Desenvolupament i escalat d'un filtre percolador per degradar els pesticides de les aigües agrícoles mitjançant fongs

Resumen

Over the last decades, the pollution of aquatic environment by numerous micropollutants is one of global problems facing humanity. Although those compounds are normally present at low concentrations, they raise considerable toxicological concerns, posing severe threat to ecosystem and human beings. Among micropollutants, pesticides, introduced inadvertently or deliberately into environment resulted from anthropogenic activities, mainly agricultural practice, are widely accepted as the key trigger of water deterioration and a major current challenge for modern societies, since their poor elimination in conventional wastewater treatment plant. Thus, the development of technologies capable of reducing them from water body is urgently needed. The richness and low-substrate specificity features of lignin-degrading enzyme system enable the high potential of white-rot fungi (WRF) in addressing this escalating world concern. The present thesis aims to develop a pilot plant that is allowed to address pesticides from agricultural wastewater in a long-term treatment by WRF under non-sterile conditions. Firstly, an optimal candidate was screened out from several ligninolytic fungi using different pesticides, which were frequently detected in two Catalonian agricultural area, as substrates. Trametes versicolor was selected for reactors set up owing to its remarked performance. In addition, the degradation characteristics of the targeted pesticides by the chosen alternative were investigated, including enzymatic system and degradation pathway. Secondly, a lab-scale trickle bed (TBR) was constructed with T. versicolor immobilized on pine wood chips. It was employed to treat agriculture water (AW) fortified by selected pesticides, and compared to the well established fluidized bed reactor (FBR) based on different aspects, such as removal efficacy, robustness, and economic cost, etc. Accordingly, TBR emerged as the preferred option in the comparative study. Then, it was subsequently applied for eliminating pesticides from real AW, turned out good results were obtained. Both spiked and real scenarios indicate that the lignocellulosic carrier not only act as nutrient source, but also played a vital role in treatment, through adsorption effect. Besides, our findings suggest that an enhanced demonstration could be achieved by retaining the biomass inside the reactor. Based on gained experiences and perspectives, a pilot-scale TBR with T. versicolor colonized on oak wood chips, was installed and successfully operated for 186 days to deal with spiked AW under non-sterile conditions in continuous mode. Throughout the long-term running period, stable and promising performances were approached. The clogging issue, as a consequence of continuous fungal growth, was effectively tackled by rearrangement of the packing bed, without damaging the biofilm. The scaled-up reactor displayed persistent bioactivity and high robustness. To sum up, this study sheds light into pesticides-contaminated water bioremediation by WRF. Also, it serves as a proof of the concept that micropollutants in the wastewater can be dismissed by a long-term white-rot fungal treatment.