Study on the removal of nitrogen and phosphorus pollutants in saline reclaimed water by Iris pseudacorus constructed wetland

Abstract

To explore the removal of nitrogen and phosphorus pollutants in saline reclaimed water by wetland plants Iris pseudacorus，five systems（CW1-CW5） with different combinations of plants，substrates and sterilizers were constructed referring to wetland system strcture. The removal effect of pollutants，biomass of Iris pseudacorus，plant accumulation and other indicators were analyzed. The differences and contribution rates of nitrogen and phosphorus removal in sewage by different composition of system were studied. The results showed that the combined plant and substrate CW2 group had the best purification effect，and the removal rate of TN，NH4+-N and TP in simulated reclaimed water reached 56.52%，75.47% and 64.53% respectively，which were superior to the other four groups. This could be attributed to the addition of substrate providing contact sites for nitrogen and phosphorus adsorption，while also providing suitable growing environment for Iris pseudacorus. The continuous aerobic respiration of plant roots promoted plant growth. On the one hand，it enhanced the absorption of nitrogen and phosphorus pollutants by the plant itself. On the other hand，well-developed roots could provide attachment carriers for a large number of microorganisms，promoting nitrification and denitrification. Further research found that in the CW2 wetland system，the nitrogen and phosphorus absorption removed by plants accounted for 24.62% and 22.62% of the total input，and the removal of nitrogen and phosphorus by substrate through interception，adsorption and other actions accounted for 13.33% and 29% of the total input. Both plant absorption and the removal effct of substrate were the main pathways for nitrogen and phosphorus removal.

Keywords

• iris pseudacorus
• saline reclaimed water
• nitrogen and phosphate pollutants
• water purification