| With the increase in the nitrogen pollution of slow-flow water bodies in China,more and more nitrogen removal technologies have been applied in the field of water pollution control.In order to reduce nitrogen effectively,various new processes have been developed,among which the most economical and efficient one is anammox process.However,the application of anammox process in nitrogen-containing organic wastewater treatment is limited.Recently,it has been found that simultaneous anammox and denitrification?SAD?can achieve synergistic nitrogen removal via coupling of anammox bacteria?AnAOB?and denitrification bacteria?DNB?.In this paper,the cultivation and enrichment of anammox granular sludge were explored,the nitrogen removal performance of SAD granular sludge under different C/N ratios was investigated,and the influence of different inorganic salinity concentrations on the optimal nitrogen removal system of SAD granular sludge was studied.Finally,the optimized regulation and stable maintainance were realized for the high efficient running of the SAD process.The main conclusions are as follows:?1?The anammox granular sludge was successfully enriched by adjusting substrate concentrations?NH4+-N and NO2--N?and hydraulic retention time?HRT??from27 h to 6.67 h?.After 319-d of operation,the nitrogen removal efficiency?NRE?was81.53%,the nitrogen loading rate?NLR?and the nitrogen removal rate?NRR?reached1.72 Kg/?m3·d?and 1.33 Kg/?m3·d?,respectively.Anammox granular sludge turned dark red in color and the particle size higher than 1.5 mm showed the highest percentage which accounted for 62.32%.At the same time,Fourier transform infrared spectroscopy?FT-IR?analysis of the granular sludge surface showed that abundant functional groups which were composed of proteins and carbohydrates.The Haldane model was used to describe the substrate inhibition kinetics,and the results showed that anammox bacteria were prone to be significantly inhibited by nitrite in both substrates.?2?The nitrogen removal was promoted with the increasing C/N ratio at lower C/N ratio levels??0.5?.Nitrogen removal efficiency?NRE?reached 90.81%at C/N ratio of0.5,and the optimal coupling of anammox and denitrification processes was realized.Meanwhile,the EPS production was triggered by organic carbon addition.The amount of EPS and the EPSp/EPSc ratio increased with the increase of C/N ratios,which induced sludge aggregation resulting in the larger particle size sludge granulation.Illumina sequencing results showed that the dominant genus of AnAOB?Candidatus Jettenia?relative abundance increased with increasing C/N ratio at lower C/N ratio??0.5?then decreased sharply at higher C/N ratio of 0.9.Finally,relative abundance of Candidatus Jettenia was promoted by decreasing the C/N ratio,and AnAOB activity was recovery.Moreover,Denitratisoma,Bacillus,Acinetobacter and Pseudomonas were responsible for denitrification all throughout the whole operational periods.?3?The nitrogen removals of the SAD process decreased with the increase in the salinity concentration,and the NRE fell to 54.59%at the salinity concentration of 100mmol/L.Then,the NRE increased by reducing the addition amount of the salinity.With the salinity increasing to 50 mmol/L,the particle size of granular sludge increased,and the content of LB-EPS and TB-EPS also showed an increasing trend,respectively.In addition,the results of high-throughput sequencing showed that Candidatus Jettenia and Denitratisoma had always been AnAOB and DNB dominant genus under different salinity conditions.It was also observed that an increase in the nitrite accumulation rate was accompanied with the increase in the salinity concentration.Meanwhile,the relative abundance of Thauera genus value also exhibited an increasing trend.When the salinity concentration reached its maximum value,the nitrite accumulation rate and the relative abundance of Thauera genus reached the largest ones,which were 0.032mg/?mgVSS·d?and 1.44%,respectively. |
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