Effect of temperature shocks on membrane fouling in membrane bioreactors

Reproducibility and applicability of the flux step test for a hollow fibre membrane bioreactor

“…Moreover, the state of the membrane at a specific applied flux is affected by previous flux steps. Some authors have attempted to overcome this limitation by introducing a period of relaxation, or operation at zero or low flux, between the flux steps [8,13,11] to control reversible fouling, i.e. the layer at the membrane surface removed by physical cleaning [5].…”

Influence of temperature and temperature shock on sludge properties, cake layer structure, and membrane fouling in a submerged anaerobic membrane bioreactor

“…This could be attributed to the combined effect of deflocculation and reduction in viscosity in the first and/or second 5 1C shock and temporarily decreased mixed liquor viscosity and improved shear stress in later temperature shocks (5 and 10 1C). Deflocculation due to temperature shock would negatively affect membrane fouling, while an increase in temperature decreases the viscosity of the mixed liquor, and consequently increase the hydraulic shearing force on the membrane surface [12]. Viscosity was found to have positive effects on membrane fouling [38] and negative effects on flux [39] shocks after the first or second 5 1C shocks, as indicated by the PSDs reported in our previous study [19].…”

“…When temperature increases, the membrane filtration resistance would be expected to reduce, because the sludge viscosity decreases and water permeability increases at high temperatures. Furthermore, the shear stress on membrane surfaces would be expected to increase with an increase in temperature, due to the reduced viscosity at higher temperature [12]. However, the higher the operating temperature, the greater the fouling resistance was observed in this study.…”

“…A decrease in viscosity at higher temperatures could enhance shear forces on membrane surfaces [12] and thus reduce the formation rate of cake layers on membrane surfaces. In addition, the change in microbial community at different operating temperatures could also be partially responsible for the change in cake formation rate.…”

“…Thus, it is highly desirable to understand the effects of temperature variation and temperature shocks on the performance of biological systems for industrial wastewater treatment. Temperature is considered to be a key factor to affect the stability and efficiency of biological treatment processes [11,12], especially for anaerobic treatment processes [13], in terms of sludge properties, effluent quality and microbial community. For a membrane bioreactor, it can be anticipated that the temperature will also affect cake layer formation.…”