the potential of reducing energy consumption of distillation/dehydration by up to 50% through the single pass removal of water from the water/ethanol stream at the beer column outlet, using a novel membrane process.Siftek™ is a polymeric membrane that can be used to dry ethanol in the vapor phase. The membrane preferentially permeates water over ethanol in a continuous process. Energy reductions are obtained because this membrane is well suited to remove large quantities of water without phase change.The Siftek™ technology has been piloted since August 2006 in a Greenfield Ethanol plant in Tiverton, Ontario, Canada. The Tiverton unit has a capacity of 1 m3/d and has been producing fuel ethanol from a feed containing between 75 and 90 wt.% ethanol in a single stage system.Based on the successful operation of the pilot, it was decided to scale-up the technology. A two-stage membrane system with a capacity of 20 m3/d was built for the Greenfield Ethanol plant in Chatham, Ontario, Canada. The unit is equipped with full-scale commercial membrane modules and is capable of treating a beer-column feed containing 60–70 wt.% ethanol, producing > 99 wt.% fuel-grade ethanol.
 
Article
Adsorption of Reactive Blue 21 (RB21) onto fly ash (FA) and sepiolite from aqueous solutions was investigated. Batch adsorption experiments were carried out to evaluate the influences of experimental parameters such as initial dye concentration (100–750 mg/l), pH (2–8), adsorbent dosage (1–4 g/l) and temperature (298–323 K) on the adsorption process. The optimum conditions for RB21 removal were pH 2, 1 g/l of adsorbent dosage and equilibrium time of 16 h, respectively. Results of the kinetic studies showed that RB21 dye onto FA and sepiolite were best described by the pseudo-second-order kinetic model. The Langmuir isotherm provided the best correlation for RB21 dye onto FA and sepiolite. The maximum dye adsorption capacities of RB21-FA and RB21-sepiolite from the Langmuir isotherm model at 323 K were 106.71 mg/g and 66.67 mg/g, respectively. Thermodynamics parameters, ΔG0, ΔH0 and ΔS0, were calculated. The values of enthalpy were found as 35.76 kJ/mol for FA and 35.08 J/mol K for sepiolite, respectively, indicating that this process was endothermic in nature.
 
Article
This study was made to analize the commercialbility and the reliability of large capacity one pass sea water reverse osmosis from both view points of pre-treatment and desalination, operating a demonstration plant.
 
Article
The use of cheap, efficient and ecofriendly adsorbent has been studied as an alternative source of activated carbon for the removal of dyes from wastewater. This study has investigated the potential use of kaolinite as alternative adsorbent for the removal of reactive blue 221 from wastewater. Therefore, a series of kinetic experiments were conducted in a batch system to assess the effect of the system variables, i.e. stirring speed, contact time, initial dye concentration, initial pH, temperature and acid-activation. The adsorption rate increased with the increasing initial dye concentration, ionic strength, solution temperature and acid-activation, but decreased with an increase in pH. The stirring speed had no important effect on the adsorption rate. The rates of adsorption were found to conform to the pseudo-second-order kinetics with a good correlation. In addition, various thermodynamic activation parameters, such as Gibbs free energy, enthalpy, entropy and the activation energy were calculated. The adsorption process of reactive blue 221 on kaolinite was found to be not a spontaneous and endothermic process.
 
Article
This article constitutes one part of the Doctorate Thesis that the author is doing at the Industrial Engineering Superior Technical School of Las Palmas. The capacity of this RO brackish water desalting plant is 370 m3/day and since January 1986 it has been operating with a LSI in the brine of about 2.2 without using acid in the pretreatment and only using the Flocon. 100 antiscalant (this is the first experience of 24.000 hours of operation in the Canaries). The RO system is equipped with Filmtec BW30-8040 RO elements. In this document the graphical evolution of all the daily operation information, pressures, rejections, cycles and cleaning products used, etc… are shown. It is intended to be used in the future as another practical support for the design of RO brackish water desalination plants.
 
Article
A laboratory model wiped-film rotating-disk (WFRD) vapor-compression compression evaporator with a capacity of 300 liters/day (80 gpd) was conceived, designed, and built in the late sixties at the Sea Water Conversion Laboratory, University of California at Berkeley. Preliminary data obtained from this model showed exceptionally high overall heat transfer coefficient, U, in excess of 28 kW/m2C (5000 Btu/hft2F). Results from later data with precise instrumentation confirmed the earlier results and showed even higher values for U.Thermoeconomic analysis of multieffect vapor-compression systems to reclaim 95 percent of agricultural drainage water at the San Joaquin Valley in California showed that the use of multieffect VC systems instead of convention single effect VC systems reduces energy consumption. It also showed that the ratio of U in the evaporator to its cost per unit area of heat transfer has very strong influence on distilled water cost; the higher the ratio, the lower the distilled water cost. The analysis also showed that because of the exceptionally high value of U in the WFRD evaporator and based on data obtained from the laboratory model at Los Banos, California uisng agricultural drainage water, its use in a 5-effect VC system will reduce product water cost by a factor of 2 and energy consumption by a factor of 3 as compared to off-the-shelf single effect conventional VC systems.A semicommercial 2500 gal/day five-effect vapor-compression WFRD evaporator module was designed, built and tested with tap water. Preliminary data were obtained. The results from these data show an average value of U to be about 20 kW/m2C (3500 Btu/hft2F) and energy consumption by the compressor between 3.6 and 5.1 kWh/m3 (13.6 and 19.3 kWh/1000 gal) of product water.
 
Article
Buckau-Walther AG (Krupp Group) handed over a ship-mounted seawater desalination plant to the Water and Electricity Department of the Government of Abu Dhabi on February 16, 1982, in Bremen. This followed a 12-month construction period and two weeks of trials. Named the “Rumaith”, this is the first self-propelled floating seawater desalination plant built for commercial use. The plant, consisting of a self-propelled pontoon-like hull carrying two centrally positioned desalination units of 1250 m3 each, will supply islands, coastal towns and major construction sites in the United Arab Emirates with drinking water and will also be deployed in the event of break-down of stationary desalination plant, to provide an emergency water supply and to alleviate plantation water shortages. After handover, the vessel, accepted by German Lloyd for class + 100 A4K, was pulled by tug to Abu Dhabi in the Arabian Gulf in 40 days. As general contractor, Buckau-Walther AG had the vessel built by a shipyard in Bremen.
 
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