Advanced water purification system developed

Researchers at King Fahd University of Petroleum and Minerals (KFUPM) and Massachusetts Institute of Technology (MIT) have developed an advanced system to purify water that comes from natural gas wells.
The energy-efficient system will benefit people in developing countries, the researchers said.
Amr Al-Qutub, director of the Center of Research Excellence at KFUPM, said the new Humidification-Dehumidification (HDH) system is significant in the wake of the growing use of natural gas to avoid greenhouse gas emissions.
“The water in gas and oil wells is highly salty and mixed with oil. The new technology developed by our researchers offers a good solution to purify this water.”
He disclosed plans to establish a Saudi company for desalination using the new technology. “It will be the first company in the Kingdom using this type of technology.” The new system will help supply adequate amounts of drinking water to homes and residential districts. More than one device can be installed on a tank, each with a capacity to produce 3,000 to 4,000 liters of water daily.
The research team include MIT's Prakash Narayan, mechanical engineering professor John H. Lienhard V, and collaborators at KFUPM.
The method is a variation of the standard distillation process, in which salty water is vaporized and then condensed on a cold surface; the salt separates from the water during evaporation. This process is energy-intensive — and therefore costly — because the water must be heated to a boiling point, while the condensing surfaces must be kept cold.
In the new process, water well below the boiling point is vaporized by direct contact with a carrier gas; the moist air is subsequently bubbled through cooler water where the purified vapor condenses.
The temperature difference between the warm and cool water is much less than in conventional devices, and the surface area provided by the small bubbles is much greater than that of a flat condenser surface, subsequently resulting in a more efficient process.
Lienhard says, “We became interested in the HDH process at the start of our collaboration with KFUPM as a means of providing water to off-grid regions of the developing world. Both the MIT and the KFUPM faculty wanted to develop a technology that would benefit people all over the world.”
At the beginning of his doctoral thesis research, Narayan was focused on ways “to increase energy efficiency and thermal efficiency, and to reduce the size and cost” for desalination plants. Such facilities are a critical need in parts of the developing world — such as in southern India — that have limited fresh water but abundant seawater.
Conventional distillation plants have efficiencies of scale — the bigger they are, the more cost-effective — but for the HDH system, the optimum size is a plant that produces about 1,200 to 2,400 liters of clean water a day, about the capacity needed for a rural village. Such plants can easily be made larger simply by adding more modules, he says.
Leon Awerbuch, dean of the IDA Desalination Academy in Winchester, Mass., says, “This is a very unique research work leading to much higher-efficiency solutions than conventional HDH, and could have a significant impact in desalination for small and medium systems.”
Solar energy, the desalination of seawater, and other technologies related to the production of fresh water and low-carbon energy will be the focus of a seven-year research and educational program launched between faculty members in MIT’s Department of Mechanical Engineering and KFUPM in Dhahran. The center of research excellence is expected to perform 16 joint research projects and eight joint educational projects over seven years. These joint projects will be funded by KFUPM.