Eutrophication caused by high concentration of nitrogen and phosphorus in water has become a global environmental problem. At present, exotic and even invasive plants have been used extensively in phytoremediation water systems in China, such as Eichhornia crassipes, Pistia stratiotes and Myriophyllum aquaticum, which can easily be taken into the wild and reproduce rapidly, making invasion and causing serious harm to the environment.
Native aquatic plants in China are rich in resources and have a wide range of species, which have high ecological safety with local nature of landscape culture, so there must be some species with both ornamental value and water restoration potential. It is important to explore the application of native aquatic plants in practice to reduce the invasion of exotic plants.
On the basis of a comprehensive investigation of wetland vascular plants in Guangdong province, two representative native aquatic plants, Ludwigia adscendens and Trapa natans were selected with Eichhornia crassipes to study their growth status, adaptability and nutrient removal potential in swine manure wastewater. And the TN and TP removal ability of different plant combinations were determined in artificial wastewater at different N/P concentrations.
Researchers found that the two native plants offered greater advantages than E. crassipes in water restoration. During the experiment, L. adscendens and T. natans exhibited excellent growth statuses, and their net biomass growth rates were 539.8% and 385.9%, respectively; on the 20th day, the stems, leaves, and roots of E. crassipes gradually whitened and further decayed and died.
The L. adscendens and T. natans could adjust the pH value of the wastewater, improve the dissolved oxygen and oxidation-reduction potential, and reduce the electrical conductivity value.
The results indicate that L. adscendens and T. natans are both promising aquatic plants for application to the restoration of swine manure wastewater in subtropical areas; the ecological risk of E. crassipes is worthy of further evaluation. The combination of Salvinia natans and Eleocharis plantagineiformis effectively removed TP and TN from lightly polluted water, suggesting that this combination is suitable for phytoremediation of eutrophic wastewater.
This study was completed by XU Lei, SU Feng et al., under the guidance of Dr. WANG Faguo and Dr. ZHUANG Ping from South China Botanical Garden of Chinese Academy of Sciences.
This research results have been published in International Journal of Environmental Research and Public Health entitled "Assessment of the Nutrient Removal Potential of Floating Native and Exotic Aquatic Macrophytes Cultured in Swine Manure Wastewater" and "Removal of Total Nitrogen and Phosphorus Using Single or Combinations of Aquatic Plants".
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