Effects of pH on ammonium nitrogen conversion efficiency and bacteria activity of microbial flocs

Abstract:

The paper studied the effects of different pH values on the cultivation of microbial floccules utilizing the waste sludge from the recirculating aquaculture system that reared Scortum barcoo. It was carried out in fresh water at 29-32℃. The results showed that there were no obvious nitrite and nitrate accumulations when the pH values were 6.5, 7.5 and 8.5, and the average removal rates of soluble active phosphorus were 1.29, 0.92, and 0.80 mg/L·d. At the end of the experiment, the average concentrations of ammonium nitrogen in the three groups were 37.71, 12.74 and 17.55 mg/L, respectively. It was found that pH value had no significant effect on the total microbial activity of microbial flocs, microbial content and activity of heterotrophic bacteria and nitrifying bacteria. Crude protein and polysaccharide of extracellular polymeric substances of microbial flocs at pH 6.5 were significantly higher than those of the other two groups; the crude protein content of microbial flocs of group pH 6.5 was 20.61%, which was higher than 18.83% of pH 7.5 group and 19.04% of pH 8.5 group. It could be concluded that:pH significantly affected the ammonium nitrogen conversion efficiency, but had no obvious effects on the activity of bacteria on the flocs. the pH 7.5 and 8.5 were more beneficial to the ammonium nitrogen conversion.