Effects of main factors on remedying northern landscaping water by hybrid ecological filter

Joumal of Harbin Instiute of Technology (New Series), Vol. 16, No. 5, 2009Effects of main factors on remedying northern landscapingwater by hybrid ecological filteruU Shu-yul'2 , MA Fang' , WU Ming-hong' , LIU Yilong' , ZHANG Jjie' , GUO Jing-bo2刘书宇,马放，吴明红，刘一龙，张杰,郭静波(1. School of Environment and Chemical Engineering, Shanghai Univerity, Shanghai 201800 , China, layu79@ yahoo. com. en;2. School of Munieipal and Environmental Engincering, Habin Institute of Technology, Harbin 150090 ,China .3. School of W ater Conseration and Architecture . Northeast Agriculurnl Univernity, Harbin 150030 ,China)Abstract: Natural zeolite and coal cinder were layered as main packing medium of the ecological filter insteadof traditional filing to remedy the static lake waler in Northem China. The ecological filer was running in acombined upward and downward flow mode. Dynamic experiments were carried out to study the effects of reten-tion time and ambient temperature on pollutants ' removal eficiency of the hybrid ecological filter. The functionof plant was also studied by contrast test. It is showed that the removal eficiencies of NH:* -N and TP are in-creased when the retention time is changed from 1 h to2 h and4 h, but the removal fficiency of TN is de-creased, the removal eficiency of NH4* -N is incresed from 91.5% to 98% and that of TP is increased from31. 8% to 52.5%。When the temperature declines , the temporal removal ffciency of NH, *-N is reduced, butthe removal eficiency of 24 h and 48 h is remained. The removal eficiency of TP alter 24 h and 48 h is de-creased when the temperature declines evidently. The retention time plays an important role in NH, ' -N and TPremoval, and the ambient temperature is significant for TP removal. The plant favors for TP and organic matterremoval but has lttle effect on TN removal.Key words: zeolite; hybrid ecological filter; landscaping water; temperature; retention timeCLC number: X52Document code: AArticle ID: 1005-9113( 2009 )050623-05The principal mechanisms of the novel hybrid eco-rules of main influencing factors of ecological filter inlogical filter composed of zeolite and coal cinder for thevarious water remediation.bioremediation of the landscaping water were physicaldeposition, filtration, adsorption and biological purifi-1 Materials and Methodscation川. The physical, chemical and biochemicalprocess during the remediation were influenced by vari-1. 1 Structure of the Ecological Filter)us factors including temperature, flow mode, matrixTwo parallel systems were operated. Commelinaselection and installation methods。There were stud-communis L, which had strong adsorption capacity toies on the single adsorption course of different ma-nitrogen and phosphorus, was planted on the surfacetrix'3]. However, influence weights of different factorssand of one system. When it was grown, the3 - 4 stalkvaried under different distribution and operation modewas stick in the soil, the final planting density wain the practical applications. Diversified ecological fil-10-15 x20, which kept both the sight efficiency andters were widely applied in treating municipalit grown need.wastewater. Influencing factors of ecological filters wereAnother system without plant was operated a8 con-diferent between landscaping water remediation andtrast to study the effects of plant on the landscaping wa-wastewater treatment. The variation of environment andter remediation of the hybrid ecological filter. Zeoliteoperational parameters were the most important factors.and coal cinder were used as matrix instead of gravelHere, different influencing factors were studied in aused in the traditional biological filter and constructedwell operated ecological filter remedying landscapingwetlands. Zeolite, a natural mineral material, was uti-water. The objectives of this research were: (1) provi-lized as main matrix for its special physical structureding theoretical framework for process design and oper-and adsorption performance. Coal cinder, a recycledation of ecological filter; (2) establishing the selectionresource, was applied as bottom matrix for its prefera-中国煤化工Received 2008-12- 16.Sponsoredt by the National Natural Science Foundation of China( Grant No. 50809037 ) ;( Crant No. 10111-07-010) and the Specialized Research Fund for the Outstanding Young Teachers of ShanghC.N MH G(Gm Bio0lueFoundation of Shanghai Univernity.●623●Journal of Harbin Instiute of Technology (New Series)，Vol. 16, No. 5, 2009ble adsorption ability. Fine sand was laid on the sur-by contoling the flow rate. The system was operatedface of the ecological filter. The structure of the ecolog-in the day time and closed in the night. Samples wereical filter was showed in Fig. 1. The ecological filtercollected for the measurement of various parameters.was 150-cent meters ( cm) long, 40 cm wide andWater used in this experiment was collected from the30 cm tall. Coal cinder of 5 cm thick was put at theeutrophicated landscaping lake of Taiyang Island, Hei-bottom, zeolite of 15 cm thick in the middle， andlongiang (45*45'N, 126938'E).10 cm thick sand on the top. Bafle was installed inthe middle of the ecological filter. Thus，downward-)istribution pipeBafleInfluent -upward flow was formulated and the water could ade-Sand语Upper efluentquately contact with different matrixes as shown. It waZeolite .5 cm higher than the botom of the filter, then the wa-Cinder甘Lower efluentter can flow in the bottom.1.2 Operation Mode and the Influent QualityFig.1 Structure of the ecological flterThe retention time was designed as1 h,2h and4h .Tab.1 Water Quality of InflowItemsp(NH4*~N)/(mg.L") ρ(TN)/(mg.L少)p(TP)/(mg.L5)pHSeale3.608-4.4284. 964-7. 1010. 082 -0.2198.5-9.08Average value3. 9395.9080.1698.87Landscape-water Standards0.50.026.5-8. s1.3 Analytical Methodsbacteria. The percentage of NH4 * -N in TN declined asThe analytical methods of different parametersmore and more NH4*-N was converted to nitrite andwere listed in Tab. 2.nitrate. However, The TN removal efficiency reducedas the retention time increased since the conversionTab, 2 Analytical methodsrate of the microorganisms was far lower than the ad-temsAnalytical methodssorption rate of the matrix. Differences of TN removalNH4°-NNeseler' reagent colorimetrie methodefficiency between2 h and 4 h were small. Comparedto the 1 h, the decline for TN removal efficiency wasTN analyzerevident.TOCTOC analyzerThe removal efficiency of TP elevated fromPICP-OFS analyzer31. 8% when the retention time was 1 h to 42.7% and52. 5% as the retention time inereased to2 h and4 h,respectively. The removal reaction of PO2 - with AI'2 Results and DiscussionsCa2* and Mg2 * involved in matrix was a slow process(4)and was influenced by the structure and physicochemi-2.1 Retention TimeAs showed in Fig. 2，the removal efficiency ofcal property of the matrixl5- 。 . Therefore, the efluentconcentration of TP was obviously reduced as sufficientNH& *-N increased formn 91.5% to 98% as the reten-contact was oblained under prolonged retention time.tion time increased from 1 h to 4 h. The effluentNH&*-N concentration was 0. 049 mg/L，which was120far lower than the NH4*-N standard value (0.5 mg只10001h口2h■4hL) of the criteria A of the Chinese National landscape-冒80water standards.NH, *-N was mainly removed by the adsorption ofthe matrix and the nitrification of the microorganisms.夏40Zeolite had strong selective adsorption to NH4* -N. The是20longer the pollutants contacted with the zeolite， themore adsorption amount would be achieved. Thus, theTIremoval eficiency of NH4 ' -N increased obviously中国煤化工when the retention time prolonged.Partial NH, * -N absorbed by the matrix was con-Fig,YHCN MH Goval emcleacy otdlverted to nitrite and nitrate by nitrosobacteria and nitro-Joumnal of Harbin Instiue of Technology (New Series)， Vol. 16, No. 5, 20092.2 Temperaturestant removal efficiency was small under different tem-The landscape-water belonged to natural water andperatures. The removal efficiency of 24 h and 48 hwould experience the variation of ambient temperature.rose. The stability of TN removal efficiency remained.The purifcation of functional microorganisms was im-This was because NH4 * -N occupied a large proportionportant for ecological filer. Temperature had greatin TN and could kept stable removal efficiency. Ieffects on the activity of microorganisms. For example ,could be inferred from Figs.3 and 4 that the instant re-the optimal temperature range for nitrobacteria was 20moval efficiency of NH&* N reduced greatly as the-30 C. In the northem area of China, seasonal vari-temperatures fell down, while that of TN was also re-ation gradient of temperature was relatively large andduced. Numerous nitrosobacteria， nitrobacteria anthis would pose great impacts on the matrix, creatureazotobacteria existed in the polluted water. As the ef-and water quality of the hybrid ecological filter. Thefluent was circulated as influent in the system, the de-average removal eficiency of NH, * - N under differentcrease of ambient temperature led to the death of func-temperatures was showed in Fig. 3.tional consortia contained in the water , including azoto-The removal eficiency of NH4 * -N decreased ob-bacteria that could synthesize nitrogen. The decreaseviously as the temperature declined from 15-25 C toor the disappearance of the nitrogen synthesis ability of5-15 C and then to0-5 9C. There were almost nothe azotobacteria resulted in the reduction of nitrogendifferences between the removal efficiency of 24 h andsynthesis quantity. Accordingly, the decrease of the48 h. The adsorption of zeolite to NH4* -N was a phys-influent TN concentration led to the increase of TN re-ical adsorption and ionic exchange process. The ionicmoval efficiency. It demonstrated that the nitrogen syn-exchange process contained there phase: the externalthesis of the azotobacteria was the main reason for thediffusion of the particles, the inner diffusion of the par-elevation of TN in the water. The removal efficiency ofticles and the ionic exchange reaction. The decrease ofTP during 24 h and 48 h descended obviously as thetemperature would slow down the diffusion of the ions.temperature dropped and the instant removal eficiencyHowever, since the filter was full of wastewater, theof TP was almost no change. TP was mainly removeddecline of the ambient temperature had lttle impact onby the adsorption and exchange of the underlayeringthe microenvironment of the zeolite ' s aperture. Thecoal cinder and was a slow process. The exchange ofexchange rate mainly depended on the inner diffusionthe adsorption had not finished when the polluted waterand afected by the selection and the interaction of theand the matrix had relatively short contact time. Thusions and the aperture. Therefore, the reduction of thethe instant removal efficiency didn ' t show muchinstant removal efficiency was primarily caused by thechange.decrease of the external diffusion ability of the partials.In Fig. 5, the removal fficiency of TP in 4 h andPrevious studies also indicated that when the tempera-48 h declined along with the descending of the temper-ture declined from 30 C to 10 C, the adsorptive ca-ature. Under sufficient contact time, the adsorption ofpacity of the zeolite only reduced a lttle, i. e. , thecoal cinder to PO4 was influenced by the temperature.temperature only has a litle impact on the NH4*-N ex-The release activity of phosphorus reduced as the tem-change capacity of zeolite. To remain relatively highperature lowered. As a result, phosphorus' S chance ofremoval efficiency when the temperature declined, thecombination with Al'+ ，Ca2+ and Mg' was also re-reolite could be utilized as the main flling in the reme-duced. Meanwhile, the temperature of the matrix hasdiation system of landscaping water, which main pollu-great effects on the plant. The water viscidity enhancedtants was characterized as NH4*-N.and the diffusion rale decreased as the water temperatureFrom Fig. 4, the amplitude of decline of TN in-dropped. Furthermore , as the temperature dropped, the0 Instant removal effieiency0 Instant removal fficiency0 Instant renoval efficiency口Removal effeienev of 24h口Removal eficiency of 24 h口Renoval efficiency of 24 h口Removal efficiency of 48h口Remioval fficiency of 48 h口Removal efficiency of 48 h00厂80f80F60个|导60员60fl0十40-40- r0个20-20 |0 15-25T 5-15T 0-5C名。15-25C 5-15C_15C: 0-5弋Temperature rangeTemperaure中国煤化工ure rneFig.3 Removal of NH:*-N inFig.4 Removal of TN:YHCNMHG1ofπPindifferent temperaturedfferent temperature.625..Journal of Harbin Instiute of Technology (New Series), Vol. 16, No. 5, 2009physiological activity of the plant root system also de-when the plant entered senescence and death phase.clined. For instance, the reduced respiration intensityThe nitrogen removal efficiency to the municipaland the enlarged protoplast viscosity of the root cellswastewater through the harvestry of plants wasless thanled to the reduction of permeability. Then the resist-20%。Thus, removal of nitrogen by plant was minorance of protoplasm membrane to water enhanced andfrom the technological perspectives. Here，n thethus the absorption speed and amount of the root syg-beginning stage, large root age did not grow and thetem to the water and the pollutants declined. Thus,fillers was tightness , oxygen transportation was blockedimprovement of NH4 * -N removal could be achieved bywhich weakened nitrification. In later stage this condi-prolong the contact time of wastewater to the matrixtions were changed by ripe plant roots ，oxygen becamewhen the temperature was over 0 C. The removal eff-enough. Some contamination was cut and aerobic bac-ciency of TP reduced along with the decrease of theteria were activated by oxygen. The system with planttemperature.could remove more nitrous contamination, TN concen-2.3 Infuences of Planttration decreased then. One reason was that a part of2.3.1 Influences to the TN removalnitride was absorbed by the roots to provide necessaryThe plant root syslem would absorb various nutri-nutrient for the plant growth, the other reason was thatent including nitrogen and phosphorus during thethe root and microbe improved microbial environment，growth. The root system would also transport the oxy-which was favored for transition of nitride.gen from the top to the root. An oxic environment wasthen formed to promote the decomposition of the organ-- Sysem withoutics and the growth of the nitrobacteria for the removalplantsof nitrogen containing compounds. The impacts of_System ，withdifferent planting density on the purification of the eco-logical filter was investigated.As shown in Fig. 6, the TN removal efficiency ofb哈A1the non-planted system was lower than that of the plan-ted ecological filter. In the early stages of the plant0T 3579111315171921 23 25tegrowth, its root system was underdeveloped. The rootsystem had weak absorption to nitrogen and almost noFig. 6 Effect of plant on TN removaladjustment ability to the inner environment of the sys-tem. The respiration of the root system could enhance2. 3.2 Influences to the TP removalthe oxygen transportation and the activity of the aerobicAs shown in Fig. 7, the efluent TP concentrationorganisms. In the natural water, most of the nitrobacte-of the planted system was always lower than the systemnia were aerobic bacteria. Meanwhile, the closenesswithout plants. The concentration differences betweendegree of the planted system in the early stage wasthe two systems were 0.03 -0. 021 mg/L. Phosphorushigher than that of the system without plants. Also, nowas absorbed and trapped by the roots of the plantsmassive root system zone formed in the matrix at theduring their growth. Although the phosphorus could beearly stage，which further reduced the transportation ofdegraded by microorganisms, the acidic phosphataseoxygen from the exterior to the inner space. Contribu-secreted by their root system could decompose a part oftion of plants to the nitrogen removal was small at theorganic phosphorus, which was beneficial for the ex-early slage. 18 d later, the efluent TN concentrationchange adsorption of the matrix and degradation of mi-of the planted system began to appear lower than thecroorganisms to the phosphorus. The phosphorus ab-non-planted system. The huge root system in the matrixsorption amount of the large-sized plants in wetland wascould trap partial pollutants and the oxygen-abundant1.8-18 g●m2●a-' and the phosphorus content inenvironment could promote the activity of the aerobicthe dry biomass of 41 types of helophyte was 0.15% -nitrobacteria. Then the efluent TN concentration of the1.05% [10]. In the trealment of municipal wastewater,two systems drove to the same and the concentrationthe phosphorus absorbed by plants was less than 5% ofdifferences between the two systems were 0. 002一the phosphorus loading rate. The phosphorus absorbed0.854 mg/L. In a word, contribution of plant to theby plants was only significant in the low-load system.removal of TN was not obvious.Hence, in the pollutants removal of the micro-pollutedPlants didn' t have predominance for TN removallandscaping-water, plants could enhance the TP re-as the majority of TN was adsorbed selectively by themove中国煤1Tlity of the ecologicalmatrix and converted by the microorganisms in a shortfiler化上rent degree, plantstime. Previous study showed that in the constructedHC N M H G applied to increasewetland system, nitrogen absorbed by plants was 0.03he phosphorus removal of the ecological filter system.-0.3 g/(m2●d) and there was no nitrogen removal.626●Jourmal of Harbin Instiute of Technology (New Series)， Vol. 16, No. 5, 20090.350.30 '- - System without plants3 Conlusions-0- System with plants0.201) The retention time was an important factor the. removal efficiency of various pollution indexes. When日0.1the retention time increased from 1 h to2 h and then to9 0.10 t4 h, removal efficiency of NH4* -N and TP increased0.05 tand that of TN declined.073广9竹2) As the temperature dropped, the instant re-moval efficiency of NH, * -N decreased. But the remov-Fig.7 ErTect of plant on TP removalal eficiency of NH, *-N after 24 h and 48 h didn' t ap-pear much difference. The reduction of matrix adsorp-2. 3.3 Influences to the organic pollutants removalAbsorption of organie pollutants was achieved bytion and exchange amount led by the decline of temper-ature could be improved by extending the contact time.the combined action of plants and microorganisms. TheRemoval efficiency of TP in 24 h and 48 h was obvi-influent and efluent TOC concentration of the plantedously reduced as the temperature fell down. Tempera-system was higher than that of the system withoutture was the main influential factor for the removal ofplants. However, the removal efficiency of the plantedNH,* -N and TP.and non-planted system was 15. 8% and 14. 2%, re-3) Plants grew on the filter surface of the systemspectively. Thus , the growth of the plants improved thecould promote the removal of TP and organic com-removal of the organic pollutants. A part of the organicpounds, but had little effect on the removal of TN.carbon was synthesized as plants ’substance duringtheir growth. Meanwhile, the oxic root system boostedReferences:the nitrification in the matrix and a part of carbon was[1] Liu Shuyu, Ma Fang. Effect of efluent recycling on nitro-taken as electron acceptor. Partial organic carbon wasgen transition in ecology filter. Environmental Science,consumed during this process and the removal efficien-2007, 5(28): 1006 - 1010.cy of the system to the organic pollutants increased.[2]Yuan Donghai, Jin Lijie, Gao Shixiang, et al. Analysis onThe activation of the micro- environment of the matixthe removal eficiency of phosphorus in some substrateswas also beneficial for the biodegradation of the organ-used in constructed wetland systems. Environmental Science. ,2005 ,26(1):51 -55. .ics. The organics would was converted to CO2and re-[3] Johnston C A. Sediment and nutrient retention by freshwa-lease from the system. Finally, compounds generatedter elands: Effects on surface water quality. 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