Comparative study on the removal technologies of 2-methylisoborneol (MIB) in drinking water

ISSN 1001- 0742Journal of Environmentad Sciences Vol. 18. No. l, pp. 47- -S1, 2006CNI!- 2629/XArticle ID: 1001-0742(2006)01-0047-05CLC number: 131.2Document code:AComparative study on the removal technologies of 2 methylisoborneol(MIB) in drinking waterLIANG Cun-zhen+2, WANG Dong sheng'", GE Xiao-peng', Y ANG Min', SUN Weil(1. State Key Laboratory of Environmental Aquatic Chemistry, Research Centcr for Eco-Environmental Sciences, Bejjing 100085, China. E-mail:sunwds@yaboo.com; 2. Department of Environmental Engineering, Beijing Institute of Pctrochenical Techinology, Beijing 102617, China)Abstract: Removal of 2-methylisobomeol (MIB) in drnking water by ozonc, powdered activated carbon (PAC), potassiumpemanganate and potassium ferrate was investigated. The adsorption kinetics of MIB by both wood-based and coat-based PACS showthat main removal of MIB occurs within contact time of 1 h. Compared with the wood-based PAC, the coat-bascd PAC evidentlyimproved the removal eficiency of MIB. The removal percentage of tracc MIB at any given time for a particular carbon dosagc wasirrelative to the initial concentration of MIB. A series of experiments wcre perfomed to determine the efect of 'pH on the ozonation ofMIB. The resuits show that pH has a significant eftet on the ozonation of MIB. It is conclusive that poassium pemanganatc andpotassium ferrate are ineffectivc in removing the MIB in drink ing water.Keywords: odor, MIB, ozonation; powdered activaled carbon; potassium permanganate; potassiumn ferratetechnologies of MIB,including PAC adsorption,Introductionozonation, potassium permanganate (KMnO4) oxid-Removing taste and odor compounds fromation and potassium ferrate (K2FeO4) oxidation, weredrinking water is a significant challenge for waterinvestigated.authorities worldwide. 2-Methylisobormeol(MIB) is an1 Materials and methodsimportant earthy-musty odorant in drinking water. Theodor threshold of MIB is as low as a few ng/L1.1 Reagents and materials(Pirbazari el ul.,， 1993). The conventional waterMIB was purchascd from Sigma- Aldrich Cotreatment process (coagulation, chlorination and sandUSA, and MIB stock solution of l mg/L was obtainedflration) is not effective to remove MIB (Anselme elby diluting the MIB solution with pure water. PAC A .al, 1988). The removal of MIB by powdered activatedand PAC B (Shanghai Activatcd Carbon Company,carbon (PAC) and ozone is applied in some waterChina) were wood-based and coat-bascd powderedplants (Lin el ul., 2002; Cook el al., 2001; Nerenbergactivated carbon, respectively. Potassium indigoel al, 2000). PAC has the flexibility to be applied astrisulfonate employed for dctermining the aqueousnceded, but it causes sludge removal and disposalozone concentration (Co) was purchased from Acrosproblem, the odor problem caused by MIB cannot be :Organics，Belgium. Potassium permanganate was offully resolved by PAC(Ferreira et al, 2003). The con-analytical grade. Potassium ferrate(K:FeO) was prep-cem of disinfection by-products (DBPs) has promptedared by hypochloritc oxidation of ferric nitratewater plants to consider the use of ozone as alternativeaccording to the method of Delaude and Laszlodisinfectant. The autodecomposition of ozone results(Delaude and Laszlo, 1996), giving a purity over 90%in the formation of OH radical. MIB is considered tofor thc recrystallized product. The purity wasbe susccptible to the attack by OH radical (Suffct et al,dctermincd by the chromite titration method(Schreyer1995). Hence, ozonation will be one of promisingel aul., 1950). The characteristics of the raw waterprocesses for the removal of MIB in drinking water,employed in the cxpcriments are shown in Table I.the study of interaction mechanism is of importance.1.2 Experimental methodsDrinking water quality in Xicun Water Plant,1.2.1 PAC adsorptionGuangzhou, has received complaints from customersA carbon slurry of 10 mg/ml prepared by mixingfor a long time for its unpleasant odors, however, no10 g of the oven-dried PAC in 1 L purc water wasevaluation of odor removal efficicncy for possiblyused中国煤化工。The adsoptionapplied processcs was conducted. MIB with aexpeshaker. In 500 mlconcentration up to 40 ng/L in raw watcr was found inbottleMYHC N M H Gth stock solution toXicun Water Plant. In this study, four kind of removalthe desired initial concentration. Cartbon was added byFoundation item: The Nutional Natural Science Foundation of China (No. 20577060) and the Hi- Tech Rescarch and Development Program (863) ofChina (No. 2002AA601 I20; 2002AA601140); * Corresponding author48LIANG Cun- zthen et al.Vol.18Table 1Characteristic of row waterwater with 2.5 mgL polyaluminum chloride(PACI) asAlkalinity, Hardness, Total organic Turbidiy,Al2O3. TOC of raw water and settled water was 4.61pHmg/L CaCO, mg/L CaCO3 carbon, mg/LNTUand 2.87 mg/L, respectively. Ozone stock solution was71-7.252-60110-130 4.5-4.9- 3.2-3.6_first obtained by bubbling ozone gas into pure water.aliquots of carbon slury. The bottle without theOzone was introduced by adding aliquots of the ozoneintroduction of carbon was used to determine thestock solution to obtain the desired ozone doses.initial concentration. These bottles were covcred withExperiments were conduced at 20C and pH 7. Thea PTFE-faced silicone septum and a screw cappH was stabilized with 50 mmol/L sodium phosphateSamples were then withdrawn at the predeterminedbuffer. After a 10-min O3 contact time, a part oftime intervals up to 240 min and were filtercd withsample was qucnched with Indigo reagent for theglass microfiber filters. The remaining concentrationmeasurement of the O3 residuai and the other sarmpleof MIB was determined immediately.was quenched by sodium sulfite for MIB analysis.1.2.2 Ozonation of MIB1.2.3 Potassium permanganate oxidationA series of experiments were performed toA stock solution of KMnO4 was prepared bydetermine the effect of pH on the ozonation of MIB indissolving crystal permanganate in pure water.a stainless-steel reactor(Fig. I). Ozonizer with a varibleAppropriate quantities of MIB spiked into 1000 mlwork voitage was purchased from Mitsubishi Electricglass bottle to prepare solutions of 100 ng/L. DifferentCorporation, Japan. Transformation ratio of oxygen toamounts of KMnO; were added to the glass bottles,ozone could be adjustcd by controlling the workand the solutions were agitated by magnetic stiningvoltage of ozonizer. Thus, ozone partial pressure inbar. Samplcs were withdrawn after an hour contactthe gas phase and the aqueous ozone concentrationand the remaining MIB concentration was analyzed.(Co, mg/L) was able to be maintained at desirable1.2.4 Potasium ferrate oxidationrangc. The feedwater was pure water buffered with aK,FeO2 stock solution at the concentration of50 mmol/L sodium phosphate solution. Ilydrochloric1000 mg/L as FeO2 was freshly prepared just beforeacid and sodium hydroxide was used to adjust thc pH.the addition to the raw water. The expecriments ofThe reactor temperature was constant at 20C. Afterremoval of MIB by K;FeO, in raw water weresteady-state conditions were obtained, MIB stockperformed at the pH value of 7.1, 7.5 and 7.9,solution was injected into the reactor to kecp therespcctively. Hydrochloric acid and sodium hydroxideinitial concentration of MIB to 400 ng/L. Whenwas employed to adjust the pH of raw water. Thsample was removed from the reactor, the ozone andconcentrations of MIB in samples were analyzed afterother oxidants in solution were at once quenched byonc hour contact.sodium sulfite.1.3 Analytical methodsOzonation of MIB at the concentrations of 100A gas chromatograph/mass spectrometricng/L spiked in raw water, settled water and pure waterdetcctor (GC/MSD) incorporated with solid phasewas performed in a 1000 ml glass bottle, walermicroextraction (SPME) concentration technique wassamples were stirred by a PTFE-coaled stiring bar.used to determine MIB concentration. The details areSettled water was oblained by flocculating the rawdescribed elsewhere (Liang et al., 2005). The indigoColorimetric method was used to determine aqueousReactorFlectrovalve forozone concentration(Faton el adl, 1995).reactor pressurepressurecontrolgauge2 Results and discussionIo venlOzone traps12.1 PAC adsorptionOxygengenerator2.1.1 Adsorption kinetics of MIB by PACFor the application of PAC in a water treatmentSlainlesssteelplant, the kinetics adsorption is of crucial importance.reactorThe effective contact time for PAC in water treatment]Sampleplants is usually on a scale. from minutes to hours,ipjctionSampleortwhic中国煤化工o reach asorptionOzone| portgeoeratorequilMHC NMH Gents at pH 7.1 forwood-based PAC A and coat-based PAC B were uscdto evaluate the MIB adsorption kinetics. ExperimentalFig.1 Schematic diagrarm o[ ozonation reatordata during 4 h batch test with initial conccntration ofNo.1Comparative study on the removal technologies of 2-methylisobomeol(MIB) in drinking water49MIB at 100 ng/L and a 20 mg/L PAC dosagc areexperimental conditions. If PAC dosage exceeds 20shown in Fig.2. The main removal of MIB occunedmg/L，PAC will affect the operation of waterwithin contact time of 1 h and their removal by PACtreatment. So it is difficult to achieve 90% removal ofA and PAC B in 1 h contact was 53.16% and 74.68%，MIB by PAC B.respectively. PAC B showed better removal than PACA. The iodine number for PAC A and PAC B was 980品100and 950 mg/g, respectively. Difference in the MIB80removal for PAC A and PAC B is not due to the50 十iodine number. It may be corrclativc with carbon40 telemental composition (Pendleton et al., 1997). The20elemental analysis results for the PAC samples arc00~shown in Table 2. MIB adsorption occurs via waterPAC B dosago, mg/Ldisplacement. Therefore, the hydrophilic character ofthe surface is the main parameter influencingFig3 Efiect of PAC B dosage on removal of MIBadsorption. Although there is one hydroxy! grouppresent in the structure of MIB, MIB is still regarded2.1.3 Effect of initial MIB concentration onas bydrophobic compound. Wood-based PAC Aremoval efficiencycontains more oxygcn than coat-based PAC B and theAdditional batch kinetic tests were perfornedformer is likely to be more hydrophilic and be morewith 20 mg/L PAC A to determine the effect of initialdiffcult for MIB to displace the adsorbed waterconcentration of MIB on the removal with timc. Asmolccules. Hence, the PAC B has higher adsorptionshown in Fig.4, the removal percentagc of MIB at anycapacity.given time for a particular carbon dosage is irrelativeto the initial concentration of MIB.Therefore,Table 2 Elemental compositionC,%H,% N,%O, %S,%Ash, %predictions of removal percentage versus time arePACA 88.121.19 0.835.910.29 3.65ralid for MIB concentration typical of natural water.PACB81.711.44 0.55_3.20.41 12 .61According to Fig3, the amount of PAC B required toreducc various episodes to the threshold odor100concentration, given different amounts of contact time罾8in an ideal reactor, may bc quickly determined.640;0 上虽20▲PACB0t1S0 200 250PAC coatac tioc, mia208口100 ng/1.Fig.2 Ratch kinetic cst data for MIB by PAC A and PAC B▲500 ng/L2.1.2 Effect of PAC dosage on removal of odor50150200 250PAC A conlact time, mincompoundsThe study was primarily aimed towards anFig4 MIB removal percentage as a function of contact timc vs.investigation of the optimum PAC dosagcs for thePAC ^ doseremoval of MIB with an initial concentration of 100ng/L in the simulated water sample. Typically, PAC2.2 Ozonationcontact time in water treatment plants is from 30 min2.2.1 Effect of pH on the ozonation of MIBto 1 h and main removal of odorants occurs duringThree experiments were conducted at an ozonecontact timc of 1 h. Thus, the cxpcriments wereconcentration of 0.35 mg/L and pH value of5, 7 and 9,conductcd with a contact time of 1 h and at fourrespe中国煤化工n the ozonation ofdifferent PAC B dosages 5, 10, 15, and 20 mgL. Fig.3MIB_oval of MIB withindemonstrates that the removal of MIB incrcases with20 mYHcNMHGand9was54.16%，,the increase of carbon dosage and there is approxi-86.03%，99.65%，respectively. High pH value pro-mately linear correlation between the removalmotedthe formation of OH radical by thepercentage of MIB and the carbon dosage under theautodecomposition of ozonc， hence the removalS(LIANG Cun-zhen et al.Vol.18efficiency of MIB increased as pH value increased.The resuits show that OH radical plays an important2.0 [日Raw watera Settled waterrole in the ozonation of MIB.营15个aPure water500pH=5; (03]=0.35 ng/虽1.0400H-7; i031-0.35 mg/LpH-9: i0Oj-0.35 ng/L).5 t300200O3 dose, og/L100Fig7 O, residual concentration in raw waler, settled water and pure30 40water after 10 min conlactReaction time, mioFig.5 Ozonation of MIB at pH value of 5, 7 and 9 (aqueous 0zUne2.3 Potassium permanganate oxidationconcentation. 0.35 mg/L)As shown in Fig.8, KMnO4 oxidation appears tobe ineffective in removing the MIB. In the pH range of2.2.2 Eflect of background organics on ozona-3 to 11.5, most KMnO, oxidation reactions proceedtion of MIBvia a three-electron transfer, leading to the formationThe raw water, settled water and pure waterof several insoluble manganese oxide species. Thespiked with 100 ng/L MIB were ozonatcd at O; dosessorptive properties of manganese dioxide [MnO2(S)]of ], 2 and 3 mg/L. As shown in fig.6, the removal ofmay cause the limited removal of MIB during theMIB increased with increasing O; dosc, up to 77%KMnO, treatment process.removal at the highest O; dose. The order of removalefficicncy for MIB was pure water>raw water>settledwater. There was an interesting phenomenon that the曾8Oremoval efficiency of MIB in the raw water was0higher than that in the settled water. As shown in Fig7, the O3 residua! concentration in samples followedthe order: pure water > settled water > raw water.0tOrganic matters in water samples did promote the0L3.0decomposition of O; leading to a lower removal ofPotassium permanganatc dose, mg/,MIB; at the same time, organic matters could initiatethe formation of OH radica! accelerating MIB removalFig. 8 Removal ofMIB by KMnO,(McGuire and Gaston, 1988). For ozonation of MIB inraw water, the latter may play a more important role.2.4 Potassium ferrate oxidationThis may bc the reason why ozonation of MIB in rawRecent studies have shown that ferrate is anwater is more effcctive than that in settled water. Theenvironmentally friendly oxidant and coagulant forremoval efficiency for MIB in pure water waswater and wastewater treatment (Lee el al, 2003; Quimproved about 5% compared with raw water; henccet al., 2003; Read et al., 2003). Its reduction potentialsthe effcct of background organics on thc ozonation ofare 0.72 and 2.20 V (versus NHE) in base and acid,MIB was not significant at the experimentalrespectively(Dc Luca et oul, 1996). [ts oxidizing abilityconditions.is directly relativc to the pH value of solution andferrate decomposes rapidly in acidic aqucous solution,100 (Pure watergenerating Fe', hydroxide and molecular oxygen.鹰Settled waterWhether ferrate is able to oxidize the target四Raw watercompounds in the water and wastewater must betested in specific pH value of aqueous solution.40Three batch expcriments were conducted in theaw water. al potassium ferratc concentration of 1020一|mg/[L中国煤化工:of71, 7.5 and 7.9,respeYHCN MHG, MIB cannot beO3 dose, ng/Lremoved' by potassum terrate at above conditions.Potassium ferrate at the concentration of 10 mg/L asFig.6 Ozonation of MIB in purc walet, stted water and raw waterFeO in the raw water fully decomposed within 40 s,No.1Comparative study on the removal technologies of 2-methylisobormeol(MIB) in drinking water517 min, 20 min at the pH value of 7.1, 7.5 and 7.9,Delaude L, Laszlo P, 1996. A novel oxidizing reagent based onpotassium frratc (VD)[J]. Joumal of Organic Chemistry, 61(18):respectively. Potassium ferrate is unstable to exist in6360- -6370.water at the lower pH of aqueous solution and itsDe Luca S J, ldle C N, Chao A C, 1996. Quality improvement ofoxidizing ability is not sufficicnt to oxide MIB atbiosolids by ferrate (VI) oxidation of offensive odor compoundshigher pH of aqueous solution. Hence, MIB in[)] Wat Sci Tech, 33(3): 119- -130.drinking water cannot be rcmoved by potassiumsaton A D, Clesccri L s, Grecnbcrg A E, 1995. Standard methods forthe examination of water and wastewatcr{M]. 19th cd. In: 4500-feratc.O, ozone. Washington DC: American Public Health Association.104-106.00 FFerreira Filhlo ss, Lage FilhoF A, Mendes R L et al, 2003. Taste andodor control for drinking water supply: a combined solution of80 Fchemical oxidation and powdered activated carbon adsorption50 t[M]. In: Chemical water and wastewater treatment VI (Hahn H.H, Hofinann E., Odegaard H. ed.). London: IWA Publishing.40 t109- -18.Liang C, Wang D, Yang M ei al, 2005. Remuval of earthy- musty20odoranrs in drinking water by powdered activatcd carbon|Joumal of Enviroumental Science and Health (Part A), 40(4):ControlpH-7.1 pl1-7.51I-7.9767- -778.Loe Y, Um I, Yoon J, 2003. Arsentic(1) oxidation by Ion(V)Ferate)Fig.9 Removal of MIB by potassium frrate of 10 mg/L as teO,"and subsequent removal of arsenic(V) by Iron(C) coagulation[J].Environ Sci Technol, 37(24): 5750- 5755.3 ConclusionsLin T F. WongJ Y, Kao H P, 2002. Correlation of musly odor and2-MIB in lwo drinking water teatment plants in south Taiwan[].The coat-based PAC B showed better rcmovalThe Scicnce of the Total Finvironment, 289: 225- -235.for MIB than wood-based PAC A. The more oxygcnMcGuire M J, Gaston J M. 1988. Overview of technology fcin PAC A may cause its low removal cficiency forcontrolling of-flavors in drinking water [0]. Watcr Sci Tech, 20(8/9):215--228.MIB. The removal pcrccntage of trace MIB at anyNerenberg R, Rittmann B F, Soucie W J, 2000. Ozone/biofiltration forgiven time for a particular carbon dosagc is irrclativeremovaing MIB and geosmin[].J AWWWA, 92(12): 85- 95.to the initial concentration of MIB. Therefore,Pendleton P, Wong S H, Schumann R et nd, 1997. Propcrtics ofpredictions of percent removal versus time areactivated carbon controlling 2-methylisoborneol adsorption [].Cartbon, 35(8): 1141- 1149.possible for MIB concentration typical of naturalPirbazari M, Ravindran V, Badriyha B N et al, 1993. GAC adsorberwater.design protocol for the removal of off- Jlavors[J]. Wat Res, 27(7):The results indicatc also that pH has a significant1153- 166.6effect on the ozonation of MIB, which supports theQu J, Liu H, LiuSet al, 2003. Reduction of fulvic acid in drinkingtheory that OH radical plays an important role on thewater by frrate川J Environmcntal Enginccring, 129 (1): 17-24.destruction of MIB. The effect of background organicsRead1 F, Graves C R, Jackson E, 2003. The kinctics and mechanism ofon the ozonation of MIB was not significant at thethe oxidation of the thiols 3. mercapto-l propane sulinic ueidexperimental conditions.and 2-mercaptoicoticnic acid by potassium frratc [小]. InorganicPotassium permanganate and potassium ferrateChimica Acla, 348:41- 49.Schreycr J M, Thompson G w, Ockerman L T. 1950. Uxidaion ofare ineffective in removing the MIB in drinking water.chromnium (I) with polassiurm frrulte (VI) [I] AnalyticalChemistry, 2(11):1 1426- 1427.References: .Suffet I H， Mallevialle J，Kawcrynski E, 1995. Advanccs iAnselme C, Suffct I H, Malevialle J, 1988. Effecets of ozonation onlastc-and-odor treatment and cuntrol[M]. In: Chupter 3. oxidationastes and odors[J]. J AWWA, 80(10): 45- -51.process: Ozone (Gramith J. T. ed.). Denver CO, USA: Am WaterCook D, Newcombe G, Sajnbok P. 2001. The aplcain of powderedWurk Assoc and Lyunnaise des Eaux. 123- 144.activated carbon for MIB and geosmin removal: preiting PACdoses in four raw waters[J]. Wat Res, 35(5): 1325 - 1333.(Reccived tfor review April 6, 2005. Accepted May 27, 2005)中国煤化工MYHCNMHG