The successful application of membrane filtration on the activated sludge process is a recent development. Two processes are most common: separate modules and submerged modules, with the former being the more promising due to the lower energy consumption. While they allow high sludge ages, conventional sludge ages are equally viable, thus allowing the use of tested and reliable dimensioning techniques. The near perfect solids retention of the membrane filtration, however, can lead to problems with the accumulation of inert solids and heavy metals in the activated sludge. In that area, further research is necessary to develop safe dimensioning methods. (C) 1998 Published by Elsevier Science Ltd. All rights reserved. [References: 7]
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