Palygorskite-mediated simultaneous nutrient removal and antibiotic degradation from aquaculture wastewater in lab-scale constructed wetlands

Abstract

In this study, palygorskite was employed as a substrate in laboratory-scale constructed wetlands (CWs) over a period of 180 days to investigate the removal efficiency of pollutants from mariculture wastewater under high loads of enrofloxacin (ENR) stress. The results indicated that the incorporation of palygorskite into CWs resulted in average effluent concentrations of total phosphorus (TP), total nitrogen (TN), chemical oxygen demand (COD), and ENR reaching 0.07 ± 0.00 mg/L, 1.07 ± 0.06 mg/L, 11.57 ± 1.04 mg/L, and 0.047 ± 0.002 mg/L, respectively. The removal efficiencies reached 96.45 ± 0.04 %, 94.62 ± 0.27 %, 88.61 ± 1.22 %, and 91.14 ± 5.00 % respectively, with phosphorus removal significantly surpassing that reported for similar CWs. This superior performance was mainly attributed to the strong binding mechanisms between phosphorus and the metal oxides and hydroxides leached from the palygorskite. The palygorskite stimulated the secretion of extracellular polymeric substances (EPS), accelerated biofilm establishment, and enhanced the relative abundance of key functional bacteria associated with carbon, nitrogen, and antibiotic removal, thus achieving rapid denitrification and efficient organic matter removal. Monitoring of metals (Ca, Fe, Mn, and Cu) in the CWs effluent suggested that their presence was insufficient to affect cytoplasmic enzyme activity or cause oxidative stress damage to plants. In conclusion, palygorskite serves as an environmentally friendly, high-nutrient removal alternative, apt as a substrate for CWs.