Aerobic treatment of digestate in the liquid phase

Since June-1-2005 in Germany residual waste is not to be deposited without an adequate treatment. To comply with the statutory stability criteria of the waste disposal order on the one hand thermal or on the other hand mechanical biological waste treatment is used. In Germany about a fourth of the emerging residual waste is treated mechanical biological by now. The anaerobic treatment of solid waste components gains biogas (methane) which can be used energetically and subsequently the energy can be used by the treatment plant itself to minimise the specific ecological and economical load of the plant. About 70 percent of the plants use a conventional rotting process like tunnel composting, tabular windrows or simply open rotting.

 Depending on the installed rotting process technology more or less energy is needed to treat the material. The energy efficiency of these rotting processes is low because the retention time (about 4 to 6 weeks) and the place requirements are high. In the course of the appreciation of renewable energy sources according to a sustainable climate protection and resource conservation the energy efficiency of the MBT-plant became more and more important. Improving several treatment components the energy efficiency of the whole plant can be increased. For this reason a new technology of the aerobic treatment process is developed. As an alternative to the conventional rotting process with dried digestate, the aerobic treatment can take place in the liquid phase. For this purpose the suspension will not be dried after the fermentation but directly conveyed into a basin where it is aerated and fully-stirred. This concept was developed on the basis of wastewater treatment methods aiming for costs- an energy saving as well as a reduction of exhaust air emission due to shortened treatment periods and last but not least less place requirement. Because it is a new technology and about only 15 % of the MBT-plants have installed this technology less experience exists. This results in a high research potential. Therefore the TU-Braunschweig (TU-BS) does lab scale and semi industrial tests. Comparing these results with results of a scientifically and technically monitored German MBT plant optimization potential of the process control unit can be identified. Currently the inducement of the tests is to verify the results of the new developed semi-industrial testing facility with results of the lab scale tests. The main focus of the analysis is the influence of the aeration ratio and retention time on the degradation performance of biochemical relevant parameters. Low aeration ratio causes low costs and less emission which will decrease the energy consumption of the whole facility.



Copyright: © DGAW - Deutsche Gesellschaft für Abfallwirtschaft e.V.
Quelle: 1. Wissenschaftskongress März 2011 - Straubing (Juni 2011)
Seiten: 7
Preis: € 3,50
Autor: Dipl.-Ing. Oliver Kugelstadt
Prof. Dr.-Ing. Klaus Fricke
 
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