Experimental Study On Anaerobic Simultaneous Denitrification Methanogenic Denitrification In UASB Reactor

Anaerobic simultaneous denitrification methanogenesis（SDM）process is a simultaneous process of methanogenesis and denitrification in the same anaerobic reactor to achieve the function of simultaneous denitrification and decarbonization.Over the past 20 years,a large number of researchers have conducted extensive research on the mechanism and application of SDM process using different types of reaction devices,including UASB reactors,to treat various simulated and actual wastewater.However,there are few researches on SDM process,such as rapid start-up and continuous stable operation.The long-term experiment of this subject is to investigate the influence of glucose and sodium acetate on the rapid start-up process of anaerobic simultaneous denitrification methane production process by using UASB reactor at 35±1℃,using anaerobic granular sludge as the inoculated granular sludge,and using simulated wastewater containing high concentration of sodium nitrate as the inlet water.After the SDM process was started,the influence of different carbon-nitrogen ratios（3:1-100:1）on the long-term continuous and stable operation of SDM was investigated.Using glucose as carbon source and SDM granular sludge as inoculating sludge,the kinetics of methane production by anaerobic and denitrification were analyzed.The conclusions are as follows:（1）In this experiment,the SDM process can be started quickly by starting with an appropriate carbon/nitrogen ratio and a lower load,and then increasing the organic load and reducing the carbon/nitrogen ratio at the same time.When glucose is used as the carbon source,the SDM process can be started at 50d.（2）Glucose is more suitable for the fast start of SDM process than sodium acetate.When the carbon source is glucose,the start time of SDM process,the removal effect of organic matter and the performance of cultured granular sludge are better than when the carbon source is sodium acetate.When the carbon source was sodium acetate,the main reason for the slow start of the reactor was that sodium acetate would hydrolyze to produce a large amount of alkalinity,resulting in the pH value of the reactor exceeding 8.0,and the activity of methanogens was inhibited.（3）When the ratio of carbon to nitrogen is 8:1～50:1,the long-term efficient and stable operation of SDM process can be realized.Neither too high nor too low carbon to nitrogen ratio is conducive to the long-term stable operation of SDM process.When the carbon-nitrogen ratio is 8:1～50:1,with the decrease of the carbon-nitrogen ratio,the removal rate of COD is maintained above 80%,and the gas production of NO₃^--N is almost completely removed gradually reduced.When the ratio of carbon to nitrogen is 10:1 and 15:1,the long-term stable operation of SDM process has the best effect.When the ratio of carbon to nitrogen was 100:1,the gas production and COD degradation efficiency decreased.When the ratio of carbon to nitrogen drops to 5:1 and 3:1,the removal rate of COD,NO₃^--N is significantly reduced,and a large amount of NO₂^--N accumulates,and even a large amount of sludge dissolves.（4）In SDM static test,both denitrification and organic degradation conform to Monod equation of a single substrate.NO₃^--N is the limiting factor for denitrification.The degradation of organic matter was mainly affected by NO₃^--N at 0～120 min.The degradation of organic matter was mainly affected by the concentration of organic matter from 120 to 270 min.