Treatment Of Tomato Paste Processing Wastewater And Microbial Community Succession By Aerobic Granular Sludge

At present,the output of tomato and tomato paste in Xinjiang rank first in Asia,and play an important role in Xinjiang’s economy.With the vigorous development of tomato paste processing industry,the environmental problems caused by the production of a large amount of high-concentration organic wastewater during processing cannot be underestimated.Therefore,it is a very important research topic to explore the economical and effective new treatment and recycling technologies for the characteristics of seasonal tomato paste production wastewater in Xinjiang.Aerobic granular sludge technology is a new technology for wastewater biological treatment,which has broadened the application prospects and great development potential In this paper,the cultivation of aerobic granular sludge,the removal performance of pollutants,the screening of optimal particle size,the succession of microbial community structure and the diversity of population in the process of granulation were studied and discussed.In the sequencing batch reactor(SBR),the activated sludge was granulated by using freshly squeezed tomato juice as a substrate.After 38 days,particles with a pale yellow particle size of about 0.5 mm appeared.The mature granular sludge has a regular shape with high bioactivity and excellent sedimentation performance.SVI reached 19 mL/g,and the ratio of SVI30/SVI5 is close to 1.The particles with 1.6-2 mm and 2 mm diameters accounted for 19%and 57%of the total sludge volume,and after 185 days,the size reached 11 mm.According to the fluorescent staining results of extracellular polymeric substances,the protein and α-polysaccharides in the aerobic granular sludge throughout the whole granule cross-section;dead bacteria were located relatively interior the granule,while live bacteria were more concentrated around the outer layer of granules and the interior pores.At the same time,aerobic granular sludge has strong adsorption and degradability to the tomato paste processing wastewater,increasing the organic load step by step,COD could also be effectively removed;the average removal rates of COD,NH4+-N,and P043--Pcould reach to 95.53%,91.87%and 86.98%,respectively.Four different granules size range were selected in the SBR to examine the sludge characteristics and the decontamination efficiency of the tomato paste processing wastewater.The results showed that the particle of 0.45～1 mm is irregular in shape and the surface porosity is small;1～1.6mm and 1.6～2 mm tend to be spherical and ellipsoidal,with a smooth surface and dense structure;Although there are more surface gullies and pores in the 2～8 mm,the stability of the system could be maintained well The presence of pores may provide conditions for the transport of internal materials and the excretion of microbial metabolites within the particles.The average sedimentation rate and specific gravity are positively correlated with the granule size;the water content is negatively correlated with the particle size,which greatly reduced the production of excess sludge.Compared with the granular sludge of 1～1.6 mm,1.6～2 mm,0.45～1 mm and 2～8 mm,the latter two particles have better ability to degrade organic matter,and the removal rates of COD are 97.8%and 94.2%,respectively;1.6-2mm has the best degradation effect on NH4+-N and PO43--P,with the removal rates of 92.7%and 99%,respectively.The removal effect of 0.45～1 mm granular sludge on PO43--P is 69%.High throughput sequencing technology was used to analyze the microbial community structure and diversity variation in the process of granulation.It was found that there are significant differences in the succession of microbial communities during the granulation process,and that there are functionally dominant populations at different times.Proteobacteria,Bacteroidetes and Firmicutes are important functional bacteria in level of phylum that play an important role in the degradation of tomato paste processing wastewater.Betaprtoteobacteria,Clostridia and Gammaproteobacteria could be adapted to changes in organic load and growth environment and are the main functional bacteria in level of class.With the formation of granules,their species abundance and diversity gradually increased,indicating that the removal of pollutants in tomato paste processing wastewater is a mutual synergy of different microorganisms and compete with each other to become dominant degrading bacteria.In addition,changed in the organic load has a significant effect on species selection in the aerobic granulation process.