Desalination technologies

Transcription

1 Desalination technologies Reverse Osmosis & Thermal Desalination for drinking water, industrial water & water recycling

2 WABAG - for over 90 years a synonym for innovative and successful water engineering solutions. WABAG is an international supplier of water and wastewater treatment systems for both municipal and industrial segments. It is one of the innovative leaders in this field and in particular, is one of the few companies in the world to offer a comprehensive spectrum of technologies for the desalination of sea and brackish water: Reverse osmosis Thermal desalination (MED, TVC, MED-XL and XXL, MVC, MSF) Electrodialysis (ED) Ion exchange (IX) With more than 30 years of desalination experience, WABAG has designed and built over 100 plants worldwide. At present, the widely preferred technologies for the desalination of sea and brackish water are: Membrane technology: reverse osmosis (RO) Thermal methods: multi-effect distillation (MED) These technologies can be utilised for both the production of potable water and industrial process water, and form the basis for optimum and customised solutions. Desalination technologies are also of increasing importance in the field of water recycling systems and demineralisation, while the employment of membrane technologies such as reverse osmosis allows the reuse of industrial effluents as highly-purified process water, e.g. as boiler feed water. What makes WABAG a preferred partner? A comprehensive desalination technology portfolio Proven process know-how and expertise as well as an understanding of entire systems The provision of complete solutions: EP, EPC, DBO, BOOT In-house R&D centres in India, Austria and Switzerland, which guarantee the optimisation and further development of desalination technologies Experience as a desalination plant operator A multinational presence and long-term experience The integration of desalination plants with water reclamation systems Freedom of choice on the most suitable membrane systems Finding new approaches through R&D On the strength of our extensive experience, our current focus is on the development of membrane distillation (MD). Membrane distillation is a thermally powered separation technology based on hydrophobic membranes, which allows higher concentration efficiency at lower cost. Pilot tests are currently under way with the aim of studying concentration performance in the case of various effluents (such as produced water) and brines (such as concentrates from reclamation plant ROs). In this context, the development and design of an ideal pre-treatment for MD is extremely important. Moreover, progress has been made in the area of minimising brine return volumes and this constitutes a step towards zero liquid discharge (ZLD). 2

3 Reverse Osmosis or Thermal Desalination The larger the salt content of the untreated water and the greater the required degree of purity at the desalination output, the higher the energy costs. In the past, reverse osmosis installations required sizeable amounts of electrical power. However, owing to increased energy optimisation, these processes have now become far more costefficient. In today s world, RO is indispensable for the supply of potable water in countries lacking adequate ground or surface water resources. It has emerged as the most economic solution where residual steam is unavailable as an energy source. By contrast, thermal seawater desalination using residual steam as an energy source is the most appropriate solution in power plants and offers major O&M savings. Thermal MED installations, for example, are operated with low pressure exhaust steam or with output steam from steam turbines. For steam pressures above 2 bar, thermal MSF would then be appropiate. When such energy is available this process is most suitable. WABAG is one among the very few companies in the world to offer both technologies on standalone or hybrid basis. REVERSE OSMOSIS THERMAL DESALINA- TION Al Ghubrah, Seawater Intake sinking 3

4 Reverse Osmosis Desalination RO the advantages: Proven and time-tested technology Relatively low investment costs as compared to thermal methods Application flexibility - from very small (< 100 m 3 /d) to large installations (> 100,000 m 3 /d) No cooling water requirement Less energy consumption than with an MED system RO is a pressure-driven process. Saline water is forced through semi-permeable membranes under pressure, thereby separating the saltwater into a freshwater stream (known as permeate) and a brine stream (concentrate). Typical process steps in an RO system: 35 Al Wasia, Saudi Arabia Brackish water RO, 200,000 m 3 /d 1 Pre-treatment (protecting the RO membranes) 2 High Pressure Pumps 3 Energy Recovery system 4 RO Membrane Modules 5 Concentrate discharge 6 Post-treatment (remineralisation, disinfection) The recovery percentage of purified water depends upon various factors that include membrane size and internal structure, temperature, operating pressure and membrane surface area. Due consideration given to the economic factors such as: Energy recovery Membrane durability Chemical consumption Process automation Raw water Product water 3 5 Nemmeli, India Seawater RO, 100,000 m 3 /d 4

5 Complete and Exclusive Customized solutions WABAG supplies RO plants for various types of raw water such as seawater, brackish water and industrial effluents. As a provider of end to end solutions, WABAG delivers the entire process from the raw water onwards, including deep seawater intake and outflow structures to the post-treatment of product water and product water pumping stations. Saving energy & costs Employing pressure exchanger systems. The RO process does not require thermal energy, but needs electrical power mainly due to the high pressure pumping required to obtain flow through the RO membranes. Brine energy recovery systems have also been optimised in order to reduce energy consumption and have proved to be highly successful. On the strength of its experience in design, construction and operation of plants of varying sizes, WABAG offers economically advantageous and technically proven solutions for every application. Highly effective pre-treatment systems are extremely important From filtration to micro- and ultrafiltration WABAG lays a special emphasis on efficient pre-treatment. In that, apart from conventional filtration technologies, highly effective micro- and ultrafiltration systems are employed. For example, WABAG designed and built the first plant in Oman (Duqm, Al Wusta region) to use microfiltration units for pre-treatment and subsequently this successful combination was also used in the desalination plant for the new Sohar International Port (start-up 2013), where an in-line RO system was successfully executed. The Nemmeli RO-drinking water plant in Chennai, which is one of the largest plants of its kind in India, employs ultrafiltration membranes for highly effective pre-treatment upstream of the RO system. WABAG is an established name in various pre-treatment technologies. 5 Duqm SWRO, Oman 6,000 m 3 /d, Pre-treatment (microfiltration) Al Kharj BWRO, Saudi Arabia 50,000 m 3 /d, Pre-treatment 5

6 Sohar International Port SWRO, Muscat, Oman Most modern desalination plant for drinking and industrial water production. Best practice references Combination of microfiltration and reverse osmosis desalination. An integrated solution. Client: Majis Industrial Services SAOC Contract type: DBO - Design-Build-Operate Commissioning: 2013 Raw water: seawater Product: potable water and process water Capacity: 20,000 m 3 /d Process: reverse osmosis with self-cleaning filters and membrane pre-treatment Microfiltration-based Inline RO system - reduced CAPEX, OPEX and footprint. Main parameter: 44,000 ppm TDS Plant recovery: 40% Process water quality: < 25 ppm TDS Potable water quality: ppm TDS Completion of a reverse osmosis (RO) based seawater desalination plant producing 8,000 m 3 /day of industrial process water and 12,000 m 3 /day of potable water, thus contributing substantially to a continuous water supply at Sohar Industrial Port Area, Sultanate of Oman. 6

7 Objectives Ensuring reliable operation even during difficult raw water intake conditions such as red seawater tides Continuous RO water production Low life cycle costs SEAWATER INTAKE SYSTEM A 2.6 km, 800 mm diameter pipeline feeds the plant through a tap off from an existing cooling water pump manifold. Two 300 micron automatic self-cleaning filters are installed midway through the pipeline. PRE-TREATMENT Microfiltration to handle inlet TSS up to 80 ppm obtaining at the output SDI of less than 1 (input SDI 35+). Configuration: 7 Skids, each with 80 modules and 420 m 3 /h capacity. DESALINATION Sea- and brackish water RO 3 units: 12,000 m 3 /d, double-stage Seawater RO 2 units: 8,000 m 3 /d, single-stage ENERGY RECOVERY SYSTEM Pressure exchanger POST-TREATMENT 1. Post-treatment for ph adjustment and disinfection of potable water. 2. Neutralization system for brine. Reduced energy consumption With its hybrid membrane system (high- and low-rejection) WABAG has met the stringent quality of product water with optimized energy consumption. Energy recovery devices are deployed to extract power from the SWRO reject stream. Modern design reduces costs In general terms, the employment of a modern process design and in particular the direct combination of microfiltration as a pretreatment with reverse osmosis plant without additional cartridge filters and feeding pumps between MF and RO, has resulted in lower investment and operational costs. In addition, the plant footprint is smaller than that of conventional RO desalination plants. Further references SEAWATER Muscat, Oman OPWP Al-Ghubrah: 192,000 m 3 /d, potable water, EPC, start-up: 2015 Ras Laffan, Qatar PUNJ-LLOYD, 12,000 m 3 /d, process water, EP, start up:

8 Nemmeli SWRO, Chennai, India Reverse osmosis to boost drinking water supply volumes. Best practice references Clean drinking water for one million people in Chennai. A complete solution. Client: Chennai Metropolitan Water Supply and Sewerage Board (CMWSSB) Contract type: DBO - Design-Build-Operate Start-up: 2013 O&M period: Raw water: seawater Product: potable water Capacity: 100,000 m 3 /d Main parameter: 43,000 ppm TDS Plant recovery: 40% Process water quality: < 25 ppm TDS Potable water quality: ppm TDS From the sea to the tap. Using technological competence and professional management. WABAG was awarded a contract for the design, construction and operational management of one of India s largest seawater RO desalination plants. The plant was built on a 16-hectare site 40 km south of Chennai and converts seawater into fresh potable water, which is supplied to one million people in the city s southern suburbs. Further references BRACKISH WATER Al Wasia, Saudi Arabia: 200,000 m 3 /d, potable water, start-up: 2010 Al Kharj Saudi Arabia: 50,000 m 3 /d, potable water, start-up: 2009 SEAWATER Duqm, Oman: 6,000 m 3 /d, potable and process water, DBO, start-up: 2010 SEAWATER INTAKE SYSTEM Pipeline (1,600mm diameter, HDPE, length: 1,050m, sea-side depth: 14.1m) Maritime intake filter Intake chamber (upflow filter and sedimentation tank) PRE-TREATMENT Disc filters, ultrafiltration ENERGY RECOVERY SYSTEM Pressure exchanger DESALINATION Reverse osmosis (spiral-wound polyamide) POST-TREATMENT Remineralisation system: carbon dioxide absorber and limestone filter Degasser tower 8

9 RO for water recycling at the Panipat Refinery, India Closing the water cycle. Highly efficient water recycling plant for a refinery expansion. A sustainable solution. Best practice references Client: Indian Oil Corporation Ltd. (IOCL) Start-up: 2006 Raw water: Product: Capacity: Technology: Plant: secondary refinery effluent and various refinery/petrochemical process effluents boiler feed water and process water for PTA production 21,600 m³/day multi-stage treatment including ultrafiltration and reverse osmosis water recycling plant Main parameter: TDS: 1,786 mg/l, silica: 98 mg/l, COD: 150 mg/l Plant recovery: 90% WATER QUALITY after RO: TDS: 12 mg/l silica: 0.09 mg/l COD: 0 90% water recovery. after demineralisation: TDS: < 0.05 mg/l silica: mg/l Completion of a tertiary treatment plant (TTP) for the refinery effluent recycling for the Indian Oil Corporation Ltd., in Panipat, India with the aim of achieving zero liquid discharge in combination with the recycling of wastewater for reuse as boiler feed make-up water. It is the first plant of its kind in India. Further references Paradip Refinery, Orissa, India: 54,000 m 3 /d, process water, start-up: 2015 Panipat Naphta Cracker Project, India: 20,900 m 3 /d, boiler feed water, start-up: 2009 Essar Oil, India: 9,600 m 3 /d, cooling and boiler feed water, start-up: 2011 Sustained focus on zero liquid discharge (ZLD). High-rate clarification Pressure sand filtration Ultrafiltration (UF) pressure-driven, hollow fibre system Cartridge filter Reverse osmosis (RO) two-pass system in combination with a brine concentrator, 3 stages Degasser tower Demineralisation: RO permeate is polished by mixed bed, ion exchange filters 9

10 Thermal Desalination technologies Multi-effect distillation Thermal desalination (multi-effect distillation) takes place in a series of vessels (effects) in which the principle of condensation and evaporation at reduced ambient pressure is applied. This permits the saline water to undergo boiling without the need to supply additional heat after the first effect. Thermal desalination the advantages Stable and proven process Minimal or no need for pre-treatment High output water purity level ( 10 ppm TDS) Ideal in combination with power plants Simple operation with low maintenance costs Achieving synergy - MED The MED desalination process is normally used for medium-sized and large-scale thermal desalination plants where thermal energy is available in the form of low-pressure steam ( 0.3 bar abs.) or waste heat, e.g. in combination with thermal power plants or industrial complexes. It therefore represents the most economic distillation process from an energy efficiency perspective. Main advantages The MED process operates at low temperatures with high thermal efficiency, providing: Low thermal energy consumption Low operating costs Selected references AVR, Rotterdam, The Netherlands: 24,000 m 3 /d, process water CMI, Marmara, Turkey: 3,360 m 3 /d, process water MED-TVC - enhanced efficiency Standard MED plants are equipped with thermal vapour compressors for enhanced efficiency. As a rule, the TVC desalination process is employed for small to large-scale thermal desalination plants where thermal energy in the form of medium pressure steam (>3 bar) is available, e.g. in combination with thermal power plants or industrial complexes and this results in low operational and investment costs. Therefore, from cost-efficiency standpoint, TVC distillation is the most advantageous, steam-heated process for medium-sized plants. Main advantages The TVC process operates at low temperatures with high thermal efficiency, providing: Small to large train sizes Low investment costs Selected references Tobruk, Libya: 13,333 m 3 /d, potable water, start-up Suralaya, Indonesia: 6,000 m 3 /d, process & potable water, start-up: 2010 Rembang, Indonesia: 6,000 m 3 /d, process & potable water, start-up: 2010 GMDC, Kutch, Gujarat, India: 2,400 m 3 /d, process water, start-up: 2006 Benghazi North, Libya: 4,800 m 3 /d, process water, start-up:

11 MED-MVC - the stand-alone solution Where an external steam source is unavailable for heating, standard MED plants are equipped with mechanical vapour compressors (MVC). These provide heat for water evaporation through mechanical steam compression. The MED-MVC desalination process is normally used for small to medium scale thermal desalination plants where thermal energy is unobtainable. The mechanical compressor is electrically or diesel driven. Main advantages No need for external thermal energy A robust process Multi-stage flash (MSF) - large-scale thermal desalination technology MSF - the big solution. The MSF desalination process is utilised mainly for large-scale, thermal desalination plants where thermal energy in the form of low-pressure steam (>2 bar) is available, e.g. in combination with thermal power plants or industrial complexes. Saline water is heated by steam and then fed into a series of vessels (effects) where reduced pressure leads to immediate boiling (flash) without the need for additional heat. Main advantages Large train sizes Low energy consumption MED XL and XXL Recently, the capacity of thermal seawater desalination units has begun to increase considerably. In response to this trend, WABAG has designed and optimised its XL (in the range of 13,500-25,000 m 3 /d) and XXL units (from 25,000 up to 45,000 m 3 /d). In these newly developed systems, all the preheaters are enclosed in an extremely compact manner, which not only prevents heat losses, but also guarantees highly efficient operations. These large units can be built as MEDs or MEDs with thermal vapour compressors (MED-TVC). Selected references Burrup Penninsula, Australia: 3,600 m 3 /d, process & potable water CHP, Taba, Egypt: 2,000 m 3 /d, potable water Selected references REFURBISHMENTS Khoms, Libya: 30,000 3 /d, process water, start-up: 2008 Zliten, Libya: 30,000 m 3 /d, potable and process water, start-up:

12 WABAG offers sustainable solutions for: Drinking water treatment Industrial and process water treatment Water reclamation Sea and brackish water desalination Municipal wastewater treatment Industrial wastewater treatment Sludge treatment Operations & Maintenance (DBO, BOT, BOOT) After Sales Services Commissioning Construction Conceptualizing Financing WABAG is one of the world s most innovative water treatment companies with know-how in specific technologies and in-house developed processes such as: Biofiltration BIOPUR Moving bed biology FLUOPUR Activated sludge Hybrid, SBR, processes MICROPUR-CAS Membrane bioreactor MARAPUR, MICROPUR-MBR Membrane filtration RO, MF, UF, NF CERAMOPUR, CERAMOZONE Denitrification BIODEN, ENR Oxidation processes ADOX, BIOZONE Adsorption processes CARBOPUR, PACOPUR Thermal desalination MED, TVC, MVC, MSF MED XXL Fine sieving MICROPUR Deep bed filtration in various designs Anaerobic sludge digestion including advanced energy recovery The WABAG Group represents a leading multinational player with companies and offices in 20 countries and a focus on emerging markets in Eastern Europe, Africa, LATAM, Middle East, South East Asia, China and India. Equipment supply WABAG Vienna WABAG Chennai Headquarters Engineering Design sustainable solutions. for a better life. VA TECH WABAG LIMITED WABAG House No.17, 200 Feet Thoraipakkam Pallavaram Main Road Sunnambu Kolathur Chennai , India Tel.: wabag@wabag.in VA TECH WABAG GmbH Dresdner Straße Vienna, Austria Tel.: contact@wabag.com