GEOCHEMICAL ENGINEERING - TAKING STOCK

Geochemical engineering makes use of optimized geochemical processes f or I:he solution of environmental problems. It has developed in a few years from a collection of unrelated scientific and technological inci dents into a coherent concept about how and where we can improve our g eo-environment. All solutions to problems of pollution are based on ne utralization/breakdown, concentration, dilution, isolation or immobili zation, which serve to eliminate the pollutant, make it more manageabl e, or prevent its entry into the mobile phase, usually water, from whi ch it can affect the biosphere. All of these solutions have their coun terpart in nature, where many examples are found of high concentration s of potentially harmful substances. A major prerequisite of geochemic al engineering solutions is that they should be compatible with the na tural evolution of the system in its geo-environment. The advantages o f this approach are that we can devise low-cost technologies (nature d oes most of the hard work itself), interfere least with nature, and qu ite often end up with useful by-products. Disadvantages are that techn ologies based on natural geochemical processes tend to be slow. The ap plication of geochemical engineering concepts requires a better unders tanding of our environment and its ongoing processes than is necessary for a 'classical' technology. In most environmental technologies the conditions are externally imposed on the system to be treated, and the natural evolution of the system is eliminated, or at best neglected. The concept of seeking a closer conformity with nature is paralleled i n other disciplines like agriculture or the medical sector, where we s ee a similar evolution in the direction of techniques that are more in harmony with nature. Geochemical engineering brings many advantages, particularly in developing countries, or in countries where the state of the economy does not permit the introduction of expensive high-tech environmental technologies. So far, most of the applications of geoch emical engineering concepts have focussed on solutions to environmenta l problems, but there ale a number of cases where the environmental is sue is more indirect, as e.g. in civil engineering. Geochemical engine ering may be practised on a large, almost global scale, down to that o f individual minerals, in accordance with the fact that geochemical pr ocesses also act on vastly different scales. An overview will be given of some of the problems that are being studied. (C) 1998 Elsevier Sci ence B.V. All rights reserved.