Effective fouling inhibition by critical flux based optimization methods on a NF membrane module for olive mill wastewater treatment

The operation of a spiral-wound nanofiltration membrane module used continuously for three years in order to purify different pretreated olive mill wastewater streams will be discussed. The membrane module was for the first time used at the beginning of year 2006 on a batch pilot scale plant for critical flux studies and wastewater treatment in our laboratories. The olive mill wastewater is a waste stream produced by the olive oil mill factories, characterized by very high organic matter load and polyphenols concentration. Without fouling inhibition at all, nanofiltration membranes will reach zero-flux conditions within days. This is not the case of this nanofiltration membrane module, which was successfully operated continuously for three years during our laboratory work. This result was reached by proper fouling inhibition control, relaying on both critical flux measurements and the development of an optimized operation method. Moreover, supercritical operation experiments were performed on another nanofiltration module of the same model in order to validate the approach. (C) 2011 Elsevier B.V. All rights reserved.