Influence of pH and Alkaline Substances on Shortcut Nitrification

The effect of pH on shortcut nitrification is not uniform and the effect of different alkaline substances on shortcut nitrification has not been reported so far. The influence of pH and alkaline substances on shortcut nitrification was studied in sequencing batch reactors (SBR) fed with artificial wastewater. The test showed that the best pH for shortcut nitrification was 8.0 and shortcut nitrification almost stopped when the pH was less than 6.6. When the initial pH was 8.0 regulated by adding different alkaline substances, the reactor regulated by hydroxide and Na₂CO₃ stopped reacting due to pH reducing. The acid buffer action of KHCO₃ was the strongest among them. Therefore, the pH of the reactor regulated by KHCO₃ reduced most slowly, thus the rate of shortcut nitrification reaction increased. The average of nitrate accumulation rate was 0.155 g/(g·d). When the pH was 8.0 in the whole process of reactions regulated by adding different alkaline substances appropriately, the KHCO₃ was the most suitable substrates. The results indicate that it is necessary to maintain the pH greater than 6.6 by adding KHCO₃ both in the engineering application feasibility and efficiency considered.