Study On The Influence Factors Of Partial Denitrification And The Characteristics Of Partial Denitrification-ANAMMOX Process

In recent years,biological denitrification technology is promoting the mainstream application of ANAMMOX process,and partial denitrification technology is a new method of nitrite accumulation,which can provide a reaction matrix for ANAMMOX.The whole anaerobic environment of the two coupled processes can reduce the operating cost of sewage treatment plants.For the purpose of strengthening the feasibility and stability of the partial denitrification coupled ANAMMOX process,the effects of the partial denitrification reaction on the reaction process at low concentration and the reaction time and period time were studied;then the initial nitrate concentration,initial COD/NO₃^--N、MLVSS、initial p H and temperature were discussed from the point of view of enzyme activity,and according to effects on nitrate reductase and nitrite reductase,found out the best conditions and analyze the principle of nitrite accumulation;finally,studied the effects of different influent concentrations and shorter cycle time on the stability of the partial denitrification-ANAMMOX process;at the same time,analyzed the changes of microbial flora in the two reactors at different operating stages.The experimental conclusions were as follows:（1）When the influent nitrate concentration was relatively low（40 mg/L、55mg/L、70mg/L）,the partial denitrification reactor can achieve the effective accumulation of nitrite.When the nitrate concentration in the influent was 110 mg/L、the reaction time was 10 min and the period time was 90 min,the highest nitrate accumulation rate was 95.73%,and the average nitrite concentration in the effluent was 83.31 mg/L.（2）The batch experiment showed that higher initial nitrate concentration was beneficial to the accumulation of nitrite.At the initial C/N=2.8,the ratio of nitrite reductase activity to nitrate reductase activity was the lowest.MLVSS=3500mg/L was the best sludge concentra-tion.When the initial p H was 7.5～9,the ratio of nitrite reductase activity to nitrate reductase activity was 0.28,which was good for nitrite accumulation.20℃～25℃was the best temperature range of partial denitrification.In a word,the main reason for the efficient accumulation of nitrite was the effective inhibition of nitrite reductase activity.（3）When the concentration of inlet nitrate in the coupling process increased from50mg/L to 140mg/L,the denitrification performance of the coupling process continued to improve,and the total nitrogen removal rate was up to 96.24%.In the output water,there was no nitrite,the concentration of nitrate kept increasing,the average COD concentration was40.46mg/L,and the average ammonia concentration was 5.80mg/L.In order to improve the treatment load,the cycle time of the coupling process was shortened from 572min to 358min.After the reactor was adapted for a period of time,the coupling process finally reached stability.The total nitrogen removal rate was 93.50%on average.Before and after the operation of the coupling process,the accumulation performance of nitrite in the partial denitrification SBR did not change,and there was weak denitrification in the ANAMMOX SBBR.（4）After long-term operation,the partial denitrification sludge gradually formed granular sludge,and after successful sludge domestication,the number of Protectobacteria increased,among which Thauera increased to 24.01%,and the Pseudomonas also appeared in the reactor.Before and after coupling,Planctomycetes increased from 29.11%to 57.64%and Protectobacteria decreased to 11.89%in ANAMMOX reactor.At a subordinate level,Candidatus Anammoxoglobus bacteria were enriched.As the partial denitrification sludge and organic matter entered the ANAMMOX reactor,denitrification bacteria and other heterotrophic bacteria appeared in it,thus the whole reactor flora richness increased and the system was more stable.