DESIGN AND DESIGN EV ALUATION OF BIOLOGICAL WASTEWATER TREATMENT PLANTS

Abstract

We are facing a rapid development of more stringent effluent standards and new biological treatment processes during the last decade. At the same time we recognise strong differences between the actual water protection situation in different countries of the world, e.g. between the western and the eastern European or northern and southern American states. We are also aware of a trend towards privatisation of the water industry, resulting in turnkey bids including even operation of the treatment plants. This development results in a new challenge for a scientific based process selection and comparison. One of the basic questions to be answered by international co-operation is: What information is necessary for the characterisation of the specific local problem to be solved, and how can the results of different design solutions be compared in regard to reliability and treatment efficiency? Reliability and even treatment efficiency up to now have not been defined exactly enough for a sound comparison of different treatment processes or sequences of processes. If this problem cannot be solved on an international basis it will be very difficult to base such comparisons on a cost benefit (=water protection) calculation. As a consequence less important and inadequate criteria will play the decisive role. One of the methods to evaluate design procedures and process selections is a scientifically based evaluation of the results from full scale treatment plants. The actual standard of reports in literature on full scale experience is not sufficient to reach this goal in most of the cases. Two schemes try to show the complexity of the design procedure and the evaluation of full scale experience for design evaluation and could be used as a starting point of an international co-operation.