[Relationship between the nitrogen removal and oxygen demand in constructed wetlands].
A simplified model of sequential N transformations and sink was applied to investigate the relationship between the nitrogen removal and oxygen demand to verify the validity of full nitrification-denitrification mechanism in a newly-built multi-stages constructed wetlands. Average net rates of N mineralization ranged from 0.01 to 0.28 g x (m2 x d)(-1), nitrification from 0.50 to 1.54 g x (m2 x d)(-1), denitrification from 0.41 to 1.13 g x (m2 x d)(-1)(3.4% approximately 35.4% of measured N removal in different stage) and plant assimilation from 0.07 to 0.26 g x (m2 x d)(-1) in the five tanks. Nitrification and denitrification occurred concurrently with BOD removal, even in the first stage receiving the higher-strength wastewater. Surprisingly, net areal nitrification rates, was correlated with BOD removal rates positively. Nitrification rates were also correlated linearly with average NH4+-N concentrations in the cascade tanks. The nitrogenous oxygen demand (NOD) required to support full nitrification of ammonia and mineralized Org-N in the wetland was in the upper range of that expected to be able to be supplied through surface and plant-mediated oxygen transfer. Some potential alternative nitrogen removal pathways with reduced overall oxygen requirements that have relevance to constructed wetlands were discussed.
He
Lian-sheng
LS
Chinese Research Academy of Environmental Science, Beijing. hls02@mails.tsinghua.edu.cn
Liu
Hong-liang
HL
Xi
Bei-dou
BD
Zhu
Ying-bo
YB
Wei
Zi-min
ZM
Huo
Shou-liang
SL
D004784:Environmental Monitoring; D009584:Nitrogen / Q000032:analysis* / Q000378:metabolism; D017672:Nitrogen Compounds / Q000032:analysis* / Q000378:metabolism; D010100:Oxygen / Q000032:analysis* / Q000378:metabolism; D014865:Waste Disposal, Fluid / Q000379:methods; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000378:metabolism; D018508:Water Purification / Q000379:methods; D053833:Wetlands
D017672:Nitrogen Compounds; D014874:Water Pollutants, Chemical; D009584:Nitrogen; D010100:Oxygen