| In recent years,the completely autotrophic nitrogen removal over nitrite(CANON)process has become a hot research topic in wastewater treatment.Its advantages include no need of additional carbon sources,lower aeration and less residual sludge.There have been extensive research and practical engineering applications in the field of treating high NH4+-N wastewater,but there are still many technical problem,including poor system stability,long growth cycle of functional bacteria difficulty in long-term inhibition of NOB activity,and high NO3--N effluent.For settle the above problems,this study is divided into three parts.First,lab-scale SBR reactor of the CANON process was run to acclimate and operated stably,exploring the launch mechanism.Then in the stable operation stage of CANON process conduct a lab-scale slow-release carbon source advanced nitrogen removal research under the condition of low temperature(15℃)and room temperature(22℃).Finally,the research results of the first two parts were verified in pilot-scale experiments and provided technical support for engineering application.Though 430 days of experimental research,this paper mainly obtains the following experimental results.Start up and stable operation of CANON:(1)During the cultivation of 176 days,the enrichment of functional bacteria was realized by gradually adjusting the ratio of influent NH4+-N and NO2--N,as well as aeration according to the theoretical oxygen demand,and the inhibition of NOB activity was realized by the phased addition of hydroxylamine,and finally realized the start of CANON process.(2)When the NH4+-N volume load reached 0.2 kg·(m3·d)-1,the NH4+-N removal rate reached 98%,and the TN removal rate reached 73%.On the 173rd day,the NH4+-N removal rate reached 9.8 mg·(L·h)-1.(3)The start process showed that the phased addition of hydroxylamine in 10 mg·(L·d)-1 had a significant effect on stimulating AOB activity and inhibiting NOB activity.The final AOB activity was 12.65 mg·(h·g)-1,while the NOB activity was less than 0.5 mg·(h·g)-1.Particles and suspended sludge coexisted in the reactor,and MLVSS increased to 4560 mg·L-1.Advanced nitrogen removal of slow-release carbon source:Set filter columns with filling ratios in the percents of 0,1,5,10,15,2 and 0,3,5,10,15 under the conditions of low temperature(15℃)and normal temperature(22℃)respectively,then compared and analyzed biological denitrification effect and effluent stability.(1)Under low temperature(15℃),the optimal filling ratio was 15%,and the average effluent COD was 19.3 mg·L-1.The denitrification mechanism was a combination of CANON and denitrification.The TN removal rate increased from 67.8%to 96.7%.(2)Under normal temperature(22℃),the optimal filling ratio was 5%,and the average effluent COD was 18.7 mg·L-1.Its denitrification mechanism was a combination of CANON,denitrification,and partial denitrification.The TN removal rate of the coupled system increased from 62.0%to about 90%.(3)The most predominant phyla in samples A.5 and A.15 with the best filling ratio both were Proteobacteria,and the bacteria with denitrification effect in the two samples accounted for 11.0%and 12.8%.The flora structure also proved the reliability of the slow-release carbon source filter column for deep denitrification.pilot-scale experiments:(1)The results showed that the start-up method of adjusting the ratios of NH4+-N and NO2--N in influent water,accurate aeration according to the theoretical oxygen demand,and phased addition of hydroxylamine inhibitors were feasible and reliable for practical engineering application.After 251 days of cultivation,the removal rates of NH4+-N and TN in the pilot-scale SBR reactor were 93%and 66%,and the removal rate of NH4+-N reached 9.4 mg·(L·h)-1 on the 245th day.(2)In the study of deep nitrogen removal from slow-release carbon source in pilot scale,after 30 days of incubation at 17-26℃,NO3--N removal capacity increased to 21.7 mg·L-1 and N03--N removal rate was 68.8%in the 5%filling ratio of slow-release carbon source filter column.(3)The nitrogen removal mechanism in the filter column was CANON and denitrification,and the average TN removal rate of the system reached more than 89%,with an increase of about 23%.Slow-release carbon sources will have a considerable application prospect in deep nitrogen removal of CANON process,which lays a solid foundation for the deep denitrification of pilot-scale slow-release carbon sources for engineering applications. |
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