【Abstract】 Protozoa in activated sludge can improve the sewage treatment,reduce the mass of sludge and indicate the quality of effluent.The following effects are reviewed:① extretion of growth factors and extracellular polymers; ②preying on bacteria.Preying changes the structure of bacteria community,stimulates the growth of bacteria in flocs and benefits the sediment of the activated sludge.Protozoa grazing on fecal bacteria and in the suspended liquor is essential for the production of good quality effluent.更多还原