Effect of Constructed Wetland Configuration on the Removal of Nitrogen Pollutants and Antibiotics in Aquaculture Wastewater

Abstract

Horizontal subsurface flow constructed wetland (HSSFCW) and integrated vertical flow constructed wetland (IVFCW) consisted of down-flow and up-flow were built to treat aquaculture wastewater under different conditions. The water treatment performance, especially the nitrogen pollutants and antibiotics removal efficiencies, were compared, and the effects of flow patterns and hydraulic retention time (HRT) on the efficiencies were studied. The results showed that IVFCW had a better removal efficiency on nitrogen pollutants, and the removal rates of TN and NH4+-N were 58% and 80% (HRT=3 d), respectively. Microbial community was further analyzed using BIOLOG microplate technique and 454-pyrosequencing. The internal structure of IVFCW was conducive to the flow and dissolved oxygen condition, which induced higher microbial activity and diversity. The richness in Nitrospira distribution was the main reason for the removal efficiency of ammonia nitrogen. HRT had a great influence on the removal of NO3--N and NO2--N, and maintaining 3-4 d could reach good efficiency for all kinds of nitrogen pollutants. Solid phase extraction-high performance liquid chromatography-tandem mass spectrometry analysis (SPE-HPLC-MS/MS) was used to test the removal efficiency of antibiotics, and the results showed that there was no remarkable difference between the two configurations. The removal efficiency of Enrofloxacin was higher than that of Sulfamethoxazole and Florfenicol. Extending HRT from 1 d to 3 d could significantly improve the removal rate of Sulfamethoxazole, reaching above 50%.