Abstract
Drought events and higher temperature will occur more often in our environment. This, along with the increased use of fertilizer in agriculture, is leading to the eutrophication and shortage of freshwater reservoirs. Irrigation-water quality standards suffer from a lack of regulation worldwide. When episodes of water scarcity occur, vulnerable populations may be forced to irrigate their crops with cyanotoxin-polluted water (from the occurrence of harmful cyanobacteria blooms). Consequently, indirect, or direct human consumption of cyanotoxins happens, which may lead to several cytotoxic pathologies.
Initial studies have suggested that constructed wetlands are promising for cyanotoxin bioremediation, despite its unknown microbial mechanisms. Therefore, it is essential to clarify what are the best operational designs, as well as system management that can optimize the degradation efficiency.
Hence, we tested two hypotheses: 1) CW systems can efficiently remove cyanotoxins while recycling the nutrients for crop irrigation. 2) The indigenous CW microbiota (bacteria and fungi) are cornerstones of the cyanotoxin removal and the cyanotoxins act as microbial community evolutionary drivers.
Due to the lack of scientific studies, mesocosms studies can be applied to explore the system variables prior to pilot and scale up implementation.
Therefore, 12-L mesocosms systems were set up using different reed species (Phragmites australis vs. Juncus effusus vs. unplanted) and porous media (gravel vs. sand) operated in saturated mode. Control and spiked systems were fed using synthetic eutrophic lake water. The latter was maintained using a 10 µg/L of two cyanotoxins, microcystin-LR and Cylindrospermopsin, mimicking a cyanobacterial bloom. Removal percentages, metabarcoding of bacterial and fungal communities and screening of transformation products were carried out intending to disclose removal mechanisms taking a holistic approach.
Removal rates showed stabilization of the systems along time and effective removal of the toxins, even indicating possibilities to meet the threshold values for drinking water proposed by WHO (1 µg/L) in most of the scenarios. The plant species is the design variable with higher effect in the removal of both toxins, followed by porous media type. Bacterial and fungal community showed a response to the toxins, having a higher effect on beta-diversity than any other variable.
To conclude, the CWs potential, at mesocosms scale, to remove cyanotoxins in surface waters was confirmed. Strong evidence suggests that the microbial community was affected by the cyanotoxins. Next steps are to use different hydraulic configurations to disclose the variables effect and to point towards an optimal design.
Initial studies have suggested that constructed wetlands are promising for cyanotoxin bioremediation, despite its unknown microbial mechanisms. Therefore, it is essential to clarify what are the best operational designs, as well as system management that can optimize the degradation efficiency.
Hence, we tested two hypotheses: 1) CW systems can efficiently remove cyanotoxins while recycling the nutrients for crop irrigation. 2) The indigenous CW microbiota (bacteria and fungi) are cornerstones of the cyanotoxin removal and the cyanotoxins act as microbial community evolutionary drivers.
Due to the lack of scientific studies, mesocosms studies can be applied to explore the system variables prior to pilot and scale up implementation.
Therefore, 12-L mesocosms systems were set up using different reed species (Phragmites australis vs. Juncus effusus vs. unplanted) and porous media (gravel vs. sand) operated in saturated mode. Control and spiked systems were fed using synthetic eutrophic lake water. The latter was maintained using a 10 µg/L of two cyanotoxins, microcystin-LR and Cylindrospermopsin, mimicking a cyanobacterial bloom. Removal percentages, metabarcoding of bacterial and fungal communities and screening of transformation products were carried out intending to disclose removal mechanisms taking a holistic approach.
Removal rates showed stabilization of the systems along time and effective removal of the toxins, even indicating possibilities to meet the threshold values for drinking water proposed by WHO (1 µg/L) in most of the scenarios. The plant species is the design variable with higher effect in the removal of both toxins, followed by porous media type. Bacterial and fungal community showed a response to the toxins, having a higher effect on beta-diversity than any other variable.
To conclude, the CWs potential, at mesocosms scale, to remove cyanotoxins in surface waters was confirmed. Strong evidence suggests that the microbial community was affected by the cyanotoxins. Next steps are to use different hydraulic configurations to disclose the variables effect and to point towards an optimal design.
| Original language | English |
|---|---|
| Publication date | 2023 |
| Publication status | Published - 2023 |
| Event | 10th International Symposium on Wetland Pollutant Dynamics and Control (WETPOL) - Brugges, Belgium Duration: 10 Sept 2023 → 14 Sept 2023 |
Conference
| Conference | 10th International Symposium on Wetland Pollutant Dynamics and Control (WETPOL) |
|---|---|
| Country/Territory | Belgium |
| City | Brugges |
| Period | 10/09/2023 → 14/09/2023 |