Removal of nitrate from constructed wetland in winter in high-latitude areas with modified hydrophyte biochars

Abstract

In high-latitude areas, nitrate treatment from constructed wetlands is often not so good in winter. The study aims to develop an efficient and economic technology to remove nitrate from constructed wetland under the conditions of winter temperature. We conducted laboratory experiments to investigate the removal of nitrate from aqueous solution and wastewater by modified hydrophyte biochars from constructed wetlands. The second-order model fit the nitrate desorption kinetics of modified hydrophyte biochars with a high coefficient of determination (R2>0.99). Freundlich isotherms performed well to fit the nitrate sorption data (R2>0.98) of modified hydrophyte biochars. Batch adsorption experiments also showed that both initial solution pH and coexisting anions could affect the adsorption of nitrate onto modified hydrophyte biochars. Our results suggested that modified hydrophyte biochars might be a promising alternative wastewater treatment technology for nitrate removal from constructed wetland in winter in high-latitude areas.