The role of chemicals in this thirsty planet



As all the chemical elements and most of their attributable compounds are known there is little scope for further discovery in the science of ‘inorganic’ chemistry. ‘Organic’ chemistry is much more exiting as it is based on carbon which can polymerise into a multitude of different compounds and different shapes. Because the number of carbon-based molecules is huge and increasing at the rate of 30,000/year, the discovery and development of new carbon compounds is inevitable, and some of these will be useful to the expansion of desalting technology.

The single greatest advance in ‘water technology’ has been the addition of chlorine to drinking water; a breakthrough ranked as one of the greatest scientific achievements of all time. Modern membrane technology is newer than chlorination and although ‘Osmosis’ was recorded by Frenchman Jean Nollet in 1748, it was more than 200 years before ‘Reverse Osmosis’ became practical following pioneering work by Sidney Loeb and Srinivasa Sourirajan. The development of the desalting membrane was a true scientific blend of physics and chemistry.

The cost of desalted water has fallen steadily as desalting technologies became more efficient. This paper reviews what major improvements are due to chemicals and asks the question ‘how much further can we go’? The author feels that the ‘great’ chemical discoveries are in the past and this thirsty planet will need to look elsewhere to sustain our insatiable demand for fresh water as chemicals alone are unlikely to result in a quantum improvement in desalting technology. Although technical knowledge doubles with each generation it is a brave man who will dare to predict what the IDA conference will be discussing just 25 years from now, never mind in 2111?

The paper suggests that the biggest scope for ‘chemical’ improvement in membrane operation is with better cleaning formulations and application procedures. Jointly these will reduce system outage, increase water production and extend membrane life, and above all reduce operating costs. Ideas on improved membrane cleaning are dealt with in some detail assuming that every membrane starts fouling the instant water passes through it. It is not easy to quantify the benefits in changing cleaning procedures from today’s well-entrenched methods. Other chemical aspects of membrane technology are likely to be close to maturity apart from better pre-treatment design and operation and improvements in materials science.

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