Purification of nitrate-rich agricultural runoff by a hydroponic system.
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.
Yang
Zhifeng
Z
State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China.
Zheng
Shaokui
S
Chen
Jinjun
J
Sun
Mei
M
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
D009566:Nitrates; D010758:Phosphorus; D009584:Nitrogen; D010100:Oxygen