Final Report 2005 Preliminary investigations for the Margaretenhöhe MBR demonstration plant

Final Report 2005 Preliminary investigations for the Margaretenhöhe MBR demonstration plant

As part of the EU-Life ENREM demonstration project the Department of Chemical Engineering, TU Berlin, was appointed to conduct the preliminary pilot trials in a representative site for verification of basic process design and operation criteria of the full-scale MBR demonstration plant. In addition to conception and construction of the pilot plant, this investigation consisted of two successive trial phases with distinct operation conditions. The first one was dedicated to the assessment of the “irregular sludge removal strategy” (the biomass is accumulating in the reactor, which is partly emptied when the sludge concentration reaches a given value). In the second trials phase normal operation conditions with daily sludge wastage were implemented with 28,5d SRT. The major outcome of the trials was that COD removal, enhanced biological phosphorus removal and the post-denitrification performed a similar way under both operational conditions. The denitrification rate was approximately 1 mgN/(h goTS). An influence of the anaerobic sludge loading on the post-denitrification rate was observed with higher rates (up to 4 mgN/(h goTS)) corresponding to higher organic loading. An influence of storage compounds built up in the anaerobic phase is assumed. Nitrification was better in the second phase when 4 mgN/(h goTS) were constantly reached while nitrification was unstable with an average of 2 mgN/(h goTS) in the phase of irregular sludge removal. The aerobic and anoxic reactors were enlarged during the regular sludge withdrawal phase by 23% resulting in 35d SRT. This led to a better COD removal and slightly better nitrogen removal. The enhanced SRT produced possibly a deterioration of biological P removal due to overloaded poly-P storage. A second possible reason is the massive reproduction of sludge worm Tubifex tubifex, which was observed after the plant enlargement. Different strategies to reduce the worm population were attempted. Ammonium dosing had no success. Copper dosing reduced the number of worms significantly but the population grew back after the dosing was stopped. The prolongation of SRT reduced the sludge yield from 0.23 gTS/gCOD at 28.5d to 0.18 gTS/gCOD at 35d.