Temporal variation of NOM and its effects on membrane treatment

Near real‐time monitoring of natural organic matter (NOM) concentration and composition in the upper Mississippi River was performed for 11 months. The monitoring found distinct seasonal trends in dissolved organic carbon (DOC) concentration and ultraviolet light absorbance at 254 nm as well as short‐term (i.e., hours to days) increases that correlated with increases in river discharge during storms and snowmelt. The permeability (i.e., transmembrane pressure‐normalized flux) of hydrophilic ultrafiltration membranes was negatively correlated with river flow (p < 0.01) and raw water specific ultraviolet absorbance (p < 0.01) but not with raw water DOC concentration (p = 0.865). Overall, the potential benefits derived from the increased data provided by an on‐line monitoring system should outweigh the maintenance requirements for such instrumentation. Such data potentially could be used for real‐time control of chemical dosing rates as well as membrane backwash and cleaning schedules.