Self-forming Dynamic Membrane Bioreactor Research Articles

Optimal operating strategies of SFDM formation for MBR application

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.

A hybrid system combining self-forming dynamic membrane bioreactor with coagulation process for advanced treatment of bleaching effl uent from straw pulping process

An innovative hybrid system combining self-forming dynamic membrane bioreactor (SFDMBR) with coagulation process was developed to treat bleaching wastewater from pulping process. Pilot-scale experimental results showed that the average removal effi ciencies of chemical oxygen (COD) demand and lignin by the SFDMBR were over 80% and 51%, respectively. The fairly good treatment performances can be attributed partly to the high biomass concentration (i.e. -10 g/L) maintained in the SFDMBR, and partly to the more efficient solid-liquid separation achieved by the self-forming dynamic membranes. It was found that the self-forming dynamic membranes can be quickly created, normally less than 60 min, during the initial stage of SFDMBR operation. Effluent turbidity was lower than 5 NTU in most cases. Membrane fouling can be effectively controlled via 5 min online air backwashing at an intensity of 3.2m3·m−2·h−1, and the separation capacity can be restored within 30 min. The effluent of SFDMBR was subsequently treate...

Fouling control of a pilot scale self-forming dynamic membrane bioreactor for municipal wastewater treatment

A pilot scale self-forming dynamic membrane bioreactor (SFDMBR) was used for municipal wastewater treatment and its fouling control was investigated. Two methods, on-line bottom aeration flushing and off-line high-pressure water flushing, were applied to control the self-forming dynamic membrane (SFDM) fouling. Aeration intensity of 22 m 3 /(m 2 ·h) and aeration time of 2 min were the optimized operational conditions. Fouling of SFDM could be on-line controlled by bottom aeration flushing to keep the bioreactor continuously working for about 50 days. However, the intervals of bottom aeration flushing were gradually shortened which suggested that fouling could be controlled to some extent but gel layer could not be removed effectively. High-pressure water flushing could remove cake layer and most gel layer, and the membrane flux could be almost 100% recovered. Through the convenient fouling control by combination of bottom aeration and high-pressure water flushing, the present SFDMBR has been normally operated for more than one year and the effluent was suitable for urban miscellaneous water consumption if disinfection was added.