Odorous composting gas abatement and microbial community diversity in a biotricklingfilter
Niantao Xue a,b,Qunhui Wang a,c,*,Juan Wang a,Jianhua Wang a,Xiaohong Sun d
a School of Civil and Environmental Engineering,University of Science and Technology Beijing,30Xueyuan Road,Haidian District,Beijing100083,PR China
b School of Environment,Tsinghua University,Haidian District,Beijing100084,PR China
c Key Laboratory of Educational Ministry for High Efficient Mining an
d Safety in Metal Mine,University of Scienc
e and Technology Beijing,Beijing100083, PR China
d Beijing Agricultural Biotechnology Centre,Beijing Academy of Agricultur
e and Forestry Sciences,Beijing100089,PR China
a r t i c l e i n f o
Article history:
Received21June2012
Received in revid form
2March2013
Accepted3March2013
Available online
Keywords:
Biotricklingfilter
Composting
Odor
Volatile organic compounds(VOC) Bacteria
Fungi
Actinomycetes a b s t r a c t
This study aimed to remove complex odorous gas produced from composting using a biotricklingfilter and to obrve the temporal and special distributions of bacteria,fungi,and actinomycetes.The removal efficiencies of the total volatile organic compounds(TVOC)were26.1%and81.5%before and after inoculation of volatile organic compounds(VOC)-degrading microbes,respectively.Especially trime-thylamine was100%degraded.In thefirst and cond composting period,the odor reduction efficiencies showed average values of86.2%and94.5%,respectively.The total average of the bacteria in the biofilm was2.06Â109CFU/g TS,which was22.2%higher than that of the control(the culture of microbes prior to the inoculation of VOC-degrading microbes).The bacteria may have played a predominant role in odor removal.The total average of the fungi in the biofilm was9.64Â106CFU/g TS,which was only6.40%of the control.The total average of the actinomycetes in the biofilm was5.10Â105CFU/g TS,which was 5.63times higher than that of the control.Findings from this study showed that usage of a biotrickling filter is a promising process for the treatment of complex odorous gas.
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1.Introduction
Odorous gas emitted from composting facilities has complicated components,which necessitate efficient,environment-friendly, and cost-effective treatments.The main ,pollut-ants)of the odorous gas are(1)nitrogen-containing compounds, such as NH3(Komilis and Ham,2006)and N2O(Fukumoto et al., 2003);(2)sulfur-containing compounds,such as H2S;(3)volatile organic compounds(VOC)(Akdeniz et al.,2010);and(4),principally airborne microorganisms and microbial constituents relead from composting process where move-ment of material is involved)(Sanchez-Monedero et al.,2003).In addition,the components and their concentrations exhibit signifi-cant changes at different composting stages.
The physicochemical properties of odorous gas are diversified. Easily and adverly biodegradable matters coexist,and some are either hydrophilic or hydrophobic.Hydrophilic substances have diver solubilities in water.Hydrophobic substances are not readily available to microorganisms,and thus inadequate for u in biological treatments(Hassan and Sorial,2010).The properties demonstrate that effective treatment of odorous gas is difficult.
In the last few decades,emission control of VOC and other odorous pollutants has become a crucial issue owing to their adver effects to humans,animals,and the environment.Most VOC are toxic and carcinogenic substances;thus,loss of the substances to the ambient air may have an adver
impact on air quality and endanger public health(Yoon and Park,2002). Anthropogenic activities will influence the conversion of natural VOC into condensable vapors to generate natural aerosols and thus, further affect climate(O’Dowd et al.,2002).Therefore,it is very important to develop effective technologies to remove the com-pounds to prerve human health and the environment.
Trimethylamine(TMA),one of VOC is a malodorous aliphatic amine frequently identified in gaous emissions of multiple in-dustrial and agricultural process.Compared with ammonia,TMA can be perceived and detected at greater distances becau of its characteristics,including persistent intensive odor and very low odor detection thresholds(Goldstein,2002).TMA pos rious
*Corresponding author.School of Civil and Environmental Engineering,Univer-sity of Science and Technology Beijing,30Xueyuan Road,Haidian District,Beijing 100083,PR China.Tel./fax:þ861062332778.
E-mail address:(N.Xue), (Q.
Wang).
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0964-8305/$e e front matterÓ2013Elvier Ltd.All rights rerved.
dx.doi/10.1016/j.ibiod.2013.03.003
International Biodeterioration&Biodegradation82(2013)73e80
ecological and environmental issues and is a strong environmental pollutant.Health effects associated with inhalation of TMA include irritation of the respiratory tract,eyes,and skin.Conquently,the nsitive determination of TMA in atmospheric and human work environments is of great importance(Cháfer-Pericás et al.,2004). Thus,TMA and other VOC disposal through usage of a biotrickling filter(BTF)was studied in this paper.
Biological process for odor treatment,including bioscrubbers, biofilters,and biotricklingfilters,are promising odor abatement technologies that take advantage of the ability of microorganisms to remove substrates from odorous organic compounds(Canovai et al.,2004).Their development owes its increasing popularity to two of its advantages:(1)It is operated at ambient temperatures (15e30 C);(2)It does not produce toxic by-products(Delhoménie et al.,2002).In a biotricklingfilter,waste air str
eams pass through a packed bed of synthetic inert material where particular microbes are immobilized to form a thin aqueous layer(biofilm)(Zilli et al., 2007).Biofilters are more popular than biotricklingfilters in the treatment of odorous composting gas.The latter are more complex and more expensive than biofilters but are usually more effective, especially in the treatment of compounds that are difficult to degrade or tho that generate acidic by-products,such as H2S(Cox and Deshuss,2000).
Biotricklingfilters have ldom been ud to treat waste-composting gas.The reason biotricklingfilters are preferred over biofilters is that they contain trickling liquid which helps avoid dryness of the packing material and allows removal of metabolites produced during degradation which can then be recycled.Smits et al.(1995)applied a biotricklingfilter to treat ammonia and odor from a composting facility.The biological elimination capacity was4g NH3/(m3$h),and the odor removal efficiency was50%for odor loads as high as5o.u./(m3$s).Pei et al.(2008)revealed that a constant TVOC removal efficiency,an odor concentration above70% and a maximum elimination capacity of130g/(m3$h)can be ach-ieved.Mao et al.(2006)found that biotricklingfilters have better deodorization capability for odor from food waste-composting plants than the biofilter and the chemical scrubber with deodor-ization efficiencies measured according to odor concentrations of 82
%,59%,and45%.It is expected to improve biotricklingfilter removal efficiency of the odor concentration.
Although the performance of biotricklingfilters depends on the type of microorganisms prent,reports on the microbial com-munity in biotricklingfilters remain scarce.Inside the biofilm of biotricklingfilters or biofilters,biodegradation is mediated by mixed cultures of bacteria,fungi,actinomycetes,and algae,all thriving in a complex ecosystem.Secondary pollutant degraders and predators,such as protozoa,metazoan,and other higher or-ganisms,are also included.Investigating changes in the microbes in biotricklingfilter will promote rearch on the microbial degrada-tion mechanism,optimization of design and operation of bio-tricklingfilters.
This study aims:(1)to gain an insight into how a biotrickling filter effectively eliminates complicated composting gas;(2)to determine the removal efficiency of biotricklingfilter for odor concentration;and(3)tofind out the spatial and temporal distri-bution of microbial community in biotricklingfilter.
2.Materials and methods
2.1.Equipment
吃苦The composting reactor schematic reprentation and the bio-tricklingfilter tup are shown in Fig.1.The upper part of thefilter was the biotrickling ction,with a working volume of5.0L.A perforated plexiglass plate,which rved as gas and liquid distributor,was placed at the bottom of the biotrickling ction. Packing material was supported on the plexiglass plate.About1.8L of trickling liquid in the holding tank was fed by a pump to the top of the BTF.It trickled through the packing material to the liquid distributor.The inlet gas pipe of the biotricklingfilter was placed under the trickling liquid,which formed the scrubber ction,to employ the absorption capacity of trickling liquid.The properties of the packing material,the operation of the composting bioreactor, and other specifications were given by Xue et al.(2010).
2.2.Gas sampling and analysis
Sampling ports were t on top of the composting bioreactor and on each ction of the biotricklingfilter.Gas samples were collected from the inlet and outlet streams using a gas sampler (Model QS-1S,Beijing Municipal Institute of Labor Protection, China).Trimethylamine was transferred into an aqueous solution and then analyzed using the picric acid spectrophotometric method(SBPCI,1999).Hydrogen sulfide was determined using gas-detection tubes made by the Beijing Municipal Institute of Labor Protection,China.TVOC was analyzed using gas chromatography
(Perkin Elmer clarus600Gc-Turbomatrix ATD650,column:Elite-62430m*320m m,detector:FID)at the Center for Test of Envi-ronmental Quality,Tsinghua University,China(EBSEPA,2003). Odor concentration(without unit)was measured through olfac-tometry,in accordance with the triangle odor bag method(SEPA, 1993).Ammonia was determined according to Nessler’s reagent colorimetric method(SEPA,1993)(SEPA etc.are abbreviations of corresponding organisms who issue the methods).
2.3.Enrichment and screening of VOC-degrading microbes
The lective inorganic salt medium consisted of the following (per liter):NaCl1.0g,MgSO4$7H2O0.7g,NH4C11.0g,KCl0.7g, KH2PO42.0g,Na2HPO43.0g,and pH7.0.A trace element solution was added after autoclaving.The trace element consisted of the following(per liter):CaCl20.2mg,FeCl3$6H2O0.5mg,CuSO4 0.005mg,MnCl2$4H2O0.005mg,and ZnSO4$7H2O,0.1mg(Wang and Shao,2006).
The microbial enrichment medium consisted of1g of peptoneþ1L of lective inorganic salt medium.
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Fig.1.Composting reactor schematic reprentation and the biotricklingfilter tup.
(1)Air compressor;(2)time relay;(3)composting air inlet pipe;(4)perforated plate;
(5)composting sampling port;(6)heating belt;(7)automatic temperature controller;
(8)composting reactor;(9)composting exhaust gas sampling port;(10)BTF air inlet pipe;(11)perforated plate;(12)trickling liquid holding tank ud as scrubber ction;
(13)biotrickling ction of BTF with packing;(14)BTF;(15)liquid distributor;(16) micro pump;(17)voltage-and current-steady power supply;(18)time relay;(19)gas sampling port;(20)air exhaust;(21)trickling liquid pipe.
N.Xue et al./International Biodeterioration&Biodegradation82(2013)73e80 74
In a previous determination,styrene,m-xylene,and chloroform were the primary refractory components in the exhaust of com-posting gas.In the prent study,100mL lective inorganic salt medium,5m L styrene,m-xylene,and chloroform were transferred into two250mL aerobic oscillationflasks.Ten mL mixed liquor from the Qinghe Wastewater Treatment Plant and the Coking Plant of the Shougang Group,respectively,were added as initial micro-bial consortia.The culture was performed in a shaking incubator at 30 C and150rpm for a2-day culture period.At the end of each culture period,10mL cultured suspension and10,20,and30m L of styrene,m-xylene,and chloroform,respectively,were added into 100mL fresh medium for the next period.After four culture cycles, VOC-degrading microbes that could degrade VOC were enriched in the microbial enrichment medium.
2.4.Biomass determination,paration,and count of bacteria, fungi,and actinomycetes
Separation and count of bacteria,fungi,and actinomycetes was performed according to the conventional dilution plate count described by Chen and Zhang(2006).Three packing spheres at the top,medium,and bottom,respectively,were removed from the biotricklingfilter.The biomass on each of the spheres was peeled off into three sterilized beakers,and then diluted to200mL as initial consortia.The initial consortia were diluted to the appro-priate multiples by ten-fold dilution method to
make microbe suspension.Take0.1mL of microbe suspension and inoculated on the surface of solid medium in petri dishes.The dishes were put into culture incubator under appropriate temperature.Three rep-licates were performed for all samples.The other biomass was evaporated to dryness on a water bath and then dried in a103 C e 105 C dry box.Incandesce in a600 C muffle furnace was ud to determine the total solids(TS)and the volatile solids(VS).
The trickling liquid was diluted to the appropriate multiples by ten-fold dilution method for paration,and count of bacteria, fungi,and actinomycetes.
Bacterial culture medium(beef extract,peptone,agar medium): beef extract3.0g,peptone5.0g,agar18.0g,sterile distilled water 1000mL,pH7.0to7.2.Petri dishes were culture in the32e34 C incubator for3days.
The fungal culture(Matin medium):peptone5.0g,gluco10g, K2HPO41.0g,MgSO4$7H2O0.5g,agar15g,1%ro bengal solution of3.3mL,water1000mL,normal pH value.When the medium was ud,0.3mL of1%streptomycin solution was added to each100mL medium.Petri dishes were put in the30 C incubator for5e7days.
Actinomycetes culture medium(modified Gao I medium):sol-uble starch20.0g,K2HPO40.5g,FeSO4$
7H2O0.01g,KNO31.0g, MgSO4$7H2O0.5g,NaCl0.5g,agar18.0g,distilled water1000mL, pH7.2e7.4.When the melted medium was ud,K2Cr2O7solution was added to inhibit the growth of bacteria and mold.One mL of3% K2Cr2O7solution was added to each300mL medium.Petri dishes were put in the28 C incubator for7e14days.
2.5.Experimental process
Before the VOC-degrading microbes were inoculated,odorous gas from the composting reactor entered the biotricklingfilter primarily to culture the microbes in the packing material.Bacteria, fungi,and actinomycetes were counted and considered as the control.Two hundred mL of microbial enrichment media contain-ing VOC-degrading microbes were mixed with the trickling liquid, and the microbes gradually in the biofilm of the biotricklingfilter. Then,the biotricklingfilter was ud to treat the exhaust gas two composting periods.During the two periods,tap water and municipal wage from an office building in the University of Science and Technology Beijing,respectively,rved as the trickling liquid.After1day,50mL trickling liquid was collected for water quality analysis,and50mL e60mL of tap water and municipal wage,respectively,were made up every day.Apart from NaOH, which regulated the pH values,no nutrient was added during the entire experiment.怎样制作ppt详细步骤
3.Results and discussion
3.1.Removal of VOC and other pollutants before and after the inoculation of VOC-degrading microbes
The removal of VOC and other pollutants before and after VOC-degrading microbes inoculation is shown in Table1.
The inoculation of VOC-degrading microbes notably enhanced the abatement of VOC.After inoculation,the removal efficiencies of toluene,ethyl acetate,and other VOC in the scrubber ction decread.However,tho of benzene,ethylenzene,p(m)-xylene, styrene,and o-xylene improved.Removal efficiencies of VOC in the biotricklingfilter exhibited similar trends.The total removal effi-ciencies of almost all VOC,except for styrene,were incread.
The total removal efficiencies of TVOC incread from26.1%to 81.5%.Prior to the inoculation of VOC-degrading microbes,TVOC removal efficiencies in the scrubber ction and in the biotrickling ction were58.0%andÀ76.0%,respectively.The results indicate that TVOC was removed in the scrubber ction,and new VOC was produced after the exhaust gas pasd through the biotrickling ction.After the inoculation of VOC-degrading microbes,TVOC removal efficiencies in the scrubber and in the biotrickling ction were dramatically enhanced by the microbes to56.7%and57.3%, respe
ctively,with a total removal efficiency of81.5%.This result demonstrated that the microbes could metabolize VOC in the influent.Hence,inoculating the VOC-degrading microbes necessary.
TMA,which is readily soluble in water,was completely removed in the scrubber and in the biotrickling ction,probably due to its easy biodegradation in the biofilm.Kim et al.(2005)claimed that hydrophilic substances are easily degraded,whereas the degrada-tion of hydrophobic substances is hindered until biological cultures produce sufficient RNA or enzyme/protein to u the substances. However,Tsai et al.(2008)noted that TMA is difficult to biodegrade becau microbes cannot easily break the molecule.Some microbes can probably degrade TMA in the biotricklingfilter effectively.
Ammonia,which accounted for90.4%and94.5%of the total pollutants in the two tests,respectively,was efficiently eliminated. Hydrogen sulfide was not detected becau an aerobic,rather than an anaerobic,composting process was employed in this study.
3.2.Reduction in odor concentration when tap water or municipal wage rved as trickling liquid
The prence of trickling liquid is the central characteristic that distinguishes the biotricklingfilter from the biofilter.In this study, trickling liquid was the water trickled over the bed in the bio-tricklingfilter driven by the continuous recirculation of the liquid in the holding tank.At certain periods,make-up wat
er,tap water or municipal wage,was added to the reactor to compensate for trickling liquid loss due to evaporation,sampling,purging,and so on.Trickling liquid provided a convenient means to control pH,salt, or metabolite concentration,and supplemented nutrients to the biomass.The additional nutrients,pH control,and larger gas/liquid interfacial area resulted in substantially higher removal efficiencies than that of biofilters(Mpanias and Baltzis,1998).
Odor concentration is a key integrated air quality indicator in the verification of odor emissions.To date,few investigations have
N.Xue et al./International Biodeterioration&Biodegradation82(2013)73e8075
been conducted on odor concentration during a composting pro-cess,especially the control of odor concentration biological pro-cess.In this study,the odor concentrations of the gas entering and leaving the biotrickling filter was measured and is shown in Fig.2.During the first period,inlet odor concentrations incread from 750to 9000.The odor reduction ef ficiencies of the biotrickling ction ranged from 42.9%to 91.7%,with an average ef ficiency of 86.2%.During the cond period,odor reduction was more stable,ranging from 87.5%to 98.3%with an average ef ficiency of 94.5%.The inlet concentrations during the cond period were higher than tho during the first period.In genera
l,odor reduction was improved during the cond period.Chen et al.(2009),Lau and Cheng (2007)found that the odor concentrations of untreated barn air varied from 8553Æ1006OU/m 3to 12171Æ1575OU/m 3,and that the average odor removal ef ficiency of a bio filter system was 95Æ3%.
3.3.Changes in biomass of the bio film
The changes in TS and VS/TS are prented in Fig.3.The biomass contents were related to the size of the packing spheres,such that sometimes the contents exhibited signi ficant differences.The fewer quantity of the end biomass compared with the initial quantity may re flect the evolution of the biomass to some extent,owing to the insuf ficient nutrients for the microbes.The average VS/TS incread from 0.586to 0.627and finally decread to 0.541,indicating that the inorganic matter build-up trend.Besides to the nutrients for the microbes,ammonia,VOCs,microbial enrichment medium,and other components in the inlet gas,no other nutrients was added to the trickling liquid.The inlet components were probably insuf fi-cient for the microbes,leading to a small decrea in biomass.
Excessive biomass accumulation,especially clogging,can reduce pollutant removal and can increa pressure drop,flow channeling,and investment cost.The factors are major hindrances to the
long-term stable operation of biotrickling filters.Various methods have been evaluated to control biomass accumulation and to pre-vent clogging.Examples are reduction of biomass growth and removal of excess biomass.The former includes nutrient limitation,addition of growth inhibitors,and u of predators that prey on other microbes the latter includes chemical washes,backwashing,periodic,and stirring of the packed filter.Reduction of biomass growth usually caus decreas in the removal ef ficiency.In this study,the nutrients available for the microbes were limited.However,the pollutant removal ef ficiencies were never reduced,as microbes readily prefer biodegradable substrates.When the sub-strates were not suf ficient for growth,the microbes were forced to metabolize other substrates.The inlet pollutants were thus sub-jected to degradation.
3.4.Microbial community diversity in the bio film and in the trickling liquid
The treatment of gaous pollutants using biotrickling filters involves a ries of complex physicochemical and biological phe-nomena,such as gas e liquid followed by liquid-bio film or direct gas-bio film mass transfer of the pollutant,pollutant diffusion within the bio film,and pollutant biodegradation in the bio film (Popat and Deshuss,2010).Fig.4shows the changes in the bac-teria in the trickling liquid.The error bars of the microbes in the bio film are the standard error of averages of the microbes at the top,medium,and bottom of the biotrickling filter,revealing changes in the scope
of microbe distribution along the vertical di-rection of the biotrickling filter.The error bars of the microbes in the trickling liquid are the standard error of sample duplicates for analysis.
Bacteria normally show a rapid substrate uptake and growth.Under favorable conditions,they can become the dominant con-sortia,although fungi may be also prent (Dorado et al.,2008).
Table 1
Removal of VOC and other pollutants before and after the inoculation of VOC-degrading microbes.Gas Inoculation In fluent (mg/m 3)Ef fluent in scrubber ction (mg/m 3)Ef fluent in biotrickling ction (mg/m 3)RE a in scrubber ction (%)RE in biotrickling ction (%)Overall RE in
biotrickling filter (%)Benzene Before 0.0060.0100.006À66.740.00After 0.0540.0360.03533.3 2.7835.2Toluene Before 0.0710.0430.05539.434.922.5After 0.1320.0810.02438.670.481.8Ethyl acetate Before 0.0160.0230.013À43.843.518.8After 0.0500.1210.027À142
77.746.0Ethylenzene Before 0.0120.0120.010016.716.7After 0.0370.0220.01840.518.251.4P (m )-xylene Before 0.0240.0290.023À20.820.7 4.17After 0.0690.0360.03847.8À5.5644.9Styrene Before 0.0100.0120.010À20.016.70After 0.0210.0110.02347.6À109À9.52o -xylene Before 0.0130.0170.013
À30.823.50After 0.0540.0150.01172.226.779.6Undecane Before 0.00500.055100/À1000After 0
/
/
/
Other VOC Before 9.120 3.749 6.67458.9À78.026.8After 8.091 3.361 1.39858.558.482.7TVOC
Before 9.277 3.895 6.85958.0À76.126.1After 8.508 3.683 1.57456.757.381.5Trimethylamine Before 2.3080
0100/
100After 10.60.018099.8100100Hydrogen sul fide Before 000///After 000/
/
/
Ammonia
Before 1098.85 1.8891.978.898.3After
331
13.9
8.67
95.8虾怎么烧
37.6
97.4
RE in scrubber ction (%)¼(In fluent ÀEf fluent in scrubber ction)/In fluent Â100.
RE in biotrickling ction (%)¼(Ef fluent in scrubber ction ÀEf fluent in biotrickling ction)/Ef fluent in scrubber ction Â100.Total RE in biotrickling filter (%)¼(In fluent ÀEf fluent in biotrickling ction)/In fluent Â100.a
RE:Removal Ef ficiency.
N.Xue et al./International Biodeterioration &Biodegradation 82(2013)73e 80
76
Bacteria can effectively remove hydrophilic compounds.Hydro-phobic and recalcitrant compounds,such as aromatic compounds,alkenes,and alkanes,are poorly absorbed by the bacterial bio film becau of their low solubility in water.However,some rearchers think that some hydrophobic and recalcitrant compounds can be removed by bacteria (Romantschuk et al.,2000).
The changes in the bacteria in the bio film exhibited notable variations (Fig.4).During days 2e 8,the odor concentrations were much higher than that of day 1,indicating the abundance of nu-trients for bacteria that thrived to 4.2Â109CFU/g TS.During days 14e 20,the bacteria count also decread becau of the decline in odor concentration.Bacterial distribution is related to odor con-centration (pollutant load),transfer by trickling liquid,bio film performance,and bacteria characters.Wu et al.(2008)claimed that the bacterial count along the packing material in a biotrickling filter that treated styrene-polluted gaous streams depended on both styrene load and gas residence time.The average total bacterial was 2.06Â109CFU/g TS,which was 22.2%higher than that of the control in the prent study.On the other hand,ammonia accounted for more than 90%of the total pollutants.In
our previous work,the results of polymera chain reaction-denaturing gradient gel electrophoresis revealed that ammonia was effectively removed by the ammonia-oxidizing bacteria Nitrosospira and the nitrite-oxidizing bacteria Nitrococcus mobilis in the biotrickling filter (Xue et al.,2011)Hence,bacteria may have played a dominant role in the removal of complex gas.
In most of the other biotrickling filters,the air inlet pipes are above the trickling-liquid level,resulting in high pollutant con-centrations at the air inlet area of the biotrickling filter.In the prent study,however,the air inlet pipe was below the trickling-liquid level,and most pollutants were absorbed.Thus,the pollutant concentrations at the outlet area of the biotrickling filter were high,affecting the microbial distribution in the bio film.
Fungi can degrade substrates in nature all the time,without resorting to extreme conditions.On the other hand,they them-lves degrade under extreme environmental conditions relative to pH,low water content,and limited nutrient (Kennes and Veiga,2004).Furthermore,the aerial mycelia of fungi,which are in direct contact with the gas,remove hydrophobic compounds faster than flat aqueous bacterial bio film surfaces.Fungi generally grow slower than bacteria,but they are capable of degrading a wide variety of contaminants and of withstanding more adver condi-tions (Van Groenestijn et al.,2001).As a disadvantage,the relea of fungal spores to the environment may occ
ur in cas of vere drying (Dorado et al.,2008).A previous study suggested that a fungal vapor pha bioreactor containing a strain of dimorphic black yeast,Exophiala lecanii-corni ,could be ud to treat a toluene-contaminated gas stream with a maximum elimination capacity of 270g/(m 3$h)in short-term tests,a value which is 2e 7times greater than the toluene elimination capacity typically reported for bac-terial systems (Woertz et al.,2001).
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Fig.4.Changes in the bacteria in the biotrickling fi
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Fig.2.Reduction in odor concentration when tap water or municipal wage rved as trickling
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Fig.3.Changes in biomass of the bio film.
优美句子20字N.Xue et al./International Biodeterioration &Biodegradation 82(2013)73e 8077
The changes in the fungi in the biotrickling filter are demon-strated in Fig.5.
Unlike that of bacteria,the fungal distributions in the bio film exhibited a continuous decline.The fung
al count was dramatically reduced during day 2e 14,and then remained stable afterward.The average total fungal was 9.64Â106CFU/g TS,which was only 6.40%of the control.On the other hand,the fungal counts were irrelevant to the inlet odor concentration.Hence,fungi may not have been effective in odor removal compared with bacteria.
Few reports are available on fungi or actinomycetes in bio-trickling filters.The studies on relative to biological treatment technologies have focud on bio filters becau of the low moisture content or the possible acid accumulation in bio filters.A perlite bio filter inoculated with he newly isolated fungus,Sporothrix var-iecibatus ,was ud for the bio filtration of gas pha styrene with styrene-loading rates of between 50and 845g/(m 3$h)and styrene removal of 65%(Rene et al.,2010).A bench-scale combined biore-actor consisting of two zones,one containing bacterial suspension and the other packed with material for attached growth of fungi,was employed to treat VOC with different water solubilities.The average elimination capacity of xylene,with its three isomers at steady state,was 62g/(m 3$h),and the total removal rate was >90%,which was 24.0%in the first zone and 67.6%in the cond (Li and Liu,2006).In this study,the pH was in the range of 5.5e 7.7,fa-voring bacterial growth.If the pH was controlled below 5.5,the fungi will be more active.
The actinomycete species are well-known saprophytic bacteria that decompo organic matter,espe
cially polymers,such as lignocellulo,starch,and chitin in soil (Crawford et al.,1993).Furthermore,they can produce an array of condary metabolites,many of which have antibacterial or antifungal properties.They are widely distributed,especially in environments with low water content,good permeability,and rich organic content,as well as tho that are neutral to weak alkaline.In the field of environ-mental engineering,actinomycetes are known to biotransform a broad variety of substrates,including pesticide (Fuentes et al.,2010),aliphatic and aromatic hydrocarbons,such as trichloroeth-ylene (Lee et al.,2000).The changes in the actinomycetes in the biotrickling filter are demonstrated in Fig.6.
During the first period,the actinomycete count reached the peak value on day 8,and then gradually decread in accordance with the change in odor concentration,indicating that actinomy-cetes could metabolize some of the odorous gas.When municipal wage was added into the biotrickling filter the cond period,the nutrient in the municipal wage promoted the growth of
actinomycetes,leading to increa in actinomycete count.However,the subquent reduction in actinomycete count in day 32may have been due to the inhibitive substances in municipal wage becau actinomycetes were nsitive to living environments.
The average total actinomycete was 5.10Â105CFU/g TS,which was 5.63times higher than that of the average of the control.Hence,actinomycetes may degrade some odorous gas.Never-theless,the average total actinomycete was only 0.25%of the average.The activity of actinomycetes evidently declined at the end of the experiment,showing that they are not as important as bacteria in pollutant abatement.
Some reports have previously discusd the function of actino-mycetes in the composting process (Yang et al.,2009).However,only a few articles have referred to actinomycetes in biological process for waste gas treatment,most reports have mainly focud on bio filters.A new species of the genus Actinomadura v.from four nitrite-producing strains have been isolated from experimental bio filters supplied with ammonia (Lipski and Altendorf,1995).In another work,ven strains capable of oxidizing methyl sul fides have been isolated from experimental bio filters filled with tree-bark compost.The results of 16S rDNA analyzes have revealed two new species:Pudonocardia v.and Pudonocardia sul fiv.(Reichert et al.,1998).
The results of statistical analysis on amounts of bacteria,fungi,and actinomycetes are given in Table 2.
TMA,ammonia,and odor concentration were considerably reduced in the scrubber ction.The trickling liquid can reduce pollutants through absorption and biodegradation.The percent-ages of bacteria and fungi in the trickling liquid were only 0.13%and
Time/ d
F u n g i i n b i o f i l m / (C F U /g T S )
-1.0E+03
4.0E+03
9.0E+03
1.4E+041.9E+04
2.4E+04
2.9E+04
3.4E+043.9E+04
4.4E+04F u n g i i n t r i c k l i n g l i q u i d / (C F U /m L )
Fig.5.Changes in the fungi in the biotrickling filter.
-5
051015
202530354045
Time/ d
A c t i n o m y c e t e s i n b i o f i l m / (C F U /g T S )
-1.0E+04
1.0E+043.0E+045.0E+04
7.0E+049.0E+041.1E+051.3E+051.5E+05
A c t i n o m y c e t e s i n t r i c k l i n g l i q u i d / (C F U /m L )
Fig.6.Changes in the actinomycetes in the biotrickling filter.
Table 2杏的功效
Statistical analysis of the amounts of bacteria,fungi,and actinomycetes in the bio-film and in the trickling liquid.
Location
Bacteria Fungi Actinomycetes Average (CFU/g TS)Bio film 2.06Â109.64Â10 5.10Â10Maximum (CFU/g TS)
Bio film 4.20Â109 4.62Â107 1.69Â106Minimum (CFU/g TS)Bio film 5.57Â1087.40Â1058.38Â104Standard deviation 1.20Â109 1.56Â107 5.44Â105Total (CFU)Bio film 4.46Â1011 2.08Â109 1.10Â108Total (CFU)Trickling liquid 5.67Â108
1.14Â107
2.15Â107
Percentage (%)Bio film 99.999.483.7Percentage (%)
Trickling liquid
0.13
0.55
16.3
N.Xue et al./International Biodeterioration &Biodegradation 82(2013)73e 80
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