Study On Start-Up And Denitrification Efficiency Of Anammox System Based On Electrolysis

The anammox process has the advantages of economy,no secondary pollution,low sludge yield and high nitrogen removal efficiency,and is considered by many researchers as a new technology for sustainable development.It is difficult to start the anammox process because of its long doubling time and sensitivity to temperature,dissolved oxygen,pH and other environmental conditions.At the same time,the urban sewage contains a large amount of dissolved oxygen,and the application of the anammox process to the urban sewage treatment is bound to face the problem of dissolved oxygen.In view of the problems that the anaerobic ammonia oxidation process is difficult to start,the anaerobic ammonia oxidation bacteria are difficult to enrich and the dissolved oxygen in the sewage is difficult to control,this paper starts with the effect of current density on the anaerobic ammonia oxidation bacteria,and constructs the anammox reaction system based on electrolysis,and uses sodium sulfite to remove the dissolved oxygen in the sewage.The rapid start-up performance of anammox under different current density was studied,and the effect of current density on the enrichment of anammox was explored after the start-up was stable.Combined with the effect of current density on water quality,the reaction in the reaction system was speculated.The effect mechanism of current density on anammox system based on electrolysis was revealed.At the same time,sodium sulfite and nitrogen were combined to control dissolved oxygen,and the feasibility of sodium sulfite controlling dissolved oxygen in anammox culture was explored.During the start-up phase after sludge inoculation,the reactor current density is in the range of 0?0.10mA/cm²,the total nitrogen load is proportional to the current density,and in the range of 0.15?0.25 mA/cm²,it is inversely proportional.When the startup reaches stability,the total nitrogen load 0.0090 g N/?L?d??0.10 mA/cm²?>0.0078 g N/?L?d??0.05 mA/cm²?>0.0037 g N/?L?d??0.00 mA/cm²?>0.0030 g N/?L?d??0.25 mA/cm²?>0.0018 g N/?L?d??0.15 mA/cm²?>0.0012 g N/?L?d??0.20 mA/cm²?.And it was found that the current density can promote the removal of NH₄⁺-N and NO₂^--N,and reduce the production of NO₃^--N in the anammox reaction.The 0.10 mA/cm² start-up period?91 days?is 10%shorter than when no current density is applied?101 days?.It is found that the current density can remove NH₄⁺-N and NO₂^--N in the water,and there is NH₄⁺-N oxidation and NO₂^--N electrochemical reaction,but NO₃^--N is not detected in the water at different current density.In the experiment of the effect of current density on the stable operation of the reaction system,the denitrification performance of the reaction system increases with the current density from 0 to 0.10 mA/cm²,while the denitrification effect is restrained from 0.15 to 0.25 mA/cm².When the current density is 0.10 mA/cm²,the removal rate of total nitrogen reaches 40.37%,and the NRR reaches 0.0091 g N/?L?d?.At the same time,it is found that the ratio of NO₂^--N/NH₄⁺-Nwas positively correlated with the current density,and reached the highest value of 1.67 at 0.25 m A/cm²,while the ratio of NO₃^--N/NH₄⁺-N applied with current density is smaller than that without current.Based on the two experiments,it is speculated that there are NH₄⁺-N oxidation,NO₃^--N and NO₃^--N reduction reactions in the reaction system based on electrolysis.In order to study the effect of sodium sulfite on the anammox system based on electrolysis,the nitrogen removal performance of the reactor with different concentrations of sodium sulfite was analyzed.The results show that the inhibitory effect of sodium sulfite on the reaction system is quite obvious,even if the optimal total nitrogen load before the test reached 0.0091 g N/?L?d?,when 600 mg/L sodium sulfite was added,the NRR decreased rapidly to 0.00131 g N/?L?d?.After comparing NRR under different currents,the low current density still maintains the ability to remove nitrogen after being impacted by sodium sulfite.0.10 mA/cm² and 0.15mA/cm² have better tolerance to sodium sulfite,especially under the condition of 0.10 mA/cm²,with the addition of sodium sulfite?0?600 mg/L?,NRR is ahead of other current density.