Fouling and Cleaning Characteristics of Reverse Osmosis (RO) Membranes

Abstract

This work deals with fouling and successive cleaning of RO membrane fouled by an organic foulant, sodium alginate using a laboratory-scale cross flow test unit. First, spiral-wound RO membrane was fouled with sodium alginate solution up to 10% and 15%, respectively at an applied pressure of 1380 kPa with flow rate of 10 lit/min. An anionic surfactant, sodium dodecyl sulfate (SDS) was used as a chemical cleaning agent for cleaning of RO membrane. The effect of cleaning chemical dose and cross-flow velocity on the membrane chemical cleaning duration to achieve 100% cleaning efficiency (i.e., to get original water flux) was also investigated. As the SDS concentration increases, the membrane chemical cleaning time decreases due to increase in the solubility of the foulant (when the surface tension decreases by an increase in the SDS concentration). Furthermore, the membrane chemical cleaning time decreases with increasing cross-flow velocity of the cleaning chemical solution (SDS). Higher cross-flow velocity enhances the turbulence at the fouling layer and hence the mass transfer of the foulant from the fouling layer to the bulk solution is improved, then the SDS has weakened the structural integrity of the fouling layer. It is observed that better cleaning is occurred with higher concentration of SDS and flow rate. The obtained results clearly reveal that SDS cleaning is proved to be an efficient cleaning method for RO membranes fouled with organic foulant.

Seawater reverse osmosis membrane fouling causes in a full scale desalination plant; through the analysis of environmental issues: raw water quality

“…In addition, by analyzing the reasons, it is possible to find a suitable method for chemical cleaning of the membranes (11). Many studies have been done in details regarding the fouling reasons through which one or two reasons have been identified, however, there are less global or comprehensive studies in this regard (12)(13)(14)(15)(16)(17)(18)(19). In a study by Gutiérrez Ruiz et al, which is similar to the recent study, chemical composition and structure of fouling agents on the membrane surface were determined using the energy dispersive X-ray microanalysis and scanning electronic microscopy.…”

Chemically enhanced backwashing for NOM removal of ceramic ultrafiltration membranes using conventional cleaning chemicals with a surfactant

“…The HA molecule is then solubilised and is removed with the cleaning solution (Li & Elimelech, 2004;Arijit Das et al, 2015). Arijit Das et al, (2015) observed a decrease in cleaning time from 25 minutes to 10 minutes with increase in SDS concentration from 0.1 to 0.3 mM. This was observed while cleaning a RO membrane fouled with sodium alginate (SA).…”

“…This research plans to use anionic surfactant, SDS, for membrane cleaning operations. SDS was chosen because of its popularity as a surfactant for typical membrane cleaning applications (Arijit Das et al, 2015;Beyer et al, 2010;Hijnen et al, 2012;Li & Elimelech, 2004;Li et al, 2005;Madaeni & Samieirad, 2010;Madaeni et al, 2009;Wang et al, 2018).…”

“…This breaks HA molecules (which is attached to the tail of SDS) from the intermolecular bridge with Ca 2+ (Beyer et al, 2010;Li & Elimelech, 2004). The HA molecule is then solubilised and is removed with the cleaning solution (Li & Elimelech, 2004;Arijit Das et al, 2015). Arijit Das et al, (2015) observed a decrease in cleaning time from 25 minutes to 10 minutes with increase in SDS concentration from 0.1 to 0.3 mM.…”

“…Reduced surface tension due to SDS is said to have allowed for easier solubilisation of SA molecules from the foulant layer into the cleaning solution (Arijit Das et al, 2015).…”