The production of biogas from renewable materials and organic waste will play an important role for the renewable energy sector in Germany. Optimal management, control and knowledge of the process are essential for an effective anaerobic digestion. An increasing level of feedstock contamination with pesticides, antibiotics and veterinary disinfectants was recently reported. Therefore, it is essential to ensure that these anthropogenic substances do not negatively impact microbiological processes and the environment.
In this work, laboratory tests were performed to detect the influence of anthropogenic substances on anaerobic digestion. Thus, active ingredients of veterinary disinfectants (quaternary ammonium compounds) and the pesticide glyphosate were tested as relevant anthropogenic substances. Apart from the study of biogas production, the fatty acid profiles were analyzed to evaluate which anaerobic microorganisms were influenced. In addition to previous studies, experiments should be included that test for synergistic effects of individual substances or mixtures of quaternary ammonium compounds. Furthermore, degradation and adsorption experiments were carried out to simulate the environmental behavior of these substances. All tests required sensitive, substance specific analytical methods from complex matrices, which were further developed and validated within this work.
The test results show that glyphosate and its metabolite aminomethylphosphonic acid do not influence the microbiological processes of biogas production in the expected concentration range. However, quaternary ammonium compounds affected the anaerobic microorganisms already at significantly lower concentrations (1 to 5 mmol·L−1). In addition, synergistic effects were observed for these substances (0.1 to 0.01 mmol·L−1). This is particularly critical, since quaternary ammonium compounds have already been detected in biogas plants in similar concentrations (0.01 mmol·L−1). An important result of this work is that the hydrophilicity of the quaternary ammonium compounds was determined as a reason for toxicity due to cell lysis with increasing membrane solubility. This mainly concerned the methanogenic archaea. The degradation of these substances could not be determined. The high elimination rate of these substances was attributed to adsorption on the sewage sludge. The results and the resulting conclusions for the use of quaternary ammonium compounds can be used as a procedural requirement for anaerobic digestions.
|Advisor:||Denecke , Martin|
|School:||Universitaet Duisburg-Essen (Germany)|
|Source:||DAI-C 81/1(E), Dissertation Abstracts International|
|Subjects:||Chemical engineering, Engineering|
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