Effect of pH Shocks on the Anammox Process and Approaches to Their Overcoming

Responses of the anammox bacterial community (oxidizing ammonium with nitrite and releasing gaseous nitrogen) to acidification and alkalization of the medium were different. While acidic shock caused temporary inhibition of bacterial activity, but not their death, alkaline shock resulted in death of most nitrifiers and anammox bacteria. Addition of chalk powder (CaCO3) as a pH-stabilizing agent was sufficient for prevention of acidic shock or overcoming its effects. Introduction of additional activated sludge proved efficient for rapid restoration of the anammox rate after alkaline shock. The sludge identical to that present in the reactor was more efficient than the sludge grown under other conditions.