Nitrogen removal in recirculated duckweed ponds system.
Duckweed-based ponds (DWBPs) have the potential for nitrogen (N) removal from wastewater; however, operational problems such as duckweed die-off regularly occur. In this study, effluent recirculation was applied to the DWBPs to solve the above problem as well as to investigate N removal mechanisms. Two pilot scale recirculated DWBPs were employed to treat municipal wastewater. The average removal efficiencies for TN, TKN and NH4-N were 75%, 89% and 92%, respectively at TN loading of 1.3 g/m2.d and were 73%, 74% and 76%, respectively at TN loading of 3.3 g/m2.d. The effluent of the system under both operational conditions had stable quality and met the effluent standard. Duckweed die-off was not observed during the study, which proves the system stability and effluent recirculation which is thought to be a reason. N-mass balance revealed that nitrification-denitrification and duckweed uptake play major roles in these recirculated DWBPs. The rates of nitrification-denitrification were increased as TN loading was higher, which might be an influence from an abundance of N and a suitable condition. The rates of N uptake by duckweed were found similar and did not depend on the higher TN loading applied, as the duckweed has limited capacity to assimilate it.
Benjawan
L
L
School of Environment, Resources and Development, Asian Institute of Technology, Pathumthani, Thailand. lukkhana@ait.ac.th
Koottatep
T
T
D029064:Araceae / Q000378:metabolism* / Q000502:physiology; D019149:Bioreactors; D009584:Nitrogen / Q000378:metabolism*; D012965:Sodium Chloride; D014865:Waste Disposal, Fluid / Q000379:methods*; D018508:Water Purification
D012965:Sodium Chloride; D009584:Nitrogen