Innovations galore but do not forget common sense
There has been an explosion of innovative desalination technologies in the past few years thanks to the growing scarcity of clean water. In the beginning, it was confined to the oil-rich Gulf countries which had plenty of cheap energy to extract water from the sea.
But swelling populations, wasteful irrigation, over-consumption, distorted pricing and generally poor management have led to a situation where water supplies struggle to keep up with demand. Thus, desalination can no longer be dismissed as an expensive option to be considered in some distant future, not even by developing countries. It is becoming an important component of the water security of nations.
While thermal distillation technologies such as multi-effect distillation and multi-stage flash reign in the Gulf countries, membrane technologies such as reverse osmosis as well as hybrids are gaining markets in other parts of the world. Along with mature desalination technologies, there are now many fledgling ones, which are at various stages of evolution, some drawing on alternative or waste energy and others distinguished by newly engineered materials. Among these are membrane distillation, forward osmosis, nano-engineered membranes, aquaporins, carbon nanotubes and solar desalination.
Most of the new technologies are presently not suitable for large, municipal applications. For example, the Memstill developed by the Dutch government requires a source of low cost (waste) heat or an application in co-generation which may not always be available.
Solar desalination faces the challenge of achieving the optimum temperature difference between the solar-generated vapour and the seawater-cooled condenser in order to maximise the reuse of latent heat of condensation. However, IBM is working with Saudi Arabia’s national research group to combine ultra-high concentrator photovoltaic cells with nanomembranes to create a solar-powered membrane desalination system, which might be a better option than direct solar desalination.
Some years back, a minister from the Indian government inaugurated a floating (pilot) desalination plant based on the concept of ‘low temperature thermal distillation’. The system was able to bring down total dissolved solids from 35,000 parts per million (ppm) to 10 ppm. The minister was confident that floating desalination plants would soon help to deliver freshwater to coastal towns in India at minimal cost. That confidence seems a trifle misplaced but it is interesting to see the spurt of technological innovation spreading across water-scarce countries.
Innovations have their importance, but let us not forget that there is no alternative to good management based on common sense. It makes little sense to have state-of-the-art desalination plants while wasteful irrigation takes away the bulk of water, while half the urban distribution pipes are leaking, while the poor stay unconnected from pipe networks and while utilities have no autonomy to even recover their operation costs.