Research On The Operation Of Low Strength Wastewater Treatment By Reflux PN-ANAMMOX Reactor

In this study,the integrated reactor of reflux PN-ANAMMOX was started with municipal wastewater as the research object.Aiming at the instability of parital nitrification in PN-ANAMMOX process at room temperature and low ammonia nitrogen,the regulation strategy and nitrogen removal performance of parital nitrification in integrated denitrification process were investigated.After PN and ANAMMOX are started step by step,the stability of effluent nitrate was controlled by adjusting the parameters and the reflux in the combined operation.Finally,pre-denitrification was combined to reduce the total nitrogen in the effluent,realizes the stable operation of the combined process and improves the denitrification capacity.The main results of this study were as follows:?1?NOB has a strong adaptability to the environment.With the increase of operation time,the NO₃^--N concentration was increased gradually,and parital nitrification is unstable.It is difficult to achieve stable inhibition of NOB by increasing FA and limiting oxygen,and the concentration of NO₃^--N in effluent is still rising after a short decline.?2?The combined process realizes the stable inhibition of NOB,and under the action of reflux,the problem of the continuous increase of nitrate nitrogen in effluent is effectively controlled.The optimal reflux ratio is 3:1,when the reflux ratio is insufficient,the nitrogen content in aerobic zone is higher than that in NOB,which is not conducive to inhibition of NOB.When the reflux ratio is too high,ANAMMOX in anaerobic zone is easily affected by DO,resulting in the accumulation of nitrite in effluent.?3?The system has good adaptability to cold temperature,stable operation conditions and good sludge interception able to maintain high AnAOB activity,in the process of continuous cooling,the effluent has no nitrite nitrogen accumulation.Under the condition of temperature about 21?,HRT:3.32 h,reflux ratio 3:1,PN-ANAMMOX was operated in stable,NRR reaches 0.2 kg·?m³·d?^-1.?4?C/N was control at 0.8,the total nitrogen of effluent was further removed,TN removal rate is more than 70%,COD removal rate is more than 90,and the overall NRR is 0.25 kg·?m³·d?^-1.?5?The results of quantitative PCR showed that the proportion of NOB was decreased gradually after reflux.From the single aerobic zone to the combined reflux,the copy number of NOB decreased from 9.87×10⁷ to 6.34×10⁶,and NOB was significantly inhibited under starvation condition.