Physicochemical pretreatment of seawater: fouling reduction and membrane characterization

Abstract

The pretreatment of raw seawater is necessary to minimize the organic fouling of seawater reverse osmosis (SWRO) membranes. To predict the membrane fouling of the pretreated seawater, the modified fouling index (MFI) with ultrafiltration (UF) was investigated in terms of molecular weight distribution (MWD) and membrane characterization. The study was conducted with seawater drawn from Collioure, France. The concentration of total dissolved solid was 32760 mg/L. The molecular weight (MW) of the initial seawater organic matter (SWOM) ranged from about 14160 Da to 280 Da. FeCl 3 flocculation removed the majority of SWOM, while PAC adsorption could not remove the lowest MW fraction of organic matter ( 1110, 750 and 280 Da) . The UF membranes with 30 kDa and 100 kDa molecular weight cut-off removed the majority of of organic matter corresponding to the peaks 14160 Da and 6560 Da in Molecular Weight Distribution.The MFI values obtained when using UF membranes of 30 kDa and 100 kDa with MF pretreatment were 19700 s/L 2 and 31000 s/L 2 , respectively. The MFI values after pretreatments of FeCl 3 flocculation and PAC adsorption significantly decreased to 6900 s/L 2 and 6700 for 30 kDa UF and to 2300 s/L 2 and 2500 s/L 2 for 100 kDa UF, respectively. Some relation does exist for both membranes between the MFI-UF values and (S pb ) values obtained during the first peiod of filtration (pore blocking). The pore blocking zone significantly decreased after flocculation and adsorption pretreatment. This suggests that the pore blocking can be used as an indicator to predict membrane propensity. The detailed membrane characterization on the clean and fouled membrane surface after MFI-UF experiments was made in terms of contact angle, zeta potential, functional group and microscopy.

A new sponge tray bioreactor in primary treated sewage effluent treatment

“…Finally, in terms of MFI value, the best index was observed at 28 and 40 mL/min with the value of 2.3 × 10 4 s/L 2 . It can be explained by the correlation between the quality of treated water in terms of organic concentration and membrane fouling (Javeed et al, 2009;Shon et al, 2009). It is proved that at flow velocity of 28 mL/min, the system obtained the highest performance in terms of pollutant removal and reducing membrane fouling.…”

Applicability of electro-osmotic flow for the analysis of the surface zeta potential

“…12 Recently, an alternative indirect measurement technique for SZP of at surfaces was introduced, 13 and is comprising phase analysis light scattering (PALS) using mostly polymeric tracer particles through electro-osmotic ow (EOF) mapping in a simple dip cell arrangement. Several studies were reported on using EOF for SZP determination in a dip cell, [13][14][15][16][17][18][19][20][21] in a coated microchannel that measures the mobility of known ZP of tracer particles close to the surface, 22 in a quartz cell having mostly non-ionic hydroxypropyl-coated polystyrene tracer particles [23][24][25][26][27][28][29][30][31][32][33][34][35] or with microelectrophoresis instrumentation modied to accommodate quartz capillaries using sulphated polystyrene latex particles. 36 It relies on the principle that the electrophoretic mobility of tracer particles dispersed in a liquid is affected by the surface when these particles approach the solid sample.…”

“…13,14 However, for a stateof-the-art SP analyser, these drawbacks have been overcome. On the other hand several authors have reported SZP results for various material types ( [13][14][15][16][17][18][19][20][21][23][24][25][26][27][28][29][30][31][32][33][34][35] ) obtained by the EOF method (in different congurations) using mostly polymeric tracer particles. The problems observed in these studies were associated with a high measurement uncertainty that consequently lowers the quality of the data 15,16,24,27,[38][39][40] especially for more complex sample surfaces (nanobers, membranes), difficulties in determining the surface IEP when oppositely charged tracer particles were exposed, 15,18,19,26,29 or the observation of polymeric tracer particles sedimentation and degradation (colour change of tracer particle dispersion), which is even more pronounced under elevated ionic strength, 15,19,24,28 that limits the applicability of the EOF method at high salinity conditions.…”

Techno-economical approach of GAC and microfiltration as a coagulant-free pre-treatment of seawater desalination

“…Since it was previously suggested that the combination of membrane fi ltration with an activated carbon pre-treatment could be a promising improvement of the fi ltration performance (especially concerning the removal of organic matter [6,7]) it was decided to technically explore this method as well, again without coagulation, as a comparable case for the stand-alone MF.…”