[Ground water improvement in the Ruhr--then and now]

The waterworks founded during the second half of the last century obtained the raw water exclusively from the Ruhr-valley; they were responsible for the water supply of the industrial area situated on the right of the river Rhine. The rapidly growing water demand, limited possibilities in water catchment, the very bad quality of the Ruhr-water and epidemic typhoid fever required new methods in the water supply. Consequently, the Hygiene-Institute of Gelsenkirchen was founded and a new method of water production developed: the artificial ground water recharge. In 1913 two associations were founded: the Ruhrtalsperrenverein responsible for the provision of water quantity, and the Ruhrverband, responsible for the improvement of water quality. These associations formed the essential base for the rapid development of the so-called "Revier". In spite of the excellent elimination of bacteria by artificial ground water recharge-operating according to the principle of slow sand filtration-a disinfection of drinking water with chlorine became necessary; this disinfection was started in 1910 by the waterworks of the Ruhr. The construction of reservoirs and clarification plants ameliorated temporary the overall situation in water resources management. These improvements were, however, destroyed by consequences arising from the rapid economical growth before the second world war and the following break-down. After this period, great efforts were necessary to enlarge the reservoirs and increase the capacity of sewage plants. The waterworks pre-purified the water from the Ruhr before infiltration into the underground in order to increase the quantity and quality of the recharged water. Downstream, the number of sewage plants increased; a more and more refined method of analysis indicates now the pollution load of the raw ater and signalized trends which lead to further treatment measures or to the change of existing ones like substitution of chlorine by chlorine-dioxide. The artificial ground water recharge-because of its many advantages-should always be the nucleus of water treatment of the river Ruhr. For the sake of the natural character of water catchment and in order not to degrade the waterworks to mere "water-manufacturers", we are all requested to handle thoroughly and cautiously water-endangering substances.