Rubbing salt into the wounds

As if the tsunami victims don’t have enough to contend with, sea water has rendered their water supplies useless and no technology is available to combat the problem. Andrew Lee and Julia Pierce report.

Those battling to help the survivors of the Asian tsunami face a formidable list of enemies including famine, disease and devastated buildings and roads.

But in the immediate aftermath of the disaster a less obvious foe can wreak havoc on stricken communities. Its name is salt, and those involved in the international relief effort are bemoaning the lack of a quick and easy desalination technology able to deal with it.

Many of the outlying coastal communities hit by the floods lack anything approaching a modern drinking water system and rely on nothing more advanced than a well or a spring for their supplies. Once overwhelmed by seawater, these wells are rendered effectively useless as drinking water sources until they can be cleaned and replenished by rainfall or another salt-free source.

Bob Reed of the Water Engineering and Development Centre (WEDC) at Loughborough University said desalination is a major headache for remote areas after floods. WEDC is a world-leading centre for research into water supply and sanitation, and Reed spoke to The Engineer about the difficulties facing the relief effort days before flying to Sri Lanka to help advise the World Health Organisation on what needs to be done.

Reed said that if — as is likely — the natural springs used by communities have been damaged or even swept away, restoring wells to usability will be crucial. ‘A major focus will be on cleaning out the water sources,’ said Reed. ‘If the good water has been contaminated with seawater, we’re going to have a problem.’

A large part of that problem lies in the limitations of available desalination technologies. These are almost all geared towards the type of industrial-scale desalination plants common in the Middle East and Mediterranean and now planned for southern England.

Reverse Osmosis (RO), the process at the heart of most desalination systems, is massively power-hungry and currently requires an engineering infrastructure akin to that of an oil refinery to support it. Even the ship-borne desalination units sent to help the tsunami relief effort are likely to prove of little help to the type of remote communities referred to by Reed, where cleaning up a single well can be all important.

‘I don’t know of any simple technology for low-cost, low-energy desalination,’ said Reed. ‘A lot of money is spent on research into desalination worldwide, but I haven’t seen anything that is applicable to a situation like this.’

But as Reed and his colleagues begin the considerable challenge of getting Asia’s coastal communities back on their feet, they may be heartened by the implications for future relief efforts of a research programme underway in the US. There is little reason for him to have been aware of it, as the agencies involved are far removed from those usually associated with humanitarian relief. They include the US Navy, NASA and the US Army’s Tank Automotive Research Engineering Centre.

The project in question is the Expeditionary Unit Water Purification (EUWP) programme, dedicated to researching new technologies that can provide the US military with safe drinking water from low-energy, low-cost systems down to the level of a handheld device that can be used in emergencies.

Desalination is a key part of EUWP. ‘Long term we are seeking to discover disruptive technologies that will dramatically reduce the costs and energetics for desalination,’ said the US Office of Naval Research (ONR) in a statement on the aims of the project.

EUWP has already handed out a number of grants to companies and universities to investigate technologies that could achieve this aim, with the prospect of up to $500,000 (£267,000) worth of support for other relevant research initiatives. A significant amount of this effort will focus on the membrane that lies at the core of the RO process.

Membranes can be configured in various ways and be composed of differing materials depending on the context in which they are to be used.

EUWP has commissioned Santa Fe Science and Technology (SFST), a New Mexico R&D specialist, to research the use of electrically conductive, hollow-fibre membranes for RO of seawater. SFST is seeking to develop a membrane with a higher surface area than conventional systems, allowing water purification at significantly lower energy levels and with an electrical conductivity that improves salt rejection. Its ultimate objective is to develop a high-throughput RO membrane capable of producing a litre of fresh water from a saltwater source in 15 minutes.

Other areas under investigation by EUWP include the use of thin-film composite membranes and the application of ozone to increase the efficiency of desalination and purification.

EUWP’s initial goal is to produce two technology demonstrators. The first will be based on existing technology and capable of purifying 100,000 gallons of water per day. The second aims to increase this to 300,000 gallons. The short-term applications are certain to be military or connected to the treatment of water during space travel. But five to 10 years down the line the research may be the best hope for providing the type of local desalination system the world’s aid agencies need in situations such as the present disaster.

The US Marine Corps has already set out its wish-list. It has asked the ONR to develop a system so small and light that individual troops can carry it into combat. Known as the Individual Water Purifier (IWP), the envisaged modular device would be able to clean and desalinate water to a high standard. The desalination element would weigh less than 2lb and be capable of quickly producing a litre of purified water from a saltwater source.In the current climate of high US defence spending the marines tend to get the technology they want. But in this case future victims of catastrophic flooding may be among the beneficiaries.

Aside from the filtering technology itself, providing power to desalination systems represents another headache for relief workers. As with the portable military system, the renewable energy community may be able to help future victims in ways unavailable now.

Following the tsunami the International Solar Energy Society is to set up a task-force aimed at developing a simple, solar-powered desalination system for use in disaster areas. This will be able to produce a reliable source of clean water even when power supplies have been destroyed.

The society’s president, Yogi Goswami, a professor of mechanical engineering at the University of Florida, has developed a solar-powered unit that uses a gravity-induced vacuum to desalinate water. However, slow commercial progress has meant that the technology, though highly efficient, will not be ready to help those affected in Asia. Goswami hopes the clear benefits of the system in disaster situations will give added impetus to commercialisation.

‘We have a working unit that could be used, but unfortunately no one is making them,’ he said. ‘We are sorry that we have nothing to offer now, but it is the ideal time to attract entrepreneurs and allow commercial products to be produced so we are ready in the future.’

Sidebar: ComMs for aid workers

Aid agencies deployed to remote areas often face damaged or non-existent communications lines. But tsunami aid workers in Indonesia and Sri Lanka are pioneering a portable hub that shares internet and phone access over a local area via a wireless link to a satellite signal.

Nethope, a consortium of aid agencies, and telecoms companies Cisco, Inmarsat and CGNET switched on the Net Relief Kit device in Banda Aceh last Sunday, and up to eight more are being flown out to affected regions. Field trials of the NRK had been planned, but the tsunami meant the NRK’s first test will be for real, he said.

Fran Boon, an Oxfam engineer who helped build the communication hub said compared with conventional satphones the NRK is cheaper and faster and allows computers and phones within 100m to access a satellite signal.