U sing circulation tests to model natural organic matter adsorption and particle deposition by spiral-wound nanofiltration membrane elements

C irculating the permeate and concentrate w aters through a spiral-wound element proved to b e a viable approach for observing the adsorption o f NOM on membrane surfaces with time. C ontinuously treating the same volume o f water a llowed the adsorption o f NOM to be detected as a l oss of NOM mass in the circulating water. B ecause differences in NOM concentrations b etween the feed and concentrate waters are s ubtle and typically within the precision of a nalytical measurement, determining adsorption b y other means such as those based on a mass b alance calculation are difficult for a flowt hrough system. Circulating the water in a c losed-loop system is a viable method for o bserving adsorption as it occurs within a s piral-wound element. I n contrast, in-line particle counters were s hown capable of detecting the subtle differences in particle numbers between those entering and E xperiment Exp(NOM0,PP=0) Exp (NOM5,PP=0) Exp (NOMI 5,PP=0) Exp (NOM25,PP=O) Exp (NOMO,PP>1.0) Exp (NOMS,PP>1.0) Exp (NOM15,PP>1.0) Exp (NOM25,PP>1.0) Exp (NOM0,P0.5-1.0) Exp (NOM5,P0.5-1.0) Exp (NOM15,P0.5-1.0) Exp (NOM25,P0.5-1.0) 0,0 10o 1.0 108 2.0 108 3.0 10a 4.0 108 5.0 10B 6.0 10B 0.5-1.0 IJm particle deposition rate== (#/hour) F ig. 10. Deposition rates for 0.5-1.0 p.m size particles for the 12 experiments.