Research Journal of Chemistry and Environment____________________________________________Vol. 18(5) May (2014)
Res. J. Chem. Environ.
Investigation of color removal from real textile
wastewaters in ABR followed by ozonation
as post treatment
Hatice Ozbebek1, Sebnem Ozdemir2, Dilek Akman2, Kevser Cirik1* and Ozer Cinar3
1. Department of Environmental Engineering, Kahramanmaras Sutcu Imam University, Kahramanmaras 46100, TURKEY
2. Department of Bioengineering and Sciences, Kahramanmaras Sutcu Imam University, Kahramanmaras 46100, TURKEY
3. Department of Environmental Engineering, Yildiz Technical University, Istanbul 34349, TURKEY
*kewss_@hotmail.com
dyeing and textile wastewater. Biological treatment
methods can be divided into aerobic and anaerobic
treatment. Although, color removal by aerobic bacteria,
such as those commonly present in activated sludge
systems, are normally less8 mainly associated with the dye
adsorption in the sludge2. On the other hand, under
anaerobic conditions, effective dye decolorization can be
reached37. However, biological treatment generally is
insufficient to remove the wastewater color.
Abstract
The textile industry wastewaters are known as one of
the main sources of severe pollution problems
worldwide. In particular, the release of highly colored
effluents is undesirable, due to toxic and resistant
effects to the environment. In this study, four stage
anaerobic baffled reactor (ABR) with a working
volume of 19 L was fed with real textile effluent
containing about chemical oxygen demand (COD) of
1000mg/L, color of 80.2 m-1(λ436), 89.9 m-1(λ525), 95.7
m-1(λ620), 3335 Pt-Co and assessed under varying
operational conditions. Initially effect of glucose as
external substrate on ABR performance was assessed.
COD and color removal efficiencies of the ABR
reached to 66.9% and 88% when influent COD was
increased to 2000 mg/L by external substrate
addition.
To achieve a marked color reduction after a biological
process, a further application of relatively expensive
tertiary treatments is required, typically performed by
techniques such as adsorption with active carbon,24
membrane
filtration,14,22
ozonation,20
coagulation
3,12
flocculation,
photocatalytic
degradation5,36
and
electrochemical techniques.6,7,18,19 Chemical oxidation with
ozone, however, is the most preferred process for the dyes
used in textile operations in order to achieve high color
removal efficiencies and to improve the biodegradability
without sludge production.
Additionally, ozonation was applied followed by
anaerobic treatment to investigate the removal of the
residual color and COD. The overall COD and color
(Pt-Co unit) removal efficiencies via post-ozonation
were 41.7% and 68.5% respectively for ozonation
time of 75min.
Ozonation is an oxidative process in which the oxidizing
agent used is ozone (O3). Interest in the use of ozone in
wastewater treatment has increased considerably in recent
years due to the numerous advantages of this process.
Although, the cost of ozone production has decreased in
recent years, the ozonation process still has a high cost.
Reactions involved in ozonation can occur directly between
ozone and the organic compounds present in effluent or
indirectly through OH− radicals.23,27,29 The ozonation
process minimally generates toxic byproducts and its prior
application to wastes also enhances their biodegradation by
converting the more slowly biodegradable COD into
simpler compounds or by reducing the amount of inert
organic matter.28 Post-ozonation, on the other hand, may
have a polishing effect on effluent quality. It is therefore
important to set the basis for the selection of the
appropriate location for ozone application.17
Keywords: Textile wastewater, color removal, ozone,
COD removal, post-treatment.
Introduction
The textile dyeing industry consumes large quantities of
water and produces large volumes of wastewater from
different steps in the dyeing and finishing processes. This
wastewater can cause serious environmental problems due
to their high color, large amount of suspended solids, and
high chemical oxygen demand.14 Standard discharge limits
of textile effluent are becoming more stringent in recent
days creating continuous problems for industries to comply
with. Generally the treatment options can be divided into
three main categories namely biological, chemical and
physical methods.6,30 Of the various treatment methods
applied to dyeing wastewater, biological treatment is one of
the most popular methods.
Results presented by Marmagne and Coste25 show that
ozone degrades all kinds of dyes except insoluble disperse
dyes and vat dyes, as it reacts slowly and requires more
time for degradation. Furthermore, it has been reported that
the removal of color in wastewater using ozonation textiles
depends on the dye concentration.21,31,33 According to
Mehmet and Hasan26, ozonation (30mg/cm3) increases the
rate of biodegradability of industrial wastewater by a factor
Biological methods are generally cheap and simple to apply
and currently used to remove organics and color from
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Research Journal of Chemistry and Environment____________________________________________Vol. 18(5) May (2014)
Res. J. Chem. Environ.
of 1.6. Jianging and Tingwei15 reported 11–66-fold to
increase in the degradation rate for wastewater containing
azo dyes while the increase reached 80-fold for wastewater
containing reactive dyes such as Reactive Yellow 84. These
results show that the increase in the degradation rate was
influenced by the type of dye and its concentration.
using a peristaltic pump to have a constant HRT of 2 days
throughout the study.
The ABR was inoculated with anaerobic sludge from a fullscale anaerobic digester located at Gaziantep, Turkey and
acclimatized to the described basal media for 90 days. The
performance of ABR was evaluated for 143 days under
three different periods (Table 2). First, the reactor was
containing real textile wastewater without carbon source
supplementation (period I, days 0–90) for acclimatization
of anaerobic bacteria. Then, the reactor performance was
evaluated at different electron donor (glucose) loadings
(period II and period III), (Table 2). The samples taken
from the reactor was analyzed 3 times per week to
determine the system performance.
Nonetheless, Gianluca and Nicola11 reported that color
removal from textile wastewater treated biologically was
dependent on the initial COD value of the textile
wastewater. The main objective of this study is removal of
COD and color of real textile wastewater by ozonation as
post-treatment followed by anaerobic degradation. In the
biological step, ABR was performed under varying external
substrate addition, corresponding to overall influent COD
of 1500 and 2000 mg/L. Afterwards ozonation was applied
as post treatment to remove the residual COD and color
from ABR effluent.
Material and Methods
Real Textile Wastewater: Real Textile wastewater was
collected once a week from the wastewater treatment plant
of Kipas Textile Industry (Kahramanmaras, Turkey). The
influent was stored at 40C and the reactors were operated at
room temperature of approximately 27 0C. It is worth
mentioning that the dyeing process of this factory is
continuous and utilizes many different reactive dyes.
Because the pH value was usually alkaline (~11), the pH
was adjusted to 7.0 with sulphuric acid (H2SO4).
Table 1
Characteristics of real textile wastewater
Parameters
Unit
Value
pH
11±0,5
Temperature
(0C)
20,6±3,5
Conductivity
(µS/cm) 6555±3375
COD
(mg/L)
620±20
NH4-N
(mg/L)
4,83±1
-1
λ436 nm
m
80.2±5
Color λ525 nm
m-1
89.9±6.2
λ620 nm
m-1
95.7±7.4
Color
Pt-Co
3335
Nitrate
(mg/L)
5.1±2.2
Sulfate
(mg/L) 1250±250
Free chlorine
(mg/L)
7.3±0.5
Fig.1: Schematic of the ABR system
Table 2
Operational conditions of anaerobic baffled reactor
Periods
Parameters
I
II
III
Days
0-90 91-127 128-143
Feed COD concentration
1000 1500
2000
(mg L−1)
Experimental procedure of ozonation stage for posttreatment: Anaerobically pretreated ABR effluent of
period III was used for ozanation experiments. The ozone
experiments were conducted in a 500 ml glass reactor at
room temperature and batch mode. An ozone generator
(Opal OG-400, Ankara, Turkey) was employed to produce
ozone from air and was bubbled at the bottom of the reactor
by means of a diffuser at the rate of 400 mg/h. All
connections in the experimental set up were made using
Teflon fittings. The sample volume was taken as five
hundred milliliter in all experiments. Ozonation
experiments were carried out at ozonation dose of 5 to 75
min and samples were taken at regular intervals to measure
pH, COD and color. The pH values were almost constant at
around 7.0±0.5 over the experimental period.
Experimental procedure for biological treatment stage:
The experiments were conducted in an anaerobic baffled
reactor (ABR). The ABR consisted of four equal
compartments separated by vertical baffles. The working
volume of the reactor was 19 L (wide: 20cm, long: 80cm,
deep: 20cm), the active volume of each compartment was
4.75 L. Each compartment was further divided into two by
slanted edge (45˚) baffles to encourage mixing within each
compartment (Fig. 1). The system was installed in a
temperature controller chamber maintained at 30 0C. The
feed solution was continuously pumped into the reactor
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Research Journal of Chemistry and Environment____________________________________________Vol. 18(5) May (2014)
Res. J. Chem. Environ.
Analytical Methods: COD, pH and color were measured
at regular time intervals. pH was measured using a pH
probe (340i, WTW, Oslo, Norway). Samples were
centrifuged using Eppendorf Centrifuge 5415R centrifuge
3000×g for 5 min before the measurement of color and
COD concentrations from the supernatant. For color
measurements, RES parameter (m-1) was applied according
to the standards of European Norm EN ISO 7887. The
absorbance measurements at three wavelengths, namely
436nm, 525nm and 620nm representing yellow, red and
blue color, respectively. Absorbance measurements were
carried out on Hach DR-5000 model spectrophotometer in
1 cm glass cuvettes. The color was measured (HACH
DR/5000) in platinum-cobalt (Pt-Co unit). COD was
measured using commercially prepared HACH testing kits.
Methods were the current US EPA approved (Standard
Method COD, 5220D) and procedures are equivalent to
Standard Methods.4
wastewater supplemented with glucose (500 mg/L) and
nutrients and found COD removal efficiencies between 62
and 66% which are close to the findings of the present
work. Zhu et al39 investigated a laboratory-scale ABR with
four compartments using soybean protein processing
wastewater as organic loading rates were investigated for
the performance and phase separated characteristics. It was
found that the COD removal efficiencies were 92–97% at
1.2–6.0 kg COD/m3.d feeding.
The performance of ABR in terms of color removal is
presented in fig. 3. In the first period of the reactor
operation, color (Pt-Co unit) reduction was around 28.4%
(Fig.3D). Increase in COD concentration from 1000 to
1500 mg/L in period II, resulted in increasing color (Pt-Co
and RES unit) removal efficiency about 52.6%. In periods
III, increasing COD concentration 2000 mg/L increased the
color (Pt-Co unit) removal efficiency to around 70% (Fig.
3D).
Results and Discussion
The influent RES values were in range of 80 m-1, 89 m-1,
95 m-1 at λ436, λ525 and λ620 respectively. For all operational
conditions applied to the ABR, color was mainly removed
at the last compartments. The color was reduced by 58%,
67% and 55% at λ436, λ525 and λ620 respectively at period I.
The COD concentration during the period was 1000 mg/L
(Fig. 3A-B-C). Similar to color, COD concentration
decreased from last compartments. In second period (days
91-127), the influent COD concentration was increased
from 1000 to 1500 mg/L. Under this period 62% (λ436),
65% (λ525) and 79% (λ620) color removal efficiencies were
observed corresponding to about 40 m-1, 44 m-1, 47 m-1
effluent (at the last compartment) RES values respectively.
Between days 128 and 143 (Period III), reactor was
operated at 2000 mg/L COD concentration. Removal
efficiencies increased to around 80%, 90% and 95% for the
absorbants at 436 nm, 525 nm and 620 nm respectively, at
the end of period III.
Part 1- Anaerobic biodegradation process: In the first
part of the study, the effect of initial COD concentration on
dyestuff and COD removal performance of the SBR was
investigated. The system was operated at three different
initial COD concentrations varying between 1000 and 2000
mg/L. The COD performance of the ABR is illustrated in
fig. 2.
The biological part of the study was composed of three
periods (Table 1). In the first period ABR was performed at
influent COD of 1000mg/L. During this period, low COD
and color removal (Pt-Co and RES unit) was observed
corresponding to 23% and 28% respectively (Fig. 2). After
day 90 (Period II, III) the influent COD was increased by
substrate additional to enhance the COD and color removal
efficiency. In period II, the influent COD concentration
was increased from 1000 to 1500 mg/L. As a result, the
COD removal efficiency reached to 48.6% (Fig.
2).Between days 128 and 143 (Period III), reactor was
operated at 2000 mg/L influent COD concentration. In this
period, COD removal efficiency increased to around 60%
and the effluent COD concentration was below 698 mg/L
(Fig. 2).
Somasiri et al34 used a UASB reactor supplemented with
nutrients and glucose to treat a real textile wastewater
(COD total = 6 g/L) and found 95% color removal, even
when the initial absorbance at wavelength of maximum
absorbance (λ580 nm) was only 0.35. On the other hand, Sen
and Demirer32 used a fluidized bed reactor (FBR) operated
at a HRT of 24 h to treat a real textile wastewater
supplemented with glucose (500 mg/L) and nutrients and
achieved color removal efficiencies between 40 and 44%.
Gianluca and Nicola11 reported that color removal from
textile wastewater treated biologically was dependent on
the initial COD value of the textile wastewater. Kapdan and
Alparslan16 reported that an anaerobic packed column
reactor was operated continuously at different COD loading
rates (1–8 g/l d) performance. COD removal efficiency was
obtained between 5% and 35% for the applied loads.
Part II- Effect of ozonation on COD and Color removal:
The characteristics of the ABR-treated effluent are given
in table 1. The influence of applied ozonation time on
color and COD removals of biological treatment effluent
was studied by increasing applied ozonation time at pH
of 7.0 ± 0.5. For this purpose ozone feeding times of 5,
10, 15, 30, 60 and 75 min were applied. Increasing the
ozonation times from 5 to 75 min increases the rate of
decolorization.
Somasiri et al34 used a UASB reactor supplemented with
nutrients and glucose to treat real textile wastewater
(CODtotal = 6 g/L) and obtained COD removal above 97%
and effluent COD of 200 mg/L which was lower than the
one from the present investigation (500 mg/L). In contrast,
Sen and Demirer32 tested FBR to decolorize real textile
47
Research Journal of Chemistry and Environment____________________________________________Vol. 18(5) May (2014)
Res. J. Chem. Environ.
PERIODS
I
2500
III
II
2250
2000
COD (mg/L)
1750
1500
1250
1000
750
500
250
80
COD remaoval efficiency(%)
60
40
20
0
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
Days
Influent
1 st Compartment
2 nd Compartment
3 rdCompartment
4 th Compartment
Fig. 2: COD removals in the anaerobic baffled reactor.
PERIODS
PERIODS
II
I
100
III
Remaoval efficiency(%)
-1
436 (m )
60
40
20
80
60
40
20
0
0
B
80
m
80
Remaoval efficiency(%)
100
60
40
20
C
Remaoval efficiency(%)
100
80
60
40
20
60
40
20
0
100
0
m
III
A
80
80
60
40
20
0
4500
0
D
80
Remaoval efficiency(%)
4000
Color (Pt-Co unit)
II
I
100
3500
3000
2500
2000
1500
60
40
20
1000
0
0
20
40
60
80
0
100 120 140
20
40
60
80
100 120 140
Days
Days
Influent
1 st Compartment
Removal efiiciency (%)
2 nd Compartment
3 rdCompartment
4 th Compartment
Fig. 3: Color absorbans, λ425 (A), color λ520 (B), color λ625 (C) and color (Pt-Co) removal performances.
Left column shows in each ABR compartment values, right column shows percent removals.
48
Research Journal of Chemistry and Environment____________________________________________Vol. 18(5) May (2014)
Res. J. Chem. Environ.
Thus, higher applied ozonation times have a positive
effect on color removal efficiencies. It can be observed
through the results presented in fig. 4B that as the
ozonation times increases, the color (Pt-Co unit and
RES) removal increases. The color (Pt-Co unit) removal
percentages were 14.3, 24.1, 44.2 and 68.5 for ozonation
times of 5 min, 25 min, 50 min and 75 min respectively.
The overall color removal efficiencies via postozonation were 82.8, 94.7 and 99.1% at λ436, λ525 and λ620
respectively for ozonation time of 75min (Fig. 3A-B-C
and Fig. 4C-D-E).
the parameters. The colors were reduced by 58%, 67%,
55%, 21% at 436nm, 525 nm, 620 nm and Pt-Co unit
respectively, for 75 min ozonation times. The best values
were obtained during operational parameters. This study
demonstrates that post ozonation is a feasible option to
reduce residual color after biological treatment.
Fig.4 shows that an ozonation time of 5 min resulted in
COD removal of 27%, which was raised to 40% at a
time of 25 min and no appreciable increase was noted
after that. In spite of having higher color removal
efficiency, relatively low COD removal was obtained.
This could be explained by the incomplete oxidation of
organic materials and production of small organic
molecular particles along with the degradation of the
dyestuff that was not being completely oxidized. Many
researchers observed a similar trend that a reduction of
COD upon ozonation is as a result of partial oxidation of
the organic substrates.9 According to Wang et al,38 these
small molecules contribute significantly to the COD and
cannot be completely removed by ozonation.
1. Abu Amr S. S. and Aziz H. A., New treatment of stabilized
leachate by ozone/Fenton in the advanced oxidation process,
Waste Manag., 32,1693–1698 (2012)
Ozone consumption and cost estimate
Ozone consumption is an important parameter of ozone
processes because it can be correlated with the energy
conservation of the treatment process. Ozone
consumption, calculated under the conditions of each
run, ranged from 0.9 kg O3/kg COD to 4.2 kg O3/kg
COD. The study yielded a good value of ozone
consumption for COD removal (1.2 kg/kg COD) at 40
min. Several experiments have been conducted ozone
consumption, with results varying from 0.63 kg O3/kg
COD1 to 1 kg O3/kg COD,13 3.5 kg O3/kg COD35 and
even 16 kg O3/kg COD38 and less than 3 kg O3/kg COD
for ozone-only systems.10
5. Arslan I. A. and Isil A. B., The effect of pre-ozonation on the
H2O2/UV–C treatment of raw and biologically pre-treated textile
industry wastewater, Water Sci. Technol., 45, 297–304 (2002)
Acknowledgement
We would like to thank the CNR research group members
for their support during this study.
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Research Journal of Chemistry and Environment____________________________________________Vol. 18(5) May (2014)
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A
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-1
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(Received 15th June 2013, accepted 19th November 2013)
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