J. Microbiol. Biotechnol. (2003), 13(2), 301–304
Removal of Hydrogen Sulfide, Ammonia, and Benzene by Fluidized Bed
Reactor and Biofilter
KIM, CHONG-WOO, JIN-SU PARK, SUNG-KI CHO, KWANG-JOONG OH1, YOUNG-SIK KIM2,
AND DONGUK KIM
School of Advanced Materials Engineering, Inje University, Kimhae, Kyongnam 621-749, Korea
1
Department of Environmental Engineering, Pusan National University, Pusan 609-735, Korea
2
Environmental Development Division, Samsung Everland, Seoul 138-160, Korea
Received: January 9, 2001
Accepted: September 30, 2002
Abstract In this study, hydrogen sulfide (H2S), ammonia
(NH3), and benzene, which represent the major odor from a
natural leather process plant, were removed using a fluidized
bed bioreactor and biofilter including Thiobacillus sp. IW and
a MY microbial consortium. The critical removal rate was
12 g m- 3 h- 1 for H2S, 11 g m- 3 h- 1 for NH 3, and 28 g m- 3 h- 1 for
benzene by the fluidized bed bioreactor, and 8.5 g m- 3 h- 1 for
H2S, 7 g m- 3 h- 1 for NH3, and 25 g m- 3 h- 1 for benzene in the
biofilter. The average removal efficiency of H2S, NH3, and
benzene by continuous operation for over 30 days with the
fluidized bed bioreactor was 95±3%, 99±1%, and 98±5%,
respectively, whereas that with the biofilter was 96±4%,
95±4%, and 97±3%, respectively. Therefore, the critical
removal rate of H2S, NH3, and benzene was higher in the
fluidized bed bioreactor, whereas the removal efficiency on
the continuous operation was similar in both bioreactors.
Key words: H2S, NH3, benzene, fluidized bed bioreactor,
biofilter, Thiobacillus sp. IW, MY microbial consortium
The natural leather process industry is essential in Korea
for the manufacture of fashion shoes, handbags, or wallets,
for domestic and international markets. The process is
composed of approximately 20 steps in which a large
number of toxic chemicals are used [9]. The industry has
a severe odor problem due to the evaporation of the
chemicals used in the plant. The major odor from the
natural leather process plants includes hydrogen sulfide,
ammonia, and benzene [9, 20]. Facilities to remove the
odor from the plant are absolutely needed to meet with
Korean environmental protection law.
*Corresponding author
Phone: 82-51-510-2417; Fax: 82-51-583-0559;
E-mail: [email protected], [email protected]
Odorous gases have been conventionally removed by
physical and chemical treatments, such as absorption in
water, adsorption on adsorbents, and catalytic oxidation
[6]. However, these methods have certain problems with
secondary contamination, a high operating cost, and low
removal efficiency [18]. As an alternative, biological treatments
have been suggested and proved to be very effective in
odor control [22]. A biological technique has an advantage
in reducing secondary contamination, while the investment
and operating costs of the treatment remain lower [8].
With biological treatments, H2S and NH3 are usually
removed by various types of biofilters, including Thiobacillus
and other bacterial strains [5, 17, 21]. VOCs, including
benzene, are conventionally treated using a biofilter including
either industrial sludge [4, 16] or specific bacterial strains,
such as Pseudomonas putida [11] and Rhodococcus
rhodochrous [7]. The removal efficiency of an odor gas
by a biofilter is generally satisfactory at a lower inlet
concentration and gas flow rate, however, the removal
efficiency was reduced significantly when the gas loading
rate increased [8]. The fluidized bed bioreactor showed
excellent removal efficiency of H2S and NH3 in relatively
higher loading rate, due to the increased mixing of gas and
liquid, and long contact time [10].
In this research, removal of odors from the natural
leather process plant was studied using biological treatment.
H2S, NH3, and benzene were used to mimic the real odor.
As the biological technique, two types of the bioreactor
were chosen: one was a conventional biofilter and the
other was a fluidized bed bioreactor which was reported to
have excellent odor removal efficiency [10]. The efficiency
of bioreactors was compared with each other for the inlet
loading rate and a continuous operation.
In the bioreactor, H2S is oxidized to SO42- by Thiobacillus
sp. IW and the dissolved NH4+ then reacts with the
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KIM et al.
generated SO42- to form (NH4)2SO4. [10]. Thiobacillus sp.
IW exhibited a Vmax and Km [2] of 0.24 g S/l d and 12.09 g/l,
respectively, and an optimum growth at 30oC, pH 7.0 [1].
The aerobic MY microbial consortium used to degrade
benzene was obtained from the Yongho sewage water
treatment plant in Pusan [14] and cultured at 30oC, pH 7.0
for 3 months in the following medium [15] (g/l): 0.5 MgSO4·
7H2O, 0.5 K2HPO4, 0.5 (NH4)2SO4, 0.01 CaCl2, 0.001 FeCl3·
6H2O, 0.001 MnCl2, and 0.0001 ZnSO4. From the sequencing
of the 16S rDNA by MicroID (Taejon, Korea), the major
microorganism in the MY microbial consortium was identified
as Rhodococcus rubber.
Thiobacillus sp. IW, isolated from acid drainage water
from coal mines in Hwa-Soon, Korea by Prof. In-Wha Lee
at Chosun University, was used to oxidize thiosulfate and
H2S [3]. In a mixed culture of MY microbial consortium
and Thiobacillus sp. IW, the following medium was used
(g/l): 8.0 Na2S2O3, 0.5 NH4Cl, 4.0 K2HPO4, 4.0 KH2PO4,
0.8 MgSO4, 0.5 Na2EDTA, 0.22 ZnSO4, 0.05 CaCl2, 0.01
MnCl2· 4H2O, 0.05 FeSO4, 0.01 (NH4)6Mo7O24, 0.01 CuSO4,
0.01 CoCl2, 0.5 (NH4)2SO4, 0.001 FeCl3·6H2O, and 2.0 yeast
extract.
As shown in Fig. 1, two types of bioreactor, either a
fluidized bed bioreactor or biofilter, were used in the
current research to remove H2S, NH3, and benzene. In the
biofilter, biosands containing cells existed in fixed bed,
and moisture was provided from the top of the colum, if
needed. In the fluidized bed bioreactor, biosands and
solution were mixed vigorously to increase to contact
between gas, liquid, and solid, and cells existed in both
liquid and solid phase. The odor gas from each tank was
first diluted with air to an appropriate concentration level
in a mixing chamber before being allowed to enter the
bioreactor (inner diameter=4 cm, height=130 cm).
Fig. 1. Schematic diagram of the bioreactor.
1, Bioreactor; 2, Measuring equipment; 3, Air compressor; 4, 0.1%
benzene; 5, 1% H2S; 6, 1% NH3; 7, Flow meter; 8, Three-way valve; 9, Gas
mixing chamber; 10, Water bath.
Biosand (Crystal bio-sand, Chungwoo art system, Seoul,
Korea) composed of 15% SiO2 and 85% H2O with a specific
surface area of 539 m2/g was used as the carrier [10]. The
liquid-phase height of the column was 82 cm, the volume of
the bioreactor was 1,040 cm3, and the empty bed residence
time for the inlet gas was 21- 62 s. To run the bioreactor
effectively, 3 ml of MY microbial consortium (~8×108 cell/
ml) was first inoculated, and then only the benzene gas
flowed through the bioreactor for 10 days to have the
stable removal efficiency of the benzene. Next, 3 ml of
Thiobacillus sp. IW (~5×108 cell/ml) was inoculated into
the bioreactor to remove hydrogen sulfide and ammonia.
In the experiment, inlet concentration ranges of H2S,
NH3, and benzene were 28- 47 ppm, 21- 44 ppm, and 1957 ppm, respectively, in the fluidized bed bioreactor,
whereas those in the biofilter were 26- 36 ppm, 21- 37
ppm, and 28- 46 ppm, respectively. The gas flow rate was
180 l/h in both bioreactors.
The concentration of H2S was measured using the
methylene blue method, while that of NH3 was measured
using the indophenol method [12]. The concentration of
benzene was measured using a gas chromatograph (Donam
Instrument, Seoul, Korea) equipped with a pulse discharge
detector (Valco Instruments, Houston, U.S.A.), autosampler
(Valco Instruments, Houston, U.S.A.), and Quadrex 007cw capillary column (0.25 mm). The oven temperature
increased from 60oC to 150oC at a rate of 20oC/min, and the
temperatures of the detector and injector were maintained
at 250oC and 60oC, respectively.
In the study, the removal efficiency, inlet loading rate,
and removal capacity were calculated according to the
following formulae;
Removal efficiency (η)=(Cin- Cout)/Cin
(1)
Inlet loading rate=CinQ/V
(2)
Removal capacity=ηCinQ/V
(3)
The removal capacity of H2S, NH3, and benzene by the
fluidized bed bioreactor and biofilter was compared with
their loading rates (Fig. 2). The critical removal rate which
removed 100% of the odor was 12 g m- 3 h- 1 for H2S, 11 g
m- 3 h- 1 for NH3, and 28 g m- 3 h- 1 for benzene by fluidized
bed bioreactor, and 8.5 g m- 3 h - 1 for H2S, 7 g m- 3 h- 1 for
NH3, and 25 g m- 3 h- 1 for benzene by biofilter. The critical
removal rate of H2S, NH3, and benzene by the fluidized
bed bioreactor was 29%, 36%, and 11%, respectively,
higher than those by the biofilter. High content of liquid
volume and increased mixing and mass transfer in the
fluidized bed bioreactor are thought to have increased the
removal efficiency, compared with the biofilter.
Figure 3 shows the inlet and outlet concentrations of
H2S, NH3, and benzene in the fluidized bed bioreactor and
biofilter for a continuous operation. In the fluidized bed
bioreactor, when the inlet concentration of H2S was
REMOVAL OF H2S, NH3, AND BENZENE BY FLUIDIZED BED BIOREACTOR AND BIOFILTER
303
Fig. 3. Inlet and outlet concentrations of fluidized bed bioreactor
(A) and biofilter (B) in continuous operation.
Fig. 2. Removal capacity of fluidized bed bioreactor (A) and
biofilter (B) relative to inlet loading rates of hydrogen sulfide,
ammonia, and benzene.
between 28 and 47 ppm, NH3 was between 21 and 44 ppm,
and benzene between 19 and 57 ppm, the average removal
efficiency of H2S, NH3, and benzene over 30 days was
95±3%, 99±1%, and 98±5%, respectively. During the
operation, the level of MLSS (mixed liquor suspended
solids) remained between 1,000 and 1,800 mg/l, and the
total cell concentration in the bioreactor solution was about
2.4 mg dry cells/ml solution. In the bioreactor, when the inlet
concentrations of H2S was between 26 and 36 ppm, NH3
was between 21 and 37 ppm, and benzene between 28 and
46 ppm, the average removal efficiency of H2S, NH3, and
benzene by the biofilter over 30 days was 96±4%, 95±4%,
and 97±5%, respectively. The removal efficiency of NH3
was higher by the fluidized bed bioreactor, whereas that of
H2S and benzene by both types of bioreactor was similar.
When the bench scale biofilter, containing yard waste
compost and granular activated carbon, was used to remove
the odors and volatile organic compounds from a wastewater
treatment facility, the removal efficiency was 100% for
3 ppm H2S and 53- 92% for 4 ppb benzene at 7.0 m3/min gas
flow rate [19]. Even though the experimental conditions
were different, the removal efficiency of benzene in our
study appeared excellent.
From the research, the critical removal rate of H2S, NH3,
and benzene was higher in fluidized bed bioreactor, whereas
their removal efficiency by both bioreactors was similar on
the continuous operation.
Acknowledgment
This research was financially supported by the Korea
Research Foundation (2001-041-E00388).
NOMENCLATURES
Cin
Cout
Km
Q
V
Vmax
η
: inlet concentration [ppm]
: outlet concentration [ppm]
: Michaelis constant [g/l]
: gas volumetric flow rate [l/h]
: volume of the bioreactor [l]
: maximum sulfur oxidation rate [g S/l d]
: removal efficiency of odor gases
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KIM et al.
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