FOURIER TRANSFORM INFRARED PHOTOACOUSTIC SPECTROSCOPIC ANALYSIS OF NATURAL ORGANIC MATTER FOULANTS ON ULTRAFILTRATION AND REVERSE OSMOSIS MEMBRANES

摘要

Due to increased demand,water scarcity and diminishing raw water quality,reverse osmosis(RO)is finding increased use in drinking water production(Gabelich et al.,2002;Redondo,2001).However,the efficacy of RO is currently limited by the extent of membrane fouling that occurs under conventional pretreatment conditions(Durham,1997;Gabelich et al.,2002).Numerous investigations have examined the influence of pretreatment methods on membrane fouling and concluded that proper pretreatment is a key to successful RO plant operation(e.g.,Isaias,2001).Typical membrane foulants include aluminum hydroxide and aluminum silicate materials(Sheikholeslami,2001;Gabelich,2002)and natural dissolved organic matter(NDOM)(Isaias,2001;Beverly et al.,2000;Winters,1997).However,additional knowledge of the fouling that results from different pretreatment methods is needed.Ongoing work by Gabelich and co-workers(Gabelich et al.,2002 and 2003;Gerringer et al.,2004)has explored the influence of different pretreatment options on RO-membrane fouling at a southern California filtration plant accepting mildly brackish Colorado River water.In the present study,new and fouled polyethersulfone ultrafiltration(UF)and polyamide reverse osmosis(RO)membranes from the same plant were interrogated by Fourier transform infrared photoacoustic spectroscopy(FTIR-PAS)to elucidate the functional group characteristics of fouling material.We compared the fouling associated with conventional pretreatment and conventional pretreatment plus ozonation/biofiltration(O_3/BF).Previous work by Beverly et al.(2000)demonstrated polyamide membrane damage by chlorine oxidation.To investigate possible oxidative damage to the RO membrane during feedwater treatment,organic fouling layers were removed from membrane subsamples and compared to unfouled background membrane samples.