Untitled

T he presented study demonstrates that the outlined modelling concept for membrane bioreactors could successfully be applied to describe the system behaviour of a pilot-scale wastewater t r e a t m e n t plant, e q u i p p e d with m e m b r a n e f iltration units. In particular, the model describing f iltration performance of submerged capillary holl ow fibre membranes could be applied to reprod uce the characteristic decrease of membrane perm eability. The semi-empirical model works with a small number of parameters and correspondingly n eeds only a small number of potentially relevant p arameters. Nevertheless the main trends in perf ormance development can be described and the i mportance o f chemical cleanings can be highl ighted. D ue to the structure of the Elman ANN the f lux and its decay could be modelled with high a ccuracy. In the light o f the large number of param eter variations, which were done, the average d eviation o f 2.7% is very good. The combination o f running a pilot plant with structured parameter v ariation and ANN modelling is a powerful tool f or design and optimisation of plants. Some inter esting aspects o f submerged membranes were d iscovered by a sensitivity analyses. The dominant e ffect of back wash pressure for stability of flux is possibly an aspect which operators of membrane p lants and even membrane designers should take m uch more into consideration. T he next step in the ongoing research will be an integration of the two modelling approaches in a hybrid-model consisting of a semi-empirical b aseline structure to incorporate some fundamental, t horoughly validated concepts (e.g. concentration p olarisation) and ANNs to estimate model paramet ers on basis o f the full set of available data. At t he same time the ANN results indicate that some p rocesses have to be investigated in more detail ( e.g. back-pulsing) and a fundamental unders tanding o f the underlying processes have to be d eveloped.