Effect of PH on the production of N2O during denitrification process

To investigate the effect of pH on the production of N
2
O during shortcut denitrification process, NaNO
2
was added into the system to ensure that the initial concentration of NO
2
⁻
-N was 40mg/L. HCl and NaOH were used to regulate pH of the system using sequencing batch reactor with volume of 2.4L.Results showed that nitrite reduction rate under different pH varied little in the shortcut denitrification system. The maximum nitrite reduction rate was 0.084mgN/(mgMLSS·h) and the minimum nitrite reduction rate was 0.071mgN/(mgMLSS·h);the production of N
2
O could reach 4.272mgN/L,which accounted for 10.68% of influent nitrite concentration during nitrite denitrification when pH was 6.5. The production of N
2
O reached only 0.573mgN/L when pH was 8.0. The reasons of high production of N
2
O under low pH during denitification process were mainly:(1) low pH had strong inhibition on N
2
O reductas; (2)low pH played a role of screening strains.