Desalination & Water Purification Technologies

Desalination & Water Purification Technologies 16
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Desalination & Water Purification Technologies Technical Information Document Government of India Department of Atomic Energy Bhabha Atomic Research Centre Chemical Engineering Group Desalination Division Trombay, Mumbai 400 085 2010 I Desalination & Water Purification Technologies Desalination & Water Purification Technologies IICONTENTS Foreword V Preface VII 1. Introduction 1 2. Desalination Technologies 2 2.1. Thermal Desalination 2 2.1.1. Multi-Stage Flash (MSF) Process 2 2.1.2. Multi-Effect Distillation (MED) 3 2.1.3. Low Temperature Evaporation (LTE) using Waste Heat 4 2.2. Reverse Osmosis (RO) 4 2.3. Hybridization 5 2.4. Cogeneration using Nuclear Energy 5 3. Challenges in Rural Areas 6 4. Role of Department of Atomic Energy in 6 Desalination & Water Purification 5. Technologies & Products Developed by BARC 8 5.1. Membrane Technologies 8 5.1.1. Brackish Water RO 8 5.1.2. Sea Water RO 8 5.1.3. Development of Membrane & Modules 9 5.1.3.1. Backwashable UF Spiral Modules 9 5.1.3.2. Candle Type UF Water Purification Device 10 5.1.4. Spin-off Membrane - Porous Polysulfone Diaphragm as Separator in 11 Electrochemical Processes 5.1.5. UF Assisted Fluoride Removal System 11 5.1.6. UF Assisted Arsenic Removal System 12 5.1.7. UF Assisted Iron Removal System 13 5.1.8. Membrane Pouch for Providing Sterile Water Solution ` from Contaminated Water 13 III Desalination & Water Purification Technologies5.2. Thermal Desalination 14 5.2.1. Multi-Stage Flash (MSF) 14 5.2.2. LTE Desalination using Waste Heat 14 5.2.3. Multi-Effect Distillation (MED) 15 6. Desalination using Nuclear Energy 16 6.1. Hybrid System 16 6.2. LTE System utilising Nuclear Waste Heat 17 7. Desalination & Water Purification Systems for Rural areas 17 7.1. Rural Application of UF based Water Purification Technologies 17 7.2. Solar Desalination & Water Purification Systems 18 7.2.1. Solar PV based Water Treatment Systems 18 7.2.1.1. Small Brackish Water RO & UF Units 18 7.2.1.2. Community size RO Plant 19 8. Consultancy 19 9. Recovery of Valuables from Reject Brine of Desalination Plant 20 10. Services 20 11. Transfer of Technical Know-How 20 11.1. Who Can Apply 20 11.2. How to Apply 20 Annexure-I Milestones in Thermal Desalination 21 Annexure- II Milestones in Membrane Technologies 22 Annexure-III Desalination & Water Purification Technologies and Products 23 Developed by BARC- Technical Features Annexure-IV Application Form for Technology Transfer from BARC 38 Desalination & Water Purification Technologies IVFOREWORD YeeYee HejceeCeg DevegmebOeeve keWÀê ìecyes, cegbyeF&-400 085 jleve kegÀceej efmevne, SHeÀSveSF&, er Smemeer (S®e meer) Yeejle efveosMekeÀ Bhabha Atomic Research Centre Trombay, Mumbai 400 085 Ratan Kumar Sinha, FNAE, D Sc (hc) Yeejle mejkeÀej India Government of India Director About 40 million people (over 75% are children) are affected by water borne diseases every year. Nearly six million children below 14 years of age suffer from fluorosis due to fluoride contamination in water. Arsenic is another dangerous contaminant in ground water. putting at risk more than 10 million people in the country. Bacteriological contamination, which leads to diarrhea, cholera, hepatitis etc., is at alert level in India. Contamination due to Iron, hardness and salinity in water are other major concern. Medical expenditure on water borne diseases is estimated to be Rs. 2400 crores annualy in the country. The need for desalination and water purification is destined to grow in the coming years as the requirment for water increases. Bhabha Atomic Research Centre (BARC) has been engaged in R&D on desalination and water purification technologies for several years and has developed indigenous technologies wich are available for know-how transfer to interested parties. I hope this technical information document will serve the purpose of creating awareness of and appreciation for desalination and water purification technologies, among the entrepreneurs, NGOs and other interested groups, so that safe drinking water can be made available to the needy population in a reliable, sustainable and affordable manner using the indigenous technologies and supplementing with market technologies in an accelerated manner on a significant scale. BARC would encourage entrepreneurs to come forward and make use of the indigenous know-how for wider deployment. (R. K. Sinha) otjYeee / Phone: + (91) (22) 2550 5300, 2551 1910 • leej:yeeke&À-cegbyeF& 400 085 � Gram : BARC-MUMBAI - 400 085 HewÀkeÌme /Fax: + (91) (22) 2559 2107, 2550 5151 � F&-cesue / E-mail: rksinhabarc.gov.in / directorbarc.gov.in V Desalination & Water Purification Technologies Desalination & Water Purification Technologies VIPREFAC E Early humans thought that the taste of the water determined its purity. The Sus’ruta Samhita, Sanskrit writings about medical concerns (2000 BC), gives evidence that water treatment may well be as ancient as humans are. The Greeks and Romans are well known for their elaborate water systems. These early water treatment professionals used a variety of methods to control taste and odor problems in their th water supplies. A correlation between water quality and health was made, in mid- 19 century in London, when a decrease in cholera deaths epidemics were noticed where slow sand filters had been installed. The World Health Organisation (WHO) has set international guidelines for drinking water. Almost all countries have drinking water quality regulations, often inspired by WHO guidelines. According to the United Nations, over 1.1 billion people are currently without safe drinking water. It is predicted that a significant fraction of the global population (over 3.5 billion people) will be living in areas facing severe water shortages by the year 2025. More than half of the world’s hospital beds are occupied by patients suffering from water borne diseases. Many of these diseases can be prevented by providing safe drinking water. The United Nations General Assembly has proclaimed the years 2005-2015 as the International Decade for Action ‘Water for Life’. Government of India has launched ‘Bharat Nirman’ Yojana which includes drinking water as an important programme. It is in this context, the role of desalination and water purification becomes very important. Desalination of water is one of the key drivers under non-power applications of DAE program. Desali- nation Division, Bhabha Atomic Research Centre (BARC) has been engaged in R&D on various as- pects of desalination and water purification technologies starting from basic research work to develop- ment and deployment efforts. Dedicated team of scientists and engineers have contributed substan- tially to the expertise gathered, technologies developed and know how generated in the research centre. The research work carried out has mainly focused on technological innovations, quality, reliability and commercialization potential of the product/ technology for deployment over large scale. State-of-the- art reliable technologies have been developed to address the growing need of good quality water for industries and human consumption. We have acquired valuable experience on operation and trouble shooting of desalination and water purification plants and are equipped to provide consultancy to interested parties on design, installa- tion, commissioning and operation of these systems. Such consultancies are provided after signing a Memorandum of Understanding (MoU). Several water technologies developed by Desalination Divi- sion have been transferred to private parties on non-exclusive basis. We are thankful to all the scientists and engineers who came forward to share their expertise and information in the formulation of this Technical Information Document. This document would not have been materialised, but for the encouragement and support of Director BARC and Chairman AEC for water technologies. The document is not intended to provide detailed technical information on various technologies, but is aimed to provide a glimpse of the technologies for the entrepreneurs, NGOs and other interested parties. The purpose of bringing out this technical document is to consolidate the work carried out by Desalination Division (BARC), so that deployment of such technologies could be accelerated through the participation of private entrepreneurs, NGOs and other interested groups. (P.K. Tewari) Head, Desalination Division VII Desalination & Water Purification Technologies Desalination & Water Purification Technologies VIII1. Introduction The world’s water consumption rate is doubling every 20 years, outpacing by two times the rate of population growth. The availability of good quality water is on the decline and water demand is on the rise. Worldwide availability of fresh water for industrial needs and human consumption is limited. Various industrial and developmental activities in recent times have resulted in increasing the pollution level and deteriorating the water quality. Water shortages and unreliable water quality are considered major obstacles to achieve sustainable development and improvement in the quality of life. The water demand in the country is increasing fast due to progressive increase in the demand of water for irriga- tion, rapid industrialization, population growth and improving life standards. The existing water re- sources are diminishing (i) due to unequal distribution of rain water and occasional drought, (ii) exces- sive exploitation of ground water sources and its insufficient recharge, (iii) deterioration of water qual- ity due to the discharge of domestic and industrial effluents without adequate treatment. This is result- ing into water stress/ scarcity. Country is currently passing through social and economic transition. The proportion of the population which is urban has doubled over the last thirty years (and is now about 30%), agriculture now accounts for about 25% of GDP and the economy has been growing at around 7-9% a year. Country has a highly seasonal pattern of rainfall, with 50% of precipitation falling in just 15 days and over 90% of river flows in just four months. There are areas like Saurashtra and Kutch, Western Rajasthan and the coastal regions of Tamil Nadu etc. which face perennial water shortage. In addition, a large number of villages in different parts of the country are known to be suffering from excess salinity, fluoride, iron, arsenic and microbial contamina- tions of ground water. Desalination is recognized as a possible means to augment the water supply using natural resources for meeting the growing demand of water. Seawater, brackish water and fresh water have different levels of salinity, which is often expressed by the total dissolved solids (TDS) concentration. Water is considered potable when its TDS is below 500 mg/L. Seawater has a TDS of about 35,000 mg/L and brackish water has a TDS between that of potable water and seawater. Waste water is another category containing dissolved salts mostly in the low brackish level. The reclaimed water from waste water can be used for irrigation, cooling water and other industrial applications. Since the projected industrial and irrigation requirements would be far exceeding that of domestic requirements, recycle and reuse of waste effluents apart from desalination make enormous sense for future water management. A holistic approach is therefore required to be considered to deal with water problem. It includes: • Seawater desalination in coastal areas • Brackish water desalination • Water purification • Water reuse • Rain water harvesting • Water supply schemes Desalination, water purification & water recovery/ reuse schemes are destined to play a major role and commercially viable indigenous technologies are thus required for deployment to suit local conditions. 1 Desalination & Water Purification TechnologiesIntegrated Water Resource Management – A Holistic Approach 2. Desalination Technologies Desalination refers to the process by which pure water is recovered from saline water using different forms of energy. Saline water is classified as either brackish water or seawater depending on the salinity and water source. Desalination produces two streams - freshwater and a more concentrated stream (brine). The two main commercial desalination technologies are those based on thermal and mem- brane processes. 2.1. Thermal Desalination Thermal processes, except freezing, mimic the natural process of producing rain. Saline water is heated, producing water vapour that in turn condenses to form distilled water. These processes include multi- stage flash (MSF), multiple-effect distillation (MED), vapour compression (VC) and low temperature evaporation (LTE). In all these processes, condensing steam is used to supply the latent heat needed to vapourize the water. Owing to their high-energy requirements, thermal processes are normally used for seawater desalination. Thermal processes are capable of producing high purity water and suited for industrial process applications. Thermal processes account for 55% of the total production and their unit capacities are higher compared to membrane processes. 2.1.1. Multi Stage Flash (MSF) Process The basic principle involved in the MSF process is to heat the sea water to about 90– 120°C using the heat of condensation of the vapour produced and supplementing with external steam. The heated sea water is subsequently flashed in successive stages maintained at decreasing levels of pressure. The vapor produced is condensed and recovered as pure water. MSF can accept higher contaminant loading (suspended solids, heavy metals, oil, grease, COD, BOD etc.) in feed sea water. It is capable of producing distilled quality product water good for power plants, process industries and several other high purity applications. Desalination & Water Purification Technologies 2Schematic Diagram of Multi-Stage Flash (MSF) Process 2.1.2. Multi Effect Distillation (MED) MED plant has two or more effects. Each effect operates at a successively lower temperature and pressure. The first effect is heated by low pressure steam (about 0.3 bar). Vapours are generated from the feed sea water in the first effect and directed to the second effect. Thus vapours from the previous effect serve as the heat source to the succeeding effect for evaporating the brine. Vapour from the last effect is condensed in the final condenser where sea water is used as the coolant. The vapour produced in each effect is passed through the demisters to next effect. It is condensed inside the tubes transfer- ring the latent heat to the brine falling outside the tube enabling a portion of the brine to evaporate. Low temperature MED unit operates at about 65°C and therefore allows the use of cheaper materials of construction due to less scaling and corrosion problems. MED is capable of producing pure dis- tilled water similar to MSF. The possibility of low temperature operation, low grade heat and waste heat utilization, low cooling water requirement and low energy consumption have made MED an attractive alternative in recent years for sea water desalination. Efficiency of MED plant can be improved by adding a vapour compressor. Mechanical Vapour Compressor (MVC) or Thermal Vapour Compressor (TVC) is used for this purpose depending on site specific conditions. Schematic Diagram of Multi-Effect Distillation (MED) Process 3 Desalination & Water Purification Technologies2.1.3. Low Temperature Evaporation (LTE) Desalination Using Waste Heat As the energy cost component is a major fraction of the desalinated water cost, utilization of waste heat as energy input for seawater desalination is an attractive option. It is one of the eco-friendly ways to produce desalinated water as it does not require chemical pretreatment of feed seawater. Ocean ther- mal energy can also be utilised for sea water desalination. The desalination unit essentially consists of three portions i.e. heater, separator and condenser. In the heater shell, vertical tubes are used. Feed sea water enters the unit at the bottom of the tubes and partly evaporates by the time it comes out from the top. After water and vapour mixture come out of the tubes, the vapour rises through the vertical shell, enters the horizontal tube bundle kept at the top of the vertical shell and condenses around the tubes (which are cooled by sea water flowing inside) pro- ducing desalinated water. The product water is pumped out. LTE Desalination using waste Heat 2.2. Reverse Osmosis (RO) RO is used for both brackish water and seawater desalination as well as for waste water treatment and water recovery/reuse. A typical RO desalting plant consists of three sections, namely pretreatment section, membrane section and post treatment section. Conventional pretreatment section typically consists of particulate filtration, micron filtration and chemicals additions. Membrane section con- sists of membrane elements housed in pressure vessels through which pretreated saline water is passed under pressure in excess of its osmotic pressure with the help of a high pressure pump coupled with energy recovery device. The post treatment section consists of lime treatment for pH correction and chlorination for disinfection as required to meet public health standards and to make the water non- corrosive to the water distribution systems. Energy consumption depends on the salt content of the feed water. Development of RO membranes of very high rejection, while maintaining high permeabil- ity, has potential to reduce the energy consumption. Development of better energy recovery devices can further reduce the energy consumption. As the success of RO desalination hinges on the proper pre-treatment of the feed water, various membranes could precede RO in order to selectively remove suspended solids (microfiltration), colloids/turbidity & organics (ultrafiltration) and hardness and sulphates (nanofiltration). Desalination & Water Purification Technologies 4Reverse Osmosis (RO) 2.3. Hybridization Hybrid thermal/membrane combinations offer several advantages including the use of warm seawater from the thermal plant as feed to RO for having an optimized feed temperature and production of water of different qualities for different uses such as high quality boiler feed make up water, process water and potable water. Combined post treatment, use of common seawater system and brine discharge facility, reduced seawater requirement, sharing the manpower and facilities are other advantages of hybridization. 2.4. Co-generation Using Nuclear Energy Co-location of desalination and power plants has the benefit of sharing the resources such as common intake of sea water/ outfall and other infrastructural facilities. Dual purpose (power & water) plants have inherent design strategies for better thermodynamic efficiency besides economic optimization. The production of potable water from seawater in a facility in which nuclear reactor is used as the source of energy for the desalination process is termed as nuclear desalination. Electrical and/or thermal energy is used in desalination process on the same site. Hybrid Desalination System Integrated with Nuclear Power Reactor 5 Desalination & Water Purification Technologies3. Challenges in Rural Areas As water scarcity and contamination problems are more acute in rural areas, implementation of desalination and water purification technologies will help in a big way in providing safe drinking water. But, the various constraints normally encountered in rural areas pose certain limitations on the efficiency and techno-economics of desalination in general. Power supply in rural areas is a serious concern. Availability of power varies from 8 to 10 hours a day and even the available power supply is highly erratic with crippling voltage fluctuations and sudden power cuts. Hence the total requirement of drinking water for the village needs to be produced in a short span of time when the power is usually available. Remoteness and inaccessibility of remote areas pose difficulties in case of equipment failure as skilled manpower and spare parts may not be readily available which results in considerable delay. To deal with such situations the critical moving parts are installed in standby mode and important spare parts are always kept ready. Due to acute summer and over exploitation of the ground water, the water table goes down, thus affecting the yield and at times rise in salinity. Hence sustenance of the quality and quantity of the product is difficult. Reject water recirculation in the design is the suitable approach which takes care of conserving the ground water resource. Because of the lack of availability of skilled man power in rural areas the design should take care that minimum human interface is called for. Design should be robust and simple. 4. Role of Department of Atomic Energy (DAE) in Desalination & Water Purification As a part of the national program to improve the quality of life in our society, BARC has been engaged in research, development and deployment of desalination and water purification technologies for a wide range of applications. It includes sea water RO for coastal areas, brackish water RO in villages for producing safe drinking water, MSF for seawater desalination using low grade steam, LTE using waste heat for seawater desalination. Ultra-Filtration (UF) based water purification for domestic and community use and waste water recycle and reuse. These processes are either used in standalone or hybrid mode to suit the requirement. The technologies have been demonstrated and deployed in different parts of the country and transferred to several parties on non-exclusive basis. BARC has been providing guidance and consultancy to several agencies in this regard. The Department has achieved several milestones in the field of thermal desalination and membrane technologies as given in Annexure I and II respectively. Desalination & Water Purification Technologies 6Desalination plant  Seawater RO Plant  Brackish water RO Plant  Seawater MSF Plant  Seawater LTE Plant  Effluent Treatment RO Plant for water recovery  RO Plant for Disaster management Technology Transfers  Brackish water RO  Domestic water purifier  Spiral UF Element  Fluoride Removal  Arsenic Removal Deployment of Desalination & Water Purification Technologies by Department of Atomic Energy (as on June 2010) In case of membrane technology, the Department has come to a level of having full-fledged facilities for indigenous development of membranes & membrane devices, capabilities for design, engineering and consultancy services for installation, commissioning and trouble shooting. In thermal desalination, efforts are continued to reduce the cost through R&D including technological innovations such as high heat transfer performance, utilisation of low grade and waste heat etc. BARC has been engaged in several international collaborations dealing with various aspects of desalination and water purification. BARC has signed Memorandum of Understandings (MoUs) for providing consultancy on design, design checkup and trouble shooting of desalination and water recycling plants. In the larger interest of providing clean water to the people and thereby improving their quality of life, DAE desires to promote wider deployment of these indigenous desalination and water purification technologies. The technical knowhow of these technologies are available through Technology Transfer & Collaboration Division (TTCD) of BARC. The entrepreneur can purchase the appropriate technology which will be transferred on a non exclusive basis. 7 Desalination & Water Purification Technologies5. Technologies and Products Developed by BARC The features of the products and technologies developed are given in Annexure III. 5.1. Membrane Technologies Reverse Osmosis (RO) and Ultra-Filtration (UF) based systems for different applications have been developed. Work on exploring the role of nano-technology on desalination and water purification also has been taken up. 5.1.1. Brackish Water RO R&D efforts in BARC has resulted in the development of brackish water desalination technology. Several community level desalination plants of capacities ranging from 5-30 Kilo-Litres/ Day (KLD) have been setup in the rural areas of Rajasthan, Andhra Pradesh and Gujarat producing clean water from brackish water. These reverse osmosis plants are not only capable of desalinating brackish water but are also capable of removing contaminants such as fluoride, arsenic, nitrate etc. Brackish Water Desalination Plants in Rural Areas (5-30 KLD capacity) 5.1.2. Sea Water RO BARC has developed the design methodology of Seawater Reverse Osmosis (RO) system and based on the experience gained from the 100 KLD RO plant at Trombay, it has setup a SWRO plant at Kalpakkam which produces 1.8 Million Litres/ Day (MLD) of potable water. A barge mounted desalination plant (50 KLD capacity) for producing drinking water from seawater has also been developed. Such desalination plants are useful for water starved coastal areas. Similar units can also be used for disaster management to provide drinking water in the coastal areas during emergency. For disaster management, desalination plants (2 nos., 5 KLD capacity each) were designed and installed in the Tsunami affected areas of Tamil Nadu. Special care was taken in the design so that the plant can operate under wide range of feed water quality in terms of physical, chemical and biological contaminants with minimal pretreatment. 5.1.3. Development of Membrane and Modules Indigenous development of membranes for various applications such as brackish water and sea water desalination and water recovery/ reuse from effluents is pursued. Cellulose acetate based membranes developed in tubular and flat sheet configurations were transferred to several parties for Desalination & Water Purification Technologies 8100 KLD SWRO Plant at Trombay 1.8 MLD SWRO Plant at Kalpakkam commercialization. R&D efforts on membrane manufacturing technology have resulted in the development of Thin Film Composite Polyamide (TFCP) membranes. These are three layered membranes, prepared in two stages. The membranes thus prepared are rolled in spiral configuration using the technology developed in-house. The poly sulfone membrane which is in the ultrafiltration (UF) range, prepared as a precursor for the TFCP has been found to be good for many applications. 5.1.3.1. Back washable UF Spiral Modules Backwashable spiral element based on poly sulfone UF membranes for delivering sterile water with six (6) log reduction of bacteria and four (4) log reduction of virus has been developed. It is a promising technology for water purification, wastewater treatment and water reuse. These devices with capacity ranging from about 0.5 LPM to 4 LPM can be deployed for community water purification or small- scale industries. As RO pretreatment system also, the unit has been perfected in the Department. It Barge Mounted Desalination plant (50 KLD capacity) 9 Desalination & Water Purification Technologiesprovides an absolute barrier to the particles present in the raw saline water regardless of the system load, operational conditions, or the fluctuations and changes. The unit is back washable either manually or automatic mode. The single step of UF pretreatment can replace the conventional pretreatment system comprising clarifier, coagulant and flocculent dosing coarse media filter and active carbon filters. The other advantages are smaller footprint/ layout area, single step process, modular expandability, less volume of discharged wastes (including sludge and chemicals), simplicity of operation, process automation etc. The technology has been transferred for wider deployment. Membrane Casting Machine at BARC Indigenously Developed Spiral Modules 5.1.3.2. Candle Type UF Water Purification Device A novel idea of coating poly sulfone on a porous candle resulted in the development of a ‘point of use’ water purifier. Unlike other devices available in the market which only deactivates the micro-organisms, this device physically eliminates them. This device does not require any electricity or any addition of chemicals. Removal of suspended particulates, color and odor are additional benefits available in these units. A typical unit provides nearly 40 liters of water per day at 3 meters pressure head and can withstand up to 40 psig pressure. These water purifiers of low capacity and zero operating cost are meant to satisfy the domestic need for safe water. The technology has been transferred to eighteen parties for commercial deployment. Desalination & Water Purification Technologies 10Water Purifier Developed by BARC 5.1.4. Spin-off Membrane - Porous Polysulfone Diaphragm as Separator in Electrochemical Processes The porous polysulfone diaphragms reinforced with non-woven support fabric has been found to be useful as separator in electrochemical processes involving highly acidic solutions for production of various chemicals such as ammonium per sulphate (NH ) S O .. These diaphragms have very high 4 2 2 8 porosity (60-70%) with submicron pore sizes resulting in low electrical resistance in electrolyte solu- tions and are stable up to 30% H SO solution. The production cost of these diaphragms is lower by 2 4 an order of magnitude compared to presently used nafion membranes with comparable properties. The polysulfone diaphragm can be used as a separator in electrolytic cell. 5.1.5. UF Assisted Fluoride Removal System While the desirable limit of fluoride in water is 1 mg/ litre (ppm), several states in the country have higher fluoride content in water. It causes dental, skeletal and non-skeletal fluorosis. Treatment of fluoride contaminated water by use of alumina column and subsequent polishing by ultrafiltration process ensures efficient removal of fluoride as well as secondary aluminum contamination. A compre- hensive technology comprising re-generable alumina followed by ultrafiltration is developed in the Department. 11 Desalination & Water Purification Technologies