Five billion people, at present the world population, inevitably affect the quality of the environment. The general public in an increasing number of countries is getting more and more concerned about this deterioration in quality. As a result many people cast doubts upon the desirability of the increase in energy consumption, the production of superfluous goods, ever-growing waste flows, harmful emissions of industrial processes, and so on. Actually, no one can simply ignore these issues. For instance, the authorities could introduce more environmental legislation aiming at a healthy environment; industries could change to cleaner production processes; the public at large should assume an even more conservation-minded attitude rather than confine themselves to shaking a finger at 'the industry'. In short, in all sectors of society there are often numerous ways and means of curbing environmental pollution. Clearly, environmental technology - the development and application of techniques to identify, quantify and reduce environmental problems - can make a substantial contribution here in many situations. Until now a large number of such new techniques have been developed. Many of these techniques not only appear to add greatly to reducing the burden on the environment, they sometimes also offer interesting economic advantages (savings in raw material and energy, etc.).