Study on Aquaculture Wastewater Treatment by Aquatic Plants

The aquaculture sector is fast developed in Vietnam, whereas untreated water pollution remains an issue. This study used three aquatic plant species, namely Ceratophyllum demersum, Alternanthera paronychioides, and Cyperus corymbosus to treat aquaculture wastewater in Quang Ninh. In the experiment with shrimp farming wastewater, after 16 days of experiment, the results showed C. demersum had the highest ability to remove organic matter (COD) up to 95.2% and the removal efficiency of NH4+-N reached 96.3%, whereas the removal efficiency of organic matter (COD) and NH4+-N of A. paronychioides were 90.5% and 97%, respectively; the removal efficiency of organic matter (COD) and NH4+-N of C. corymbosus were 66.7% and 81.8%, respectively. In the experiment with fish farming wastewater, C. corymbosus had the highest ability to remove organic matter (COD) up to 96% and the removal efficiency of NH4+-N reached 100%, the removal efficiency of organic matter (COD) and NH4+-N of A. paronychioides were 91.8% and 86%, respectively; the removal efficiency of organic matter (COD) and NH4+-N of C. demersum were 83.7% and 76.4%, respectively; whereas in the control sample, the removal efficiency of organic matter (COD) and NH4+-N were only 34.7% and 56%, respectively. In the experiment with shrimp farming wastewater, NO3--N treatment efficiency in the C. corymbosus, C. demersum and A. paronychioides system was 76.1%, 78.7% and 82%, respectively after 3 days of experiment, however NO3--N concentration gradually increased until the 16th day. In the experiment with fish farming wastewater, NO3--N concentration gradually increased during 16 experimental days in systems using three aquatic plants (NO3--N < 3 mg/L at the end of the experiment). The results prove the ability to treat organic matter and ammonium of C. demersum, A. paronychioides and C. corymbosus, however, further studies need to be conducted to limit the increase of NO3--N concentration in aquaculture wastewater treatment. Keywords: wastewater, aquaculture, aquatic plants.