Enhanced phosphorus removal of constructed wetland modified with novel Lanthanum-ammonia-modified hydrothermal biochar: Performance and mechanism

Abstract

• A novel La-A-HC was successfully applied as modified substrate in CW to enhance P removal. • The addition of La-A-HC promoted the metabolism of phosphorus accumulating bacteria. • Hydrothermal method prevent P release from the raw material of biochars. • La-O-P inner-sphere complexation was the primary mechanism of enhanced P removal in La-CW. The defective phosphorus (P) removal performance of biochar (BC) inhibited its application in constructed wetland (CW). In this study, a novel Lanthanum-ammonia-modified hydrothermal biochar (La-A-HC) was prepared and used as a modified substrate for CW to enhance its P removal. Results showed that La-A-HC had satisfactory P adsorption ability ( q m = 43.1 mg P/g) under various pH, ionic strength, and competing ions. TP removal rate of La-A-HC modified CW ( i.e. , La-CW) was 14.8% higher than CW modified with BC, which was mainly attributed to the formation of La-O-P inner-sphere complexation. Substrate adsorption accounted for 90.9% of P removal in La-CW. Furthermore, the dissolved organic matter (DOM) of La-A-HC promoted the growth of γ-Proteobacteria and the proliferation of phosphate accumulating organisms ( PAO s, 4.02 ± 0.03 × 10 5 copy numbers g −1 ). The plants in La-CW also showed higher photosynthesize rate since La-A-HC enhanced its tolerance to stronger light.