Showing papers in "Desalination and Water Treatment in 2010"
TL;DR: In this paper, a review of the properties of seawater is presented in terms of regression equations as functions of temperature and salinity, and the available correlations for each property are summarized with their range of validity and accuracy.
Abstract: Correlations and data for the thermophysical properties of seawater are reviewed. Properties examined include density, specific heat capacity, thermal conductivity, dynamic viscosity, surface tension, vapor pressure, boiling point elevation, latent heat of vaporization, specifi c enthalpy, specific entropy and osmotic coefficient. These properties include those needed for design of thermal and membrane desalination processes. Results are presented in terms of regression equations as functions of temperature and salinity. The available correlations for each property are summarized with their range of validity and accuracy. Best-fi tted new correlations are obtained from available data for density, dynamic viscosity, surface tension, boiling point elevation, specifi c enthalpy, specific entropy and osmotic coefficient after appropriate conversion of temperature and salinity scales to the most recent standards. In addition, a model for latent heat of vaporization is suggested. Comparisons are carried out amo...
1,008 citations
TL;DR: In this article, the authors analyzed the thermodynamic performance of various HDH cycles by way of a theoretical cycle analysis and proposed novel high-performance variations on those cycles, such as multi-extraction, multi-pressure and thermal vapor compression cycles.
Abstract: Humidification dehumidification desalination (HDH) is a promising technology for small-scale water production applications. There are several embodiments of this technology which have been investigated by researchers around the world. However, from a previous literature [1], we have found that no study carried out a detailed thermodynamic analysis in order to improve and/or optimize the system performance. In this paper, we analyze the thermodynamic performance of various HDH cycles by way of a theoretical cycle analysis. In addition, we propose novel high-performance variations on those cycles. These high-performance cycles include multi-extraction, multi-pressure and thermal vapor compression cycles. It is predicted that the systems based on these novel cycles will have gained-output ratio in excess of 5 and will outperform existing HDH systems.
250 citations
TL;DR: In this paper, a hybrid forward osmosis-nanofiltration (FO-NF) process for seawater desalination is proposed and seven potential draw solutions for the FO-NF process were investigated.
Abstract: A hybrid forward osmosis-nanofiltration (FO-NF) process for seawater desalination is proposed in this study. Seven potential draw solutions for the FO-NF process were investigated using laboratory-scale forward osmosis (FO) and nanofiltration (NF) test cells. Results from both FO and NF tests suggested that the hybrid FO-NF process is a feasible process for seawater desalination. Water fluxes of about 10 L/m2 h, for both FO and NF processes could be achieved. Solute rejection of the FO membrane was maintained at over 99.4% for all seven draw solutes tested. Solute rejection of the NF membrane for the four selected draw solutions could achieve a maximum of 97.9%. A hybrid FO-NF process with two-pass NF regeneration is proposed to achieve good quality product water that meets the recommended drinking water total dissolved solids (TDS) guideline, of 500 mg/L from the World Health Organisation. It is possible to desalinate seawater with this system configuration to obtain product water with TDS of 113.6 mg/L....
179 citations
TL;DR: In this article, the authors examined the character of freshwater algal populations and their algogenic organic matter from a coagulation/flocculation (C/F) perspective and reviewed C/F for their removal.
Abstract: A continuing worldwide problem for drinking water treatment industry is the presence of algae in source water. Algae in drinking water supply can cause significant disturbances including taste and odour, production of disinfection by-product, obstruction to coagulation, clogging of filter, and assimilable organic carbon for growth of biofilm. Algae removal by conventional treatment is more difficult than inorganic particle, due to their low specific density, motility, morphological characteristics and negative surface charge. This review examines the character of freshwater algal populations and their algogenic organic matter from a coagulation/flocculation (C/F) perspective and reviews C/F for their removal. It was suggested that the coagulation mechanism was “one of mutual attraction and charge neutralisation (CN) of the algae and the incipient hydroxide flocculi” and as such the hydroxide precipitant should be positively charged. It was observed that on adjusting the zeta potential of an algal suspensi...
159 citations
TL;DR: The challenges still facing concerning the economic and technological feasibility and the developing path of reverse electrodialysis are discussed, with a focus on the development of low-cost membranes, pre-treatment in relation to stack design and operation, and the economics of reverseElectrolysis.
Abstract: Reverse electrodialysis is a conversion technique to obtain electricity from salinity gradients. Over the past few years, the performance of reverse electrodialysis on laboratory scale has improved considerably. In this paper, we discuss the challenges we are still facing concerning the economic and technological feasibility and the developing path of reverse electrodialysis. We focus on the following issues: (i) the development of low-cost membranes, (ii) pre-treatment in relation to stack design and operation, and (iii) the economics of reverse electrodialysis. For membranes, the challenge is to increase availability (>km2/year) at reduced cost (<2 €/m2). The membranes should be manufactured at high speed to meet this challenge. For pre-treatment, a capital-extensive microscreen filter with 50 μm pores was selected and tested. Such a straightforward pre-treatment is only suffi cient given the fact that the reverse electrodialysis stack was redesigned towards a more robust spacer-free system. For the eco...
156 citations
TL;DR: In this paper, a review of dye processing industry, its fundamental characteristics and environmental implications is presented, together with the effects of adsorbent dosage, concentration, contact time, pH, particle size, temperature competition, and isotherms, kinetic and thermodynamic studies for adsorption of dyes onto activated carbons.
Abstract: Water scarcity and pollution rank equal to climate change as the most intricate environmental turmoil for the 21st century. Today, the percolation of textile effluents into the waterways and ecosystems remain a fastidious conundrum towards the public health and food chain interference. In such circumstances, it becomes mandatory for each dye emitting industry or facility to opt for proper dye control measures. With the renaissance of activated carbon, there has been a steadily growing interest in this research field. This paper attempts to postulate a state of the art review of dye processing industry, its fundamental characteristics and environmental implications. Moreover, the key advance of proposed precursors, activated agents, together with the effects of adsorbent dosage, concentration, contact time, pH, particle size, temperature competition, and isotherms, kinetic and thermodynamic studies for adsorption of dyes onto activated carbons are summarized and discussed. Conclusively, the expanding of adsorption science in dye treatment represents a plausible tool for accruing the worldwide environmental benefit and shaping the national economy.
153 citations
TL;DR: In this article, the transition process in reverse osmosis (RO) module configuration has been discussed and a transition from cellulose acetate membranes to thin film composite polyamide flat-sheet membranes in a spiral wound configuration is discussed.
Abstract: During the half century of development from a laboratory discovery to plants capable of producing up to half a million tons of desalinated seawater per day, reverse osmosis (RO) technology has undergone rapid transition. This transition process has caused signification transformation and consolidation in membrane chemistry, module design, and RO plant configuration and operation. From the early days, when cellulose acetate membranes were used in hollow fiber module configuration, technology has transitioned to thin film composite polyamide flat-sheet membranes in a spiral wound configuration. Early elements — about 4 inch in diameter during the early 70s — displayed flow rates approaching 250 L/h and sodium chloride rejection of about 98.5%. One of today's 16-inch diameter elements is capable of delivering 15–30 times more permeate (4000–8000 L/h) with 5–8 times less salt passage (hence a rejection rate of 99.7% or higher). This paper focuses on the transition process in RO module configuration, and how i...
111 citations
TL;DR: In this article, a semi-permeable membrane optimized for osmotic power has been designed and constructed for use in the Norwegian power company Statkraft, where the power density of the membrane has increased from less than 0,1 W/m2 up to today's membra...
Abstract: The mixing of freshwater and seawater where rivers flows into the salty ocean releases large amounts of energy. This energy can be harvested and made into electricity using pressure retarded osmosis (PRO). This is the concept of osmotic power, a new and yet unexploited source of renewable energy. The idea of exploiting the energy from mixing fresh water and sea water with PRO was first developed by Prof. Sidney Loeb in the early seventies. After some years in the eighties with limited progress in the field, the Norwegian power company Statkraft engaged in technology development in the mid nineties aiming at cost-effective osmotic power production. Today Statkraft is the world leader in development of osmotic power, and have made state of the art achievements during the last few years. The work has been focused on the design and production of a semi-permeable membrane optimized for osmotic power. During these years the power density of the membrane has increased from less than 0,1 W/m2 up to today's membra...
108 citations
TL;DR: The electrodisinfection (ED) as discussed by the authors is a common unit process used in water supply and wastewater treatment, which can destroy a wide variety of microorganisms from viruses through bacteria and algae to larger species, such as Euglena.
Abstract: This review concerns chemical disinfection and electrodisinfection (ED). Chemical disinfection is a common unit process used in water supply and wastewater treatment. Traditionally, chlorination is the most dominant method of disinfection. However, there are serious safety concerns and great ecological risks involved in the use of chlorine. Other methods, such as ozonation, UV radiation and ClO2 application, are still more expensive or less convenient than chlorination. It has been reported that ED can destroy a wide variety of microorganisms from viruses through bacteria and algae to larger species, such as Euglena. The ED process has the potential to be developed as a robust, cost-effective and environmental friendly alternative of disinfection, particularly for saline sewage effluent and for seawater in cooling and other industrial usages. During ED, water is forced through a disinfector that is equipped with electrodes on which current is charged. This practice is different from conventional electro-c...
105 citations
TL;DR: In this paper, a multi-pronged process-optimization approach for reverse osmosis desalination is presented, where a theoretical framework discussed for optimizing energy consumption with and without energy recovery devices (ERDs), considering the impact of membrane replacement and brine management costs.
Abstract: Reverse osmosis (RO) water desalination is now well established as a mature water desalination technology. With the current generation of seawater and brackish-water RO membranes, it is now both economically and technically feasible to desalt brackish water and seawater on a large scale. In order to further expand the applications of RO desalting technologies, optimal process conditions must be selected to minimize water production costs associated with energy consumption, membrane replacement costs, chemical usage, and residual brine concentrate management. In the present review, a multi-pronged process-optimization approach for reverse osmosis desalination is presented. A theoretical framework discussed for optimizing energy consumption with and without energy recovery devices (ERDs), considering the impact of membrane replacement and brine management costs. The approach enables quantification of the optimal water recovery of RO desalting, considering various factors including the use of energy recovery...
97 citations
TL;DR: In this article, the photodegradation of acid black 1 (AB 1) using ZnO as photocatalyst in aqueous solution has been investigated under different conditions.
Abstract: The photodegradation of Acid Black 1 (AB 1) using ZnO as photocatalyst in aqueous solution has been investigated under different conditions. The degradation is higher with UV/ZnO process than with UV/TiO2-P25 process at neutral pH 7. The influence of operational parameters such as the amount of photocatalyst, dye concentration and initial pH on degradation by ZnO has been analyzed. At pH 7, maximum degradation efficiency is observed and the leaching of Zn2+ due to photocorrosion is also significantly reduced when compared to pH 3 and 5. The addition of oxone increases the dye removal where as KIO4, KIO3 and H2O2 fails. The degradation of AB 1 follows pseudo-first-order kinetics according to the Langmuir-Hinshelwood model. GC-MS analysis reveals the formation of azobenzene, 3-aminobenzene-1,2-diol, 2-aminobenzene-1,4-diol and 5-aminobenzene-1,3-diol as intermediates. The degradation of AB 1 has also been confirmed by COD measurements.
TL;DR: In this article, nanocomposite RO membranes containing multi-walled carbon nanotube (MWCNT) were developed to enhance the chlorine resistance of polyamide membranes.
Abstract: Aromatic polyamide membranes, which are prepared by interfacial polymerization of m-phenylene diamine (MPDA) in water solution and trimesoyl chloride (TMC) in organic solution, have been widely used as reverse osmosis (RO) membranes for desalination of seawater. However, it has been pointed out that polyamide RO membranes have weak resistance to chlorine, causing deteriorated separation performance. In this study, nanocomposite RO membranes containing multi-walled carbon nanotube (MWCNT) were developed to enhance the chlorine resistance of polyamide membranes. The resulting membranes were analyzed and tested to see the desalination performance. Nonionic surfactant (Triton-X-100) was used in the interfacial polymerization of organic/inorganic nanocomposite RO membranes to improve the dispersion of MWCNTs in the polymer matrix. Scanning electron microscopy (SEM) images and X-ray diffraction (XRD) spectra confirmed that MWCNTs were uniformly distributed in the polymer matrix. When 0.1–1 wt% of MWCNTs were ad...
TL;DR: In this paper, the design of carbon nanotube (CNT) based composite material membranes for direct contact membrane distillation (DCMD) was reported. But, the authors did not report on the performance of the composite CNT membranes in a DCMD setup.
Abstract: New technologies are required to improve desalination efficiency and increase water treatment capacities. One promising low energy technique to produce potable water from either sea or sewage water is membrane distillation (MD). However, to be competitive with other desalination processes, membranes need to be designed specifically for the MD process requirements. Here we report on the design of carbon nanotube (CNT) based composite material membranes for direct contact membrane distillation (DCMD). The membranes were characterized and tested in a DCMD setup under different feed temperatures and test conditions. The composite CNT structures showed significantly improved performance compared to their pure self-supporting CNT counterparts. The best composite CNT membranes gave permeabilities as high as 3.3 x 10-12 kg/(m x s x Pa) with an average salt rejection of 95% and lifespan of up to 39 h of continuous testing, making them highly promising candidates for DCMD.
TL;DR: In this article, a pilot plant study was conducted to monitor the fate of TEP through the treatment process and to investigate their effects on the operational performance of a seawater UF-RO plant.
Abstract: For many years, transparent exopolymer particles (TEP) were found abundant in various marine and freshwater environments, which are currently the main sources of raw water in desalination plants. Just recently, TEP have been identified as a potential foulant capable of causing organic and biological fouling in membrane systems. A pilot plant study was conducted to monitor the fate of TEP through the treatment process and to investigate their effects on the operational performance of a seawater UF-RO plant. Using spectrophotometric measurements, particulate (p-TEP > 0.4 mm) and colloidal (0.05 < c-TEP < 0.40 mm) species of TEP were measured at selected points in the plant. TEP monitoring in the raw water recorded a significant increase in both p-TEP and cTEP starting in early spring (March). This period was also marked by an increase of chlorophyll-a and total organic carbon (TOC) mainly attributed to an algal bloom occurrence in the water source. Total TEP from the raw water were partially removed by the micro-strainer (11–21%) and the UF system (*28%). Low fouling rates in the UF were observed in January and February but severe fouling were observed in late March and April, coinciding with the increase in TEP level. The severe fouling was mitigated by applying in-line coagulation before the UF for which irreversible fouling was significantly reduced. Deposition analyses indicated that significant amounts of p-TEP and c-TEP were deposited in the RO system. However, there was no significant decrease of RO normalized flux during the 4 months of operation in the plant. Long term monitoring is needed to better assess the adverse effects of TEP accumulation in the RO systems.
TL;DR: In this article, the authors presented the thermo-economic analysis of the adsorption desalination (AD) cycle that is driven by low-temperature waste heat from exhaust of industrial processes or renewable sources.
Abstract: This paper presents the thermo-economic analysis of the adsorption desalination (AD) cycle that is driven by low-temperature waste heat from exhaust of industrial processes or renewable sources. The AD cycle uses an adsorbent such as the silica gel to desalt the sea or brackish water. Based on an experimental prototype AD plant, the life-cycle cost analysis of AD plants of assorted water production capacities has been simulated and these predictions are translated into unit cost of water production. Our results show that the specific energy consumption of the AD cycle is 1.38 kWh/m3 which is the lowest ever reported. For a plant capacity of 1000 m3/d, the AD cycle offers a unit cost of $0.457/m3 as compared to more than $0.9 for the average RO plants. Besides being cost-effective, the AD cycle is also environment-friendly as it emits less CO2 emission per m3 generated, typically 85% less, by comparison to an RO process.
TL;DR: A brief review of the principles of forward osmosis and membrane distillation can be found in this paper, where the authors discuss the strengths and limitations of both processes in a broad spectrum of applications.
Abstract: Osmotically-driven membrane processes, including forward osmosis (FO) and pressure retarded osmosis (PRO), are emerging technologies that have come under renewed interest and subjected to numerous investigations in recent years. In FO, water is extracted from a feed solution utilizing the high osmotic pressure of a concentrated draw solution (DS) that flows on the opposite side of an FO membrane; RO or a distillation process can be utilized to reconcentrate the DS for reuse in the FO process and to produce purified water. The main advantages of FO include operation at very low hydraulic pressures, high rejection of a broad range of contaminants, and lower membrane fouling propensity than in pressure-driven membrane processes. Existing and potential applications of the osmosis phenomenon extend from water treatment and food processing to power generation and novel methods for controlled drug release. While FO relies on osmotic pressure driving force to separate water from a feed streams, thermally driven membrane processes, such as membrane distillation (MD), rely on vapor pressure difference across a microporous hydrophobic membranes to facilitate separation of volatile solvent (water from salt solution) or volatile solutes from impaired feed streams. The vapor pressure gradient is usually achieved by maintaining temperature differ ence between a warm feed solution and a colder distillate that flow on the opposite side of the mem brane. In thermally-driven membrane processes, desalination and production of highly-purified water can be achieved in one step compared to osmotically-driven membrane processes, at much lower temperatures compared to distillation processes, and at much lower pressures compared to pressure-driven membrane processes. It can be most effectively and beneficially used when low-grade heat is readily available. Furthermore, compared to other membrane processes, in MD the salinity of the feed stream minimally affects the driving force for mass transport through the membrane; salts, even at high concentrations, only slightly reduce the partial vapor pressure of such feed streams. Thus, MD can be beneficially used to enhance water recovery in many desalination processes. In this paper, a brief review of the principles of FO and MD is provided. Special aspects of mass transport as well as the membranes used in the processes are discussed, and relevant results from recent studies are presented. Strengths and limitations of the FO and MD processes in a broad spectrum of applications are reviewed and discussed.
TL;DR: In this paper, Nanofiltration (NF) membranes were used to filter acid mine drainage at two different pressure levels of 20 and 30 bar and at different concentrations of acid mine sludge.
Abstract: Acid mine drainage (AMD) is recognized as one of the more critical environmental problems in the mining industry, with the potential of severe contamination of surface and groundwater, as well as soils. Different conventional methods are used to treat AMD such as lime neutralization, in which lime is added to AMD to raise pH and then precipitate the dissolved toxic heavy metals. In addition to a high concentration of sulphate, the sludge produced by this process has no economic value and has to be disposed of in large areas of land. Nanofiltration (NF) membranes are a new alternative method employed to treat AMD in this work. First, neutralization of AMD collected from the copper mine in Chile using both sodium hydroxide and lime will be investigated to find the optimum formed sludge. Then, three commercial NF membranes (NF99, DK, GE) have been used to filter AMD at two different pressures of 20 and 30 bar and at two different concentrations. The results showed that NF membranes successfully treated AMD w...
TL;DR: In this article, the evaporation from the WAIV unit demonstrated enrichment in the magnesium ion compared to the calcium and the sodium ion, including over a twofold enrichment of magnesium relative to calcium as would be expected by the equilibrium solubilities of different minerals.
Abstract: In this study bench pilot WAIV units (∼ 1 m2 evaporation area loaded on 0.17 m2 footprint) were operated on two different desalination brines (RO and ED) as well as on a mineral brine concentrate under arid conditions of the Negev Highlands. The evaporation rate with the WAIV unit on these feeds often gave evaporation rates per footprint that were 10-fold or greater than the pan evaporation rate obtained from the local meteorological station at Sde Boker. Desalination brines were concentrated up to 23% TDS when operating on ED concentrate. The evaporation from the WAIV unit demonstrated enrichment in the magnesium ion compared to the calcium and the sodium ion, including over a two-fold enrichment of magnesium relative to calcium as would be expected by the equilibrium solubilities of the different minerals. Despite precipitation of minerals, there is not a large buildup of deposit on the flexible evaporation surface, and this helps establish the feasibility for recovering minerals from the desalination b...
TL;DR: In this article, a static layer crystallizer for freezing desalination of sea water was developed, which consists in a tube immerged in a cylindrical double jacketed tank cooled by means of a second thermostatic bath.
Abstract: This work aims in developing a static layer crystallizer for freezing desalination of sea water. The experiments were performed with a simple system of H2O-NaCl and with samples of sea water from Rabat. The pilot crystallizer consists in a tube cooled bymeans of a thermostatic bath. The tube is immerged in a cylindrical double jacketed tank cooled by means of a second thermostatic bath. The brine is poured into the tank and the crystallization takes place on the external surface of the tube. The global process is divided into 4 steps: (i) crystallization of the ice layer by controlling the cooling rate in the tube (ii) draining off the concentrated brine (iii) purification of the layer by sweating and (iv) melting of the ice to recover the fresh water. A parametric study of the effect of the operating parameters has allowed us to quantify the role of the different key parameters of the crystallization step. Within the studied domain, the purity of the crystalline layer was mainly affected by the initial s...
TL;DR: In this paper, the authors focus on fundamental studies on shear stress exerted by rising bubbles and on optimising the geometries of tank and module accordingly in order to obtain an improved deposition control at minimum energy input.
Abstract: Since aeration is the largest cost factor in membrane bioreactor (MBR) operation it is clear that the biggest leap towards energy and operational costs savings can be achieved by improving the use of air. Many basics of the complex two-phase fl ow in membrane modules and in the overall MBR tank as well as their interactions, however, are still poorly understood. This work focuses both on fundamental studies on shear stress exerted by rising bubbles and on optimising the geometries of tank and module accordingly in order to obtain an improved deposition control at minimum energy input. For both, parameter studies were carried out by numerical simulations which were validated with experimental measurements. The optimum bubble size/channel width combination depended on the superimposed liquid velocity. The relationship between the liquid circulation velocity and the aeration intensity was measured for different reactor and module geometries. A modifi cation of the Chisti model for airlift loop reactors was a...
TL;DR: In this article, the stability and control of the MCr process has been investigated and the experimental tests have been carried out on streams representing nanofi ltration and reverse osmosis retentate streams of the desalination plants.
Abstract: Membrane crystallization (MCr) can be used to process highly concentrated aqueous solutions. In MCr, membrane distillation is used to recover water and to generate the desired supersaturation in a crystallizer tank where crystals can be precipitated. In this paper the stability and control of MCr process has been investigated. The experimental tests have been carried out on streams representing nanofi ltration and reverse osmosis retentate streams of the desalination plants. The deposition and accumulation of crystals on membrane surface and inside the membrane module has been prevented by recovering the produced crystals and by controlling the temperature of the solution flowing along the membrane module. The obtained almost constant trend of the trans-membrane flux has been the demonstration of the good carried out operations. The produced particles have been characterized in terms of shape, dimension, crystal size distribution (CSD), coeffi cient of variation (CV) and growth rate. The obtained CVs are ...
TL;DR: In this article, an attempt has been made to develop thermal model of double slope passive solar still on the basis of energy balance of east and west condensing covers, water mass and basin liner.
Abstract: In this article an attempt has been made to develop thermal model of double slope passive solar still on the basis of energy balance of east and west condensing covers, water mass and basin liner. Analytical expressions for water temperature, inner and outer condensing covers temperature and distillate yield have been derived as a function of climatic and design parameters. Experimental validations have been carried out by using heat and mass transfer relation given by Dunkle. It is observed that there is a good correlation between theoretical and experimental results with correlation coefficient varies from 0.6958 to 0.9867. The monthly data of yield of double slope passive solar still has been used to evaluate CO2 emission, mitigation and carbon credit earned for different water depth and life of the system on the basis of energy and exergy.
TL;DR: In this paper, an electromagnetic treatment-doubled electrocoagulation of humic acid (HA) using response surface method and raw waters of two Dams (Ghrib and Boukerdene) was investigated.
Abstract: This study concerns electromagnetic treatment-doubled electrocoagulation of humic acid (HA) using response surface method and raw waters of two Dams (Ghrib and Boukerdene). This paper has two principal aims to achieve: firstly, enhance the efficiency of removal of HA by electrocoagulation (EC) adopting the following approach: EC in series using two electrocoagulators (BI-EC, doubled EC) and BI-EC assisted by electromagnetic (EM) field or in other words EM treatment (EMT) followed by EC in series (EMT-BIEC); secondly, substitute coagulation process (which is used in water treatment chain) with BI-EC or EMT-BIEC process in performing tests on raw waters (Boukerdene and Ghrib Dam's, Algeria) using different electrodes (Al, Fe and stainless steel). According to the obtained results, BI-EC and EMT-BIEC processes are globally efficient in HA removal and water treatment. Indeed, removal of microorganisms and reduction of turbidity, conductivity and organic matter (OM) suggest that these processes would be used o...
TL;DR: The feasibility of the surface water contamination monitoring by IR thermography is based on three different key points: (a) thermal sensors able to measure the thermal energy radiating from water and land surfaces with high sensitivity and accuracy; (b) the thermal gradient existing between land/water surfaces and within these; (c) the rendering of the IR raw data, that produce images with a visible augmentation of the anomalies Illegal sanitary sewer and storm-drain connections, illicit discharges and other “anomalies on the surface waters could be easily identified by their thermal infrared signatures RE
Abstract: The feasibility of the surface water contamination monitoring by IR thermography is based on three different key points: (a) the thermal sensors able to measure the thermal energy radiating from water and land surfaces with high sensitivity and accuracy; (b) the thermal gradient existing between land/water surfaces and within these; (c) the rendering of the IR raw data, that produce images with a visible augmentation of the anomalies Illegal sanitary sewer and storm-drain connections, illicit discharges and other “anomalies” on the surface waters could be easily identified by their thermal infrared signatures If sources of pollution leak, seep or empty into creeks, streams, rivers, lakes and seas their thermal signatures vary from their surroundings and they can be highlighted accurately; in fact, the plume of liquid joining and flowing downstream with the body of water is visible in the thermal infrared spectrum due to the difference in temperatures of the two liquids Standards methods of pollution-so
TL;DR: In this paper, the impacts of droughts on the fresh water potential of the karstic spring of Almyros (Heraklion-Crete) were discussed.
Abstract: Frequent and intense drought episodes threaten the water balance of the fragile water systems in the coastal areas of the Mediterranean. Coastal brackish karstic springs offer a challenging solution for increasing water availability in case of temporary or permanent water shortages for alleviating the impacts of droughts and aridity in these areas. The paper discusses the impacts of droughts on the fresh water potential of the karstic spring of Almyros (Heraklion-Crete). Both time series of water quantity and quality of the spring are studied using a gross annual water balance model for the spring. Drought years are represented by the (Reconnaissance Drought Index)-RDI of the nearby meteorological station of Heraklion. Statisfactory correlation between RDI and water characteristics of the spring are derived. Finally, trends in the fresh water annual volumes time series are identified.
TL;DR: In this article, the authors reviewed the energy consumption of different desalination processes and showed that forward osmosis is a high energy consumption process, however, advanced cost effective backwash techniques.
Abstract: Water, energy and environmental issues are on the top list of the world problems. Energy is needed for augmenting our water resources. Renewable energies are hardly the answer since innovative techniques based on biofuels and biodiesel consume an incredible amount of water. The modern desalination techniques in use consume different energy levels from different sources. Thermody namics sets the absolute minimum limit of the work energy required to separate water from a salt solution. Unavoidable irreversibilities augment the actual energy consumption. Modern desalination techniques have succeeded in narrowing considerably the gap between actual and minimum energy levels. The implication of this small gap is that only marginal energy reductions are possible. Energy consumption of different desalination processes are reviewed. Forward osmosis is shown to be a high energy consumption process. It offers, however, advanced cost effective backwash techniques. The limitations of power generation by osmotic processes is discussed. Sidney Loeb together with Sourirajan were the pioneers that opened the door and introduced the RO process that allows us to desalinate seawater and brackish water at affordable energy consumption. Loeb continued during his last years to develop the osmotic energy machine, and even tried to develop an air condition system based on water evaporating from tubular membranes.
TL;DR: In this article, laboratory experiments were carried out to investigate electrocoagulation (EC) of Ghrib Dam's water (Algeria) in batch using aluminium and iron electrodes without addition of chemicals, without pH modifi cation, and without agitation.
Abstract: Laboratory experiments were carried out to investigate electrocoagulation (EC) of Ghrib Dam's water (Algeria) in batch using aluminium and iron electrodes without addition of chemicals, without pH modifi cation, and without agitation. The optimal conditions are an applied voltage of direct current of 8 V and a current density 74 A m−2 (0.35 A) during 45 min for both electrodes. The microbial pollution is completely removed by essentially electrical fi eld whereas conductivity and turbidity are reduced at 27 and 85% respectively for Fe electrodes and 22 and 97% for Al electrodes by metallic cations. These results prove that water treatment by EC using Al electrodes (flotation) for low turbid water (7 NTU) is more convenient than Fe electrodes (sedimentation) for both turbidity and organic matter removal. A new parameter to be taken in consideration for EC reactor design the ratio r active volume on reactor volume which is full of water is introduced where the active volume is the active surface multiplied ...
TL;DR: In this paper, the degradation and detoxification of two commercially important products being widely used in the tannery industry as synthetic tannin (ST) and degreasing agent (EP) containing 0.1% of nonylphenol ethoxylate (NPE) as well as degreases wastewater from re-tanning was investigated using Fenton (FO) and Photo-Fenton (PFC) oxidation processes.
Abstract: In the present experimental work, the degradation and detoxification of two commercially important products being widely used in the tannery industry as synthetic tannin (ST) and degreasing agent (EP) containing 0.1% of nonylphenol ethoxylate (NPE) as well as degreasing wastewater from re-tanning was investigated using Fenton (FO) and Photo-Fenton (PFC) oxidation processes. FO and PFC oxidation experiments were performed in batch reactors for 30 min at pH 3 ± 0.2 and 40–45°C, considering the actual temperature and pH values of retanning bath effluents. For the FO experiments the effect of varying Fe2+ and H2O2 concentrations and UV-C light irradiation on oxidation measured by the parameters COD, UV254 and UV280 absorbancies was studied. Toxicity of untreated and FO, PFC-treated synthetic solutions to the freshwater cladoceran Daphnia magna was also tested. PFC provided appreciably high COD (>80%) and UV254 and UV280 (>90%) removals for ST. The toxicity could be drastically reduced in the PFC-treated ST sa...
TL;DR: In this article, the removal of remazol brilliant blue (RB) dye from aqueous solutions through batch adsorption technique was examined for removing remazola brilliant blue dye from whitewashed oak sawdust, a timber industry waste.
Abstract: Activated carbons prepared from oak sawdust, a timber industry waste, have been examined for the removal of remazol brilliant blue (RB) dye from aqueous solutions through batch adsorption technique. Activated carbons were prepared from oak sawdust by chemical activation with 10% HNO3 (AC1) followed by pyrolysis at 500°C in the absence of air and by physical activation at 500°C in the absence of air (AC2). Activated carbons were characterized by SEM, BET and FTIR. Also pHpzc was followed by pyrolysis at 500°C in the absence of air and by physical activation at 500°C in the absence of air for both activated carbons was determined. The effect of pH, adsorbent dose, agitation speed, contact time and initial dye concentration on remazol blue (RB) adsorption were studied. Equilibrium data were fitted to Langmuir, Freundlich and Temkin isotherm models. The equilibrium data were best represented by the Langmuir isotherm model. The kinetic data were fitted to pseudo-first-order, pseudo-second-order, Elovich and in...
TL;DR: In this paper, a brief description of the application of electrocoagulation (EC) as a new seawater pretreatment process throughout the work of Sanfan and Qinlai (1987) until the work by Yi et al. (2009) via the workof Sanfan (1991); all of them are published in Desalination.
Abstract: In the first journal in the desalination world, Desalination, during the last 20 years, there is the birth of a new seawater pretreatment process: electrocoagulation (EC). In order to note some facts of this birth, relate its context, and understand its circumstances, this review concerns a brief description of the application of EC as a new seawater pretreatment process throughout the work of Sanfan and Qinlai (1987) until the work of Yi et al. (2009) via the work of Sanfan (1991); all of them are published in Desalination. The first paper (1987) discusses the mechanism of removing some ions from the brackish water using EC method. Experiment results present some major parameters for the EC process. The most important one in operation is electric current density (CD). Moreover, the fi rst paper suggests the method of selecting optimum density and some ways could raise economic property of EC and could reduce handling costs. In the paper of Sanfan (1991) the further research results of improving economic ...