The Cultivation And Features Of Anammox Granular Sludge

Anammox granular sludge is considered to be an effective method to retain Anammox bacteria with high total nitrogen removal rate,impact load resistance and good sedimentation performance.However,in recent years,studies have found that Anammox granular sludge will also appear serious sludge floating phenomenon,resulting in a large number of sludge loss,which makes the denitrification performance of the reactor decline or even collapse.The floating of Anammox granular sludge seriously limits the engineering application of Anammox process.The floating of granular sludge is due to the change of its particle characteristics.Therefore,in order to learn the change of granular sludge characteristics during the formation of Anammox particles and the impact of load increase on the characteristics of Anammox particles,this study started two UASB reactors for cultivating Anammox sludge.Under the two culture modes of fast and slow load lifting,the differences in stability,sedimentation and coagulation of the granular sludge of the two reactors were investigated by measuring the particle size,surface structure and sedimentation rate of Anammox granular sludge during the culture process and comparing the EPS content and component changes of the granular sludge.The conditions and factors affecting the characteristics of Anammox granular sludge were discussed,and the following research results were obtained:(1)Anammox granular sludge can be cultivated faster in the culture mode with fast load raising.Under the two modes of fast and slow load increasing the EPS content of granular sludge increased by 299.42mg/gVSS and 230.5mg/gVSS respectively,PN/PS increased by 5.9 and 5.2 respectively.The median particle size of the corresponding Anammox sludge increased from 100?m to 800?m and 600?m respectively.The settlement velocity increased from 4m/h to 58m/h and45m/h,respectively.In the process of Anammox granular sludge culture,the higher the content of protein in EPS,the higher the PN/PS value within a certain range,and the higher the agglomeration and sedimentation of granular sludge.(2)In the culture mode with fast load increase,the water quality fluctuates greatly,and Anammox sludge will secrete more EPS and its EPS content was305mg/gVSS,protein content was 253mg/gVSS,PN/PS was 4.87.EPS content of granular sludge was 70mg/gVSS,protein content was 68mg/gVSS,and PN/PS value was 1.17,which were higher than that in the culture mode with slow load increase.In the culture mode with fast load increase,the average particle size of granular sludge is0.86mm and the sedimentation rate is 58m/h,which are respectively 1.65 times of the average particle size and 1.29 times of the sedimentation rate of granular sludge in the culture mode with slow load increase.In the culture mode with fast load increase,Anammox sludge secreted more EPS,the protein content in the secreted EPS component was more,the PN/PS value was larger,and the agglomeration,sedimentation and stability of granular sludge were better.(3)The proportion of T-EPS increased,and the tryptophan fluorescence substance contained in T-EPS was beneficial to the aggregation of granular sludge.In the culture mode with fast load increase,the content of T-EPS in Anammox was92.71%,and the fluorescence intensity of tryptophan was 400AU/(mgC·L),which was respectively 1.85%and 100AU/(mgC·L)more than that in the culture mode with slow load increase.In the culture mode with rapid load increase,the content of T-EPS in Anammox granular sludge was higher,the fluorescence intensity of tryptophan in T-EPS was higher,and the coagulation,sedimentation and stability of granular sludge were better.(4)When Anammox granular sludge denitrification load increased to 3.2kgN/(m~3·d),the content of EPS in granular sludge was 400mg/gVSS,including protein content of 343mg/gVSS,polysaccharide content of 57mg/gVSS,PN/PS value of6.02.The average granule size of granular sludge reached 2.5mm,and the surface structure of particles appeared to float upward.Under high denitrification load,Anammox granular sludge would secrete excessive protein content,PN/PS value exceeded a certain range,the granular structure was loose,and the stability decreased.(5)The proportion of T-EPS in floating granular sludge is 76.38%,the tryptophan fluorescence intensity in T-EPS was 200AU/(mgC·L),compared with the settled granular sludge,the proportion of T-EPS content decreased 5.3%,tryptophan fluorescence intensity decreased 20AU/(mgC·L),fluorescence substances h?mic acid and fulli acid were appeared.With the decrease of the proportion of T-EPS content,the decrease of the fluorescence intensity of tryptophan in T-EPS and the appearance of h?mic acid fluorescence substance made the particle structure loose,the stability decreased and the granule floated up.