Anaerobic fluidized membrane bioreactor polishing of baffled reactor effluent during treatment of dilute wastewater

Abstract

BACKGROUND: In this study an anaerobic fluidized bed membrane bioreactor (AFMBR) is added as a second stage to an operating anaerobic baffled bioreactor (ABR) to form a staged anaerobic baffled-fluidized membrane bioreactor (SAB-FMBR) operating at ambient temperature. RESULTS:The ABR first stage was operated at 3 h hydraulic retention time (HRT) and was followed by the AFMBR operated at 0.93 to 1.16 h HRT. The SAB-AFMBR system was fed with complex synthetic wastewater with COD averaging 250 mg L −1 . GAC fluidization increased the critical flux of the AFMBR due to fouling reduction associated with the cleaning action of the GAC particles on membrane surfaces. However, sustainable flux for long-term operation of the AFMBR was lower than the critical flux determined in short-term tests. Overall COD removal by the SAB-FMBR system when operating at a sustainable flux (8-9 L m −2 h −1 ) was 96% with effluent COD of about 11 mg L −1 and suspended solids concentration near zero. The electrical energy required for system operation in the AFMBR was 0.0087 kWh m −3 , much less than that of an anaerobic MBR using biogas sparging to control membrane fouling. CONCLUSION:The AFMBR was applied successfully as a second stage polishing system for an ABR treating complex synthetic wastewater at a temperature of 25 ∘ C.

Anaerobic Fluidized Bed Membrane Bioreactors for the Treatment of Domestic Wastewater

“…In addition, larger particles may enhance the transport of smaller particles by scouring and sweeping them away from the membrane by shear-induced conditions (Chellam and Wiesner 1997). Also observed was that GAC fluidization in the AFMBR disaggregated microbial flocs, producing smaller compressible materials in the AFMBR, in the range of 0.1-1.2 µm, than were originally present in the feed suspension (Lee et al 2015). Similar results were found in another type of submerged aerobic MBR system with polypropylene materials added as suspended carriers (Huang et al 2010).…”

Design of anaerobic membrane bioreactors for the valorization of dilute organic carbon waste streams

“…Possible development pathways include the use of physical media for scouring of the membrane surface 34,35,49 or membrane vibration. 18,50,51 Including GAC in an AnMBR has many benefits (e.g., decreased membrane fouling, 35,52,53 higher fluxes, 52 and removal of trace contaminants), 35 but its use needs to be further evaluated through longterm experimental studies to better quantify trade-offs between an increased flux and a potential decrease in membrane life (increasing maintenance costs). To the degree possible, research efforts should focus on physical medium selection and membrane geometry to achieve membrane cleaning without damage, and simultaneously target cheaper, smaller, and lower density particles 49 to reduce upflow velocity requirements for bed expansion (e.g., reduce upflow velocity to <7.5 m·hr −1 while keeping HRT below 1.6 hrs).…”

CFD-accelerated bioreactor optimization: reducing the hydrodynamic parameter space

“…The hydrodynamics of fluidized-bed reactors have been investigated experimentally 28,29 and with simulations, 30–34 but membrane bioreactor studies of microbial activity have largely focused on experimental testing. 35,36 These studies do not track particle dynamics at high volume fraction (low porosity), but instead focus on macroscopic behavior such as fluidization stability and expansion. 37,38 The range of bed expansion in fluidized beds fluctuates between 20% and 70% with a qualitative understanding that low expansion leads to flow short-circuiting and high expansion leads to biofilm loss.…”