P I S C

VOL 2012

Journal of Scientific Theory and Methods

ISSN 2200-7830

270

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,

273

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)

276

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.

277

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

278

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).

279

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

281

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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