THESSALONIKI – A material that acts as a natural filter might be just what is needed to save the country’s rivers, lakes, dams and wetlands from pollution; a material that is in abundant supply in Greece, but has its use restricted. Compared with practice in other countries, it is almost unexploited. Zeolites are a microporous crystalline solid which, due to their physical and chemical properties are suitable not only for improving the quality of drinking water but in cleaning urban, industrial and even radioactive liquid waste. Or so think geology professors at Thessaloniki University. In Greece there are zeolite deposits in several areas, the largest and most commercially viable being in the prefectures of Evros and Rhodope and on the islands of Samos, Milos, Kimolos and Santorini. Professors A. Philippidis and A. Kasoli-Fournaraki have been studying the potential uses of zeolite for some years and propose specific measures in which the mineral, acting as a sponge, can retain harmful substances and improve the quality of water. In certain cases, according to Philippidis, and depending on the quality of the zeolite as well as the elements existing in the water, the minerals can have up to twice the capacity of other materials used for absorbing these substances. Particularly in the governance of aquatic ecosystems, the ion exchange (water softening and purification) capacity of Greek natural zeolites (there are also synthetic ones) ranges from 96 to 216 meg/100g. They are able to absorb considerable quantities of metals, radio-nucleides and organic substances when in aqueous solutions. They can replace up to 20-99 percent of radio-nucleides and 30-53 percent of organic substances. They can also adjust the pH factor of water. In fact, some water filters currently on the market contain zeolite, and it is also used in other sectors such as livestock breeding. In Greece and with regard to the environment, only experimental applications have been made in order to explore the possibilities of this mineral, its saturation point, and its quality and quantity, among other things. In 12 European countries, the US, Canada and Australia, the use of zeolites is widespread, but it is in Japan that the greatest use is made of the mineral. Its use in artificial wetlands and for other water control purposes as well as in farming does much to improve the quality of water supplies, and reduces the leaking of trace elements (toxic soils and pesticides) into the aquatic environment. It also lessens the problem of eutrophy in water and helps conserve up to 50 percent of irrigation water for farming. According to the two professors’ research, presented at a recent conference, the use of Greek natural zeolites in lakes and other enclosed water systems would enrich the water with oxygen and reduce the growth of phytoplankton and seaweed, thereby improving the environment for fish and other organisms. As to why zeolites have not been used to their full potential in Greece, Philippidis believes that the price of Greek zeolites is still rather high, making applications to industry and aquatic systems unprofitable.