The fermentation of wastewater has gained increasing importance over the past few years. On the one hand higher organic loads can be treated, technically and economically, by anaerobc treatment. On the other hand it is possible to win back energy with the biogas produced by the fermentation process; a real benefit both economically and environmentally. For these reasons anaerobic wastewater treatment is installed in many industries, such as in the paper, milk and breweries.
One application, for example, is the treatment of wastewater from mechanical-biological solid waste treatment.
In mechanical-biological solid waste treatment high organic loads are washed out of the municipal waste and leave the process in the aqueous phase. The fermentation of this organically highly loaded water takes place in a hybrid fixed bed system where the biological production of biogas occurs in the mesophilic temperature range. The biomass is immobilised by using an internal substrate. The fixed bed process is thereby extremely stable in the face of varying inlet loads that can be quite common when treating solid waste.
A further characteristic of our fermentation system lies in the acceleration of the biological conversion to biogas. An important factor in anaerobic degradation is the size the organic fraction that biologically, is easily accessible, since this can offer significant economic advantages with regards to the size of the plant. Depending on the task at hand, our fermentation systems comprise of an upstream hydrolysis stage which can, if required, be operated under aerobic conditions.
In certain situations the combination of an aerobic and anaerobic environment works to the advantage of the entire biological degradation process. This results in a simultaneous short retention time/high biological degradation and biogas production.
The fermentation process reduces the organic loading of the wastewater (BOD5, COD, organic acids, etc.). Often however, further groups of pollutants (e.g. Nitrogen compounds, hard COD) that are present in the wastewater are not sufficiently degraded. Further treatment for the removal of nitrogen compounds and the remaining organic contamination is therefore installed subsequent to the fermentation process. The combination of anaeobic and aerobic wastewater treatment has been successfully implemented in our company for many years. Our SBR- and membrane bioreactor process work extremely well in this tertiary capacity.