Effect of salinity on nitrous oxide emission in the biological nitrogen removal process for industrial wastewater.
The effects of wastewater salinity on both nitrogen removal efficiency and N2O emission rate were investigated in a single nitrification process, a single denitrification process and an anoxic-oxic activated sludge process. In the single nitrification process, by increasing the salt concentration from 1.0 to 2.0 wt%, the N2O conversion ratio in the steady state increased by 2.2 times, from 0.22 to 0.48%. In the single denitrification process, a minimal change in the N2O conversion ratio was observed in the steady state even when the salt concentration was increased from 3.0 to 5.0 wt%. From the results of the anoxic-oxic activated sludge process, it was found that a salt concentration increase from 1.6 to 3.0 wt% significantly increases the N2O conversion ratio from 0.7 to 13%. It is suggested that an increase in salt concentration markedly influences N2O emission both directly and indirectly via the inhibition of N2O reductase activity. The indirect inhibition is due to the high concentration of dissolved oxygen which is transported from the oxic tank to the anoxic tank through the circulated liquid. Thus, the salt concentration should be maintained below 3.0% to suppress N2O emission in an anoxic-oxic activated sludge process.
Tsuneda
Satoshi
S
Department of Chemical Engineering, Waseda University, 3-4-1 Ohkubo, Shinjuku-ku, Tokyo 169-8555, Japan. stsuneda@waseda.jp
Mikami
Makio
M
Kimochi
Yuzuru
Y
Hirata
Akira
A
D018685:Anesthetics, Inhalation / Q000032:analysis*; D019149:Bioreactors; D007220:Industrial Waste; D009584:Nitrogen / Q000378:metabolism*; D009609:Nitrous Oxide / Q000032:analysis*; D012965:Sodium Chloride; D014865:Waste Disposal, Fluid / Q000379:methods*; D014867:Water / Q000737:chemistry
D018685:Anesthetics, Inhalation; D007220:Industrial Waste; D014867:Water; D012965:Sodium Chloride; D009609:Nitrous Oxide; D009584:Nitrogen