The Start-up And Performance Of Completely Autotrophic Nitrogen Removal Over Nitrite

Compared with conventional nitrification/denitrification processes, CANON(completely autotrophic nitrogen removal over nitrite)process consumes 60% less oxygen and 100% less organic carbon,produces about 90% less sludge. Therefore, CANON process is a cost-effective nitrogen removal method, especially in treatment of low C/N wastewater such as digester supernatant, landfill leachate, swine wastewater and coking wastewater. Nevertheless, a current restriction on the widespread application of the CANON process is the long start-up period due to the low growth rate and biomass yield of AnAOB(Anaerobic ammonium oxidizing bacteria).In this study, a lab-scale sequencing biofilm batch reactor(SBBR) was applied for the fast start-up of(CANON) process from activated sludge inoculum. The long start-up period of the CANON process was shortened with the optimization of start-up strategy, and PCR-DGGE was used to identify the functional bacteria in the reactor. Finally, the effects of aeration on the performance of CANON were investigated. The main research conclusions are as follows:(1) In SBBR, the partial nitrification was firstly achieved with continuous aeration, then the reactor was supplied with intermittent aeration and the CANON process was successfully obtained less than 50 days with the removal of ammonium loading rate, ammonium removal efficiency and total nitrogen removal efficiency of 0.17kg- N/(m3·d), 98.68% and 80.87% respectively.(2) For the start-up of CANON process, a persistent and stable nitrite accumulation stage was not essential. When the nitrite accumulation rate reached 63% with ammonium removal efficiency of 84%, the reactor was immediately operated with alternating aerobic periods of 2 hours and anaerobic periods of 2 hours to start ANAMMOX process. Intermittent aeration was benifical for fast start-up of CANON process which prevented from nitrite concentration continuously increasing that may inhibit AnAOB, also enrichment of AnAOB and washing out of NOB(Nitrite-oxidizing Bacteria) proceeded simultaneously.(3) In the CANON system, Candidatus Brocadia was identified as the dominant species of AnAOB and Nitrosomonas was identified as the dominant species of AerAOB.(4)With the aeration flow rate increasing from 48L/h to 88L/h, the average total nitrogen removal rate rose from 0.29 kg-N/(m3·d) to 0.57 kg-N/(m3·d) and the partial nitrification was rate-limiting step in nitrogen removal system.