Abstract:As an eco-friendly wastewater treatment method, constructed wetlands have been widely used in purifying aquaculture wastewater. However, due to the effects of salt stress of seawater, the feasibility of treating mariculture wastewater in constructed wetland with different plants needs further study. To investigate the water contaminant removal efficiency, two integrated vertical flow constructed wetlands (IVCW) were constructed. Phragmites australis and Spartina alterniflora were selected as the constructed wetland plants. The salinity tolerance of P. australis was significantly different from that of S. alterniflora. The content of ammonia nitrogen (NH4-N), nitrite nitrogen (NO2-N), nitrate nitrogen (NO3-N), phosphorus, total phosphorus (TP), and potassium permanganate index (CODMn) were determined for 14 d. The two constructed wetland were filled with fine sand, vermiculite, and corallite. The results showed that the optimum salinity of P. australis was 20 and that of S. alterniflora was less than 35. The physical and chemical properties of the purified water were: temperature (28.60±0.71)℃, pH 7.60±0.04, and dissolved oxygen (DO) (5.32±0.45) mg/L. This demonstrated that the efficiency of P. australis wetland and S. alterniflora wetland in the removal of NH4-N and CODMn was (85.48±0.50)% and (57.74±4.40)%; and (95.01±1.18)% and (72.84±2.64)%, respectively. The efficiency in the removal of phosphate and TP were 40.00%~50.00% by both the constructed wetlands. These results suggested that the salt tolerance of S. alterniflora was better than P. australis. There were significant differences in NH4-N and CODMn between P. australis wetland and S. alterniflora wetland (P<0.05). However, the difference between the wetlands was not significant for phosphate and TP (P>0.05). In the short term, the efficiency of the removal of NH4-N and CODMn from mariculture effluents by S. alterniflora wetland was better than by the P. australis wetland. Under high-salinity stress, S. alterniflora had strong salt tolerance and grew better in seawater, and had better purification efficiency than P. australis. However, the efficiency in the removal of phosphate and TP exhibited no significant difference between the two wetlands.
