KNOWLEDGE-BASED DIAGNOSIS OF SOLIDS-LIQUID SEPARATION PROBLEMS

Often the suspended solids concentration in activated sludge treatment plants may display both large amplitudes and unnaturally fast changes . If the sensor calibration has been found satisfactory, the abnormal appearance has to be explained by the process itself. There may be thr ee principal reasons for such a behaviour: severe hydraulic conditions , poor flee separation properties or very high sludge blanket. During these circumstances it is very informative to qualitatively examine th e relationships between the suspended solids concentration variations and important influencing variables, such as the flow rates and the sl udge blanket level. This kind of knowledge based diagnosis is superior to dynamic models for such odd behaviour. A simple on-line method to perform the diagnosis is presented. The method has been tested on a ma ssive set of data from a full scale wastewater treatment plant in Swed en and shown unexpected good ability to supply early warnings. It is a lso shown that small hydraulic disturbances may purposefully be inject ed into the settler in order to analyse the risk for process failure. Copyright (C) 1996 IAWQ. Published by Elsevier Science Ltd.