Study On The Characterizations And Regulation Optimizations For Biological Nitrogen Removal MBR-SNAD Process

With the accelerating process of urbanization in China,the problem of nitrogen pollution in the water environment has become increasingly serious,and the eutrophication of water body has become one of the hot issues of global concerns.How to remove nitrogen compounds from wastewater and protect the receiving water body effectively has become an urgent problem to be solved.ANAMMOX is currently the most economical and novel-type autotrophic biological nitrogen removal technology,whereas it has limitations for nitrogen-containing organic wastewater.Recently,simultaneous nitrification,anammox and heterotrophic denitrification(SNAD)process has received more attention.The paper has established the biological nitrogen removal of SNAD system based on the membrane bioreactor(MBR)and study the rapid start-up of the MBR-SNAD process,the influences of influent C/N ratios on biological nitrogen removal of the MBR-SNAD process,and the membrane fouling characteristics of the MBR-SNAD process.The conclusions from this study are shown as follows:(1)The rapid start-up biological nitrogen removal of MBR-SNAD process.The first stage is the start-up of Anammox process period:the Anammox process was started up successfully by shortening the hydraulic retention time(HRT)(from 24 h to 4 h)and strengthening the enrichment of anaerobic ammonia-oxidizing bacteria(AnAOB),with ammonia removal efficiency(ARE),total nitrogen removal efficiency(TNRE)and nitrogen removal rate(NRR)reaching 95%,82.5%and 0.49 kg/(m~3·d),respectively;the second stage is the start-up of Completely Autotrophic Nitrogen removal Over Nitrite(CANON)process period:the CANON process was started up successfully by controlling the intermittent aeration(stop-time:aeration-time,mim/min)of 4:10 at the sequencing operational period and controlling HRT of 8 h at the continuous operational period,with ARE,TNRE and NRR reaching 93.1%,80.5%and 0.54 kg/(m~3·d),respectively;the third stage is the start-up of SNAD process period:the SNAD process was started up successfully by adding the the carbon source(sodium acetate)and controlling the influent C/N ratio of 0.5 and intermittent aeration(aeration-time:stop-time,mim/min)of 4:10,with COD,ARE,TNRE and NRR reaching 82.4%,93.1%,80.5%and 0.54 kg/(m~3·d),respectively.(2)The influences of influent C/N ratio on biological nitrogen removal of MBR-SNAD process.When the influent C/N ratio increased from 0.25 to 2,the activities of aerobic ammonia-oxidizing bacteria(AerAOB)and AnAOB in the reactor were not significantly inhibited and the ARE,TNRE,and NRR reached 90%,85%,and0.55 kg/(m~3·d)in the system,respectively;when the C/N ratio increased to 3,the activities of AerAOB and AnAOB were significantly inhibited,and ARE,TNRE and NRR in the system reduced by 36.4%,32.5%and 29.1%,respectively.when the influent C/N ratio decreased from 3 to 1,the activities of AnAOB and AerAOB and the process performance could be recovered successfully.(3)The membrane fouling characterizations of biological nitrogen removal of MBR-SNAD process.The system was operated under the constant flux condition(20L/m~2·h).After the successive Anammox,CANON,and SNAD processes,the average particle size of granule sludge increased and the settleability was also improved,which resulted in a dramatic decrease in membrane fouling rate.Fourier-transform infrared spectroscopy(FT-IR)analysis of membrane foulants showed that carbohydrates and proteins were the main compositions of membrane foulants.