Enhancing Effects And The Distribution Of Aluminum In The Process Of Aerobic Sludge Granulation

Aerobic granules have good settling ability,high biomass retention,and withstand highstrength wastewater,but the longer granulation time limits its development.In order to shorten this time,we added aluminum to strengthen the granulation during the process of aerobic sludge granulation.In order to investigate the effect of aluminum enhancing the granulation of aerobic sludge,the characteristics and shape of granules which cultivated with different coagulants were analyzed,the content and distribution change of aluminum in the sludge were revealed,and the content changes of Extracellular Polymeric Substances(EPS)and its component were also investigated.In addition,the removal of pollutants from three reactor sludges were also investigated.The results showed that:(1)PAC and aluminum sulfate were dosed into different Sequencing Batch Reactors(SBR)to strengthen the granular sludge during the 10 th to 16 th day in this study.It could accelerate the formation of granules in R2 and R3,the granulation time were shortened by 10 days compared with the R1,and the particle size of the granular sludge increased rapidly.The MLSS of the aerobic granular sludge in R1?R2 and R3 were 3.9 g/L?5.0 g/L?5.2 g/L;while SVI were 74 m L/g?78 m L/g?58 m L/g during32 th day.The effect of adding aluminum sulfate is better than PAC.(2)Results of EPS showed,during the granulation of aerobic sludge(8-25 d),the contents of LB-EPS and TB-EPS in aerobic sludge were increased,the content of LB-EPS increased larger in the granular sludge,thus accelerating the formation of granular sludge.And protein in LB-EPS and TB-EPS was first increased then decreased,finally increased.The three-dimensional EEM spectra showed that duringgranulation,the fluorescence intensity of peaks B?D and E in 21 th day were larger than50 th day,dosing PAC and aluminum sulfate had little effect on the chemical structure of granular sludge,while the FTIR spectra showed that there were functional groups of Amide ? and PS in the EPS.(3)During the period of 16-29 d,the quality of aluminum in the sludge adding with PAC decreased from 30.46% to 0.43%.While the quality of aluminum in the sludge added with aluminum sulfate decreased from 45.69% to 13.29%.The quality of aluminum in the sludge added aluminum sulfate was 1.09% at the 42 th day,which was significantly higher than that of PAC in the sludge(0.02%).(4)Aluminum coagulants may play different roles in the granulation process: at the aspect of PAC,the promotion of EPS secretion can aggregate the microorganism through the bridging effect,and then enhance the aerobic granulation;while for aluminum sulfate,a nucleation is formed after coagulant dosing and the EPS content increases at the same time,therefore,the formation of granules can be accelerated.(5)In the stage of the granule forming,the total number of bacteria in three reactors showed an increasing trend.And total number of bacteria in R2(dosing PAC)and R3(dosing aluminum sulfate)were more than R1(no aluminum).The effect of dosing coagulant on the total number of bacteria in sludge was not obvious.At days30-41,the total number of bacteria was basically stable,the bacteria in R1,R2 and R3 aerobic sludge were 6.7×109 cfu/g ?1.03×1010 cfu/g and 7×109 cfu/g.We found the sludge after dosing coagulant with FISH in 18 th day,the microorganisms were evenly distributed in sludge of R2,while R3 were relatively not evenly,and the central microorganisms were less.The sludge in R2 and R3 are similar to the circular shape,but sludge edges is irregular in R1.(6)The average removal rate of COD was 98% with granular sludge in R2(dosing PAC)and R3(dosing aluminum sulfate),while the sludge without coagulant was 93%.The removal rate of ammonia nitrogen with aerobic granular sludge in R1?R2 and R3 were about 75%?81% and 75%.