Preozonation of bromide-bearing source water in south China

ISSN 1001--0742Jurnad of Entirnmenta Sciences Vol. 18, No.2, pp.209 -213, 2006CN11-2629/XArticle ID: 1001-0742(2006)02-0209-05CLC number: X703Document code: APreozonation of bromide-bearing source water in south ChinaGUO Zhao-hail, YANG Min', ZHANG Yu, PEI Yi-shan', ZHANG Jing song, FAN Jie,Junji HIROTSUJP(1. Research Center for Eco-Environmental Scienccs, Chinese Acadcmy of Sciences. Beijing 100085, China. E-mail: yangmin@reccs.ac.cn; 2.Shenzhen Waler (Group) Co. Ltd, Shenzhcn 518031, China, 3. Advanced Technology R&D Cenler, Misubishi Electric Corporation, Japan)Abstract: The efectiveness of prcozonation was evaluated on treating a bromide-bearing dam source water in south China throughbatch-scalc experimnents. Preozonation at ozone doses of0.5- 1.0 mg/L (at ozonc consumption base) enhanced tolal organic carbon(TOC) removal through coagulation, and rcsulted in an alnost linear reduction of ulraviolet absorbance at 254 nm (UVs). Theremovals of TOC (aftcr coagulation) and UV24 at the 0zone dose of 1.0 mg/L were 36% and 70%，respectively. Preozonation at anozne dosc betwecn 0.5 and 1.0 mg/L resulted in the removal of dsinfection byproducts formation potential (DBFP) includingtrihalomethane formation potential (THMFP) and haloacctic acid formation potential (HAAFP) for about 50%. The rcmovals ofTHMFP and HAAFP decreased with thc further increase of ozone dose. Ozonation of bromide bearing water (bromide concentration,34 ug/L) produccd a bromate concentration under the detection limi(2 μg/L) at 0zonc doscs <1.5 mg/L. However, bromate >10 μg/Lcould bc produced when the bromide concentration was increased to 96 ug/L.Keywords: ozone; drinking water; preozonation; disinfcction byproducts formation potential (DBFP); bromate formationbeen observed (Duguct et al, 1986; Farvardin andIntroductionCollins, 1989; Prados el al, 1995; Orren et al, 2000).Primary and secondary disinfections are usuallyPolymerization occurred during ozonation of simpleperformed with chlorine during drinking waterphenolic compounds or humic substances aidedtreatment. The primary disinfection(prechlorinization)coagulation, resulting in the enhanced removals ofis used mainly for the cradication of microorganismsnatural organic matters(NOM), the principal precursorprescnt in raw water to ensure that the subsequentof chlorinated DBPs (Chrostowski et al, 1983;coagulation, sedimentation, and sand filtration will notFarvardin and Collins, 1989; Sudha et al, 1995).be hindered by the excresccnt microorganisms. TheHlowever，some contradictory results regardingsecondary disinfection is the use of a disinfectantpreozonation have been reported by differentresidual in water ditribution systems to prevent therescarchers (Becker and O'melia, 1995, 1996). It isre-growth of biological contaminants. Cl (or hypo-speculated that the different prcozonation resultschlorite) is still the most widcly uscd disinfeetant. It isoriginated from different source water characteristics.nearly unrivaled in its potency as both a primary andFor exampl, although preozonation has been widelysecondary disinfectant(USEPA, 1996).utilized in European countries, no preozonationHowever, prechlorization produccs a number oftreatment has been adopted in Japan in spite of theundesirable and potentially cancer-causing organicwide use of post ozonation for drinking waterdisinfection byproducts (DBPs). Among these,treatment. Thereforc, what kind of source water istrihalomethanes (THMs) and haloacetic acids(HAAs)suitable for preozonation remains an intcrcsting topicare the dominant specics found in finished waterfor further exploration.(Rook, 1976). Because of health risks, U.S. Environ-On the other hand, the formation of bromate .mental Protection Agency (USEPA) began to regulate(BrO), a major DBP gencrated from ozonation ofthe lcvels of these DBPs in finished water by Stage Ibromide-containing source waters, should bc con-of disinfectants/disinfection by-products rule (D/sidered when ozone is selectcd for drinking waterDBPR), which cstablished a maximum contaminanttrcalment. Bromate as a carcinogen is currentlylevel of 80 g/L for total THMs and 60 g/L for five ofregulated in treated drinking watcr under the Stage IHAAS (HAA5). To minimize the production of theseD/DBP Rule of the Safe Drinking Water Act (2) at acompounds, preozonation was recommended rathermaximum contaminant level(MCL) of 10 ug/L. Therethan prcchlorization in drinking water treatment(Amyis currently no economically feasible technology toel al., 1991; Orren e1 al.. 2000).rem中国煤化工So, clarifying thePreozonation has been utilized in water works incondill be hclpful for thesome Furopcan countrics because of its high oxidationproc(fHCNMHGpotential (Lefebvre et al， 1995; Bohme, 1999;Preozonation has becn adopted for treating aGeering, 1999; Lowndes, 1999), and enhanced TOCbromide-bearing dam source water with a low specificremoval through coagulation during preczonation hasultraviolet (UV) absorbance, low hardness, and highFouha石数据The Hi-ech Research and IDevelopment Progan(863) of ChinaNo.2002AA601 120); *Coresponding author210GUO Zhao-hai et al.Vol.18 .algae (6X10*- 3X 107 cll/L) in one water works inTOC of liquid samples was analyicd by a TOCsouth China since 2001. The suitability ofanalyzer (Phoenix 8000, Tekmar Dohrmann, USA),preozonation on lrcating such kind of source water,and turbidity was measured by a portable turbidityhowever, had not been systematically investigatedmetcr (2100P, HACI Co, USA). UV absorbance wasbefore.The objective of this research was tcmeasured at 254 nm (UV2zs) using a UV-visibleinvestigate the effects of preozonation on treating suchspectrophotometer (Cary 100 UV-VIS， Variana source water, and explore the feaibility andAustralia Pty, Mulgrave, Victoria, Australia). Prior toefficiency of using the preozonation process to removeanalysis, the samples were filtered through 0.45 μmthe precursor of DBPs while controlling the formationmembrane filters. The particle number was measuredof bromate. Variations of the disinfection by-productby a particle number counter (IBR Inter Basicformnation potential (DBPFP) were examined by theResources Inc., USA). THMFP/IIAAFP was analyzeddetermination of THMFP and HAAFP during prc-with gas chromatorgraphy (Lin et al, 2003). Bromatcozonation treatment. The effeets of preozonation onin the ozonated water was also determined by ionremovals of turbidity, particle numbers, TOC andchromatography (ICS-1500 lon ChromatographyUVzs4 were also followed.System, DIONEX, USA) with a minimum quantifi-1 Materials and methodscation limit of 2 μg/L BrO; (Liu and Shifen, 2004).Ozone measurement was performcd using the1.1 Experimental set-upiodometry method, and the ozone dose was calculatedFig.l shows the schematic diagram of theby detracting ozone amount in the effluent gas frombatch-scale experimental set-up in this study. Twothat in the influent gas.similar reactors in parallel (A and B) were adopted in1.3 Experimental methodsexperiment. Reactor A was used to treat raw water[wo litre raw water was injected into a singleand rcactor B to correctly measure ozone gencratcd.glass contact column, and the reaction was initiated byThe ozonation reactor was constructed of a glassfeeding oz0ne gas of diffcrent ozone concentrationscontact column with an effective volume of2.0 L (780through the perforatcd platc. After ozonation for 4mm X70 mm i.d). Ozonc gas produced was intro-min, oxygcn gas from the PSA was introduced into theduced from the bottom through a perforated glassrcactor to purge the remaining ozonc into K Iplatc. A PSA(FY-3, Beijing Beichen Technology Co,absorption container for 15 min. Afer sampling, 1 LChina) was used for generating oxygen gas(O2 >90%),of the treated water was Lransferred intoa 1.5 L glassand the gas flow rate supplicd 10 the ozonizer(OS-IN,beaker, trealed with polyaluminium chloride (PAC;Mitsubishi Electrice Co, Japan; rated ozone output, 1Al2O3 content, 10%) on a jar-testor under the follow-/h) was fixed at 18 Lh. The effluent gas wasing conditions: PAC dose, 1.67 mg/L (Al.O; content);introduced into a KI absorption solution for mcasuringfast mixing (200 r/min), I min; slow mixing, I5 minthe ozone amount exhausted. The sampling outlet was(the first stage, 150 r/min, 5 min; the second stage,installed on the bottom of the reactor. Following100 r/min, 5 min; and the third stage. 50 r/min, 5preozonation, coagulation was conducled in amin). Supernatants were taken following a sedimen-jar-testor with a polyaluminium chloride (PAC; AlO;tation time of 35 min.content, 10%) dosc of 1.67 mg/L.To investigate bromate formation at differentbromide concentrations, sodium bromide was spiked▲Tail gas absorberinto the sourcc watcr to prepare solutions containingbromide varying from 34 μg/L (raw water) to 298μgL. .WaterFlocculation mixerAll samples were refrigerated at 4C untilanalysis, and the samples were analyzed within oneweck aftcr reception.个年⑦_gcoerm向2 Results and discussion2.1 Raw water characteristicsPSA]Table 1 shows the average parameters of sourecwat中国煤化工W water was takenFig.1 Schematic digran of bench- scale experimental scl-upfrontince, China. WatertcmpI YHC N M H Gt varied bctwccn 191.2 Analytical methodsand 22C. The dam water had a relatively low TOCAl1 the analysis was conducted according to thecontent, alkalinity, hardness, and UV2s4. The turbidityfourth edition of The Standard Methods of Water andwas generally low and stable, and the algac contentWastewater Monitoring of China (EPB, 2002). Thewas at a medium leve|(9X 10^ cell/L). The ammoniumNo.2Prcozonation of bromide-bearing source water in south China211concentration was not so high, indicating that thecomplexing agent (e.g. calcium) because of moresource water was not heavily polluted from municipalligand sitcs (such as oxalic acid) formed uponwastcwatcr. It should bc noted that the waterozonation. This process resulted in the adsorption ofcontained 18- 35 μg/L bromide ions.organic matter onto particles, thereby leading to aTable 1 Parumeters of raw walerreduction in particle stability through surface chargereduction (Camel and Bermond, 1998). In this study,ParameterRangeMeanhowever, the ratio of hardness via TOC was less thanH6.8 7.i6.916， which might be a reason why coagulation-Turbidity, NTU3.48- 14.26enhancing effects were not observed. Adverse effectsAlkalinity, mgCa0/L13.04-- 15.8113.8of preozonation on coagulation werc probably alsorelated to the existence of algae(9X 109 ell/L in mostAmmonium, mg/L0.32- -3.611.85cases). It was speculated that cytoplast released byHardncss, mg CaCOyI31.7- -43.68.5algae under the attack of ozone interfered with theTOC, mg/L1.95 - 2.622.3coagulation reactions through complexation betwccnC0D, mg/L1.48 -5.232.8organic and Al ions. The details, however, remain toUVsn cm'0.01-0.050.03be explored.Br. ug/L18-35- Smaple l#- + Smaple 2#+ Smaplc 4#Algae. cl/L6X10*- -3X10'9X 10*.2 t2.2 Algae removal-王The effect of ozone dose on the removal of algaeafter sedimentation is shown in Fig.2. The removal of一王algae increased with ozonc dose when the dose was0.4 ;below 1.0 mg/L. Further increase of ozone did nothave much effct on the removal of algae becausc0.1.1.52.0most of algae were already removcd at an ozone doseOzone consumoptio, mg/Lof 1.0 mg/L.Fig.3 Efects of ozone duse on lurbidity removal12Fig.4 shows the effect of ozonation on particulatecounts after sedimentaion (particulate sizc, >2 um).The turibidity of the 3 raw water samples werc similar0|(1#, 7.4 NTU; 2#, 8.1 NTU; 3#, 7.8 NTU). It is clearthat the particulatc counts in samples treated with070NC were significantly lower than thosc without2ozonation. It is possible that sorme paricles(like algae)were destroyed by o20nC. Howcver, further studies are3.0requircd to investigate if more smaller particles, whichOzone consumptio. mg/could be not detected by the monitor, were formed onFig.2 Algac profle under diterent szone dlosesozonation.JWithout ozonc OWith orone2.3 Turbidity and particulate removalsThe efTects of prcozonation on turbidity removal12000by coagulation were investigated, and the results are更00000shown in Fig.3. Raw water with different turbidity8000(sample 1#, 1.56 NTU; sample 2#, 4.51 NTU; sarmple60003#, 7.27 NTU; and sample 4#, 13.58 NTU) was used4000for the tests. The turbidity increased slightly with theincreasc of 0oz0nc dose in most cases, especially when2000the ozone dose was over 1 mgL. According to中国煤化工3#previous studies (Chang and Singer, 1991; Chan-YHCNMHGdrakanth et al, 1996), enhanced turbidity removalFig.4 Effect of o7zonation on pariculatc counts(ozone dose, 0.5 mg/L)through coagulation during prcozonation easilyoccurred in waters with hardness-to-TOC ratios >252.4 TOC removalmg CaCO/mgTOC. It is speculated that organicThe effects of ozone on TOC removal are showncompounds_ became more easily associated with ain Hig.5. It is clear that preozonation did not directly212GUO Zhao-bai et al.VoL.18result in the perceptible reduction of TOC. Thecrcase of ozone dose because of direct destruction ofremoval of TOC by direct ozonation was roughly 0. lUV absorbed structures by ozone. However, themg TOC removed per mg ozone consumcd. This isreduction of UV2s4 became much slower after ozonereasonable because of the low oz0nc dose and highdosc reached 1.0 mg/L. For reducing UV absorbancc,selectivity of ozonation at ncutral pH. However, thea proper ozone dosc is 1.0 mg/L.TOC after coagulation decreased with the increase of2.6 Removal of THMFP and HAAFPozone dose, indicating that preozonation enhanced theSince preozonation resulted in the reduction ofremoval of TOC through coagulation. Some studiesUV absorption and cnhanced TOC removal throughhave shown that the coagulation process couldcoagulation, it is easy to speculate that ozonationeffectively remove hydropbobic organics (Collins etmight also be effective for enhancing the removal ofal, 1986). However, this does not explain thethe chlorinated DBPFPs， namely THMFP andenhanced rcmova! of TOC in this study sinceHAAFP. Fig7 shows the profles of THMFP andozonation generally reduces the hydrophobility ofHAAFP under different ozone doses. The averageorganics in water. Polymerization of NOMs might beTHMFP for raw watcr ranged between 181 to 190the main reason for the enhanced removal of TOCμg/L and the average HAAFP was between 281 to 295(Chrostowski et al., 1983; Farvardin et ul, 1989;ug[L. The THMFP and HAAFP after coagulationSudha et ul., 1995).decrcased with the increasc of ozone dose, andreached the lowest levels at an ozonc dose of 0.6- -1.03.0 rmg/L. The highest removals for THMFP and HAAFPwerc 54% and 52%, respectively. It should be notedthat both the THMFP and HAAFP increased when theozone dose was increased from 1.0 mg/L to 1.5 mg/L,which was not observcd in the profiles of TOC andR 1.0UV2s4. Ozone oxidation may produce some ncw士Scdiment walerTHMFP while destroying the original THMFP(Dorc et+ - Preozone waleraul, 1978). It seemed that the ozonation by-products00.1.5 2.0produced at an o70nc dose higher than 1.0 mg/L bad ahigher potential to form THM and HAA withOzonc consumption, mg/L.chlorines.Fig.5 Remoral of T0C400←TIMFP●HAAFPThe TOC removal reached 36% under an ozonedose of 1.0 mg/L. However, TOC removal did not300increase with the further increase of ozone dosc. So,an ozonc dose of 0.5- -1.0 mg/L is enough for200enhancing TOC removal through coagulation.2.5 Reduction in UV absorbanceOzone is known to cleave the aromatic carbonstructures of NOM that are responsible for absorption°。一 0..01.2.0of UV radiation at 254 nm (Paralkar and Edzwald,Ozone coDsumplion, mg/L1996). Fig6 shows the effects of preozonation andFig.7 Removal of 0BPFPcoagulation on the reduction of UV2zs+ The removal ofUVs4 mainly occurred during o/onation. The reduc-2.7 Bromate formationtion of UV2s4 increased almost linearly with the in-Since the source water contained bromidc, thepossibility of bromate formation had to be considered+- SttedRawbefore that an ozone process was adopted(von Gunten+ Preozonated/Rawand Hoigne, 1992, 1994). Considering the bromideconcentration in the source water might be affccted byseawater, bromide concentation varied from 34 μg/L。0.(raw water) to 291 μg/L by spiking bromide. Bromate2 0.6更。forn中国煤化工nt bromidc concen-trati i_gL was adopted in0.2FiglC N.M H Gation was below thedetection limit (2 μg/L). It is clear that bromate was).51.01.52.under the detection limit in an ozone dose rangcOzone cosumption, mg/lbetween 0 and 1.7 mg/L when raw water wasFig.6 Removal of iVzeozonated, indicating that preozonation of the sourceNo.2Preozonation of bromide-bearing source water in souh China213water at its present bromide level will not be aBihme A, 1999. Ozone lechnology of German industrial enlerprises[J].Ozone Sci Eng, 21: 163-176.problem in terms of bromate formation. Similarly,Camel V, Bermond A, 1998. The use of ozone and asciated oxidationGaley et al.(2001) found that preozonation (up to 1.2processes in drinking water treatment [J]. Water Res, 32(11):mg/L) had no significant impact on BrO; formation3208-3222.with Br concentrations of 30- -42 μg/L in sourceChandrakanth M s, Amy G L, 1996. Hfects of ozone on the colloidalstability and aggregation of particles coated with natural organicwater. However, when the bromide was increased tomatter[]. Environ Sci Technol, 30: 431- -443.96 μg/L, more than 10 μgL bromate (drinking waterChangS I), Singer P C, 1991. The impact of ozonation on particlestandards of thc USA and Japan), will be formed at anstability and the removal of T0C and THM precursors [] Jourozone dose of 1.6 mg/L. However, even for raw waterAWWA, 83(3): 71-79.Chrostowski P C, Dietrich A M, Suffel I I, 1983. Ozone and oxygenwith a bromide concentration of 291 μg/L, theinduced oxidative coupling of aqucous pbenolics []. Watcr Res,bromatc concentration was only 4 μg/L at an ozone17: 1627- 1633.dose of 0.8 mg/L. So, thc preozonation strategy couldCollins M R. Amy G L, Comelius S, 1986. Molecular wcightstill be an option for waters with a rclatively highdistribution, carboxylie acidiy, and humic substancs content ofaquatic organic matter: implications for removal during waterbromide conccntration if proper ozone dosage istreatment[J]. Hnviron Sci Technol, 20( 10): 1028- 1032.sclccted.Dore M, Mcrlct N, Blanchard T et al, 1978. Influcnce of oxydisingtreatments on tthe formation and the degradation of haloform2:34 ug/Lreaction precursor[] Prog Wat Tech, 10: 853Duguet J P, Dussert B, Bruchet A et al, 1986. The potential use of20160 Hg/Lozone and peroxidase for removal of atomatic compounds from230 pg/L里◆- 291 ug/Lwaler by polymerization\小. 0zone Sci Eng, 8:247- 260.EPB(Enironmental Protcctio Burcau), 2002. The standard methods of110water and wastewater monitoring of China[S]. Fouth ed.Farvardin M R, Colins A G, 1989. Preozonation asan aid in thecoagulationhumic substances-optimum prcozonation dose[].Waller Res, 20: 1383 - - 1392.Galey C, Veronique M D G;, (iary A et al, 2001. Coroling bromatc0..1.1.52.0formation[Z]. J AWWA, Peer-Reviewed: 105-115.Oconc consumption, mg/LCiecring F, 1999. Ozome ppliation: the state of the art in Switzerland[1]. Ozone Sci Eng. 21: 187- -200.Fig8 Formation ofbromateLefebvre E, Racaud R, Parpaillon T et ud.. 19959. Resuls of bromide andbromate monitoring at several water trealment plants []. OzoncSci Eng, 17:311- -327.3 ConclusionslinX P, LuY X, Zhang D M et al, 2003. Dcerminatiornethod forTHMFP and IIAAFP []. China Wiater and Wastewiller, 19(10);:The effectivencss of preozonation in treating dam98-100.source water with low specific ultraviolet (UV)Liu Y J, Shifen M, 2004. Determination of bromate and chlorinatedabsorbance and hardness was investigated, and thehaloacetic acids in bltled drinking water with chromalographicmethods{J]. Chemosphere, 5Ss: 1253 1258.following results were obtained.Lowndes R, 1999. Slales of the art for 0zone- -UK. experience [.TOC removal through coagulation could beOcone Sci Eng, 21:201205.cnhanced by preozonation at an ozone dose of 0.5一Orren DS, John F T, 2000. Preozonation efects on coagulation [J] J1.0 mg/L. Turbidity removal, however, was notParalkar A, Edzwaid 」K, 1996. Efiet of ozone on NOM andimproved by preozonation.coagulation[J]. J AWWA.88(4): 143.A suitable ozone dose for the removals of bothPrados M, Pillard II, Roche P. 1995. Hydruxy1 radical oxidationTOC and DBPFP is 0.5-1.0 mg/L, under whichprovesses for the removal of triazine from natural water[J]. 0zoneabout half the DBPFP was removed through thSci Eng, 17: 183-194.Rouk」J, 1976. Haloforms in drinking waler [小. J AWWA.68(3);:combination of preozonation and coagulation.168-172.Bromate formation will not be a serious problemSuJha G. Raymond M H, Edward J B. 1995. Biodegradation of NOM:for prcozonation at the present bromide level. AtEffect of、OM source and ozone dose []. J AWWA.91: 90-higher bromide conccntrations, however, ozoneUSEPA (U.S. Environmenmtal Prolection Agency), 1996. Nationaldosage should be carefully determined.drinking water clearinghouse[S]. Tech Brief: Disinfection (Junc).von Gunten U, Hoigte J, 1992. Fuctors contolling the formation ofReferences:bromate ion during ozonation of brumide-containing waters{U]. JAmy G L., Tan L, Davis M K, 1991. The efects of vzonation-AnWater Supp Res Technol, 41(5): 299- -304.activated cearbon udsorption on trihalomethane speciutioan [].von (nution during ozonation of中国煤化]n of uzone and hydroxy1Wiater Res,25: 191- -202.Becker W C. O'melia C R, 1995. The elfect of ozonc on the coagulationCol, 28: 1234-1242.of turbidity and TOC[C]. In proceedings of the 12th 0o7one worldWatal.MYHC N M H G, Mismss Okada.203.3congress.l, France, Mayl5- 18, 1:251- -261.DOC removal by multi-stage ozonation-biological treatment[].Becker W C, O'meia C R, 1996. O>zone, oxalic acid, and organic matterWater Rescarch, 37: 150- -1S4.molecular weight efcts on coagulation [J]. Oone Sci Eng, 18:311-324.(Reccived for review June 2, 2005. Accepted July 26, 2005)