TEXTILE WASTEWATER TREATMENT BY A COMBINATION OF ANAEROBIC
AND AEROBIC PROCESSES: FROM LABORATORY TO INDUSTRIAL SCALE
Tjandra Setiadi, Yeni Andriani and Mela Erlania
Department of Chemical Engineering, Institut Teknologi Bandung, Jl. Ganesa 10, Bandung 40132,
Indonesia
Fax: 62-22-250 1438; Email: [email protected]
Abstract In this study, the ability of a combination anaerobic and aerobic processes to treat a denim process wastewater and its
application in industrial scale was reported. Laboratory experiments were conducted with the varied hydraulic retention time (HRT)
in anaerobic process, i.e. 12, 18 and 24 hours. In the aerobic process, the HRT were 12, and 24 hours, and the SRT (Solid
Retention Time) was maintained at 20 days. All experiments performed in room temperature. Each experiment was run for about 90
days. From the laboratory study, it was found that increasing HRT would increase color removal on the anaerobic processes,
however no significance different for COD removal. However, the majority of color was removed in the anaerobic process, on the
other hand majority of COD was removed in the aerobic process. The combination of anaerobic and aerobic processes was able to
reduce COD, BOD and color up to 91, 94 and 96 %, respectively. The color removal was consistently high and visually, no color has
been observed in the final effluent. Based on the laboratory results, the industrial scale to treat the wastewater was established.
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The design flowrate was 20 m /hour. The biofilter was selected as an anaerobic process with the HRT of 24 hours. The aerobic
process was determined extended aeration with the HRT was also 24 hours. The system has been completed on March 2002 and
steady state condition was achieved on June 2002 with a performance not much different to the laboratory scale results. Although, a
slightly less COD and color removal was observed. From 4 months operation, the COD, BOD and color removal was 87, 93 and 90
%, respectively. At the moment, the treated effluent was recycled back to the denim processing plant and used in washing
machines.
Keywords Aerobic, anaerobic, decolorization, industrial scale, textile wastewater.
INTRODUCTION
Textile industries developed rapidly in Indonesia in the last ten years. The development of textile industry can be seen
from the increasing value of textile (include textile products) export. It was recorded as much as US$ 2.02 billion in
1989 and has increased up to around US$ 7 billion in 2002. Thus, textile industry becomes one of the most important
sources of foreign exchange for Indonesia. However, textile industries have caused serious environmental problems
because of their wastewater. Most textile industries produce wastewater with relatively high in BOD, COD, suspended
sludge and color. In addition, the wastewater may also contain heavy metal depending on the type of coloring
substances used. In general, the objectives of textile industry wastewater treatment are to reduce the level of organic
pollutants, heavy metal, suspended solids and color before releasing to the environment. At present however, the
Indonesian government has not included color as one of the parameter in the regulation for textile industry effluents. In
reality, wastewater containing color may cause environmental and aesthetic problems.
Color substances are used during dyeing and printing process. The wastewater from these two processes is the most
polluted wastewater in a textile industry. Wastewater treatment technology either biological, chemical, physical or the
combination of the three can be used to treat textile wastewater. Chemical coagulation is frequently practiced in
Indonesian textile industries and sometime it is the only mean to treat the wastewater. The main disadvantage of this
method is that it produces a lot of sludge which need to be disposed of. Moreover, according to the current Indonesian
Government Regulation (Peraturan Pemerintah No. 18, 1999), textile sludge may be classified as a hazardous waste,
therefore the sludge should be treated in a proper way. This means that the sludge disposal causes a substantial
increase in the cost of wastewater treatment.
Furthermore, in the past decades, the use of synthetic compounds in the textile processes has increased. Thus, the
amount of more complex compounds, which has a characteristic of slowly biodegradable by aerobic processes, in the
textile effluent has increased consequently. On the other hand, aerobic processes have been widely used for treating
textile wastewater. Therefore, to meet the stricter regulation, a more effective and efficient system to remove organic
pollutants and color, and to reduce sludge production has to be found.
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Several scientific research have reported that a biological process consisting an anaerobic and aerobic process in series
is a promising method for treating textile wastewater [Loyd et al., 1991, Seshadri et al., 1994 and Zaoyan et al.,
1994]. The anaerobic microorganisms reduced the color and increased the biodegradability of the waste [Setiadi et al.,
1997 and Minke and Rott, 1999]. This will render the effluent more amenable to subsequent aerobic treatment.
Moreover, the sludge production will be reduced due to no chemical added to remove color. However, the report on
the industrial application of these processes is very limited. Therefore, in this study, the ability of a combination
aerobic and anaerobic process to treat denim process wastewater was investigated and the application in the industrial
scale was reported.
MATERIAL AND METHODS
Wastewater preparation. The wastewater was from a textile plant performing denim processing operations where only
indigo dyes being used with the indigo CI Vat Blue 1 as the major dyes. The sturcture of the dye was given in Figure
1. The COD, BOD, color and pH range of wastewater was 400 978 (689) mg/L, 100 700 (504) mg/L, 12 300 (90)
mg/L and 8 14 (10), respectively. Together with the above data, the average value was given in parentheses. A
necessary amount of nitrogen and phosphorous was added to the wastewater to make the ratio of COD : N : P of 100 :
5 : 1. And also the pH of wastewater was adjusted to neutral.
Figure 1. Structure of Indigo CI Vat Blue 1 Dye
Reactors. The anaerobic and aerobic reactors were made of Plexiglas having of working volume of 6 and 7 liters,
respectively. The anaerobic reactors were baffled reactors with the basic design was a rectangular box with internal
vertical baffles alternatively hanging and standing. These baffles divided the reactor into 2 compartments. The aerobic
reactors were a simple completely mixed activated sludge reactor where the box was divided into two chamber, i.e.
aeration and settling chamber [Reynolds, 1982]. The experimental set-up is shown in Figure 2.
Influent
Tank
Aerobic Reactor
Peristaltic
Pump
Anaerobic Reactor
Effluent
Tank
Figure 2. Experimental Set-up for Treating Textile Wastewater by a Combination of
Anaerobic and Aerobic Process
Acclimatization and Reactor Operation. Sludge from an activated sludge process treating textile mill effluents was
used as an initial inoculum for anaerobic reactors. Then, the cultures were developed anaerobically by feeding the
textile wastewater with the necessary amount of nitrogen and phosphorous. Anaerobic conditions were achieved by
overgassing the reactors with oxygen-free nitrogen for 30 minutes. This acclimatization period was carried out for
about 3 months. The detailed procedure of acclimatization was presented elsewhere [Setiadi et al., 1997].
For the aerobic reactors, the sludge from an activated sludge process was acclimatized by the textile wastewater in
aerobic conditions. The necessary amount of nitrogen and phosphorous were also added. After the acclimatization
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period has been completed, the steady state performance was conducted with the different hydraulic retention time
(HRT) at each reactor. The HRT variation of this study is given in Table 1 with sludge retention time (SRT) of the
aerobic process was maintained at 20 days for all experiments.
Analytical procedure. Influents and effluents of each reactor were collected and analyzed regularly for the following
parameters: MLSS (mixed liquor suspended solids), pH values, COD, and BOD. These parameters were measured in
accord with Standard Methods [Standard Methods, 1992]. The supernatant was also analyzed colorimetrically at the
wavelength of 486 nm using Spectronic 20. The color concentration was quantified by converting the absorbance
figures to the equivalent dye concentrations using a calibration curve. Some of the samples were analyzed by a
scanning spectrophotometer to identify the dye degradation products.
Table 1 HRT variation in the laboratory scale study
Denim process wastewater
Run
Anaerobic
Aerobic
I
12
12
II
12
24
III
24
12
IV
24
24
V
24
48
Note: The HRT in each reactor has the unit of hours
RESULTS AND DISCUSSION
This section will be divided into two parts: a). results and discussion of laboratory studies, b).results and discussion of
industrial scale operations.
Laboratory scale studies
As has been mentioned above that the textile plant produced denim fabric with only indigo dyes used in the process,
specifically Indigo C.I. Vat Blue 1 having a double bond of C=C. The COD, BOD and color removal in each process
is presented in Table 2 and 3 with the overall reduction is shown in Table 4. The reduction of COD, BOD and color
shown in Table 2 and 3 were calculated based on the influent and effluent of each step. Table 5 shows the effluent
quality of the wastewater after treating through anaerobic and aerobic processes. A range and average values of final
effluent are presented in the table.
Table 2. Reduction of COD, BOD and Color in the Anaerobic Process
Run
HRT (h)
COD reduction (%) BOD reduction (%) Color reduction (%)
I
12
44.4
31.2
57.0
II
12
45.5
32.3
53.0
III
24
45.0
29.4
84.5
IV
24
44.0
30.5
80.1
IV
24
40.1
33.9
78.2
Note: all the above value is an average value of steady state operation
Table 3. Reduction of COD, BOD and Color in the Aerobic Process
Run
HRT (h)
COD reduction (%) BOD reduction (%) Color reduction (%)
I
12
55.4
90.0
67.0
II
24
58.0
88.0
68.3
III
12
77.4
88.5
73.2
IV
24
83.0
91.5
78.7
V
48
78.5
90.5
76.4
Note: all the above value is an average value of steady state operation
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Table 4. The Range and Average value of COD, BOD and Color Reduction in the Overall Treatment
Run
I
II
III
IV
V
COD reduction (%)
range
average
65 90
75.2
75 93
87.2
63 94
87.5
74 98
90.5
74 98
87.3
BOD reduction (%)
Range
average
80 95
93.1
74 95
91.9
75 95
92.0
83 99
94.1
76 99
93.7
Color reduction (%)
Range
average
70 90
85.8
73 91
85.1
73 98
96.1
79 99
95.8
80 88
95.0
Table 5.. Final Effluent Quality
Run
I
II
III
IV
V
COD (mg/L)
range
Average
83 210
170.8
90 - 187
157.7
33 176
85.9
12 144
65.6
30 134
87.5
BOD (mg/L)
range
average
20 75
34.7
25 75
40.9
20 60
40.9
10 45
29.8
10 51
31.6
From Table 2, it can be seen that the COD reduction in anaerobic process was relatively similar for each run, but it was
much lower in color reduction for Run I and II. It could be understood that the HRT of the first two runs were half of
the others. Thus, increasing HRT would increase color removal in the anaerobic process, however no significance
different for COD reduction. . On the other hand, the aerobic process reduced much of organic content and less of
color. About of 30 to 50 % of initial COD removed in the aerobic process and only less than 30 % of total color
reduced in the aerobic one. This finding is in accord with other studies [Seshadri et al., 1994, Battacharya et al., 1990
and Setiadi et al., 1999].
A typical absorption spectra of the sample is presented in Figure 3. In the influent sample (Fig. 3.a), there were 10
peaks appeared with wavelength of 220, 226, 244, 250, 486, 496, 510, 518, 552 and 560 nm. Then, only 2 peaks
appeared at wavelength of 202 and 486 nm after treating in the anaerobic reactor (Fig. 3.b). Finally, there were 2 peaks
left at wavelength of 202 and 486 nm in the final effluent (Fig. 3.c). Although, a peak of 486 nm was still recorded in
the absorption spectra of anaerobic effluent, but visually the color was completely decolorized. This finding confirmed
that the anaerobic process has played a greater role in the decolorization and degradation of dyes than that of aerobic
one as has been pointed out by others [Carliell et al., 1995 and Setiadi and Hasibuan, 1999].
The final effluent quality as shown in Table 5 revealed that the COD and BOD values for anaerobic HRT of 24 hours
were consistently low. This value will meet the newly Indonesian effluent standard for textile wastewater being 150
and 60 mg/L for COD and BOD, respectively. Therefore, the HRT of 24 hours in anaerobic and 24 hours in aerobic
process was recommended for treating denim plant wastewater to meet the current Indonesian effluent standard.
a. Influent
b. Anaerobic Effluent
c. Aerobic Effluent
Figure 3. Typical Absorption Spectra of Influent, Anaerobic Effluent, and Aerobic Effluent (the y-ordinate is
absorbance value and the x-ordinate is wavelength)
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Industrial scale operations
Based on the laboratory results, the industrial scale to treat the wastewater was established. The design flowrate was
20 m3/hour. After discussion with the respected engineers in the factory and consultants, an upflow biofilter was
selected as the anaerobic process. The biofilter was a fixed bed type of reactor and packed with plastic media, however
the detail of reactor is not able to be disclosed here. Basically, the HRT of 24 hours was determined in the anaerobic
reactor having a diameter of 9.5 m and height of 9 m..
The aerobic process was determined extended aeration with the HRT was also 24 hours with the length, width and
depth of 12 m, 12 m and 3.5 m, respectively. The picture of the industrial scale installation is given in Figure 4, with
the anaerobic tank on the background and aerobic one on the foreground. The system has been completed on March
2002 and steady state condition was achieved on June 2002 with a performance not much different to the laboratory
scale results. Although, a slightly less COD and color removal was observed. From 4 months operation, an average of
COD, BOD and color removal was 87, 93 and 90 %, respectively. At the moment, the treated effluent was recycled
back to the processing plant and used in washing machines. Figure 5 gives an example of influent (A), effluent of
anaerobic reactor (B) and final effluent of the aerobic process (C). Visually, the color in final effluent was removed
almost completely with an average value of removal about 90 % from the average original concentration of dyes of 90
mg/L.
Figure 4. The Industrial Scale Installation
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Figure 5. An example of influent (A), anaerobic process effluent (B) and final effluent (C) from the industrial scale
CONCLUSIONS
Results found in this study for treating denim plant wastewater with the combination of anaerobic and aerobic are as
follows:
1. Increasing HRT would increase color removal on the anaerobic processes, however no significance different for
COD removal.
2. The majority of color was removed in the anaerobic process, on the other hand majority of COD was removed in
the aerobic process.
3. The combination of anaerobic and aerobic processes was able to reduce COD, BOD and color up to 91, 94 and 96
%, respectively. The color removal was consistently high and visually, no color has been observed in the final
effluent.
4. An industrial scale application has been established quite successfully with a performance was not much different
to the laboratory scale results
ACKNOWLEDGEMENTS
The first author would like to thank to the students of the Department Chemical Engineering ITB who have been
involved in this research since 1994. Some of the names of the students are on the references. He would also like to
express his gratitude to all institutions having provided financial support to this research, namely : OPF-ITB
(1996/1997); the ESA-UNET Project, the European Union, Directorate General I, 1996-1997 : The Asahi Glass
Foundation, Japan, 1998 1999, and also to PT Garuda Mas and PT Aquakultura Lestari for providing the industrial
scale data.
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