Biofilm-based membrane reactors – selected aspects of the application and microbial layer control

Abstract

The membrane, a selective barrier, could serve also as a carrier for biofilm (a microorganism layer) immobilization. Then, it forms the so-called catalytic (active) membrane. The aim is to maintain a layer of controlled thickness and activity. The use of membrane as a biomass carrier is justified when the membrane performs an additional function. Such applications are discussed in the paper. Particular attention is given to the reactors in which microorganisms are immobilized on the membrane surface and the membrane simultaneously serves to provide substrate transport from a liquid and/or gas. The most interesting case is membrane oxygenation. The resulting different zones of aeration of biofilm allow simultaneous aerobic and anaerobic processes to occur in a single reactor. This integration can be applied in the treatment of any kind of municipal wastewater. A promising application of biofilms is their location on an ion-exchange membrane. In this case, catalytic membrane serves as a fuel cell. In the simplest solution, microbial fuel cells change the chemical energy collected in compounds (wastes, renewal biomass) into the energy necessary to support the biological functions of microorganisms and additionally create a supply of electrical energy. Keeping a stable thickness of the microbial layer is a key to provide the process at stable efficiency. Selected methods for in situ disposal of redundant biofilm are presented.

Recent progress using membrane aerated biofilm reactors for wastewater treatment

“…Nylon silk was also used as the membrane material for surface water treatment (Zhong et al 2019), but its long-term durability and impact on mass transfer and biofilm formation need further investigation. Overall, PVDF, PP, and nylon silk are classified as microporous membrane materials which have negligible mass transfer resistance (Janczewski & Trusek-Holownia 2016). These membrane materials are generally favored in lab-scale MABR studies because high oxygen transfer flux through pores promotes aerobic biochemical reaction rates (Syron & Casey 2008a;Nerenberg 2016;Lu et al 2020).…”

“…As the constituents in the gas stream diffuse through the membrane while other substratesF (in the bulk liquid diffuse through the liquid boundary layer, biological activity is the highest in the center of the MBfR biofilm, where both gaseous and liquid substrates are sufficient. This counter-diffusion property of MBfRs ensures high functional stability against shock loads and toxic inhibitors Janczewski & Trusek-Holownia 2016;Nerenberg 2016).…”

Biofilm re-vitalization using hydrodynamic shear stress for stable power generation in microbial fuel cell

“…So far, several methods such as oxygenation, flow rate, rotation, chemical (antibiotic), enzymatic treatment, mechanical cleaning etc. have been implemented to remove inert biomass (dead cells) from the surface [13][14][15]. However, these systems cannot be considered as sustainable and feasible method due to their toxicity, conflicting environmental issues and inapplicability in large scale systems [14,16].…”

Ultrasound Driven Biofilm Removal for Stable Power Generation in Microbial Fuel Cell

“…Among the available methods, ultrasound treatment is one of the most potential in vitro methods since it can successfully remove the thick biofilm within a short period of time. 15 Ultrasonic treatment causes detachment of bacteria by using strong shear forces and thus prevents the deposition of a dense bacterial layer on the surface as shown in Figure 1 (schematic diagram). The figure illustrates that ultrasound can create cavitation bubbles in the liquid adjacent to the surface, or in the narrow volume between the surface and loosely attached inert biomass; thereby, multilayer biofilm can easily be dispersed from the surface.…”

“…Among the available methods, ultrasound treatment is one of the most potential in vitro methods since it can successfully remove the thick biofilm within a short period of time . Ultrasonic treatment causes detachment of bacteria by using strong shear forces and thus prevents the deposition of a dense bacterial layer on the surface as shown in Figure (schematic diagram).…”