Ultrasonic irradiation for ultrafiltration membrane cleaning in MBR systems: operational conditions and consequences

Abstract

Ultrasonic irradiation is one of the most promising membrane cleaning techniques for membrane bioreactors (MBRs) because of several advantages such as high flux-recovery capacity and in situ application without interrupting the filtration process. However, significant contradictions may be found and, consequently, this method has not yet been widely developed. In this paper, four MBRs equipped with hollow-fibre polyvinylidene fluoride ultrafiltration membranes were operated continuously. The cleaning method applied consisted of sonication at low power (15 W) with different frequencies (20, 25, 30, and 40 kHz) for each module and aerated backwashing. The different MBRs were analysed comparatively between them and with a conventional MBR in order to check the effects of the irradiated waves on membrane integrity, effluent quality and process performance. Effluent turbidity and chemical oxygen demand, total and volatile suspended solid concentration and activated sludge viscosity were affected by biomass fragmentation or membrane cake removal, mainly at lower frequencies. The best transmembrane pressure control was achieved at the frequency of 20 kHz without a significant effect on membrane integrity. The results showed that under these operational conditions, no negative effects on effluent quality or membrane integrity were found, suggesting that this method was suitable for this type of membrane.

A Review on the Mechanism, Impacts and Control Methods of Membrane Fouling in MBR System

“…Moreover, pretreatment of the wastewater by ultrasonic irradiation or by hybrid ultrasound methods prior to MBRs can decrease the organic loading of the wastewater and subsequently postpone the fouling of the membrane. Moreover, the ultrasonic method can be combined with other cleaning methods, i.e., chemical cleaning and backwashing, to improve the cleaning efficiency [174].…”

Development of Environment-Friendly Membrane for Oily Industrial Wastewater Filtration

“…There are so many membrane cleaning methods reported in the literature: pneumatic cleaning [ 55 , 56 ], ultrasonic cleaning [ 57 , 58 ], sponge ball cleaning [ 59 , 60 ], and chemical cleaning [ 61 , 62 ] However, backflushing is the most accessible and cheaper technique to obtain maximum recovery among all. Anyhow, the effect of membrane cleaning methods on the NBR-GO membrane will be evaluated in the next study.…”

Biofouling Removal from Membranes Using Nonthermal Plasma

“…The ultrasonic power intensity of 0.18 W cm −2 and the time of 3 min h −1 (i.e., operate 3 min for each hour) were considered as optimal. Ruiz et al [51] applied sonication at low power (15 W) with various frequencies (i.e., from 20 to 40 kHz) for the cleaning of fluorinated polyvinylidene membrane. The best control of transmembrane pressure was achieved at 20 kHz without significantly affecting membrane integrity.…”