Influencing Factors Of Extracellular Polymeric Substances In Sequencing Batch Reactor Sludge Process(SBR) For Biological Denitrification

Biological denitrification technology is an important research direction in the field of water pollution control,which has the characteristics of good treatment and low energy consumption.The removal of NH₄⁺-N was carried out by nitrification and denitrification,that is,the conversion of NH₄⁺-N to NO-3-N under the action of nitrifying bacteria,followed by the conversion of nitrate nitrogen to nitrogen under the action of denitrifying bacteria Escaped in water.Microbial denitrification process,the composition of the substrate or growth of environmental conditions change,will affect the growth of nitrifying bacteria and denitrifying bacteria and reduce the removal of ammonia nitrogen effect.Extracellular Polymeric Substance?EPS?is a part of sludge flocs,which is the macromolecular organic matter secreted by the relevant bacteria in the process of growth.It has influence on the composition of floc and the denitrification performance.Domestic and foreign scholars believe that SBR operation mode and temperature have a certain impact on biological denitrification performance.In order to investigate the effects of SBR operating modes?aerobic/anoxic?O/A?and anoxic/aerobic?A/O??and temperature on biological denitrification and EPS and their components,SBR was used in the study.?O/A and A/O?and temperature were used to investigate the biological denitrification performance of SBR system and the characteristics of EPS and its components.The results of the study are as follows:?1?The effects of two kinds of operating modes on the biological denitrification performance and EPS component of SBR reactor were investigated.The main conclusions are as follows:1)Under the O/A and A/O operating conditions,SBR reactors achieved higher ammonia removal rates,with removal rates of 97.5% and 98.0%.2)The nitrification rates were 6.4±1.9 mg/?gVSS·h?and 6.3±2.0 mg/?gVSS·h?at the RO/A and the RA/O systems.The SBR operating mode conditions had little effect on the nitrification rate.3)The rate of nitrification increased with the increase of NH₄⁺-N load,and positively correlated.4)The operating mode has no effect on TB-EPS and its components?PN,PS and DNA?;and LB-EPS content and its components?PN and PS?,A/O mode was O/A mode 1.4,1.38 and 1.56 times.5)The percentage of TB-EPS/EPS was more than 80%,The percentage of LB-EPS/EPS was 16% to 20% at RO/A and RA/O system.Therefore,TB-EPS was dominated in EPS.6)At RO/A and RA/O system,The percentage of PS/EPS and PS/TB-EPS were 67% to73% and 48% to 51%.PS was dominated in EPS and TB-EPS,and PN was dominated in LB-EPS,PS/TB-EPS was 54% to 56%.7)EPS had a certain effect on the settling property of activated sludge.With the increased of EPS production,the settling performance of sludge was worse,EPS was positively correlated with SVI.?2?The effects of temperature on biological denitrification property of SBR and EPS constituent were investigated under the conditions of 15?,25? and 35?.The main results are as follewed:1)The removal rates of NH₄⁺-N were 96.9%,98.3% and 96.6% at R_15? ,R25?and R35?.Under the three temperature conditions,the NH₄⁺-N removal rate was achieved in the SBR reactor,and the sufficient NH₄⁺-N removal effect was obtained.2)The nitrification rates were 3.2±0.26 mg·?g·h?-1,4.3±0.47 mg·?g·h?-1,7.9±0.86mg·?g·h?-1 at R_15? ,R25?and R35?,showing that the rate of nitrification significantly increased with the temperature increases.The temperature had an important effect on the rate of nitrification reaction.3)NH₄⁺-N removal of R_15? showed full nitrification.NH₄⁺-N removal was completed on the basis of full biological denitrification and short-range biological denitrification at R25?,while the steady-range nitrification was realized in the R35?system,indicating that the high temperature condition was favorable for short-nitrification was achieved and a higher nitrification rate was achieved.4)The temperature had certain influence on EPS,LB-EPS and TB-EPS.With the temperature increased,content of EPS,LB-EPS and TB-EPS decreased.In addition,TB-EPS was dominated in EPS?the percentage of TB-EPS/EPS was 69.0-79.5%?,with the temperature rised,TB-EPS content gradually decreased,LB-EPS content gradually increased?the percentage of LB-EPS/EPS was 20.5³1%?and TB-EPS/LB-EPS ratio gradually decreased,between 2.2 to 3.8.5)Had a significant effect on the content of PN,DNA and PS in EPS.The contents of PN and DNA in EPS,TB-EPS and LB-EPS decreased with rasing temperature.With the temperature rasing,the constitute of PS in EPS and LB-EPS increased and the content of PS in TB-EPS decreased.In addition,PN is the main component of EPS,TB-EPS and LB-EPS at R_15? ,R25?and R35?,PS was the main component in EPS and TB-EPS,PS and PN were the main component in LB-EPS,the proportion was49%.6)Under different temperature conditions,the variation of EPS and its components in the process of biological denitrification showed a certain difference.At 15?,EPS and its components increased?nitrification process?,and then gradually decreased?denitrification process?.At 25 ? and 35?,EPS and its components decreased firstly,then increased?nitrification process?,and then increased slightly.