Retention of humic acid from water by nanofiltration membrane and influence of solution chemistry on membrane performance
Membrane technology and the related separation systems such as reverse osmosis (RO) and nanfiltration (NF) membranes are now widely recognized as the best technologies for water treatment (Zularisam et al., 2006). However, fouling remains as one of the major challenges in membrane applications. Fouling of RO and NF membranes causes significant loss of productivity and added operational cost. Natural organic matter (NOM) has been identified as one of the major foulants for these membranes (Tang et al., 2007). NOM is abundant in natural water resources and is derived both from natural degradation of some organic substances within the ecological systems and from human activities. Although, NOMs are considered harmless, but they have been recognized as disinfection by-products (DBPs) precursors during the chlorination process. Formation of DBPs highly depends on the composition and concentration of NOM which can be broadly divided into two fractions of hydrophobic (humic) and hydrophilic (non-humic) substances (Zazouli et al., 2007). Humic substances (HS) are comprised of humic and fulvic acids and non-humic substances (non-HS) include carbohydrates, lipids, and amino acids (Croue et al., 1993; Owen et al., 1995).