| Anaerobic ammonia oxidation（Anammox）process has become a hot research topic due to its low energy consumption,no external organic carbon source,and low sludge yield,etc.The growth rate of An AOB is slow,therefore,how to achieve rapid enrichment and effective retention of An AOB becomes the key to its engineering application.The granular sludge technology has become the main form of anaerobic ammonia oxidation research application because it can effectively control the sludge loss.However,the actual wastewater contains high concentrations of organic carbon sources,and the presence of organic carbon sources can lead to the growth of heterotrophic bacteria such as denitrifying bacteria,resulting in reduced stability and changes in the internal microstructure of anaerobic ammonia oxidation granular sludge,which directly affects its effectiveness.The current research mainly focuses on the effect of organic carbon source on the morphological structure,EPS composition and stability of granular sludge,however,the research on the change pattern of granular sludge microorganisms and their response genes under the stress of organic carbon source is still relatively weak.Domestic and foreign scholars often use biochar for wastewater purification research,which has a high removal rate of pollutants and plays an important role in the migration,transformation and bioavailability of pollutants in the environment.Therefore,based on the study of the effect of organic carbon source on granular sludge,appropriate amount of biochar was added with the aim of improving the treatment capacity of anaerobic ammonia oxidation granular sludge.Studying microbial community diversity,exploring its denitrification pattern,and focusing on the change pattern of functional microorganisms inside the organic carbon source-stressed granular sludge and the response mechanism of functional genes under the dosing of charcoal materials will provide theoretical references for the application of anaerobic ammonia oxidation granular sludge.（1）The effect of bamboo charcoal（BC）-mediated different COD concentrations on anaerobic ammonia oxidation granular sludge was investigated in a UASB reactor.The results showed that the average TN removal efficiency decreased from 85.9%to81.4%when the COD concentration was increased from 50 mg-L-1.However,the TN removal efficiency of the BC-mediated reactor was significantly higher than that of the reactor without BC by 3.1 to 6.4%,with maximum values of 31.4%,25.2%and21.3%,respectively.The average diameter was 0.13 mm higher than that without BC.the settling velocity increased with increasing COD concentration and decreased with the addition of BC.In addition,EPS and VSS/SS increased with BC addition.High-throughput Miseq sequencing analysis showed that COD addition decreased the diversity and abundance of bacteria,Candidatus Brocadia and Candidatus Kuenenia,which are common genera of the phytoplasma phylum Anammox denitrification system.Macrogenome sequencing results showed that the abundance of denitrification-related functional genes both increased with increasing COD and decreased with anaerobic ammonia oxidation.The addition of BC enhanced the functional genes related to denitrification and anaerobic ammonia oxidation in all reactors.（2）The effect of different biochar-mediated concentrations of different COD on anaerobic ammonia oxidation granular sludge was investigated in a UASB reactor.It was found that the nitrogen removal performance of the anaerobic ammonia oxidation granular sludge system was significantly different under different concentrations of organic matter stress at 100 and 150mg·L-1and with different biochar dosing.At 100mg·L-1,the average removal rates of ammonia were 83.46%for R1（blank）,79.22%for R3（coconut charcoal）,82.50%for R4（peach charcoal）,83.12%for R5（date charcoal）,80.48%for R6（lychee charcoal）,77.05%for R7（walnut charcoal）and78.30%for R8（sycamore charcoal）.The average removal rate of ammonia nitrogen at150mg·L-1was 71.19%for R1（blank）,69.48%for R2（bamboo charcoal）,68.91%for R3（coconut charcoal）and 68.91%for R4（peach charcoal）,respectively.R4（peach charcoal）68.75%,R5（date charcoal）68.07%,R6（lychee charcoal）73.69%,R7（walnut charcoal）70.14%and R8（sycamore charcoal）72.34%,respectively.The inhibition of organic matter on granular sludge Anammox reaction was obvious and strengthened with the increase of organic matter concentration,and the resistance of biochar to the impact of organic carbon source was no longer obvious at high organic matter concentration;the nitrite removal rate of each system was above 95%,and the nitrite removal effect was good;the total nitrogen removal rate was improved by0.88%～4.70%after each system was stabilized with the addition of biochar.The addition of biochar could promote the overall denitrification performance of the Anammox granular sludge system,and the system had the best total nitrogen removal capacity at 100 mg·L-1.With the increase of stress concentration,the anaerobic ammonia oxidation granular sludge changed from brick red to black,and the size of inoculated granular sludge was mainly distributed in 1～2 mm,accounting for 56.8%.At COD concentrations of 100 mg·L-1and 150 mg·L-1,respectively,the particles with diameters of 1～2 mm decreased and those with diameters of 2～3 mm increased,among which,R7（walnut charcoal）had the most obvious effect in promoting granulation,with a maximum increase of 9.5%.the EPS content gradually decreased and at 150 The decrease was particularly dramatic at 150 mg·L-1,and the concentration of R7（walnut charcoal）promoted the growth of granular sludge particle size,mechanical strength,settling performance,and EPS content.The settling speed of R1 reactor was found to be lower than that of R0 after the addition of organic carbon source,indicating that the addition of organic carbon source reduced the settling speed,but the settling speed of the reactor with the addition of biochar was higher than that of R1 reactor,indicating that the addition of biochar improved the settling performance of granular sludge,and the larger the particle size,the higher the settling speed,and the higher the COD concentration,the better the settling performance.The density of granular sludge was basically greater than the density of water,and there was no obvious phenomenon of sludge floating.With the addition of organic matter,the anaerobic ammonia oxidation activity of R1 reactor decreased,and the reactors with biochar addition all had higher activity than R1.High-throughput sequencing results showed that the phyla that were more abundant in each sample were Proteobacteria,Chloroflexi,Planctmycetota and Acidobacteria.Both ACE and Chao indices of microorganisms in the reactor increased,indicating an increase in the total number of species.With the increase of COD concentration,the relative abundance of all the floating enzyme bacteria belonging to An AOB decreased,and the relative abundance of all the green curvularia phylum increased up to 78.4%. |
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