In this paper, 1.5 g·L-1 of magnetic activated carbon with different particle sizes being 80, 140, 200, and 300 mesh (numbered 2, 3, 4, 5) were inoculated into the same sequencing batch reactor (SBR). The sludge volume index (SVI), particle size distribution characteristics, changes of extracellular proteins (PN), polysaccharide (PS), and polymeric substances (EPS) and their decontamination capability were studied and compared with a control group without addition (numbered 1). The results show that different particle diameters of magnetic activated carbon have certain influences on the granulation process. For example, it is easier for activated sludge to form aerobic granular sludge (AGS) when particle size are 140 mesh and 200 mesh acting as an inner core. Under these conditions, the AGS has a close structure and good sedimentation characteristics. Gaussian distribution was adopted to analyze the characteristics of Tparticle size distribution and standard deviations. The average diameter of the sludge in 3# and 4# all reached 780 μm within 50 days, which was higher than other reactors, with the same standard deviations being 318.9 μm and 362.3 μm respectively, which is lower than 2# and 3#. Besides, the granular sludge formed in both reactors was uniform in size and stable in operation. Different particle sizes of magnetic activated carbon were beneficial for the enhancement of proteins (PN), especially those with appropriate diameters (140 and 200 mesh), but had little effects on polysaccharides (PS). The formation of aerobic granular sludge based-magnetic activated carbon was in accordance with the inert kernel model. Meanwhile, the PN/PS in 3# and 4# were obviously higher than other SBRs with the same removal rate of TN and TP reaching 50% and 60% respectively.
Keywords: aerobic granular sludge; magnetic activated carbon; particle size; sludge granulation.