Improving AOC degradation rate by intensified biological process in advanced water treatment

Journal of Harbin Institute of Technology (Nev Series), Vol. 14. No. 1, 2007Improving AOC degradation rate by intensified biologicalprocess in advanced water treatmentAN Dong'2, u Wei-guang' , SONG Jia-xiu', CUI Fu-yi'安东李伟光，宋佳秀,崔福义(1. School of Munieipal and Envinnmental Engineeing, Habin Istiute of Technology，Harbin 150090,China ,E-mail; andonghit@ 163. com;2. Shanghai Shibei Walerworks Co. Ld. , Shanghai 20086, China; 3. Shanghai Normal University , Shanghai 200234 . China)Abstract: The object of is to evaluate asmilable organic carbon( AOC) degradation rate by intensifed biologi-cal technique in advanced water treatment. By rifiallyl acclimating and culivating strains atched onto car-bon surface, the selected strains can be intensified for their degradation to organie matters.cates that ozonation process increases AOC concentration considerably , however, it is beneficial to microdegra-dation. Temperature and empty bed contact time (TEc ) are two important factors ffcting microbiology. From14 to 27 C, intensified biological carbon can remove AOC better compared with granular activated carbon(GAC). Under identical TE , itensfed technique increases more than 10% AOC reduction.Key words: activated carbon; asimilable organic earbon; emply bed contact time; advanced water treatmentCLC number: TU991.2Document code: AArticle ID: 1005-9113(2007 )01 0093-04Assimilable organic carbon ( AOC) or biostabilityin drinking water is recognized as a new problem in wa-lMaterials and Methodster treatment. AOC is defined as heterotrophic bacteriagrowth potential sustained by organic matrix namely ut-1.1 AOC Determinationmost character of bacteria growth" . The appearance ofAOC determination was created by Van der Kooijorganic substances leads to bacteria regrowth which de-first then improved by LeChevallier and Kaplan etteriorates water quality in the distribution system. Theal3-4). Inoculated strains were Pseeudomonas fluores-regrowth, mainly oCcurs as a biofilm, and may cause in.cens P17 and Spirilum NOX in the whole method. P17creased colour and turbidity in the water. W hen patho-was easy to make use of biodegradated organic mattersgen bacteria such as Klebsiella spp. and Enterobacterin water such as amino acid, fusidic acid, ethanol andspp. grow in biofilms , they show increased resistance tohydrocarbons etc. Oxalic acid was not degradated byfree chlorine compared to single bacteria in the water.P17. For ozonation producing oxalic acid it was neces-AOC is based on the measurement of biomass growth,sary to complement NOX as test strain. NOX as a kindeither by plate count or by adenosine triphosphateof matrix for oxalic acid growth made up the disadvan-( ATP) measurement. The most reported method usestage of P175. Two strains was inoculated successive-standard bacteria for inoculum ，usually Pseudomonasly. Incubation temperature was (25 +1)C with 40 mlfluorescens PI7 and Spirllum NOX.water.Inoculated time was 48 h and 72 h in substrateIn advanced water treatment ozone activated car-LLA, respectively. .obn is adopted to remove natural. organic mallers 1. 2 Waterworks Flow Skill( NOM). Many pathogenes or contaminants that can beThe experiment was carried out in test base of adisinfected，altered or removed via an oxidation processSouthem waler plant. As shown in Fig. 1, in the exper-will be affected by ozone. Ozone decomposing NOM byiment pre-and post-disinfections by chlorination was a-its strong oxidation ability is help to more contaminantsdopted，the raw water treated by water treatmentremoval for sequential activated carbon. However, 020-processes of coagulant mixing, reaction and sedimenta-nation increases AOC concentration inevitably andtion and filtration in V-filter, then further treated byphysical adsorption by activated carbon is limited. Theozonazation and granular activated carbon ( GAC). Exintensified biological technique based on ozone activa-xept for the intensified hinlarical skill adopted in BACted carbon is very effective in decreasing AOC concen-the| |中国煤化工e two columns. Watertration and guarantees safe drinking water for its bio-AnowYHCNMH Gwards wih maximumdegradation.Received 2004 -05 -31.Sponsored bhy China Postdoetoral Science Foundation( Grant No. 20060400178) and Shanghai Prtdotoral Seicnife Program( Grant No. 06R214204).●93●Journal of Harbin Institute of Technology (New Series)，Vol. 14，No. 1, 2007TEmc of5 -25 min. Ozone was dosed in 0.5 -2. 5 mg/Lcle time of intensified biological activated carbonand contact time 16 rmin. During stable operation GAC(IBAC) was longer than that of CAC.was backwashed in cycle of 4 -5 d and backwashing cy-other raw wateralkalsed alumina, linconsumerpost-disinfeetion↓^mixingreactionsedimentation tankfitertankpre-hlorinationGAC02onizution]←towerIBACFig. 1 Experimental Flow ProcessIn the course of experiment the average AOC con-amount of microbe was enough for the experiment. Thecentrations in traditional treatment skill was summa-GAC column fixed by engineering strains was bach-rized in Fig. 2. Pre-chlorination increased AOC contentwashed time after time with filtration water before u-in source water by 9. 9%，sedimentation and filtrationsing.decreased AOC accordingly.2 Results and Discussion!120146,2.1 Ozone Dosage”1201141000Ozone dosage was relative to not only the contami-760nants removal efficiency by intensified biological acti-vated carbon but economical aspects. Investigation be-fore was showno only a small part of organic matterssoue water pre -rhlorination settled oulet filtered ouletoxidized under low ozone dosage but under high ozoneFig.2 Average AOC concentrations in individual outlet ofdosage the corresponding matters would inevitably pro-water treatmentduce CO2 and H2O which was disadvantage to biodeg-radation by BAC and the operation cost was high ac-1.3Acclimation and Cultivation of Engineeringcordingly.StrainsLarge and long chain molecules was oxidized into .There were 28 strains seperated from raw water bysmaller building blocks which was prone to biologyadopting preferential nutrient medium. Different liquidgrowth as substrate, therefore ，ozonazation producednutrient mediums were necessary for microbial acclima-high AOC concentration which was beneft to IBAC.tion and cultivation. The object of cultivation and ac-As shown in Fig. 3, AOC concentration increased lttleclimation was to separate those strains which can be ac-when dosing 0.5 mg/L ozone because large molecularcustomed to given water quality and be provided withmatters was not decomposed effectively with low ozonehigher activity and finally make them engineeringdosage. AOC-NOX concentration increased with higherstrains with special function.ozone dosage therefore oxalic acid gradually came intoThe seperated 28 strains were elutriated from thebeing, for example when oz0ne dosage was 2.5 mg/L ,slant media by the sterilized water. Different nutrientAOC-NOX increased by 240% . Though the concentra-mediums were added in turn and then parked in sha-tion of AOC-P17 in water was higher than that of AOC-king table. The acclimation course was finished in theNOX it increased lttle with different ozone dosage. Incondition of rotate speed 150 r/ min，cultivation forchanged based on the24 h in constant temperature of 37 C.AOC中国煤化工was 1.5 mg/L andThe acclimated engineering strains will be culi-2.5CNMHGsedby48% and720%vated continuously for increasing their quantity in spe-12Tuar nou eascu ijy 72% and 137% ,cial container. Every day nutients were added for theirspectively. So advice must be valuable to applygrowth. After some days, cultivation stopped when the1.5 mg/L oz0ne dosage to the advanced treatment for●94●Journal of Harbin Instiute of Technology (New Series)。 Vol. 14, No. 1, 2007the aim of reducing cost and cotoling AOC concen-High reduction to total AOC was gained with high tem-tration.perature. Based on the artificially intensified bioactivi-ty along with the rising of temperature biodegradation◆-A0C-NOX- -A0C-P17 - + Total AOCprocess was enhanced also.口soure water口GAC■IBAC:50 r心20150 t2500tr, 200'50。1500.1.01.5.02.5cozone dosagv/( mg.1,"); 100Fig.3 Relations betwen ozone dosage and AOC concen-trations山4161719202223242622.2 Temperature1/CTemperature as a primary parameter to contami-nant removal such as ammonia nitrogen and nitrite etc.Fig.4 Total AOC concentration as a function of temperaturewas important. High temperature was more effective toremove manifold contaminations than low tempera-- +GAC- IBACture'7,The removal of most organic contaminant sub-stances was sensitive to temperature change. The effect60of temperature included the change of biomass and bio-f 40activity attached onto BAC especially the latter aspect.马20More difference of removal eficiency for contaminantsubstances was found with the same biomass and differ-14161820222426 28ent bioactivity in GAC and IBAC. The aim of intensi-fied biological process was to enhance bioactivity olstrains selected so it can improve contaminants removal-+GAC--IBACrate. AOC removal trend by IBAC and GAC was shownin Figs. 4 and 5. The water temperature in the experi-ment was at the range of 14 -27 C. When the water长3temperature was below 20 C AOC-P17 removal ratewas almost the same by the two methods but when tem-R 2(perature was above 20 C IBAC removed more AOC-P17 compared with GAC. From Fig. 5 AOC-NOX re-导10duction increased along with the rising of the tempera-01416182022242628ture. . The removal was improved when the temperaturet/Cwas high and AOC-NOX reduction varied lttle whilethe temperature was 20 -27 C. After long time opera--◆-CAC- -IBACtion microbiology would attach to the surface of the80 rGAC then came into being so called BAC but the highbioactivity of the natural microbiology was not expec-ted. The reduction of AOC-NOX by GAC was obvious-ly lower than that by IBAC. AOC-P17 removal was notthe same with AOC-NOX. W hen the temperature below2017 C the removal rate seemed alike. Low temperaturewas disadvantage to the microbiology which was respon-182426sible to remove AOC-P17 so degradation process was中国煤化工repressed. AOC-PI7 renoval was lower than 50% byFig.. of temperature(1=GAC but it was up to 74% by IBAC while the tempera-MYHCNMHGture was higher than 17 C. The removal trend of totalAOC was similar to AOC-P17. GAC could remove total2.3 Infuence of TEBcAOC 40% - 50% compared with up to 70% by IBAC.TEBc as an important parameter for GAC operation.95●Journal of Harbin Institute of Technology (New Series), Vol. 14, No. 1, 2007to biology behaved in the time controlment of biodegra-dation and adsorption. Indeed, prolonged TεBc was3 Conclusionsbeneficiary to biodegradation. For multitude of organicmatters long TEBC was favorablet. The relation be-1 ) Ozonation increases AOC concentration in watertween AOC removal and TEBC at the temperature 20 -because ozone breaks down large and long chain mole-22 C was shown in Fig. 6. When TEBC equaled 5 mi-cules into smaller building blocksnutes AOC-NOX reduction by CAC was 4% and that2) AOC removal is affected by water temperature.by IBAC was 27%. The TBc rose to 25 min the remov-From 14 to 27 C AOC-NOX removal rate by IBAC isal rate was 25% and 42%，respectively. With the ris-higher than that by GAC. Above 20 C there has noing of TEBc AOC-NOX removal rate increased rapidly byobvious increasing of its removal by CAC. Below 17 CGAC because prolonged TEBc was in favor ot GAC ad-AOC-P17 remnoval is similar for the two methods. Unersorption but the biodegradation varied slowly. GAC ad-the same condition IBAC removes more contaminatantssorption was not affected by the occurrence of biology.in high temperature compared with GAC so IBAC isHigh fficiency was observed of A0C-NOX removal allmore favorable to remove contaminants in high temper-the time in Fig. 6. AOC-P17 transition was similar toature.3) Biodegradation process is determined by Temctotal AOC because AOC-P17 was the main form in totalAOC. CAC remained 34% - 38% removal rate withdirectly. In the experiment prolonged TEBc leads toTENC between 15 and 25 min however in this rangemore AOC removal. Compared with the absorption ofIBAC could remove 42% -49% total AOC.GAC to remove AOC , intensifed biological process in-creases AOC removal by 10%. AOC removal by IBACworks well when TEac is between 10 and 25 min.-◆A0C-NOX-一-A0C.-P17 -★toal AOCReferences:e5[1 ] Wang Zhanshen, LIU Wenjun. Micropollution W ater Treat-40 tmenBeijing: Chinese Architecture Industry Puhlishing=要Company, 1998 :272 - 273.20 t[2] Olivieni V P, Bakalian A E, BossungK w, et al. Recur-rent coliforms in water distribution systems in the presenceof free residual chlorine. Environmental Protection Agency,1015201984.Tm:/ min[3] Van der Kooj D. The occruence of Pseudomonas spp. insurface water and in tap water as determinated on ecitrate(a)CACmedia. Microbiol, 2001 ,43:225 - 240.[4] LeChevallier M W, Shaw N E, Kaplan L A, et al. Devel--◆A0C-NOX- ●A0C-P17 - ★total AOCopment of a rapid assimilable organic carbon of method for60-water and appl. Environ Microbiol , 1987 ,53 :2714 -2724. .50-[5] Liu Wenjun, Wang Zhansheng. Study of AOC determina-昌40Ftion in drinking water. Water and Wasterwater, 2000 .26里30[[6] Zhang Jinsong, Zhu Jia. Study on ozone BAC pararneters.县1Treaing Water Technique, 2000 ,3(18) :28 -31.0152025[7] Andersson A, Laurent P. Impact of temperature on nitrifi-cation in biological activated carbon( BAC) filters used for(b)IBACdrinking water treatment. Water Research, 2001 ( 35 ):2923 - 2934.Fig.6 Removal rate of AOC by GAC and IBAC as a func-[8] Pryor M J, Nozaic D, FreeseS D, et al. The use of granu-tion of TEnclar activated carbon for the treatment of impounded surfacewater. Wat Sei Tech, 1999, 10(39):197 - 200.中国煤化工MYHCNMHG.96●