title: Purification of nitrate-rich agricultural runoff by a hydroponic system.
abstract: The purification of nitrate-rich agricultural runoff by a floating-raft (FR) hydroponic system was investigated at 3-, 2- and 1-d hydraulic retention times (HRTs) with particular emphasis on nitrogen conversion and removal through the system. The FR system has a dissolved oxygen (DO) environment similar to the horizontal subsurface flow system, generally 0.00mgL(-1), that facilitates denitrification. An efficient nitrate-nitrite-nitrogen (NOx-N) removal, 91%, 97% and 71% on average at 3-, 2- and 1-d HRT, respectively, was frequently achieved. The mean retentions were 17-47% for chemical oxygen demand, 31-64% for total nitrogen, and 8-15% for total phosphorus for the FR system. Mass balance analysis implied that the detectable DO concentration in the reactor, as low as 0.7mgL(-1), played a very important role in the conversion and removal of NH3-N and NOx-N, which finally affected the NOx-N removal at 3-d HRT.
authors.affiliation: State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China.
authors.forename: Zhifeng
authors.initials: Z
authors.lastname: Yang
authors.forename: Shaokui
authors.initials: S
authors.lastname: Zheng
authors.forename: Jinjun
authors.initials: J
authors.lastname: Chen
authors.forename: Mei
authors.initials: M
authors.lastname: Sun
mesh_terms: D000383:Agriculture; D018527:Hydroponics / Q000379:methods*; D009566:Nitrates / Q000302:isolation & purification*; D009584:Nitrogen / Q000302:isolation & purification; D010100:Oxygen; D010758:Phosphorus / Q000302:isolation & purification; D013997:Time Factors
chemical_list: D009566:Nitrates; D010758:Phosphorus; D009584:Nitrogen; D010100:Oxygen