Effect of pH Value on Autotrophic Denitrification Process of Zero Valent Iron Substrate

Abstract

Using a substrate with zero valent iron and nitrate, the research determined the change of pH value in the iron autotrophic denitrification process and the effect of pH on zero valent iron autotrophic denitrification activated sludge using batch experiments and a continuous flow fermenter denitrification rate. Batch experiments were carried out with four reactor bottles with sludge addition. The initial pH values were 6.2, 6.7, 7.5, and 8.8, respectively, and there was an initial pH of 6.7 in a bottle without sludge addition. The results showed that the initial pH value of 6.7 obtained the highest nitrogen removal rate. For the bottle without sludge addition, the pH rose to about 10. The pH value of the four batch experiments was concentrated between 7.5-7.8 in the follow-up process, so there was no significant difference in the effects of pH on denitrifying bacteria. However, the pH value in the fermenter can be controlled stably by an acid-base pump. With five pH gradients of 6, 6.5, 7, 7.5, and 8, the adaptability and activity of microorganisms under a constant pH value were observed separately. The sludge activity was the highest at pH 6.5, and the highest nitrogen removal rate was 1.35 mg·(L·h)-1.