Abstract: Changes in nitrifying granule diameter had great influences on nitrifying effect.Experimental investigations based on three granule diameters of 649 μm,1 171 μm and 1 571 μm in 90 days had shown that their nitrifying effects,average specific diameter growth rate μ_d and biomass growth rate μ_g were not the same and decreased with increasing of diameters,which resulted from the variations of ecological environment,microbe species,microbe biomass and its distribution inside the granules.The growth of granules...