Fouling reduction effect in MBR system by ozone injection

Abstract

Membrane Bioreactor (MBR) process is increasingly being used as a more advanced technology for biological wastewater treatment. However, due to membrane fouling, MBR system is often restricted in field application. Membrane fouling in MBR system may cause high maintenance cost, and reduction in membrane’s lifespan. Membrane fouling reduction in MBR system was investigated using ozone in the study. Ozone is being employed in wastewater treatment, and it may change microbial characteristics in MBR system by changing the water environment to more oxidative one. Experimental results of this work were analyzed with respect to various parameters, such as BOD5, CODCr, Total Nitrogen (TN), Total Phosphorus (TP), Extracellular Polymeric Substances (EPS) production, tensile strength, Sludge Volume Index (SVI), Oxidation Reduction Potential (ORP), field emission scanning electron microscope (FE-SEM) photos, and permeability or effluent flow rate of membrane. MBR system applied with ozone injection in aeration tank showed high performance in removing water quality parameters such as BOD5, CODCr, TN, and TP. Especially removal of TP was remarkably enhanced from about 45% to 87% by ozone dosage. Before ozone dose, backwash was needed once in every two weeks. However after the ozone injection, backwash was not required for more than 4 months. When the MBR system was in operation for two weeks, membrane was in need of a backwash. However, permeability of the used membrane has gradually recovered to the level of backwashed state, and maintained the same permeability rate thereafter.