The selection of the appropriate desalination technology between evaporation and reverse osmosis is grounded on several factors, including investment cost, maintenance cost, degree of availability, heaviness of the duty, and the required purity of the desalinated water. The main factor is often the running cost of the plant, and specifically the cost of the consumed energy. This paper intends to demonstrate that the real value of the steam bleed is a function of several factors, mainly of the cost of fuel and of its importance in the total cost of the energy. The lower the cost of fuel, the less is the value of the steam bleed up to the extent that the cost of the energy consumption can be lower for evaporation than for reverse osmosis.
Supported Liquid Membrane (SLM) is an emerging trace metal pre-concentration technique. It has the ability to decontaminate radionuclides even from lean secondary effluent. SLM can be considered as a part of process intensification, which implies a closed loop operation. It has reduced space requirement as well as minimised secondary effluent generation and the number of unit steps. Proper selection of molecular design criteria helps in deciding performances such as selectivity, compatibility, permeability, etc., that is attributed to both feed and desired strippant characteristics, and great effort has been applied for nuclear plant waste treatment generated in the uranium metal plant of Trombay, India. This paper articulates basic views of SLM, selection of carrier by experimental verification with respect to both feed and strippant for further processing, and structural aspects with evidences (from FT-IR studies).
The present work is the second part of the authors’ innovative method for radioactive wastewater-stream management, by volume reduction, by a mutual heating and humidification of a compressed dry air introduced through the wastewater. In this part, to determine the optimal operating conditions, a theoretical model describing volume reduction of the radioactive wastewater stream is achieved. A set of first-order simultaneous differential equations describing the bubble humidity, temperature, liquid temperature, and mass diffusion to the bubbles variations, are obtained through the mass and energy conservations. A set of coupled first-order differential equations are used to solve for the humidity ratio, water diffused to the air stream, water temperature and humid air stream temperature distributions through the bubbling column. These coupled differential equations are simultaneously solved numerically by a developed computer program using the fourth-order Runge–Kutta method. Therefore, the behaviour of the air bubble state variables with column height can be predicted and optimised. Moreover, the design curves of the volumetric reduction of the wastewater streams are obtained and assessed at the different operating conditions. An experimental set-up was constructed to verify the suggested model. Comprehensive comparison between suggested model results, recent experimental measurements and the results of previous works was carried out and assessed. A good agreement between experimental and theoretical model is obtained. A semi-empirical correlation is obtained together with design curve of bubbling column.
A low-cost optical sensor built-in strip has been developed from a composite obtained with application of in-situ chemical polymerisation, using polyaniline in the emeraldine oxidation state, doped with HCl onto poly(ethylene terephthalate) (PET) film, used to measured the pH of water. The absorption of UV-Vis spectra was used to evaluate the optical response to pH change of natural water. The strip showed a reversible colour change upon variation of the pH. The pH range used to calibrate the optical sensor was from 2.0 to 12.0. These kinds of sensors show the potential to investigate the pH of natural waters, with application to limnological studies, as well as to investigate the influence of the ionic strength. This paper describes new techniques that can be used to conduct research with pesticides in water using electrochemistry and biosensors, and an electronic tongue with conductive polymers for global quality evaluation.
Water is the natural resource on which human life, food security and the health of ecosystems depend. The requirement for water is increasing rapidly owing to progressive increase in the demand for irrigation, rapid industrialisation, population growth and improving living standards. The existing water resources are diminishing due to (a) unequal distribution of rain leading to drought, (b) excessive exploitation of groundwater sources and (c) deterioration of water quality owing to the discharge of domestic and industrial effluents without adequate treatment. A large number of villages in India and several other parts of the world are known to be suffering from excess salinity, fluoride, iron, arsenic and microbial contaminations of ground water. There are areas that face perennial water shortage. Thus, the sustainable management of water is one of the key challenges that our society is facing today. This paper discusses different challenges and approaches to integrated water resource management.
The heavy metals, such as uranium and vanadium, are some of the valuable metals in desalination effluents. Metal Chelate Embedded Polymers (MCEP) in leaflet form were prepared using the post-irradiation induced graft polymerisation technique, with different non-woven thermally bonded fibrous substrate materials. The novel sorbents, synthesised by using accelerator energy beams of 1.25 MeV and 2 MeV, were characterised for their radiation, chemical and mechanical characteristics. The novel sorbent was evaluated under different parametric conditions, in order to study the influence of grafting levels, initial concentration, dissolved solids and contact time. The standard isotherm and diffusion models were fitted to the experimental sorption data and model parameters were evaluated. The sorption characteristics of MCEP for recovery of heavy metals such as uranium and vanadium from desalination effluents were investigated.
Thin film composite type positively charged nanofiltration membrane developed by in situ polymerisation of functionalised polyethyleneimine and acid chloride has been used in various aqueous stream separations. The membrane contained fixed quaternary ammonium moieties which contributed to its positive charge. The membrane was tested for its performance in single solute feed systems containing salts of various combinations of univalent and bivalent ions (NaCl, Na 2 SO 4 , CaCl 2 and MgSO 4 ) in test cells as well as spiral module where it gave differential separation profile for these solutes with high rejection for CaCl 2 and low rejection for Na 2 SO 4 . The 2512 spiral module of the membrane was further used for separation of a simulated effluent solution containing uranyl nitrate, which is a common effluent generated in the nuclear industry. The membrane gave a high separation for uranyl nitrate and low separation for ammonium nitrate indicating that both the solutes can be fractionated by the membrane when they are present together in the nuclear effluent.
This paper presents the collaboration between the French Atomic Energy Commission (Commissariat a l'Energie Atomique, CEA) and the Indian Bhabha Atomic Research Centre (BARC) on the use of nuclear reactors for desalination. The joint R&D effort aims at developing optimised nuclear desalination systems, producing large amounts of desalted water at the lowest cost and in a sustainable manner. It focuses on two areas: (a) development and validation of process models for thermal and membrane-based desalination plants; and (b) extraction of valuable materials from the concentrated brine rejected by water plants. The results achieved during phase I of the collaboration include the development, implementation and partial validation of models describing the behaviour of multi-effect evaporators (MEE) equipped with a mechanical vapour compression device (MVC), the assessment of the influence of the feed water properties on the performance of the reverse osmosis (RO) process and the identification of methods and protocols for the extraction of valuable materials from brine reject. This effort will continue during phase II of the project with a particular emphasis on model extension, validation and application.
Currently, several IAEA Member States have shown interest in using nuclear energy for seawater desalination, not only because recent studies have demonstrated that nuclear desalination is feasible, but also because it is economical and has already been demonstrated in several countries. Therefore, this paper will provide a highlight on seawater desalination using nuclear energy as a potential for a sustainable development around the world, and an overview of the IAEA activities related to nuclear desalination. Special emphasis is placed on past, present and future nuclear desalination experience in various IAEA Member States. The IAEA activities on nuclear desalinations aim at facilitating cutting-edge developments in the area of seawater desalination using nuclear energy, and establishing a framework for facilitating activities in Member States through information exchange and provision of technical assistance.
As the need for fresh water and electricity increases rapidly in Algeria, the authorities launched a study to assess the potentialities of using nuclear energy for electricity and potable water production. This study which started in 2007 is held under the framework of an IAEA Project and its objective is to provide a document which will be used to support the government's decision to introduce the nuclear desalination in Algeria. To that end, one site has been selected to host nuclear desalination plant. This site is located in North West region of the country. In this study, we present the results achieved under this project and which corresponds to the economical evaluation of coupling several nuclear reactors: GT-MHR, PBMR, AP1000 & PWR900, with two desalination processes MED and RO. The results are compared with those obtained with fossil energy sources: Natural Gas Turbine and Natural Gas Combined Cycle.
Recent climate changes and population growth throughout Australia have highlighted the need for more diverse and climate-independent water sources. Australia is the world's driest inhabited continent and the unpredictable climate means that the Australian population generally requires up to five times the water storage than does an equivalent population in the UK. Although 85% of its people live within 50 km of the coast, the country has only begun to consider large-scale seawater desalination within the past five years (Crisp, 2009). The total potable and industrial water consumption in Australia is around 50,000 ML/d (Hoang, 2009). In 2008, the total volume of water desalinated for potable and industrial use was about 0.6% (300 ML/d) and this is expected to increase more than seven times to 4% by 2013. A brief review of current (2010) desalination capacity in Australia follows and includes major seawater plants, brackish water and wastewater reuse.
The act of enrichment or improving the quality of product concentration, i.e. 'pre-concentration', has been studied with respect to uranium plant effluent, which contains uranium in 10?30 ppm level intermingled with a huge number of interfering ions, such as magnesium, in percent level. The effects of different operating conditions, such as concentration of uranium in the effluent, pH, the time required for uptake of uranium and the effect of the presence of other elements in the effluent, in batch experiments have been investigated. Using this in-house novel resin for preferential uranium uptake, the sorbed matrix has been eluted with different eluant concentration for further enrichment of radionuclides in the elute. High uptake values for uranium ions prove its selectivity, and fractional elution ensures further reuse of sorbent and significant improvement in uranium enrichment.
Polysulphone hollow fibres were spun according to phase inversion process under different conditions by extrusion of dimethylformamide solution of the polymer through double orifice spinneret using water or water-DMF mixture as gelation medium. The membrane surface was modified by in situ interfacial polymerisation of m-phenylenediamine with trimesoyl chloride. The nominal molecular weight cut-off (MWCO) values of the virgin fibres were 44,000?94,000 g/mol, which were decreased to 10,000?14,000 g/mol upon surface modification. The contact angle of the virgin fibres was about 87° and was decreased to about 65° by surface modification. HF modules exhibited pure water fluxes of 40?70 litre/m²h at 25 psi, and 4?5 log reduction for microorganisms like cocci, E. coli and bacillus when tested with water containing 1010 cfu/ml of bacteria. Fibres were tested for the treatment of municipal sewage water for a period of 20 days and constant rejection-flux profile was observed throughout the period.
The cost of product water is a key factor in determination of acceptability of any desalination system and plant. In case of Sea Water Reverse Osmosis plants, most of the energy consumed is in the form of electricity. The High Pressure Pump (HPP) is the single major energy consuming equipment with a share of above 75%. Hence reduction in energy consumed by HPP will have a substantial effect on the overall energy consumption. The high starting torque requirement of high pressure pump results in increased acceleration time of the motor which subsequently increases the strain on the upstream electrical system from motor feeder to transformer. Provision of a Variable Frequency Drive can be a solution for both the above problems. This paper studies the techno-economic feasibility of providing variable frequency drive for HPP motor at NDDP, Kalpakkam.
The objective of the present work is to study the performance of ejector vapour compression desalination plant with water spray on horizontal tube bundles. The effects of the operating conditions and the ejector geometry on the total distilled collected water are studied. The amount of evaporation rate due the flash evaporation is calculated by applying the mass and energy of the sprayed water governing equations. The evaporation rate of the falling liquid film around the horizontal tube bundles is evaluated by the non-dimensional mass, momentum and energy equations solved numerically using the finite difference method. The results presented the effect of the change in evaporation pressure, inlet liquid temperature, hot surface heat flux and inlet sprayed mass flow rate. Also, the results determine the effect of the ejector geometry, motive steam temperature, evaporator temperature and the compression ratio across the evaporator on the performance of the vapour compression plant.
CIRUS is a 40 MWth, light water cooled research reactor located at Trombay, Mumbai. The reactor was shut down in 1997 for refurbishment and restarted in 2003. At Bhabha Atomic Research Centre R&D activities on desalination have led to development of desalination technologies based on Multistage Flash (MSF) evaporation, Reverse Osmosis (RO) and Low Temperature Evaporation (LTE). Based on LTE, a 30 cubic metre per day pilot plant was designed and integrated to CIRUS during refurbishing outage as part of demonstration of utilisation of waste heat of nuclear reactors for seawater desalination. The work involved design, installation and commissioning of set-up to transfer heat from primary coolant of CIRUS to desalination unit through an intermediate Demineralised (DM) water circuit. The unit has been operated at its rated capacity and product water has been used to augment the demineralised water inventory of the primary coolant system. This paper highlights the experience gained during installation, commissioning and operation of the desalination unit.
Provision of safe drinking water is a challenging problem requiring immediate attention. The skewed distribution of rainfall, inefficient use of water, presence of a variety of contaminants, such as fluoride, arsenic, iron and salinity, in most of the sources, and pollution by various economic activities have been the factors responsible for inadequate resources against the increasing demand due to growth in population, agriculture and industrial activities. The conflicting demand for a variety of uses of water, high volume requirements, problems in distribution and operating economics have compounded the problem. Being an essential requirement for the survival of living beings no effort can be spared in addressing the problem and implementing a viable and sustainable solution. A multi-pronged approach synergising the technology, financial aspects, public awareness and user participation is the need of the hour. This paper is an attempt to analyse the issues to evolve an implementable model.
When a nuclear reactor is used to supply steam for a desalination plant, the method of coupling has a significant technical and economic impact. The exact method of coupling depends on the type of reactor and the type of desalination plant. As a part of Nuclear Desalination Demonstration Project (NDDP), BARC has successfully commissioned a 4500 m 3 /day multi-stage flash desalination plant coupled to Madras Atomic Power Station at Kalpakkam. A desalination plant coupled to nuclear reactor of pressurised heavy water reactor type is a good example of dual-purpose nuclear desalination plant. This paper presents the thermal coupling system analysis of this plant along with technical and safety aspects.
With advances in nanotechnology, different types of nanomaterial are emerging for applications in water purification and water treatment devices owing to their effectiveness against both chemical and biological contaminants. This paper discusses the application of nanoscale materials that are being evaluated or developed as functional materials for water treatment, e.g. nanomembranes (nanocomposite RO and NF and carbon nanotubes), metal nanoparticles, nanoadsorbents, magnetic nanoparticles, bioactive nanoparticles, carbonaceous nanomaterials, zeolites, dendrimers and nanofibres. Nanomaterials are intrinsically better in terms of performance than other substances used in water treatment because of their high surface area (surface/volume ratio). Owing to these characteristics, these may be used in future at large scale for water purification.
This paper deals with some aspects concerning the dual objectives of cost-effectiveness and favourable environmental impact of desalination plants, resulting in a sustainable alternative source of fresh water for future needs. These include some case studies on the use of waste heat for the thermal desalination plants, replacement of conventional pre-treatments in membrane plants with cleaner processes, deployment of hybrid desalination systems and use of non-fossil fuel sources for both types of desalination plant. In particular, the role of nuclear and renewable energy sources (wind and solar) has been examined. The environmental impact of the desalination processes has been discussed and benefits from suggested technologies under CDM have been outlined. With the current environmental concerns, it is desirable to consider use of alternate energy sources for desalination, even though at present these appear not that economical. They may become so once credit for clean energy is available. A real breakthrough in development of near ideal membranes will of course go a long way in desalination economics. Efforts need to be continued in this area.
