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Physicochemical and Ecotoxicological Evaluation of Raw and
Biologically-Treated Textile Effluent
Ajao, A.T. (Corresponding Author)
Department of Biology,Institute of Basic and Applied Sciences,
Kwara State Polytechnic, Ilorin, Nigeria.
Oke, M.A.
Department of Microbiology,
University of Ilorin, Ilorin, Nigeria.
Ajijolakewu, A.K.
Department of Microbiology,
University of Ilorin, Ilorin, Nigeria.
Odebisi, M.B.
Department of Microbiology,
University of Ilorin, Ilorin, Nigeria.
Journal of Scientific Theory and Methods
Volume 2012, 270-287
http://journalofscientifictheoryandmethods.com
271
Physicochemical and Ecotoxicological Evaluation of Raw and
Biologically-Treated Textile Effluent
Abstract
The physicochemical characterization and aquatic toxicity
bioassay of effluent emanating from International Textile
Industry Nigeria was evaluated. The results indicated that the
effluent was highly polluted. Pseudomonas aeruginosa and
Bacillus subtilis found to have degradative capacity were
immobilized on agar-agar and transferred into a bioreactor for
bioremediation processes for 15 days. The immobilized cells
significantly reduced COD to 200mg/l, BOD to 20mg/l, and TS<
300mg/l that are upper limit for disposal into surface water.
Heavy metals were also reduced considerably. Acute toxicity
study of both the raw and biologically-treated effluent was also
carried out using Daphnia magna as an experimental animal model.
ATU, 48h-LC50, efficiency of the treatments, linear regression,
standard deviation and coefficient of variation were calculated.
It was concluded that immobilized cells represent promising
application in the bioremediation of textile effluent and that
it is necessary to combine physicochemical and bioassay tests in
evaluating the efficiency of effluent treatment.
Keywords: physicochemical, immobilized cells, acute
toxicity, Daphna magna
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Introduction
Water pollution has become a major threat to the
existence of living organisms in aquatic environments. A large
amount of pollutants in the form of domestic and industrial
effluents is emptied directly or indirectly into water bodies,
which has severe impact on their biotic and abiotic environments
(Tyagi et al., 2007). Treatment of domestic and industrial
wastewaters is crucial for protection of the receiving water.
The standard evaluation of effluent has been based on
the control of global parameters such as pH, dissolved oxygen,
BOD, COD, TOC, TDS, and TSS. However, these parameters cannot be
used for evaluation of toxicity effect on receiving water due to
some specific defects (Movahedian et al., 2005). The
physicochemical analysis is not only complicated, expensive and
time-consuming but also lacks information on the additive,
antagonistic or synergistic effect of various chemicals on the
biotic community in aquatic ecosystem (Tyagi et al., 2007); and
that analytical approach does not allow for mixture toxicity,
nor does it take into account the bioavailability of the
pollutants present.
Toxicity tests are bioassays used in pollution control
for determining the maximum permitted concentration of a given
chemical agent for the development /survival of certain living
organisms (Pelegrini et al., 2007, Burratini et al., 2004,
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Bertollet, et al., 1998 and Zagatho et al., 1987). The best way
to evaluate effluent toxicity effect is to use biotoxicity test
(David and Ford, 1992; Tchobanoglous et al., 2003). Water flea
(Daphna magna) tests are currently the only type of fresh water
invertebrate bioassays that are formally endorsed by
international organizations such as the US EPA, the EEC and OECD
and that are required by virtually every country for regulatory
testing (Persone and Janseen, 1994). Daphnia magna is the most
commonly used zooplankton in toxicological tests in wastewater
treatment due to its short doubling time, high sensitivity, and
simplicity. Therefore, it was used as an indicator in this study
(APHA, AWWA, WEF, 1992; Official Gazette, 1996; USEPA,2000).
Toxicity tests have been used for the evaluation of
domestic and industrial wastewater effluents by many researchers
(Tisler and Zagorc, 1999; Villegas-Navaro et. al., 1999; Richard
et al., 2000). However, it has been observed that although the
effluents met all physicochemical requirements, but regarding
their toxicity, they may still cause considerable negative
effects in receiving water (Movahedian et al., 2005).
An awareness of environmental problems and potential
hazards caused by industrial wastewater has prompted many
countries to limit the discharge of polluting effluents into
receiving water (Okerentugba and Ezeronye, 2003; Ezeronye and
Ugbogu, 2004; Ezeronye and Ubalua, 2005). Textile manufacturing
274
yields a large quantity of black and highly toxic wastewater
that contains high concentrations of chromium, phenol, suspended
solids, and high values of biochemical oxygen demand and
chemical oxygen demand (FEPA, 1991). The biological treatment
methods are attractive due to their cost effectiveness and the
diverse metabolic pathways and versatility of microorganisms
(Banett et al., 1996; Singh et al., 2004; Mendez-Paz et al.,
2005; Pandey et.al., 2007).
In this present work, acute toxicity using D. magna as a
toxicity indicator was combined with physicochemical analysis to
measure the efficiency of bioremediation process of textile
industrial effluent using immobilized Pseudomonas aeruginosa and
Bacillus subtilis.
MATERIALS AND METHODS
Sources of Samples: The textile effluent was collected from
International Textile Industry located in Nigeria. Effluent
samples were collected in sterilized glass bottles, stored in
ice and then transported to the laboratory after which they were
stored at 40C to prevent deterioration.
Physico-chemical analysis: The effluent collected was
analyzed in triplicates in the laboratory for BOD, COD,
turbidity, total solids and selected heavy metals (APHA, 1995;
Ademoroti, 1996). Heavy metal content was analyzed by atomic
275
absorption spectrophotometer (model-GBC-932 plus) using standard
protocol as described by Hayat et al. (2002). The procedure has
been described previously in Ajao et al. (2011).
Bioremediation Process
Mixed culture of Pseudomonas aeruginosa and Bacillus
subtilis were immobilized on agar-agar following the method of
Ellalah et al. (2005) with little modification. The
bioremediation process has been described in previous work (Ajao
et al., 2011) following the method of Margesin and Schinner
(2005). Physicochemical parameters were determined after 15 days
of bioremediation process.
Ecotoxicological studies of both the raw and biologically-
treated effluent were carried out using Daphna magna as test
organism. Daphnids employed as test organisms for the
toxicological assay were from a single source and were
identified using an appropriate taxonomic key (US EPA, 2000).
Propagation and culture were carried out according to the
methods of Davis and Ford (1992) and Movahedian et al. (2005).
Determination of 48h – LC50.
A 250ml sample was taken from both the raw textile effluent
and 15 days biologically-treated effluent; both samples were
diluted by 5, 10, 20, 30, 40, 50, 60, 70, 80, 90 and 100% (v/v).
The tests with Daphna magna were performed in 200 ml glass
beakers. They were filled with 100ml test solution and ten (10)
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daphnids were added to each solution. Each test sample container
was examined and the number of dead organisms counted (looking
for the absence of swimming movements). Daphnids in dilution
water served as control.
A test was regarded as valid when the mortality in the
control is less than 10%. Five replicates per concentration were
carried out and an aerator pump was used to provide oxygen. At
the end of the experiments, acute toxicity unit (ATU) and
efficiency values were determined following the method described
by Movahedian and Asghari, (2005):
A T U = 100/LC50 X 100
R = (ATUr – ATUt) × 100
ATUr
where ATUr = Raw effluent, ATUt = Treated Effluent, R =
Efficiency.
Results and Discussion
Table 1 represents the results obtained after the initial
physiochemical characterization of the sample of effluents that
emanated from International Textile Industries, Nigeria and the
values obtained after fifteen days of treatment using
Pseudomonas aeruginosa and Bacillus subtilis immobilized on agar
–agar.
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Table 1: Physicochemical parameters of raw, treated
effluent and overall percentage reduction of textile industrial
effluent.
Parameter Raw
Effluent
15days
Treated
Effluent
Overall
% Reduction
Total solid (mg/l) 4300±3.41 270±0.14 93.7
Suspended
solid(mg/l)
1250±18.93 150±2.18 88.0
Dissolved solid
(mg/l)
3200±5.09 120±7.78 96.3
BOD (mg/l) 750±6.80 23±0.13 96.9
COD (mg/l) 1200±10.23 200±1.06 83.3
Pb2+ 0.10±0.02 0.062±0.03 38.0
Cu2+ 1.096±0.067 0.43±0.131 60.8
Cr2+ 0.061±0.00 0.037±0.021 39.3
Mn2+ 1.05±0.032 0.313±0.02 70.2
Fe2+ 8.73±0.314 0.51±0.127 94.2
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The detection of the parameters mentioned in Table 1 alone
is not sufficient as the wastewater generated from this textile
industry may contain large amount of chemicals, many of which
may be present in low and undetected concentrations and for many
of them, the analytical techniques are inadequate (Tyagi et al.,
2007). Therefore the above parameters and Daphnid test were used
for the ecotoxicological assessment of the textile effluents.
The high BOD (750 mg/ml) and COD (1200 mg/ml) values of the
raw effluent obtained in this work are indications of the
pollution strength of the effluent as suggested by Yusuff and
Sonibare (2004). Similarly, Wynne et al. (2001) noted that
textile effluents are highly coloured and saline, contain non-
biodegradable compounds, and are high in BOD and COD. They
further reported that the presence of metals and other dye
compounds inhibit microbial activity and in some cases may cause
failure of biological treatment system. According to Sawyer and
McCarthy (1978), high COD levels imply toxic condition and the
presence of biologically resistant organic substances.
Total solid determined in this study was very high (4300 ±
32.41 mg/l) and this has great implications in the control of
biological and physical wastewater treatment processes (Srivosta
and Sinha, 1996; Tobata et al., 2007, Ashish and Yogendara,
2009).
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The results obtained after the treatments indicate a
very good relationship with the method of Raja Mohan and
Karthikayam (2004) who reported the reduction of COD load of
effluent below the upper limit of 250 mg/L. In this case, the
overall COD reduction was from 1200 mg/l to 200 mg/l after 15
days of treatment. BOD (96.9%) and other physicochemical
parameters such as TS (93.7 %) and DS (96.3%) were reduced
considerably while some selected heavy metals were also removed.
The result obtained for the present investigations
showed that textile effluents are highly polluted and this is in
close agreements with the works of Randall and King (1980),
Kertel and Hill (1982) and Nosheen et al. (2002). The removal
efficiency of the physicochemical parameters suggests the
adoption of immobilized mixed culture of Pseudomonas aeruginosa
and Bacillus subtilis for the bioremediation of textile
industrial effluents. The efficiency of the two organisms in
reducing the toxicity of the effluent could be further improved
by several strain improvement techniques such as protoplast
fusion, mutagenesis and recombinant DNA technology.
The efficiency of toxicity evaluation of textile
effluents assessed based on physicochemical parameters alone has
been said to be inadequate for a complete assessment (Villegas-
Navarro et al., 1999). Therefore in line with our findings, the
use of D. magna as a toxicity indicator combined with
280
physiochemical characterization of the effluent is essential in
the evaluation of effluent quality.
Table 2 shows that the 48h- LC50 for the raw textile
effluent and treated effluent was 60% and 80% respectively while
acute toxicity unit was also found to be 1.667 and 1.25
respectively.
Table 2: Average number of dead organisms after 48 hour
contact time and five (5) repetitions from each sample
Textile No of
organisms in
each
dilution
Raw
effluent (R)
Deadorganism
Treated
effluent (T)
dead
organism
5 10 0 0
10 10 1 0
20 10 1 0
30 10 2 1
40 10 2 1
50 10 4 2
60 10 4 3
70 10 6 3
80 10 7 5
90 10 8 6
100 10 10 6
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LC50% (v/v) 60% 80%
ATU 1.667 1.25
Linear
regression
equation
Y = - 0.95 +
0.10x
Y = 1.04 +
0.07x
Standard
deviation
23.8 19.5
Coefficient
of
Variation
32.3% 25.1%
Efficiency of the Treatment = 25%.
The linear regression equation was calculated as y = 0. 95+
0.10x for the raw effluent while that of the biologically
treated effluent was calculated as y =1.04+0.07x. The
coefficient of variation for the raw and treated effluent was
32.3% and 25.1% respectively.
As it is almost impossible to identify the specific
substance responsible for the toxicity in the textile effluent,
therefore, biotoxicity test is an economical and technical
method for direct measurement of toxicity in industrial
effluents (Movahedian et al., 2005). The removal efficiency of
the physiochemical parameters alone is not sufficient in
282
obtaining reliable information on treated textile effluent.
Toxicity test must be performed in combination with
physiochemical analysis in order to ensure safety of aquatic
lives.
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