Treatment of domestic sewage by CANON process under alternate oxic/anoxic intermittent starvation

Abstract:

To explore the stability of the completely autotrophic nitrogen removal over nitrite (CANON) process in the treatment of actual domestic sewage, sequencing batch reactor (SBR) was used to inoculate the CANON sludge that is stably operated in the laboratory, and actual domestic sewage was used as the influent. Actual domestic sewage has complex water quality, contains organic carbon sources, and has low ammonia nitrogen content, which brings about the problem of proliferation of nitrite-oxidizing bacteria (NOB) and heterotrophic bacteria (such as denitrifying bacteria). It is necessary to improve the operating parameters in response to this problem. In this work, the CANON reactor was operated in a hydraulic screening and alternate oxic/anoxic intermittent starvation mode. In continuous dynamic experiment, the reactors ran in a cycle of 3 d starvation and 3 d recovery. During intermittent starvation, two alternate oxic/anoxic ratios (1∶1 and 2∶1) were adopted for the flocculent sludge discharged by R1 and R2 for oxic/anoxic intermittent starvation. The contribution rate of autotrophic denitrification of both reactors exceeded 80%, while that of the denitrification pathway was less than 1% on the 50th day. The alternate oxygen intensification of intermittent starvation effectively inhibited NOB and denitrifying bacteria in the system. The final ammonia nitrogen removal rate was stabilized at 87.78% and 94.14%, and the total nitrogen removal rate reached 75.59% and 82.07% respectively, which can realize the stable operation of CANON process for domestic sewage treatment with low ammonia nitrogen. The CANON sludge cultured by domestic sewage had a darker color. On the 50th day, the volume average particle size of the R1 and R2 reactors reached 673 and 659 μm respectively. The mass fraction of extracellular polymeric substance (EPS) was affected by multiple factors such as total nitrogen concentration and organic carbon source, and maintained a trend of slow growth.