Effect of particle size on the performance of aerobic granular sludge in tomato sauce wastewater

The biological activity, mass transfer effect of the particles and the structural distribution and synergistic relationship of the internal flora are affected by the culture substrate and particle size of the granular sludge, thus determining the effluent quality. The granular sludge was successfully cultured in sequencing batch reactor activated sludge process (SBR) reactor with tomato paste wastewater and maintained for 185 d, four kinds of particles with different particle sizes were screened out for simultaneous sequencing batch test to investigate the characteristics of the sludge and its deconfliction efficiency for the tomato paste production wastewater. The results showed that 0.45~1.00 mm granular sludge was irregular in shape and the surface porosity was small; 1.0~1.6 and 1.6~2.0 mm granular sludge tended to be spherical and ellipsoidal, with a smooth surface and dense structure. Although there were more surface gullies and pores in 2~8 mm granular sludge, the stability of the system could be maintained well. The presence of pores probably provided conditions for the transport of internal materials and the excretion of microbial metabolites within the particles. The average sedimentation rate and wet density were positively correlated with the granule size. The water content was negatively correlated with the particle size. Granular sludge with larger particle size greatly reduced the production of excess sludge. Compared with 1.0~1.6 and 1.6~2.0 mm granular sludge, 0.45~1.00 and 2~8 mm granular sludge had better ability to degrade organic matter, and the removal rates of chemical oxygen demand (COD) were 97.8% and 94.2%, respectively. 1.6~2.0 mm granular sludge had the best degradation effect on NH4+-N and PO43--P, with the removal rates of 92.7% and 99.2%, respectively. The removal effect of 0.45~1.00 mm granular sludge on PO43--P was 69.5%. © 2021, Editorial Office of FINE CHEMICALS. All right reserved.