Optimization of Air Backwash Frequency during the Ultrafiltration of Seawater

Abstract

The main objective of this paper is to study the effect of new air backwash on dead-end ultrafiltration of seawater with a pilot at semi-industrial scale (20 m3/day). To control membrane fouling, two different backwashes were used to clean the membrane: classical backwash (CB) and new air backwash (AB) that consists of injecting air into the membrane module before a classical backwash. To evaluate the efficiency of AB and CB, a resistance in series model was used to calculate each resistance: membrane (Rm), reversible (Rrev) and irreversible (Rirr). The variation of the seawater quality was considered by integrating the turbidity variation versus time. The results indicate clearly that AB was more performant than CB and frequency of AB/CB cycles was important to control membrane fouling. In this study, frequencies of 1/5 and 1/3 appear more efficient than 1/7 and 1/9. In addition, the operation conditions (flux and time of filtration) had an important role in maintaining membrane performance—whatever the variation of the seawater quality.

Ultrafiltration as tertiary treatment for municipal wastewater reuse

“…Therefore, optimum conditions BW1/3 and BW1/4 used in 3.3 are confirmed as they are more suitable for long term operation at industrial scale. This result is similar to the result on seawater [17], who concluded that AB was more effective to control fouling resistance in conditions of BW1/3 and BW1/5, than that in conditions with lower AB frequency BW1/7 and BW1/9, all under the same J = 60 L⋅m − 2 ⋅h − 1 and t = 60 min.…”

“…To control fouling, filtration conditions (flux, filtration time, cleaning) need to be optimized because they can directly affect either the formation and nature of the fouling layer, or the removal mechanism of the foulants. For example, the filtration flux and filtration cycle time will affect the density and the thickness of the fouling layer deposited on the membranes [17]. Besides, frequent cleanings for membranes are required, including physical and chemical washing, to maintain good filtration performance.…”

Impact of Chlorinated-Assisted Backwash and Air Backwash on Ultrafiltration Fouling Management for Urban Wastewater Tertiary Treatment

“…The flow chart of physical backwashes can be found in Figure 1 . The AB has shown their excellent efficiency to remove the fouling whatever the type of water [ 39 , 40 , 41 ]. Through comparison, one backwash sequence (CB CB CB AB) in all conditions has the same consumption of permeate volume, same energy demand for backwash and air injection, and duration for backwash, the differences among them was only the addition of NaClO or not.…”

Ultrafiltration to secure shellfish industrial activities: Culture of microalgae and oyster fertilization

“…The flow rate was 60 Lh − 1 m -2 with a filtration duration of 30 min; the backwash is programmed every 30 min and alternated with an air backwash (AB) at a frequency of 1 AB for three backwashes. These parameters were optimized by Cordier et al (2020a). The membrane permeability (Lp) was calculated and recorded continuously every minute.…”

“…Moreover, UV radiation can generate toxic molecules (Souissi et al, 2013). To avoid this limitation, Cordier et al investigated the benefits of using ultrafiltration (UF) in aquaculture activities, which can provide a good and stable quality of seawater (Cordier et al, 2018(Cordier et al, , 2019a(Cordier et al, , 2020a(Cordier et al, , 2020b. Ultrafiltration is a membrane process which a molecular cut off around 10 nm.…”