Duckweed is a common aquatic plant that offers invaluable assistance in water management. It is a free-floating plant that is significantly cost-effective and known for its phytoremediation capabilities. It is commonly found in paddy fields and ponds and thrives in eutrophic waters. Duckweed has already been identified as a successful solution to eutrophication, and this article will delve deeper into the numerous benefits of this incredible plant.
The Need for Duckweed
Globally, anthropogenic actions have significantly affected water quality and severely impacted aquatic ecosystems. These actions include poor water management systems, dumping of liquid wastes, and intensive agriculture. Efforts to recover these water bodies are greatly needed, mainly including the remediation of nutrient levels (phosphorus and nitrogen) and heavy metal contamination.
Duckweed offers a solution to these issues by growing in the affected areas, and essentially creating a bioactive mat that produces an anaerobic environment which discourages the eutrophic process from furthering, and also by absorbing excess nutrients and causing eutrophication to be reversed. This aquatic plant has the potential to remove 50-60% of total nitrogen and up to 99% of phosphorus in domestic wastewater. Evaluation of aquatic plants and their phytoremediation capabilities concluded that duckweed is recognized to be the most effective.
Duckweed is an extraordinary plant that offers various remediation solutions. Excess nutrients and pollution is an issue that threatens global hydrological cycles. With duckweed as an affordable and accessible solution to some of these issues, there is hope for these systems to thrive for decades to come. Some of the areas that this plant has been studied include wetlands, agricultural pollution, dairy industry pollutants, pharmaceutical pollution, and heavy metal pollution.
The incorporation of duckweed into wetlands that receive wastewater has several benefits. These wetlands offer numerous ecosystem services, such as providing homes to multiple fish, bird and plant species; preventing erosion; maintaining water quality; and managing water flow. However, with many of these wetlands being sites for holding wastewater, they are prone to algae blooms and eutrophication due to high nitrogen and phosphorus quantities which threaten these ecosystems. Many of these wetlands’ nutrient levels surpass the wetland’s self-purification capability, so introducing this aquatic plant to these spaces offers additional ecosystem support without causing further damage compared to alternative methods consisting of chemical alterations or destruction and reconstruction of the ecosystem.
Agricultural pollutants from intensive agriculture and the pesticides and herbicides they use significantly contribute to excess nutrients in waterways. One of the major pollutants from this industry includes 1,4-dioxane, which is a probable carcinogen by the International Agency for Research on Cancer, so remediation of this pollutant is crucial. Duckweed as a remediation for agricultural pollution is a practical, low-cost and sustainable approach to this issue.
Duckweed also has the potential for significant improvement in the dairy industry. This plant is an excellent remediation for dairy wastewater and offers an excellent nutrient source for animal feed.
Pharmaceuticals and personal care products also need remediation in global water bodies due to their effect on water quality. One study conducted on the remediation capabilities of duckweed on pharmaceutical and personal care product pollution came to a positive conclusion, but further research is encouraged.
Duckweed offers numerous remediation capabilities for water bodies experiencing the effects of excess nutrients and pollutants, including heavy metal accumulation. Heavy metal accumulation has been a significant global issue, with the World Health Organization warning that water with levels of silver over 0.1 mg could pose a health risk (2011). This toxicity also threatens the ecosystem by affecting fish, bacteria, plants and other organisms. With the talk of the benefits of this amazing plant studies set out to evaluate the effectiveness of heavy metal remediation. These studies concluded that duckweed effectively uptakes these heavy metals in these spaces. However, the toxicity of these plants as food and their threat to organisms in these ecosystems still needs more research.
Limitations of Duckweed
Along with limited research into the effect of metal accumulation on duckweed within the aquatic food chain, there are a few other limitations to this plant. Further research into the toxicity of the plant as animal feed for other animals after a remediation process is necessary. There is also limited research into the frequency necessary to apply or remove this plant. This includes whether the reintroduction of duckweed each season is necessary, if it will maintain itself annually, as well as if and when it is necessary to extract a portion of the plant after substantial reproduction. These limitations highlight a gap in knowledge on the success of this aquatic plant.
Research into maintaining the high reproduction rate of duckweed is also limited but crucial in understanding optimal remediation methods. This is a plant that reproduces quickly, so it can quickly get out of hand and create a blanket cover that depletes any sunlight or oxygen access to the water. While this may help restore nutrient levels quickly, it could also make the water body uninhabitable to fish and aquatic insects. This excess growth threatens these ecosystems but maintaining reasonable levels of this aquatic plant is also challenging because its high volume makes it difficult to dispose of.
Duckweed is an incredible resource that is accessible, affordable and sustainable, making it an excellent candidate for water management. However, limitations in research on optimal methods of this plant as a remediation tool inhibit widespread use.
Chen, T., Zhang, N., Xu, Z., & Hu, X. (2019). Integrated comparisons of thorium(IV) adsorption onto alkali-treated duckweed biomass and duckweed-derived hydrothermal and pyrolytic biochar Ecomed. doi:10.1007/s11356-018-3789-x
Hemalatha, M., & Venkata Mohan, S. (2022). Duckweed biorefinery – potential to remediate dairy wastewater in integration with microbial protein production Elsevier. doi:10.1016/j.biortech.2021.126499
Lalau, C. M., Simioni, C., Vicentini, D. S., & Ouriques, L. C. (2020). Toxicological effects of AgNPs on duckweed (landoltia punctata) Elsevier. doi:10.1016/j.scitotenv.2019.136318
Landesman, L., Fedler, C., & Duan, R. (2010). Plant nutrient phytoremediation using duckweed. Eutrophication: Causes, Consequences and Control, 341–354. https://doi.org/10.1007/978-90-481-9625-8_17
Li, J., Zhou, Q., & Campos, L. C. (2017). Removal of selected emerging PPCP compounds using greater duckweed (spirodela polyrhiza) based lab-scale free water constructed wetland Elsevier. doi:10.1016/j.watres.2017.09.002
Osama, R., Ibrahim, M. G., Fujiia, M., & Tawfik, A. (2019). Potentials of duckweed (lemna gibba) for treatment of 1,4-dioxane containing wastewater using duckweed multi-ponds system Elsevier Ltd. doi:10.1016/j.egypro.2018.11.233
Park, J., & Richard, J. (2020). The effect of floating plant on water purification: Comparison of the water purification capability of Water Hyacinth, Duckweed, and Azolla. Emerging Investigators. Retrieved from https://emerginginvestigators.org/articles/the-effect-of-floating-plant-on-water-purification-comparison-of-the-water-purification-capability-of-water-hyacinth-duckweed-and-azolla