Advanced purification of filtered water by aerobic IBAC

Journal of harbin Institute of Technology(New Series), Vol. 14, No 1, 2007Advanced purification of filtered water by aerobic IBACMA Fang, QIN Song-yan, HUANG Peng, S N. Sin马放秦松岩,黄鹏单羿School of Municipal and Environmental Engineering,, Harbin Institute of Technology, Harbin 150090, China;2. Joint Research Centre for Water and Wastewater Treatment Technology, Department of Civil and Structural EngineeringHong Kong polytechnic University, Hong Kong, China)Abstract: Conventional water purified processes have low removal efficiencies for low concentrations of ammo-nia nitrogen, nitrite nitrogen and micro-pollutants. The efficiency and mechanisms of a novel immobilized bio-logical activated carbon( IBAC)process to remove those pollutants from treated potable water was investigatedOperated at a hydraulic retention time of 24 minutes, the IBAC process achieved ammonia nitrogen, nitrite nitrogen and organic micro-pollutants (measured as COD equivalent )removal efficiencies of 95%, 96 and37%, respectively. A GC/MS analysis of the organic micro-pollutants revealed that the initial 24 organic com-pounds in the in-coming water were reduced to 7 after the IBAC treatment. The organic micro-pollutant removalefficiency decreased with decreasing in-coming concentrations. Pollutant reduction in the Ibac process was achieved by a rapid physical adsorption on the activated carbon, which effectively retained the pollutants in thestem despite the short hydraulic retention time, followed by a slower biological enzymatic degradation ofKey words: Dongjiang river; IBAC; GAC; ammonia and nitrite nitrogen removeCLC number. X703Document code: AArticle I:1005-9113(2007)0l40029404Dongjiang River, the main drinking water source of need by the water purifiedGuangdong province and the only fresh water source ofFixed-film bio-nitrification technique is used wideHong Kong sar, is an eutrophic-shock water body bely to remove Ammonia and Nitrite Nitrogen and providecause of high concentration of Ammonia and Nitrite Nitrogood quallty effluent from drinking water. Dahab andgen caused by rapid urbanization, commercial-industrial Lee used 1. 2 m tall columns for bench scale modelsactivities. Fig. 1 showed that Ammonia and Nitrite Nitro- to treat water with NO3 -n 100 mg/L using aceticgen concentration is average up to 3. 5 mg/L and 0. 5 mg/ acid as the extermal carbon source. Nitrate removal effiL respectively through the year of 2002, which overtop ciencies of nearly 100% were reported throughout theNational Standard of Drinking Water as 0.2 mg/L and entire study. Yasushi Takeuchi deal with ozone treat0.05 ng/L, Through the data provided by water supply ment of raw water followed by BAC treatment to removplants along riverside which intake Dongjiang River as raw al organic substances using batch tank reactor/ywater,conventional purification process that is pre- chlo- Granular Activated Carbon GAC) has been particularrine disinfection-coagulant-sediment-sand filter can't rIy focused on in order to remove various substances withmove ammonia and nitrite nitrogen efficiently. So efficient adsorption ability 3-4. Recently, in addition to the reammonia and nitrite nitrogen removal facilities are in great moval of substances by the"adsorption effect"of GACthe removal by the "bio-film effect"of bacteria that isAmmonia nitrogengrowing on the external surface of GAC has been fo8Nitrite nitrogencused on 5!. However, bacteria growing on the GACnaturally can't form homogeneous film. Abundance6species of bacteria that determine the removal rate ofsubstances also can't be controlled. So Here IBAC,Immobilization Biological Activated Carbon( IBAC),amethod artificially fixed special acclimated bacteriaJan. Feb. Mar. Apr. May Jun. July Aug. Sep. Oct. Nov. Dec,which are isolated and cultivated to degrade certainMonthsubstance on carbon to form bio-film, is widely usedFig. 1 NH, -N and NO-N concentration of purified waterBecauselittle sludge, long period of backwash interof Dongjiang, 2002val. high removal efficiency of certain substanceReceived 2004-04-13Journal of Harbin Institute of Technology( New Series), Vol. 14, No. 1, 2007Pretreated1 Materials and Methodswater1.1 Ammonia and Nitrite Nitrogen Removal SystemThe systen utilized in this work consisted of IBACcolumn reactor and GAC adsorption column an airump and a tub pump The reactors were fabricated using plexiglass tubes, 100 mm in inner diameter and1 000 mm in height. Sampling ports were installed atAir也dg150 mm intervals along the side wall of the reactor tocollect water sample and carbon sample, Une columnFig 2 Scheme of the IBAC-GAC systemis filled with IBAC, which is artificially immobilizedammonia and nitrite nitrogen biodegradation bacteri2 Result and discussionbelong to Nitrosospira, Nitrosococcus, NitrobacterNitrospira, Nitrococcus as well as micro-pollutant bio- 2.1 Empty Bed Contact Time(tEBc)degradation bacteria on the activated carbon bed at theEmpty bed contact time is an important of IBACheight of 500 mm to form bio-film. The other column is operating parameter. Assuming a constant concentrafilled with gac bed at the height of 500 mmtion of NH3 and NO2-n. in principle, the shorter the1.2 Water SampleTEBC, the higher the influent loading. As shown in FigDongjiang River water taken by water supply plant, 3, at TEBC of 49 min, 39. 25 min, 32. 71 min, 26. 17was pretreated by coagulation with Poly-Aluminium Fer- min, 17.84 min, the ammonia and nitrite removal effiric Chloride( PaFC)at a concentration of 10. 5 mg/L. ciencies were in the range of 91. 09%-100%.TheseAfter sedimentation and filter, the purified water taken results indicate that different TeBc s had no significantthrough filter was introduced as influent of IBac coleffects on nh, and no-n removal which can be at-umn, Effluent from IBAC flow in to GAC column to ad- tributed to the fact that the affinity of carbon and degrasorb residue bacteria. Ammonia and Nitrite nitrogen dation bacteria-film is deep-set, once bacteria are fa-concentration varied in situ because of different quality miliar with water. It appears that the TeBc could be reof Dongjiang River day to day. Micro-organic com- duced further to a bottom line without decreasing thepounds containing in the influent water provide carbon removal efficiency. Nevertheless, 26. 17 min was thesource for micro-pollutant biodegradation bacteria.shortest time because from this point NH3 removal rate1. 3 IBAC and GAC Treatmentdecreased and at 17. 84 min it falls to nearly 40%0The entire experiment program was divided into meanwhile the concentration of no - n of effluent istwo stages. The IBAC column was first operated in ahigher than that of influent. This indicated that suffiseries of different empty bed contact time(TEBc )valuescient contact time was required between water and mi-for two months to find the shortest TEBc by changing flux croorganism. The intention of determining the shortestof influent,80 mL/ min, 100 mL/min, 120 mL/ min, TEac value is the result in considerable reduction in150 ml/ min, 220 ml/ min which correspond to ancapital expenditures since smaller tanks could be usedTEBc )of 49 min, 39. 25 min, 32. 71 min, 26. 17 minleading to savings in capital investments in both space17.84 min. Then under certain flux of Ibac. The flowand total tankage volume requirementsscheme, as show in Fig. 2, was arranged in such a manner that IBAC reactor received total load and the gACreactor received the effluent from IBAC thereby begin120ning cyclic operation. Air pump changed air flux50100to provide different dissolved oxygen(do)concentration4 Analytical MethodsThe Ammonia and Nitrite nitrogen concentration ofinfluent and effluent was analyzed using standardtrophotometric method. Micro-pollutants were analyzed- Ammonia remoyal efficiencby GC/MS, COD was also analyzed. The controllingparameters of drinking water as pH, temperature andturbidity were monitored simultaneously. The microbial8080100100120120120150152022020populations were enumerated through plate cultivationflux of IBAC/(mL, .min")CountingFig. 3 Ammonia removal efficiency at diffeferent T(IBAC reactor)30Journal of Harbin Institute of Technology( New Series), vol 14, No 1, 20072.2 Efficiency of Combined IBAC-GAC SystemNitrosospira belonging to autotrophic microorganism2. 2. I Turbidity change of IBAC-GAC systempropagated so slowly that the regencration of nitrogenAs shown in Fig 4, in the first slage-IBAC sole degradation bio-film was also stagnant, the wholeoperation phase, The phenomenon that average elfluentcommunity"of carbon granule and bio-film had strongturbidity at 0. 7 NTU of Ibac was always higher than affinity, So just a little bacteria of outer bio-film werehe average value at 0. 4 NTU of the influent should be brushed by the water flow. The heterotrophic bacteriagiven attention because it is suspected to be caused byhave a higher biomass yield and thus can dominate theliving microorganism that will endanger human health. surface area of fixed-film systems over nitrifying bacte-Although those bacteria can be killed by disinfectant ria. As the same principle, nitrogen degradation bacte-such as Cl, and ClO2, too much of them willconsumeria on bio-film of GAC also formed slowly. Ilarge quantity disinfectant, which will remain high con-living bacteria in the effluent, GAC will perform as acentration residual chlorine in potable water, also harmsafety-net to fix bacteria on the carbon and graduallyto people. So GAC as an adsorption and filter was con-form bio-film to degrade NH2-n and NO2-Nnected behind IBAC to provide better quality of efflu- 2. 2. 2 COD removal of IBAc columnentFig 5 showed an direct connection between CODconcentration of influent and effluent. One of principle-fluent *Eluent of [+Efluent d GAconcerns in this experiment is the removal of micro-pol4mutant as electron donor in aerobic oxidation by the m1.2cro-pollutant heterotrophic bacteria. The substrate utilization rate in biological systems can be modeled with0.8the following expression for soluble substrate: It06kixs where r u is the rate of substrate concentrationKs +s0.2change due to utilization, k is the maximum specificsubstrate utilization rate, X is the biomass concentra579113151719tion, S is the growth-limiting substrate concentration insolution. Ks is the half-velocity constant. This equationFig 4 Turbidity change of IBAC-GAC combined processIs expressed as TsuEXS. the first-order model whenrough one month operation, GAC performs wellthe biological treatment process will be operated at reto decrease turbidity and COD value. The amount ofatively low substrate concentrations. So the removalCOD reduction of IBAC reactor is greater than that ofrate of soluble micro-organics by heterotrophic microorganism can be expressed asR, =r/SkX here rGAC column because some bacteria which can degradeis the removal rate. removal rate fluctuated in a smallmicro-organic pollutant were immobilized on the IBACat the beginning of whole experiment. The decrease in range because it also be effected by biomass abun-dethe IBaC effluent probably was associated mostly withanceadditional biomass growth in the reactor. As to the reduction amount of GAC column mainly depend on adsorption ability of GAC. However, the disadvantage of50this IBAC-GAC combined process is the unstable Nll3n and NO,-n removal efficiency of GAC, concentrations of these two removal objections in the effluent ofGaC Sometimes were higher. sometimes lower than thatin the influentThe microbial population in the effluent20of GAC and IBAC were enumerated by plate counting-cod of influmethod. There were average 1 520 cfu/L of micro-pollutant bio-degradation bacteria in the IBAC effluent00and 1 10 cfu/l of that bacteria in the effluent of GAC1471013l618222528average 30 cfu/L NH, -N and NO, -N removal bacteriain the effluent of IBaC and 5 cfu/L of GAC. This reFig 5 COD concentration and removal rate of IBac columnssult can be support by one fact that Micro-organic pol-mutant bio-degradation bacteria, a short generation age 2. 2. 3 Micro-organic compounds removal by IBACorganotrophic microorganism, can proliferate quicklyMicro-pollutant amount reducing from 24 in influand form extra bio-mass leading to bacteria desquama- ent to 7 in effluent present good treatment effect on miting from carbon. Nitrogen degradation bacteria such asJournal of Harbin Institute of Technology( New Series), vol. 14, No I, 2007cro-organic substance of IBAC. Hydrophobe hydrocar- colonization of Nitrobacter bacteria may occur and stabon and phenolic compounds are predicted to be re- bility is bettermoved by adsorption of activated carbon, The removalof fatty acid and hydroxyl substance mainly depend on120micro-biodegradation. To the bio-recalcitrant and toxic金士 9OOC-0OO。。QQQsubstance such as 1, 2, Benzenedicarboxylic acid, bis2-methylpropyl )ester and 4-( 1-methylprOpyl)405Phenol, although they can't be removed completely by2IBAC, the quantity of them decreased in the effluentThe result of gc/ms is shown in Tab. 120Tab 1 Micro-organic compounds in influent and effluentof IBac147101316182225283Raw IBAC influent IBACOrganic compoundsWater Filter effluent )effluent—NO,- n of influentNO-N of effluer2(3H)-BenzolhiazolorNHxn of influent一NH- n of effluentBenzaldehydeNHINNO,-N1, 2, Benzenedicarboxylic acidFig 6 NH3-Nand NO2 -n change of IBACbis(2-methylpropyl)ester3 Conclusioneoxadecane2, 5-bis(1, 1-dimethykthyl )-Phenol+4-(1-methylprOpyl )-PhenolThe conclusion can be drawn from the result of the44-(1-methylethylidene )-Disphenol+study that IBAC processes can be successfully used to3-Acelylphenanthrenedvance purify filter water produced by eutrophic rawButylatewater for its high removal efficiency in ammonia, nitriteXyleneand micro-organics. It was noted that the final effluent十ality was better so IBAC can be used for further ex2-EthylidenecyclohexanoneI'(1, 4phenoylene)bis-ethanoneperiments. An effluent that is low in nitrogen with shortDiphenyletherTEBC can be obtained with this system. Future work canButylated Hydroxyanisolelso be directed towards scaling up the process to pilot(+ means remaining, -means removedscale for eutrophication suffered water treatment plant2.2. 4 Ammonia and nitrite nitrogen removal by IBacIn most situations, any accumulation of nitrite inReferencestransient since the specific growth rate of Nitrobacter is[63 Incomplete ni[1]Woodbury B L, Dahab M F, Mihaltz P, et al. Evaluationlarger than that of Nitrox somonasof reversible fixed-film static-bed bio-denitrification reac-trification with nitrite accumulation has been observedtors. Wat Sci Tech,1998,38(1):311-318.when the Nitrobacter sp. is more severely inhibited[2] Mochidzuki K, Takeuchi Y. The effects of some inhib-itoThe Fig. 6 shows the inlet and outlet ammonia concencomponents on biological activated carbon processes. Wattrations and nitrite concentrations It was seen that bio-Res,1999,33(11):2609-2616logical-oxidation of ammonia started to occur soon after[3 Hoek van der J P, Hofman J A M, Graveland A. The useof biological activated carbon filtration fur the removal ofthe process was made continuous day. The effluentnatural organic matter and organic micropollutants from wa-from the IBaC in the first ten days contained higherter. Wat Sci Tech,1999,40(9):257-264concentrations of nitrite in outlet then inlet and almostJ Nishijima W, Kim W H, Shoto E, et al. The performanceno nitrate. This may be due to in the reactor containingof an ozonation biological activated carbon process underlower numbers of the nitrobacter bacteria which arelong term operation. Wat Sci Tech, 1998, 38(6): 163responsible for the conversion of nitrite to nitrate. Orthe initiation of nitrification. No-n concentrations be- [5 Dimova G, Mihailov G, Tzankov T. Combined filter foing greater than NH4-N concentrations is becauseammonia removal-part I Minimal zeolite contact time andrequirements for desorption. Wat Sci Tech, 1999, 39(8)growth of nitrite-oxidizing bacteria cannot occur until123-129the ammonia-oxidizing bacteria generate nitrite. After[6 GAO Guo-min, ZHAO Qing-xiang, SUN Xian-bo, et alten days, the nitrate concentration increased and theCharacteri-zation of nitrifying and denitrifying bacteria CO-nitrite concentration decreased as the oxidation of am-immobilized in PVA and kineties model of biological nitromonia to nitrite became the limiting reaction. The dis-en removal by co-immobilized cells. Enzyme and microbiappear of this phenomenon after ten days illustrate theal Technology, 2002, 30: 49-5532