Optimal operating strategies of SFDM formation for MBR application

Abstract

This study develops process of self-forming dynamic membrane (SFDM) formation on mesh filter and investigates the capability of such process in treating municipal waste water. The formation process is mainly divided into two stages, i.e., the agitation and the aeration. At the agitation stage, the dynamic membrane is built up by deposition of suspended sludge particles on the mesh surface. The just-complete suspension of sludge flocs is performed using mechanical axial-flow agitator. Four imposed fluxes are applied to obtain the optimal flux for SFDM. Three parameters, i.e., effluent chemical oxygen demand (COD), filtrate turbidity, and trans-membrane pressure (TMP) are simultaneously measured to determine the time required for SFDM formation at agitation stage. The optimal aeration rate is also determined to steady operate the self-forming dynamic membrane bioreactor (SFDMBR). At the aeration stage, the rest of dynamic membrane is gradually formed during continuous operation. The compressibility index of dynamic membrane is also measured at the aeration stage. The results indicate that variations of the trans-membrane pressure correspond to the variations of compressibility index. Scanning electronic microscopy is also utilized to observe the development of SFDM. The performance of SFDMBR is evaluated in terms of total dissolved solids (TDS) and COD removal. The results reveal that the SFDMBR can be substituted for conventional membrane bioreactors. A clean surface of mesh filter is restored by using two cleaning methods, i.e., air scouring and water backwash. Based on Fourier transform infrared analysis, proteins and carbohydrates are the dominant substances comprising the SFDM.