Studies on the minimisation of NOM fouling of MF/UF membranes with the help of a submerged 'single' capillary membrane apparatus

摘要

This paper looks into the problem of fouling of UF/MF membranes due to NOM present in surface waters.NOM can be divided into paniculate,colloidal and dissolved fractions.The idea here is to fractionate the surface water into the above-mentioned fractions,and to tesi the fouling characteristics of each fraction on a MF membrane,with and without pre-treatment by coagulation.Coagulation was performed at a pH of 7.5,using poly aluminium chloride(PAC)(2.5 mg/L A1~(3+)),and the flocculated solution was slowly transferred into the feed tank of the filtration unit.A lab-scale single membrane capillary(SMC)test unit was used for the filtration test runs.The bulk surface water was fractionated using 0.45 urn(MF),5kD(UF)and/or 3.5 kD dialysis bags.Membrane performance was measured using permeability decline and its recovery after each backwash.Feed and permeate samples were analysed using UVA_(254)(m~(-1))to estimate the organics removal through filtration.It could be shown that(1)particulates(organic/inorganic)helped minimise irreversible fouling,(2)the colloidal organics are the most irreversible fouling causing fraction,and(3)coagulation pre-treatment plays a significant role in improving and stabilising membrane performance.