| Zdroj: |
Escola, M, Tue Kjærgaard Nielsen, T, Hansen, L H, Ooi, G & Bester, K 2015, ' Microbiological and chemical approaches to degradation of mecoprop in a Moving-Bed Biofilm-Reactor ' AquaConSoil, Copenhagen, Denmark, 09/06/2015-12/06/2015, . |
| Popis: |
Micro-pollutants are ubiquitous in wastewater effluents. Therefore, in-situ treatments of highly polluted water or polishing treatments after classical wastewater treatment have been proposed as a solution. Moving Bed Biofilm-Reactors (MBBRs) are a recent-developed biofilm technology for wastewater treatment. MBBRs consist incontain biofilms which are grown on small (1-4 cm diameter) plastic chips that are suspended and mixed in a water tank. These systems have been recognized as robust and versatile. Besides, biofilm systems fdescribe acilitatedemonstrate a clear, but slow, biodegradation of some recalcitrant compounds. For all these reasonsThus, MBBRs are pointed as a valuable tool for the elimination of micro-pollutants. Several studies have focused in on describing degradation processes in biofilm by quantifying the loss of micro-pollutants over time. This can be helpful foraid optimizing optimization of biofilm treatment processess but it does not describe the full degradation process. In many cases, the degradation kinetics of micro-pollutants is are unclear and not fitting the theoretical models. The key to solve this problem may rely lie in understanding the relations between compound degradation and biofilm communities. This study wanted to answer howfocussed on the response of the microbial communities respond to the presence of micro-pollutants in different concentrations. To do this, MBBR chips, grown and used for wastewater effluent polishing, were exposed to the same real wastewater effluent; spiked at with different concentrations of mecoprop. Mecoprop was chosen because it is a well-studied pesticide which commonly appears in wastewater effluents and groundwater. The microbial communities were determined and followed over the experiment, by high-throughput sequencing of the 16S genes. In parallel, the concentrations of mecoprop and its metabolites were also determined. BesidesFurthermore, mecoprop exists as a mixture of two enantiomers which could bewere also quantified. This factor is important because since enantiomers might may differ in their pharmacological and biological activity, leading to different responses in living organisms and therefore different degradation rates. The MBBR chips contained a small number of microbiological communities, some of them being known as degraders. As expected, MBBR chips degraded mecoprop. In the lowest tested concentration (10 µg/L) mecoprop showed a half-life of 120 hours. Interestingly, at this concentration the degradation process showed to be enantioselective. In this way, the half-life of R-mecoprop was around 50 hours while the half-life of S-mecoprop was about 150 hours. When looking at the three concentrations, a clear saturation of the systems could be observed. For the lowest (10 µg/L), middle (100 µg/L) and high (1000 µg/L) concentrations, the % removal at the end of the experiment was 90%, 25% and 0%, respectively . No enantioselectivity could be distinguished for the middle and high concentrations. Regarding the metabolites, 4-Chlorocatechol was formed and later degraded in all concentrations, with maximum concentrations at around 200 hours. |
