This study was to experimentally investigate organic fouling development in a 1-m long RO membrane channel using alginate as a model organic compound. Five parallel local permeate fluxes with a distance interval of 20 cm along the channel were monitored continuously during the organic filtration tests. It was found that organic fouling became more severe towards the outlet of the channel. This might be mainly attributed to the salt concentration polarization formation along the channel. The higher salt concentration downstream increased the interactions involved in organic fouling such as charge-screening and alginate-calcium bridging, which intensively promoted organic fouling formation in the downstream. A higher feed flow was a common option to mitigate fouling at most lab-scale RO research work, but not the case in this long membrane channel. A higher feed flow changed the organic fouling development profile along the channel, but would not eliminate organic fouling.
Keywords: concentration polarization, long channel, organic fouling, reverse osmosis (RO)