Abstract
Experiments are reported on the discharge of microbial germs by biofilter systems used for the treatment of waste gases containing volatile organic compounds. The systems investigated concern six full-scale filter installations located in the Netherlands in several branches of industry, as well as a laboratory-scale installation used for modelling the discharge process. It is concluded that the number of microbial germs (mainly bacteria and to a much smaller extent moulds) in the outlet gas of the different full scale biofilters varies between 103 and 104 m−3, a number which is only slightly higher than the number encountered in open air and of the same order of magnitude encountered in indoor air. It is furthermore concluded that the concentration of microorganisms of a highly contaminated inlet gas is considerably reduced by the filtration process. On the basis of the experiments performed in the laboratory-scale filter bed, it is shown that the effect of the gas velocity on the discharge process results from two distinctive mechanisms: capture and emission. A theoretical model is presented describing the rate processes of both mechanisms. The model presented and the experimentally determined data agree rather well.
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Abbreviations
- a s m−1 :
-
specific area of the packing material
- C m−3 :
-
microbial gas phase concentration
- C e , C i m−3 :
-
microbial concentration in the exit and inlet gas resp.
- CFU:
-
colony-forming-units
- d c , d m m:
-
diameter of collecting and captured particle resp.
- D m:
-
diameter of the filter bed
- E :
-
single particle target efficiency
- H m:
-
bed height
- k c s−1 :
-
first order capture rate constant per unit of bedvolume
- k e m−3 :
-
emission rate constant per unit of bedvolume
- n :
-
number of observations
- r c , r e m−3 s−1 :
-
capture and emission rate per unit of bed-volume
- Re =:
-
\(\frac{\varepsilon }{{(1 - \varepsilon )}}\frac{{\varrho u{\text{ }}d_c }}{\mu }\) Reynolds number
- S t =:
-
\(\frac{{\varrho _m u{\text{ }}dm^2 }}{{9\mu {\text{ }}d_c }}\) Stokes number
- u m s−1 :
-
superficial gas velocity
- u m m s−1 :
-
superficial gas velocity at which C e = C i
- ɛ:
-
void fraction of the filter bed
- ϱ kg m−3 :
-
density of the gas phase
- ϱ m kg m−3 :
-
density of captured particle
- μ Pa s:
-
dynamic gas phase viscosity
- η =:
-
\(1 - \frac{{C_e }}{{C_i }}\) filter bed efficiency
References
Klages, S.; Hatami, M.: Vergleichender Mikrobiologische Untersuchungen an Biofiltern zur Abgasreinigung. Diplomarbeit, Universität Stuttgart, März 1987
Kingston, D.: Selective media in air sampling, a review. J. Appl. Bact. 34 (1971) 221
Luckiesh, M.; Taylor, A. H.: Heating, piping, air-conditioning 19 (1947) 113
Bovallius, A.; Bucht, B.: Three year investigation of the natural airborne bacterial flora at four localities in Sweden. Appl. and Env. Micr. 35 (1978) 847
Elliot, L. F.; Mc Calla, T. M.; Deshazer, J. A.: Bacteria in the air of housed swine units. Appl. and Env. Micr. 32 (1976) 270
Clark, C. S.; Rylander, R.; Larsson, L.: Levels of gram-negative bacteria, Aspergillus fumigatus, dust and endotoxin at compost plants. Appl. and Env. Micr. 45 (1983) 1501
Adams, A. P.; Spendlove, J. C.: Coliform aerosols emitted by sewage treatment plants. Science 169 (1970) 1218
Ladd, F. C.: Airborne bacteria from liquid waste treatment units. M.S. Thesis, Oklahoma State University, 1966
Verstraete, W.: Mededelingen faculteit landbouwwetenschappen Gent 39 no. 1 (1976) 259
Gaden, E. L.; Humphrey, A. E.: Fibrous filters for air sterilizations. Ind. and Eng. Chem. 48 (1956) 2173
May, K. R.; Marper, G. J.: The efficiency of various liquid impinger samples in bacterial aerosols. Brit. J. Industr. Med. 14 (1957) 287
Gutfinger, C.; Tardos, G. I.: Theoretical and experimental investigation on granular bed dust filters. Atm. Env. 13 (1979) 853
Lembke, L. L.; Kniseley, R. N.: Airborne microorganisms in a municipal solid waste recovery system. Can. J. Micr. 31 (1985) 198
Lembke, L. L.; Kniseley, R. N.; Van Nostrand, R. C.; Hale, M. D.: Precision of the all-glass impinger and the Andersen microbial impactor for air sampling in solid-waste handling facilities. Appl. and Env. Micr. 42 (1981) 222
Sorber, C. A.; Bausum, H. T.; Schaub, S. A.: A study of bacterial aerosols at a waste water irrigation site. Journal W.P.C.F. 48 (1976) 2367
Jones, W.; Morring, K.; Morey, P.; Sorenson, W.: Evaluation of the Andersen viable impactor for single stage sampling. Am. Ind. Hyg. Ass. J. 46 (1985) 294
Gillespie, V. V.; Clark, C. S.; Bjornson, H. S.; Samuels, S. J.; Holland, J. W.: A comparison of two-stage and six-stage Andersen impactors for viable aerosols. Am. Ind. Hyg. Assoc. J. 42 (1981) 858
Placencia, A. M.; Peller, J. T.; Oxborrow, G. S.; Danielson, J. W.: Comparison of bacterial recovery by Reuter centrifugal air sampler and slit-to-agar sampler. Appl. and Env. Micr. 44 (1982) 512
Friedlander, S. K.: Particle diffusion in low-speed flows. J. Colloid Interface Sci. 23 (1967) 157
Tardos, G.; Abuaf, N.; Gutfinger, C.: Diffusional filtration of dust in a fluidized bed filter. Atm. Env. 10 (1976) 389
Gutfinger, C.; Tardos, G. I.: Theoretical and experimental investigation on granular bed dust filters. Atm. Env. 13 (1979) 853
Paretsky, L.; Theodore, L.; Pfeffer, R.; Squires, A. M.: Panel bed filters for simultaneous removal of fly ash and sulphur dioxyde. J. Air Pollut. Control Ass. 21 (1971) 204
Gutfinger, C.; Tardos, G.; Abuaf, N.: Analytical and experimental studies on granular bed filtration. Proc. Symp. Transfer Util. Particulate Control Technol. 3 (1978) 243
Doganoglu, Y.; Jog, V.; Thambimuthu, K. V.; Clift, R.: Removal of fine particulates from gases in fluidised beds. Trans. I. Chem. E. 56 (1978) 239
Thambimuthu, K. V.: Gas filtration in fixed and fluidized beds. Ph.D. Thesis, Cambridge 1980
Ottengraf, S. P. P.; Van den Oever, A. H. C.: Kinetics of organic compound removal from waste gases with a biological filter. Biotechn. and Bioeng. 25 (1983) 3089
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Ottengraf, S.P.P., Konings, J.H.G. Emission of microorganisms from biofilters. Bioprocess Engineering 7, 89–96 (1991). https://doi.org/10.1007/BF00383584
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DOI: https://doi.org/10.1007/BF00383584