[A New Model for the Treatment of Low Ammonia Nitrogen Wastewater by CANON Process]

Automatic aeration and recirculation of effluent were used to start CANON process with up flow sludge bed reactor, and the start-up and operation characteristics of the process were studied. The results showed that the CANON process could be started quickly and stably by the method of reoxygenation reflux under the conditions of sludge volume fraction 25%, NH₄⁺-N 157 mg·L^-1, HRT 2 h. After 50 days of operation, the total nitrogen removal rate increased from 1.31 kg·(m³·d)^-1 to 1.47 kg·(m³·d)^-1; the reoxygenation reflux manner could effectively control the amount of dissolved oxygen in the reactor, resulting in DO<0.01 mg·L^-1, which had a good inhibitory effect on the NOB in the system, and meanwhile provided a good growth environment for AnAOB; By controlling the reflux flow, the production rate of NO₂^- could be precisely controlled, reaching a good balance with NO₂^- consumption rates, and thus avoiding the accumulation of NO₂^- and occurrence of nitration reactions. Therefore, reoxygenation reflux CANON process showed a great advantage in the operation stability, which provided a new model for the start-up and stable operation of CANON process.