Study On Decarbonization And Nitrogen Removal Characteristics And Pathway Of Municipal Wastewater By A/M/A-SBR Process

At present,China’s municipal sewage have presented a trend of low carbon to nitrogen ratio,usually requiring additional carbon source and high exposure energy consumption to achieve a good decarbonization and nitrogen removal efficiency.It would not only increase energy consumption and operating costs,but also increase excess sludge production and greenhouse gas emissions.While the anaerobic ammonia oxidation process could save aeration and 100%organic carbon demand.Taking it as a supplementary route to low COD/TIN municipal sewage treatment,namely the"partial anaerobic ammonia oxidation"process,have gotten the attention of researchers and become one of the research hotspots.At the same time,the experimental process also need to be verifyed whether the anaerobic ammonia oxidation bacteria（An AOB）can achieve self-enrichment and stable retention without biomass vector and 25°C at the temperature.This paper directed at the problem of high aeration energy consumption and high carbon source cost in the traditional municipal sewage treatment process and proposed a new low-consumption and high efficient nitrogen removal process:A/M/A-SBR process.The process inhibited nitrite-oxidizing bacteria（NOB）and realized the self-enrichment of An AOB in the SBR reactor under anaerobic/micro-oxygen/anoxic operation mode.The main research contents of the paper are as follows:（1）Phase I:In the sludge recovery stage,the sludge stored for 8 months were recovered with 4 h cycle of anaerobic/aerobic/anoxic（A/O/A,85/90/40min）for 60 d.During the recovery process,the removal efficiency of COD was more than 90%and the removal efficiency of total inorganic nitrogen（TIN）was 40%-70%.The amount of sludge increased from 1.1 g/L to about3.0 g/L.Meanwhile,small particles appeared in the system.（2）PhaseⅡ,the micro-oxygen environment adaptation process.The cycle time was adjusted to 6 h in anaerobic/micro-oxygen/anoxic（A/M/A,120/120/100 min）.DO was adjusted to 0.7-0.8 mg/L,the adaptation stage maintained for 40 d,and the removal effect was gradually optimized.NH₄⁺-N and TN removal rate increased from about 30%to over 70%.（3）PhaseⅢ,Ⅳ,stable operation stage,DO was adjusted to 0.4-3 mg/L,and the accumulation of NO₂^--N at the end of micro-oxygen phase increased.During the stable operation of the system for 130 days,the short-cut nitrifica-tion and denitrification efficiency of micro-oxygen segment was above 80%,while the post-internal denitrification efficiency of anoxic segment was below20%.The results of batch experiment showed that the activity of ammonia oxidizing bacteria was 2.96 mg/g SS·h and that of denitrifying bacteria was3.4 mg/g SS·h in the stable operation stage,The activity of NOB was inhibited.In order to improve ammonia nitrogen removal efficiency and inhibit NOB at the same time,DO was adjusted to 0.5-3.5 mg/L.self-enrichment of anaerobic ammonia oxidizing bacteria was achieved by 90 d,during which the performance was optimized,and the removal efficiency of COD,NH₄⁺-N and TN were above 90%,75%and 75%,respectively.（4）According to high-throughput sequencing,The results show that Proteocteria,Chloroflexi,Bacteroidota accounted for 88.08%,94.17%,93.7%in three stages,respectively.Planctomycetes increased by 0.5%and An AOB accounted for 3%in it.Among them,Candidatus Scalindua accounted for29%,Candidatus Brocadia accounted for 57%,Candidatus Kuenenia accoun-ted for 10%and Candidatus Jettenia accounted for 4%.（5）Through metagentic test,we deeply explored the proportion of nitrification genes（amo,hao,nxr）and denitrification genes（nar,nir,nor and nos）in the system and then analyzed the N cycle in the system.The expression of amo,hao,nxr,nar,nir,nor,nos were 6.74,4.76,285.1,251.78,49.67,99.7,0.89,respectively.Among them,the expression of denitrification genes was greater than nitrification,which was consistent with high-throughput sequencing results.