Sludge production in membrane bioreactors under different conditions

With membrane bioreactors, the production of surplus sludge is lower than w ith conventional activated sludge systems, a fact that has been confirmed i n a large number of analyses. There is, however, no consensus about the dim ension of the reactions and their respective causes. in order to examine th ese, at the University of Hanover a pilot plant with a capacity of 220 l wa s run for one year without any extraction of surplus sludge. The plant was started with 2 g MLSS/l; after one year, this value had risen to approximat ely 18 g MLSS/l. In order to be able to set the plant for different sludge loads (0.04 to 0.2 kg COD/(kg MLSS(.)d)), the wastewater was artificially s tocked up. The emerging result was that in contrast to conventional systems the sludge growth was lower, but still continuously existing. Then, compar isons with theoretical approaches were run - among others with the ASM1-Mod el - which confirmed the findings. One possible reason could be the differe nt biocoenoses, which was assumed to be the cause after several microscopic examinations had been run.