Comparative Study Of Achieving Partial Denitrification With Primary And Residual Sludge As Seed Sludge

As a traditional nitrogen removal process,nitrification-denitrification has many defects,such as high energy consumption and greenhouse gas generation.Anaerobic ammonia oxidation consumes less oxygen and does not require the addition of an electronic donor.It can also reduce the remaining sludge content by 90% and is highly energy efficient.Whether the NO₂^--N can be provided stably for ANAMMOX bacteria is one of the key factors in the current process promot ion and application.Partial nitrification can provide NO₂^--N for ANAMMOX,but in practical application,the control means are complex and the effect is easily destroyed.Partial denitrification provides a new idea for the supply of NO₂^--N.In this paper,the primary sludge and residual sludge in domestic wastewater treatment plant were used to realize partial denitrification,and the characteristics of the two reactor during the start-up process and under the influence of different factors were compared.Meanwhile,the functional bacteria were explored from the perspective of microbial community structure,so as to promote the practical application of partial denitrification.?1?PSPD-SBR and RSPD-SBR were constructed,and the start-up strategies as well as characteristics of partial denitrification with different seed sludge in domestic wastewater treatment plant were studied.After 273 cycles,the NRR and NTR of PSPD-SBR were increased to 88.0% and 77.1%,and the NRR and NTR of RSPD-SBR were increased to 84.4% and 75.0%,respectively.The NO₂^--N accumulation performance of PSPD-SBR was slightly better than that of RSPD-SBR.Full-cycle monitoring showed that both PSPD-SBR and RSPD-SBR could achieve stable accumulation of NO₂^--N,as a result,partial denitrification was feasible to become a stable source of NO₂^--N for ANAMMOX.In addition,the sedimentation of sludge in both systems was improved and the sludge granulated gradually.?2?The effects of FA,Fe²⁺,Fe³⁺ and Mn²⁺ on PSPD-SBR and RSPD-SBR were investigated,and the feasibility of maintaining good partial denitrification performance at high temperature by increasing sludge concentration at low temperature was explored.Both PSPD-SBR and RSPD-SBR have the best performance of accumulation of NO₂^--N when FA concentration is 20 mg/L,and the corresponding NH₄⁺-N concentration is 39.2 mg/L,which is consistent with the concentration of NH₄⁺-N in municipal sewage.Therefore,it is speculated that both of them can be combined with ANAMMOX achieve good results in mainstream wastewater treatment applications.With the increase of Fe²⁺ concentration,both PSPD-SBR and RSPD-SBR showed the phenomenon that NRR increased while NTR decreased.When PSPD-SBR reached the optimal performance,the Fe²⁺ concentration was 0.085 mmol/L,and RSPD-SBR had a better NO₂^--N accumulation effect without the addition of Fe²⁺.The increase of Fe³⁺ concentration will make the NRR of PSPD-SBR and RSPD-SBR increase while the NTR decrease.In PSPD-SBR,the partial denitrification performance is the best without the addition of Fe³⁺,and RSPD-SBR has a better NO₂^--N accumulation effect under the influence of 0.08 mmol/L Fe³⁺.The NTR and NRR of PSPD-SBR and RSPD-SBR increased with the increase of Mn²⁺ concentration.When the Mn²⁺ concentration was 0.05 mmol/L,the partial denitrification performance of PSPD-SBR and RSPD-SBR reached the optimal.It is not feasible for PSPD-SBR to keep the denitrification performance at low temperature by increasing the sludge concentration.It is feasible for RSPD-SBR while the effect is not as good as its performance at high temperature.?3?The characteristics of microbial community structure in PSPD-SBR and RSPD-SBR were revealed.The diversity of PSPD-SBR and RSPD-SBR seed sludge was high,the microbial richness and diversity decreased with domestication,and the microorganisms in PSPD-SBR could be enriched faster and at a higher degree.The sludge in PSPD-SBR and RSPD-SBR contained the same main microbial species at the phylum level,including Proteobacteria,Actinobacteria,Chloroflexi,Bacteroidetes,Acidobacteria,Firmicutes and Nitrospirae,but the microbial abundance of different sludge samples varied greatly.After PSPD-SBR and RSPD-SBR were started,Thauera was the absolute dominant bacteria genus,accounting for 63.0% and 57.0% respectively,suggesting that Thauera was the main functional bacteria genus for partial denitrification in this study.