Characteristics of membrane foulants at different degrees of SWRO brine concentration by membrane distillation

Fouling development at different degrees of SWRO brine concentration by a DCMD system was investigated in this study. The experiments were done with a 60 degrees C feed inlet temperature and 20 degrees C permeate inlet temperature to investigate the fouling dynamic based on the distillate flux and detailed organic and inorganic characterizations. The fouling test was classified into 4 phases based on the flux declint percentage. The initial distillate flux (40.1 +/- 1.0 kg/m(2) h) was reduced by 96.6%, when the feed concentration factor reaches 3.0 of uninterrupted operation. The fouling mass increased nearly 378 times from VCF 1.1 (1.3 g/m(2)) to VCF 3.0 (490.9 g/m(2)). The deposit morphology and the composition of the foulants at each phase have been determined using SEM-EDS, XRD, ICP-OES, ATR-FTIR and LC-OCD. The fouling data revealed that membrane fouling is dominated by deposited inorganic foulants in combination with organic foulants. The accumulation of small mass of organic foulants (0.3 parts per thousand) promoted fouling development because of their adhesion to the membrane and salt bridging. In addition, some organic materials penetrated the membrane despite a lack of apparent membrane wetting. (C) 2016 Published by Elsevier B.V.