Abstract
Introduction: Drought and higher temperatures occur more often in our environment, together with too much fertilization in agriculture, is leading to eutrophication and shortage of freshwater resources. When episodes of water scarcity occur, vulnerable populations may be forced to irrigate crops with water contaminated with cyanotoxins from cyanobacterial blooms. Consequently, indirect, or direct human consumption of cyanotoxins happens, which may lead to cytotoxic pathologies. Constructed Wetlands (CWs) are a promising approach for cyanotoxin bioremediation, although the removal mechanisms are not clear. Therefore, we tested two hypotheses: 1) CW systems can efficiently remove cyanotoxins while leaving the nutrients for crop irrigation; 2) The indigenous CW microbiota (bacteria and fungi) is essential for the removal and the cyanotoxins which on the other side influence the composition of the microbial community.
Methods and data: We set up thirty-two 12-L systems using different reed species, porous media, operational modes, and different seasons. Control and spiked systems were fed using synthetic eutrophic lake water. The spiked systems were fed using a 10 µg/L of microcystin-LR and cylindrospermopsin, mimicking a cyanobacterial bloom. Removal percentages, analysis of bacterial and fungal communities’ structures and screening of transformation products were carried out intending to disclose removal mechanisms by taking a holistic approach.
Results: Mesocosms CWs in two operational conditions (Saturated and Unsaturated) showed removals of up to 99% for both cyanotoxins. We reported cylindrospermopsin removal, by CWs mesocosms, for the first time. For both operational modes, the variables influencing the cyanotoxin removal were consistent; plant type had the highest influence, followed by the operational mode and then the porous media type. The evapotranspiration factor was taken into consideration in summer campaigns, allowing us to calculate mass removals and different water quality scenarios. Taking mass removal into consideration, Phragmites australis is by far, the best plant species, while for better effluent quality (lower evapotranspiration) Juncos effusus is preferrable. Moreover, transformation products data show no coincidence with the available knowledge on cyanotoxins TPs, indicating that the known enzymatic pathways from the literature might not be occurring in complex environments. Microbial communities responded to the spiking of toxins, more profoundly in Spring season. Differential abundance tests in Saturated systems indicated that several bacteria associated with cyanobacterial blooms were statically more present in the spiked mesocosms, This indicates that the CW systems were robustly mimicking natural blooms, however it is not clear if the associated bacterial community is responsible for the cyanotoxin removal.
Discussion and take-home message: Data is consistent through the seasons demonstrating promising technical application of the CWs for controlling cyanotoxins contamination. Different scenarios depending on the perspectives of different regulatory policies will be presented at the conference. The study advocates the importance of gathering prior information before full-scale implementation, as the design highly impacts the performance and highlighting the importance of the associated bacterial communities, often disregarded in such systems usually applied as black boxes.
Methods and data: We set up thirty-two 12-L systems using different reed species, porous media, operational modes, and different seasons. Control and spiked systems were fed using synthetic eutrophic lake water. The spiked systems were fed using a 10 µg/L of microcystin-LR and cylindrospermopsin, mimicking a cyanobacterial bloom. Removal percentages, analysis of bacterial and fungal communities’ structures and screening of transformation products were carried out intending to disclose removal mechanisms by taking a holistic approach.
Results: Mesocosms CWs in two operational conditions (Saturated and Unsaturated) showed removals of up to 99% for both cyanotoxins. We reported cylindrospermopsin removal, by CWs mesocosms, for the first time. For both operational modes, the variables influencing the cyanotoxin removal were consistent; plant type had the highest influence, followed by the operational mode and then the porous media type. The evapotranspiration factor was taken into consideration in summer campaigns, allowing us to calculate mass removals and different water quality scenarios. Taking mass removal into consideration, Phragmites australis is by far, the best plant species, while for better effluent quality (lower evapotranspiration) Juncos effusus is preferrable. Moreover, transformation products data show no coincidence with the available knowledge on cyanotoxins TPs, indicating that the known enzymatic pathways from the literature might not be occurring in complex environments. Microbial communities responded to the spiking of toxins, more profoundly in Spring season. Differential abundance tests in Saturated systems indicated that several bacteria associated with cyanobacterial blooms were statically more present in the spiked mesocosms, This indicates that the CW systems were robustly mimicking natural blooms, however it is not clear if the associated bacterial community is responsible for the cyanotoxin removal.
Discussion and take-home message: Data is consistent through the seasons demonstrating promising technical application of the CWs for controlling cyanotoxins contamination. Different scenarios depending on the perspectives of different regulatory policies will be presented at the conference. The study advocates the importance of gathering prior information before full-scale implementation, as the design highly impacts the performance and highlighting the importance of the associated bacterial communities, often disregarded in such systems usually applied as black boxes.
| Original language | English |
|---|---|
| Title of host publication | 18th DWF Water Conference 2024 : Proram and abstract catalogue |
| Publisher | Danish Water Forum |
| Publication date | Feb 2024 |
| Pages | 69-69 |
| Publication status | Published - Feb 2024 |
| Event | 18th Danish Water Forum - Copenhagen, Denmark Duration: 30 Jan 2024 → 30 Jan 2024 |
Conference
| Conference | 18th Danish Water Forum |
|---|---|
| Country/Territory | Denmark |
| City | Copenhagen |
| Period | 30/01/2024 → 30/01/2024 |