Study On Start-up And Nitrogen Removal Performance Of CANON Coupling With Denitrification Process

In recent years,quantities of municipal sewage treatment plants and the amount of wastewater generated are constantly increasing,in China,make the effluent quality standards more stringent.In order to achieve the A level of discharge standard of pollutants for municipal wastewater treatment plant(GB18918-2002),traditional biological nitrogen removal process will increase more economic input,the capital investment and high operating costs.CANON as an efficient nitrogen removal process is mainly applied to high NH4+-N,low C/N wastewater treatment,while most of studies on municipal wastewater with low NH4+-N are still in the laboratory research stage.In this research,Carrousel 2000 oxidation ditch with the effective volume of 5.6 m3 was adopted as the reactor to start up partial nitrification(twice)and the influence of temperature and HRT were discussed.Under the condition of high ambient temperature,the partial nitrification was started successfully in the pilot-scale oxidation ditch through the 32-day limited oxygen control and dosing inhibitor,the NAR was maintained at above 90%.Under the conditions of normal low temperature,through the exchange of aeration measures and dosing inhibitor,after 44 d,the secondary start of partial nitrification was successfully in the oxidation ditch.High-throughput sequencing analysis of the second start-up of partial nitrification sludge showed that Nitrosomonas accounted for 9.39%.The specific ammonia oxidation rate of the first start-up was 0.037 kg N/(kg MLSS·d)and the specific ammonia oxidation rate of the second star-up was 0.030 kg N/(kg MLSS·d).The experimental facility of channel constructed reactor with the effective volume of 60 L was adopted to start up the CANON coupling with denitrification for preliminary study.Treating domestic wastewater,the effluent average NH4+-N was 1.41 mg/L,effluent average TN was 3.55 mg/L,TN removal rate was 83.93%,respectively,reaching the A level of discharge standard.Then sludge and fillers containing AnAOB were added in the pilot oxidation ditch,the CANON was started up successfully after 9 periods operation(9 d),the influent NH4+-N was about 40 mg/L,the effluent average NH4+-N was 2.81 mg/L,effluent average TN was 7.80 mg/L,TN removal rate was 82.17%,respectively,reaching the A level of discharge standard.Through batch experiments,the AnAOB activity was 0.018 g/gVSS-d and 0.110 g/gVSS·d in the sludge and the biological film,respectively.The influence of aeration/non-aeration time ratio in the CANON process was discussed.In order to ensure low NH4+-N and TN effluent,aeration/non-aeration time of 1 h/1 h was recommended.After that,CANON process was coupled with denitrification process by treating actual domestic wastewater.After 5 days of commissioning,effluent NH4+-N,TN and COD could reach the A level of discharge standard.Sludge activity test analysis showed that AnAOB was still the predominant species on the fillers,and the removal load of AnAOB on the free sludge and biological film were 0.017 g/gVSS·d and 0.089 g/gVSS·d,respectively.The influence of HRT and aeration/non-aeration time ratio on the nitrogen removal of the process were discussed during the operation of the reactor.The HRT of 15 h and the aeration/non-aeration time ratio of 3 h/1 h were the optimal operating parameters of CANON coupled denitrification process in pilot oxidation ditch.