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Membrane distillation desalination for small-scale fresh water supply

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Membrane distillation desalination for small-scale fresh water supply

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In this project, the membrane distillation (MD) process was optimized with respects to membrane fouling, energy consumption and process efficiency. Both experimental and simulation works were approached in the project.

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Desalination is the process to remove salt from saltwater to obtain fresh water. Saltwater can be seawater and brackish water. Salinity (i.e. the dissolved salt contents) is a key property to classify saltwater. While seawater has global average salinity of around 35,000 mg/L, the salinity of brackish water is in the range from 1,000 to 15,000 mg/L.

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Desalination has been a workable solution to fresh water scarcity in the world

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Desalination has been a workable solution to fresh water scarcity in the world

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Seawater has been a source of fresh water supply in many countries around the world with the available desalination technologies. Given technological advances, the cost of fresh water produced from seawater via desalination has been reduced markedly in recent decades, making desalination a feasible means to provide fresh water. Desalination technologies are divided into two groups: thermal distillation and membrane processes. Thermal distillation technologies are multi-effect distillation, multi-stage flash, and mechanical vapor compression. Membrane processes include reverse osmosis (RO), electro-dialysis (ED), forward osmosis (FO), and membrane distillation (MD).

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Desalination is a well established method of removing salts from water in order to produce process water, ultrapure or potable water. This is accomplished through using membranes (reverse osmosis and nanofiltration) and thermal processes (multi effect distillation, evaporation and crystallisation).

This mainly involves the production of freshwater from saltwater by introducing energy to pump the water through a semi-permeable membrane or a heat source for evaporation. It can also be used to recover valuable products for the manufacturing industry.

The different water qualities can be produced by a selection of systems including membrane or thermal technologies designed to treat industrial or municipal wastewater, seawater, brackish groundwater, surface water or potable water. The alternative solutions include:

Membrane processes - reverse osmosis and nanofiltration

Thermal processes - multi effect distillation, evaporation and crystallisation technology

Of the world's total water supply, only 3% is fresh water. Seawater constitutes the remaining 97%. With Veolia Desalination technologies, seawater is converted to process water for industry and potable water for municipalities. Complete the enquiry form to get more info on our desalination technologies.
Almost one quarter of the world's population lives within less than 25 kilometres of the coast and seawater covers 71% of earth's surface. Desalination therefore presents an effective solution to the challenges of rapid population and economic growth that are leading to water shortages. Veolia Water Technologies has over 100 years of desalination experience dating back to the first thermal desalination units in 1890.

Processes & Technology

Reverse osmosis (RO)

Multiple effect distillation (MED)

Multi-stage flash (MSF)

Hybrid systems using thermal and reverse osmosis

Selection of the most appropriate solutions

The development of the technologies over the last ten years has reduced capital, operating costs and especially the energy consumed.

However, the careful selection of the most appropriate solution depends on the source of the feed and the treated water quality required so that the costs and environmental impact of the solution can be minimised.
Approximately 15% of the world's desalination plant capacity was designed and constructed by Veolia internationally. Veolia - we know water! Contact us to speak to a Veolia expert about your desalination technology needs.
Membrane solutions

Membrane desalination processes are typically applied to treat water with a lower dissolved salt content as they are less energy intensive than equivalent thermal processes. Recent improvements in energy recovery systems have increased performance of membranes and pre-treatment processes. In addition, high efficiency process designs have led to a reduction in energy consumption, while still maintaining a high product water quality.

Reverse Osmosis (RO)

RO involves pushing water under pressure through a membrane that lets through the water but retains the salt and other impurities.

Membrane separation processes are used for:

Desalination of seawater

Production of process and potable water

Polishing and demineralisation of boiler feedwater and pharmaceutical water

Rehabilitation and recycling of process and municipal effluent

As part of an integrated zero liquid discharge process

Thermal solutions

Thermal desalination processes are best applied to water and process streams with a high dissolved salt content, where the applied pressure required for an equivalent membrane system would be excessive. The use of a low-cost energy source, such as available from co-generation power plants, is advantageous with respect to reducing energy cost, if available. Another option is to use low temperature, high-efficiency vacuum evaporation systems that can be operated on waste heat and a low electrical energy demand.

Various Multiple Effect Distillation Configurations

Multiple Effect Distillation (MED)

Multiple Effect Distillation with Thermal Vapour Compression (MED-TVC)

Multiple Effect Distillation with Mechanical Vapour Compression (MED-MVC)

A Multi Effect Desalination MED unit is an evaporator where sea water is evaporated in one or more ( up to 14 ) evaporation stages at low temperature ( < 70°C ) in order to produce clean distillate water.

MED process is designed to produce distilled water with waste heat from power production or chemical processes, and to produce potable water.

Previous Projects

Veolia Water Technologies, parent company of Veolia South Africa and world leader in water treatment, has reference sites across the globe, most notably in Israel, Australia and Spain.

Veolia South Africa has used this technology for various projects:

I'm interested in achieving process and / or potable water through desalination technologies

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Desalination is a well established method of removing salts from water in order to produce process water, ultrapure or potable water. This is accomplished through using membranes (reverse osmosis and nanofiltration) and thermal processes (multi effect distillation, evaporation and crystallisation).

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Fresh water scarcity is a real challenge to Vietnam and many other developing countries.

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People access clean water in Tà Lùng Commune, Điện Biên District in the northern mountainous province of Điện Biên. The country will conduct more studies on water and environment safety to tackle challenges in the field. - VNA/VNS Photo Trần Việt

Viet Nam News

HÀ NỘI - With a growing population, increasing demand for water and the negative impacts of climate change, Việt Nam faces major challenges in ensuring water security.

Now is the time for the country to speed up studies on water security and environmental security to develop a legal framework and solutions to tackle the challenges, said director of the National Centre for Water Resources Planning and Investigation Triệu Đức Huy.

According to the Ministry of Natural Resources and Environment (MONRE), Việt Nam now has about 830-840 billion cubic metres of surface water, some 63 per cent of which originates in neighbouring countries upstream.

This means Việt Nam's water security heavily depends on actions taken on international rivers like Hồng (Red) River or Mekong River, said deputy minister of MONRE Lê Công Thành.

He added neighbouring countries upstream of the rivers tend to exploit the water resources, creating more pressure on Việt Nam's water security.

Within the country, rivers and lakes have suffered from the negative impacts of socio-economic development, with many bodies of water now being polluted.

Water resources for daily use and livelihood have sharply decreased and even disappeared in some localities as increasing demand for water has not been in line with proper measures for water resource protection and water use efficiency.

In addition, the country has underground water reserves of about 63 billion cubic metres per year.

About 80.6 billion cubic metres of water is exploited and used in Việt Nam yearly. Of the exploited water, more than 80 per cent is used for agricultural production.

Meanwhile, about 60 per cent of Việt Nam's surface water is in the Mekong Delta, some 20 per cent is in Red River and Đồng Nai River, and most of the water availability is in the rainy season.

During dry season, which lasts between six and nine months in Việt Nam, water volume accounts for only 20-30 per cent of total water volume of the year.

The difference of water availability by time and geography causes water scarcity and water shortages in dry seasons.

A view of the DNP Bắc Giang Clean Water Plant. With capacity of 80,000cu.m per day and night, the plant is expected to meet the increasing demand for water in the province. - VNA/VNS Photo

Director of the National Center for Water Resources Planning and Investigation Triệu Đức Huy said that in 2008, MONRE issued regulations on underground water protection, including criteria to identify areas where underground water exploitation is allowed or banned.

However, few localities nationwide have identified areas where underground exploitation is restricted or banned.

Meanwhile, overexploitation or exploiting underground water without planning have caused land subsidence in Hà Nội, HCM City and some areas in the Mekong Delta.

"To ensure water security in a changing era, Việt Nam needs to speed up studies on the issue so that it could have better legal framework and solutions for managing and responding," Huy said.

At the same time, the country must improve its capacity in forecasting and early warning about the impacts of works built on major rivers' upstream of the country, for example, drought or saltwater intrusion, he said.

"It is also necessary to develop water resources planning for Mekong Delta region and implement planning under climate change scenarios and water exploitation activities by countries on river upstream," Huy said.

Hoàng Văn Bẩy, head of MONRE's Department of Water Resources Management, told Vietnam News Agency that in 2012, the National Assembly approved the amended Law on Water Resources, adding regulations on water resources protection.

The country also has a national action plan to improve efficiency in water resources management, protection and usage from 2014 to 2020.

Bẩy said water resource management faced difficulties, for example, water resources planning is slow, there is a lack of databases and illegal underground water exploitation is rampant.

Bẩy said that MONRE has proposed a plan on water resource surveys to the Prime Minister.

The plan includes surveys and assessments on the country's surface water and underground water, expected to help produce a national report on water resources every five years.

The ministry also expects to complete and start a surveillance system on the operation of about 70 major reservoirs on basins of 11 rivers nationwide.

Another surveillance system is expected to work to control water exploitation and wastewater release into water resources.

"It is expected that by 2050, water resources surveys and studies could provide sufficient data to help manage, exploit, use and protect water resources sustainably," Bảy said. - VNS

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Việt Nam faces challenges in ensuring water security

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People access clean water in Tà Lùng Commune, Điện Biên District in the northern mountainous province of Điện Biên. The country will conduct more studies on water and environment safety to tackle challenges in the field.

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Dr. Hung's research on membrane technologies for desalination

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Dr. Hung's research on membrane technologies for desalination

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Pilot scale investigation of the membrane distillation process for seawater desalination.

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Pilot scale investigation of the membrane distillation process for seawater desalination.

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Evaluating energy consumption of air gap membrane distillation for seawater desalination at pilot scale level

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Optimizing the small-scale seawater membrane distillation desalination for improved process efficiency.

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Optimizing the small-scale seawater membrane distillation desalination for improved process efficiency.

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This project optimized the MD process with respects to membrane fouling, energy consumption, and process efficiency.

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Optimising thermal efficiency of DCMD by brine recycling