Influence of static mixer on the formation and performance of dynamic membrane in a dynamic membrane bioreactor.

Graphical abstract Highlights • Homogeneous formation of dynamic membrane (DM) with minimum effluent turbidity using static mixer in DMBR. • Size and place of static mixer had significant effects on the formation, stability, and filtration resistance. • The shortest formation time of DM was obtained with elevation of the static mixer size. • Membrane fouling improved with changes in static mixer place. • Role of static mixer was more prominent in reduction of operational costs and energy consumption. Abstract Homogeneous formation of a dynamic membrane (DM) on macroporous materials (such as mesh filter) in a dynamic membrane bioreactor (DMBR) is very important. In this research, an economical and efficient method was introduced for homogeneous formation of DM using a static mixer. To investigate the effectiveness of the static mixer in formation and filtration of DM, in comparison with the state without a static mixer, the size of the static mixer was examined at different aeration rates. The filtration characteristics of DMBR including formation time, stability time and fouling propensity were obtained. Further, the properties of DM including the mean particle size (M ps), soluble microbial product (SMP), average thickness and porosity of DM were measured to analyze the formed DMs in the bioreactor. The results indicated that the static mixer size (r p = −0.892) has the maximum effect on the formation time. With the crossflow velocity control, the static mixer contributed to homogeneous formation of cake layer and increased share of large particles on the mesh filter surface at the very beginning, such that the minimum formation time was achieved. Moreover, to achieve suitable conditions for the site of static mixer in the bioreactor, the effects of the place of the static mixer were examined in the best DM formation state (formation time < 5 min). It had a great impact on the stability time (r p = −0.941) and fouling propensity (r p = 0.926). Based on the obtained results, application of static mixer can contribute to saving energy and promoting the DMBR technology in wastewater treatment through shortening DM formation time and decreasing membrane fouling. [ABSTRACT FROM AUTHOR]