1、Journal of Membrane Science 242(2004)4755Removal of natural organic matter(NOM)in drinking water treatmentby coagulationmicrofiltration using metal membranesTorove Leiknes,Hallvard degaard,Hvard MyklebustDepartment of Hydraulic and Environmental Engineering,NTNU,Norwegian University of Science and T
2、echnology,S.P.Andersensvei 5,N-7491 Trondheim,NorwayReceived 4 March 2003;received in revised form 10 May 2004;accepted 12 May 2004Available online 15 July 2004AbstractDrinking water sources in Norway are characterized by high concentrations of natural organic matter(NOM),low pH,low alkalinity andlo
3、w turbidity.The removal of NOM is therefore in many cases a general requirement in producing potable water.Drinking water treatmentplants are commonly designed with coagulation direct filtration or with NF spiral wound membrane processes.This study has investigatedthe feasibility and potential of us
4、ing inorganic metal microfiltration membranes in a submerged membrane configuration with coagulationpre-treatment for drinking water production.Variations in operating modes and conditions were tested,from dead-end operation to semisequencing batch operation using air scouring and backwashing cycles
5、 for membrane cleaning and fouling control.Fluxes around 180 LMHat transmembrane pressures below 0.3bar where achieved over production cycles in excess of 50h.Treatment efficiencies in general showed95%colour removal,85%UV removal,6575%TOC removal and 0.2 NTU turbidity and non-detectable suspended s
6、olids in thepermeate.The initial results show that MF metal membranes is an interesting alternative to sand filtration in coagulation/direct filtration fortreating drinking water.2004 Elsevier B.V.All rights reserved.Keywords:Natural organic matter;Coagulationmicrofiltration;Metal membranes1.Introdu
7、ctionAbout 90%of Norwegian drinking water supplies arefrom surface water sources,generally from lakes which typ-ically have very low turbidity,alkalinity and hardness buthigh colour resulting from natural organic matter(NOM).One of the major problems of using surface water sources innorthern climate
8、s is high content of NOM and total organiccarbon(TOC).Removal of NOM is required since colouredwater is unattractive to consumers,results in colouring ofclothes during washing,can cause odour and taste,increasescorrosionandbiofilmgrowthinthedistributionnetwork,andis a precursor to the formation of d
9、isinfection by-products(DBP)when water is disinfected.Halogenated compoundsresulting from chlorination of drinking water containingconcentrations of NOM has been a major concern sinceCorresponding author.Tel.:+47 7359 4759;fax:+47 7359 1298.E-mail address:torove.leiknesntnu.no(T.Leiknes).their disco
10、very in the early 1970s as some of the chlorina-tion by-products are carcinogenic.Drinking water sourcesin Norway are commonly described as having high colour,low pH and low alkalinity where typical values are given inTable 1.The removal of NOM is therefore a major treatmentrequirement in the produc
11、tion of potable water where con-centrations typically in the 3080mg/L Pt true colour rangeare reduced to less than 10mg/L Pt.The most common drinking water treatment plant designsin Norway are based on coagulation and direct filtration ornanofiltration(NF)membrane filtration processes 13.Co-agulatio
12、n direct filtration plants(enhanced coagulation)arestill the dominant treatment plant design option with a typ-ical flow scheme as illustrated in Fig.1.In the last 1015years membrane processes based on nanofiltration(NF)us-ing spiral would module configurations have been success-fully used in Norway
13、 for removing NOM,and approxi-mately 100 membrane plants are in operation today.The NFmembrane plants are commonly designed to operate with aconstant flux of 17Lm2h1(LMH)at a transmembrane0376-7388/$see front matter 2004 Elsevier B.V.All rights reserved.doi:10.1016/j.memsci.2004.05.01048T.Leiknes et
14、 al./Journal of Membrane Science 242(2004)4755Table 1Typical water source composition and drinking water standard require-mentsRaw water parameterDrinking water standardsHigh color(3080mg/L Pt)20(1)High TOC(36mg/L C)5(3)mg/L of CHigh COD(48mg/L COD Mn)5(2)mg/L of O2Low turbidity(1 NTU)One from WTP,f
15、our at consumersLow alkalinity(0.5mEq./L)Alk.:0.61.0mEq./LLow hardness(95%colouris removed,around a 85%UV254-absorbance and between65 and 75%TOC removal is achieved.Suspended solids(SS,mg/L)could not be detected in the permeate and thepermeate turbidity was 95%of true colour,87%ofUV-absorbing compou
16、nds,and 6575%of DOC.A consis-tent high permeate quality was achieved for all experimentsirrespective of operating modes investigated.Initial studieswith dead-end operation and variations of backwashing andair scouring showed that membrane fouling was reversibleand primarily cake formation.This cake layer was easily re-moved when the membrane was cleaned extensively and themembrane performance was returned to its initial state.The performance of the membrane system was found tobe best when operat
