Effect of sludge properties on membrane formation and fouling in a dynamic membrane bioreactor

The dynamic membrane formation and membrane fouling characteristics of normal sludge,bulking sludge and deflocculated sludge were investigated in a submerged nylon mesh dynamic membrane bioreactor(DMBR),and the fouling mechanisms were explored from the aspects of extracellular polymeric substances(EPS),relative hydrophobicity(RH),sludge viscosity(μ) and contact angle.The results showed that the bulking sludge could cause severe cake fouling due to adsorption and bridging of filamentous bacteria.The deflocculated sludge reduced the effective filtration area,which resulted from the deposition of colloidal particles and soluble matter that deposited on the membrane pores.Comparatively,normal sludge had a slightly lower membrane fouling tendency and thus the best performance.It was also found that the EPS content and its composition,and the sludge morphology were the two major factors affecting sludge properties and fouling behaviors of the DMBR.