Microbial content of abattoir wastewater and its contaminated soil in Lagos, Nigeria

Abstract

Microbial content of wastewater in two abattoirs and the impact on microbial population of receiving soil was studied in Agege and Ojo Local Government Areas in Lagos State, Nigeria. Wastewater samples were collected from each of the abattoirs over three months period and examined for microbial content. Soil samples contaminated with the wastewaters were also collected and analysed for microbial content as compared to soil without wastewater contamination in the neighbourhood (control). Some physico-chemical parameters of the samples such as total dissolved solid, chemical oxygen demand etc were examined. The wastewater samples from both abattoirs were highly contaminated; Agege abattoir showed mean bacterial count of 3.32x10 7 cfu/ml and Odo abattoir showed mean count of 2.7x10 7 cfu/ml. The mean fungal populations were 1.6x 10 5 and 1.2x0 5 cfu/ml for Agege and Odo abattoirs respectively. In the contaminated soil sample, mean bacterial count was 3.36x10 7 cfu/ml compared to the 1.74x10 6 cfu/ml of the control sample. High microbial load in abattoir wastewater with negative effects on microbial population in soil, in this study, further confirmed the need to treat wastewater rather than discharging it to the environment.

Full text

African Journal of Biotechnology Vol. 5 (20), pp. 1963-1968, 16 October 2006
Available online at http://www.academicjournals.org/AJB
ISSN 1684–5315 © 2006 Academic Journals
Full Length Research Papers
Microbial content of abattoir wastewater and its
contaminated soil in Lagos, Nigeria
Adesemoye A. O.1*, Opere B. O.2 and Makinde S. C. O.3
1Microbiology Department, Adekunle Ajasin University, Akungba-Akoko, Ondo State, Nigeria.
2Microbiology Department, Lagos State University, Ojo, P. M. B. 1087, Apapa, Lagos, Nigeria.
3Department of Botany and Centre for Environment and Science Education, Lagos State University, Ojo, P. M. B. 1087,
Apapa, Lagos, Nigeria.
Accepted 25 August, 2006
Microbial content of wastewater in two abattoirs and the impact on microbial population of receiving
soil was studied in Agege and Ojo Local Government Areas in Lagos State, Nigeria. Wastewater
samples were collected from each of the abattoirs over three months period and examined for microbial
content. Soil samples contaminated with the wastewaters were also collected and analysed for
microbial content as compared to soil without wastewater contamination in the neighbourhood
(control). Some physico-chemical parameters of the samples such as total dissolved solid, chemical
oxygen demand etc were examined. The wastewater samples from both abattoirs were highly
contaminated; Agege abattoir showed mean bacterial count of 3.32x107 cfu/ml and Odo abattoir showed
mean count of 2.7x107 cfu/ml. The mean fungal populations were 1.6x 105 and 1.2x05 cfu/ml for Agege
and Odo abattoirs respectively. In the contaminated soil sample, mean bacterial count was 3.36x107
cfu/ml compared to the 1.74x106 cfu/ml of the control sample. High microbial load in abattoir wastewater
with negative effects on microbial population in soil, in this study, further confirmed the need to treat
wastewater rather than discharging it to the environment.
Key words: Abattoir, bacteria, environmental pollution, fungi, microbial population, soil, wastewater.
INTRODUCTION
Efforts have been geared towards curbing the menace of
pollution around the world, particularly by the United
Nations organs e.g., United Nations Environmental
Programme. There are many international conferences
and protocols to this effect. Rio de Janeiro Conference of
1992 was a major effort, collating previous environmental
issues and bringing them to the fore (Oyesola, 1998).
Nevertheless, in many parts of the world, human active-
ties e. g., animal production, still impact negatively on the
environment and biodiversity. Some of the consequences
of man-made pollution are–transmission of diseases by
water borne pathogens, eutrophication of natural water
bodies, accumulation of toxic or recalcitrant chemicals in
the soil, destabilization of ecological balance and negati-
ve effects on human health (McLaughlin and Mineau,
1995; Sinha, 1997; Bridges et al., 2000; Boadi and
Kuitunen, 2003; Amisu et al., 2003).
*Corresponding author. E-mail: semoyet@yahoo.co.uk.
The continuous drive to increase meat production for
the protein needs of the ever increasing world population
has some pollution problems attached. In many count-
ries, pollution arises from activities in meat production as
a result of failure in adhering to Good Manufacturing
Practices (GMP) and Good Hygiene Practices (GHP).
Consideration is hardly given to safety practices during
animal transport to the abattoir, during slaughter and
during dressing. For example, during dressing, the oeso-
phagus of cattle and sheep should be sealed to prevent
leakage of animal contents. These ineptitudes often lead
to contaminations from hides, hooves and content of
alimentary tract during evisceration and negatively impact
on the environment, including microbes in the soil and
surface and ground water (Hinton et al., 2000; Laukova et
al., 2002; Amisu et al., 2003).
A specific example of what happens is logging of
contaminated water in the soil. In that situation, oxygen
becomes less available as an electron acceptor, promp-
ting denitrifying bacteria to reduce available nitrate into

1964 Afr. J. Biotechnol.
gaseous nitrogen which enters the atmosphere with
resultant negative effects. Also, anaerobic archaea (met-
hanogens), may produce excessive methane at a higher
rate than aerobic methane oxidizing bacteria (methano-
trophs) could cope with, thus contributing to green house
effect and global warming. Increase in methane is a
concern because it is five times more effective as a green
house gas than CO2 (Madigan et al., 2003; Rusanov et
al., 2002; Tourova et al., 2002; Tortora, 1997). Leaching
into groundwater is a major part of the concern,
especially due to the recalcitrant nature of some
contaminants (Lapygina et al., 2002; Shah and Thakur,
2002; Tortora et al., 1997; Federov et al., 1993; Bitton
and Harvey, 1992). The processes of adsorption and
trapping by fine sandy materials, clays and organic
matter can remove pathogenic organisms and some
dissolved organic matter during passage of polluted
water through the soil, thus reducing the microbial load.
However, if there is too high departure of conditions from
normalcy, beyond the carrying capacity of the natural
process, diversity of autochthonous species could
diminish while count of individual species that are able to
survive may increase with possibility of grave consequen-
ces on groundwater (Baker and Herson, 1994; Atlas and
Bartha, 1998; Lapygina et al., 2002).
Different methods of waste treatment have been
developed, for reasons of public health and conservation,
which results in the destruction of pathogens and the
mineralization of the organic components of sewage prior
to discharge. Anaerobic wastewater treatment using
granular sludge reactor is one of such methods (Liu et al.,
2002; Boadi and Kuitunen, 2003). However, in Nigeria,
like many developing countries, the discharge of untrea-
ted wastes into the environment is still a problem, despite
the establishment of Federal Environmental Protection
Agency (FEPA) since 1998 (Adeyemo, 2003). Better
inspection of abattoir and strict enforcement of the law
are needed to be able to reduce environmental contami-
nation and related diseases especially zoonotic diseases.
Attempts to control the hygiene of slaughter house should
include visual assessment of premises and animals
themselves, and those that are "visibly unacceptably
dirty" or are affected by diseases should not be allowed
for slaughter (Salami, 1998; Hinton et al., 2000; Inglis and
Cohen, 2002; Amisu et al., 2003).
This study aims to examine the extent of contamination
in untreated wastewater of two abattoirs in Lagos, Nigeria
and the impact on the ecology of microorganisms in the
soil receiving part of the wastewater. In the two abattoirs
examined in this study, different species of cattle are
usually slaughtered with their blood, part of the dung and
abdominal content washed on cemented pavements. The
wastewaters run through open drainage of the abattoirs
to bigger adjoining drainages in the neighborhood without
any treatment. Part of the wastewater get washed directly
to the ground within the neighborhood and may affect the
whole biological community, including species diversity
and contaminant accumulation in the food chain.
Previously, some authors have reported different
contaminants in soil and aquatic environments in different
parts of Nigeria (Nwachukwu et al., 2001; Adeyemo,
2003; Akpan, 2004; Adewoye and Lateef, 2004; Efe,
2005). Besides contributing to knowledge, hopefully, this
report will re-awaken concerned government agencies
and other stakeholders.
METHODS
Collection of wastewater and soil sample
Wastewater samples were collected from two abattoirs with Bijou
bottles. The abattoirs were located in Agege (Agege Local
Government) and Odo (Nigerian Army Cantonment Ojo, Ojo Local
Government), both within Lagos State, Nigeria. The Bijou bottles
were used to aseptically draw part of the wastewater running off the
drainage system just as it was leaving the slaughter pavements.
Sample bottles were placed on ice during transport to the
laboratory. Soil samples were collected from Agege abattoir
contaminated area and the neighbourhood without wastewater
contamination to serve as control. Agege abattoir was chosen for
soil sample collection because slaughtering activities was relatively
higher and the abattoir was well demarcated with a fence.
Whatever contamination observed from the soil samples was
therefore attributed to the wastewater. Samples were collected at
10 days interval over a period of three months. All samples were
transported to the laboratory for analyses immediately after
collection. Samples were collected three times per month at an
interval of 10 days over a period of three months from each abattoir
and labeled appropriately. There were a total of nine replicates for
each sample.
Analyses of wastewater samples for physico-chemical
properties
Samples were analysed for the following physico-chemical
parameters: hydrogen ion concentration, temperature, turbidity,
total suspended solid, total dissolved solid, biochemical oxygen
demand (BOD), chemical oxygen demand (COD) and conductivity.
The pH value of the samples were determined with a pH meter
(Unicam 9450, Orion model No. 91-02). Temperature was
measured with mercury thermometer immediately after sample
collection. Turbidity was determined with Milton Roy (USA)
Spectronic 20D meter. Gravimetric method involving filtration and
evaporation were used to measure total suspended solids and total
dissolved solids. Methods recommended by APHA (1998) were
followed for the measurement of BOD and COD. Wastewater
sample was drawn into a 250 ml bottle, incubated in the dark for
five days at 20°C and at the end of five days, the final dissolved
oxygen (DO) content was determined. Decrease in DO between the
final DO reading and the initial DO reading was corrected for
sample dilution and recorded as the BOD of the sample. The COD
was estimated by determining equivalent amount of oxygen
required to oxidize organic matter in the samples. Conductivity was
determined using a conductivity meter (Metrohm 640, Switzerland).
Preparation of media and total viable count
All the media used in this study were prepared and sterilized
according to manufacturer’s instructions. The media used include

Adesemoye et al. 1965
Table 1. Physico-chemical properties of wastewater from two abattoirs in Lagos, Nigeria
Parameters measured Agege Odo
Colour Ox-blood to yellowish red Ox-blood to yellowish red
Appearance Turbid Turbid
Temperature 27±1.1C 26±0.72C
pH value 4.6±0.3 4.7±0.45
Conductivity (µScm-1) 34.0±2.1 34.6±1.2
Turbidity (NTU) 7.6±0.6 7.1±0.3
Total suspended solids (mgl-1) 1800±20 1750±25
Total dissolved solids (mgl-1) 630±8.3 610±5.0
Biological oxygen demand (mgl-1) 35±1.5 30±2.0
Chemical oxygen demand (mgl-1) 142±6.2 140±2.8
Values are means of three repeated sampling of three replicates each.
potato dextrose agar (PDA), Nutrient agar (International Diagnostic
Group, UK), centrimide agar (Schleicher and Schuell, UK),
McConkey agar, No.3 (Oxoid, UK), Robertson’s cooked meat
medium, malt extract agar, Man, Rogosa and Sharpe (MRS)
medium and Eosin methylene blue (EMB) agar (Fisher Scientific,
USA). In estimating total fungi, potato dextrose agar (PDA) plates
which had been supplemented with streptomycin (100 g/ml),
meant to inhibit the growth of bacteria, were aseptically inoculated
with serial dilutions (10-2 to 10-6) of samples by spread plate
technique using a glass spreader (hockey stick) and incubated at
30°C for 72 h (Adesemoye and Adedire, 2005). The numbers of
organisms on the plates with distinct growth were counted after
incubation; fungal population was then estimated and recorded as
colony per ml. In estimating total bacteria, method similar to Boulter
et al. (2002) was used. Sterile nutrient agar plates were aseptically
inoculated with aliquot of serial dilutions (10-4 to 10-9) of the samples
and incubated at 30°C for 24 h. After incubation, plates with distinct
colonies were counted, total bacteria was estimated and recorded
as colony forming units per ml.
Preparation of diluents, isolation and identification of isolates
A measure of 10 g of soil sample, crushed and slightly heated (or
10 ml in the case of wastewater) was diluted in 90 ml of sterile
distilled water, followed by serial dilution. Then, the serial diluents
were aseptically inoculated onto different plates of melted sterile
medium after cooling to 45°C and glass spreader was used to
spread the inoculum. Sub-culturing was done until distinct colonies
(pure cultures) were obtained. In identifying fungi, microscopic and
macroscopic examinations including staining for morphological
characteristics were carried out on fungal isolates and identification
was done based on the characteristics. For bacteria, pure cultures
were isolated followed by biochemical tests to identify the isolates.
Biochemical tests done using standard methods include; Gram
stain, motility, urease activity, carbohydrate utilization, starch
hydrolysis, gelatin hydrolysis, oxidase, catalase, indole production,
citrate utilization, nitrate reduction and hydrogen sulphide
production (Anon, 1994; Cappuccino and Sherman, 1998).
Data analysis
Data obtained were analyzed using SAS 9.1 software (SAS
Institute, Cary, USA) and means were separated by least significant
differences (P  0.05).
RESULTS
Summary of the physico-chemical properties of
analyzed wastewater
The results of the physico-chemical analyses are
presented in Table 1. Physico-chemical parameters
analyzed were not statistically different for the waste-
waters from both abattoirs (Agege and Odo). For
example, mean temperature was 27±1.1°C in Agege
abattoir and 26±0.72°C in Odo abattoir. The pH value
was 4.6±0.3 and 4.7±0.45 for Agege and Odo abattoirs
respectively.
0
5
10
15
20
25
30
35
40
A B C D
10
6
cfu/ml
Figure 1. Population of bacteria in (A) Agege abattoir, (B) Odo
Abattoir, (C) contaminated soil and (D) soil without abattoir
contamination. Populations are means of three repeated
sampling of three replicates each.
Total viable count of bacteria in wastewater and soil
samples
The mean bacterial counts from Agege and Odo abattoirs
were not statistically different. The mean total bacterial

1966 Afr. J. Biotechnol.
Table 2. Microbial isolates from two abattoir wastewater samples.
Table 3. Microbial isolates from Agege abattoir soil samples.
Organism Contaminated soil Uncontaminated soil
Bacteria Lactobacillus plantarum Bacillus sp
Pseudomonas aeruginosa Pseudomonas aeruginosa
Bacillus sp. Bacillus subtilis
Vibrio sp. Pseudomonas putida
count of the replicates taken from Agege abattoir was
3.32x107 cfu/ml while that of the Odo abattoir was
2.7x107 cfu/ml. Meanwhile, mean bacterial population of
the wastewater contaminated soil samples from Agege
abattoir was 3.36x107 cfu/g, which was statistically
greater at p  0.05 than 1.74x106 cfu/g counted from the
uncontaminated soil (soil without wastewater contamina-
tion) in the neighborhood (Figure 1).
0
20
40
60
80
100
120
140
160
180
A B
10
3
cfu/ml
Figure 2. Population of fungi in (A) Agege abattoir (B)
Odo Abattoir. Populations are means of three repeated
sampling of three replicates each.
Total viable count and microbial isolates in analyzed
soil
Mean total fungi/yeast counted from the Agege abattoir
was 1.60x105 cfu/ml and the mean count from Odo
abattoir was 1.20x105 cfu/ml (Fig. 2). Bacterial and
fungal/yeast isolates are shown in Table 2. Bacterial
isolates from soil samples with or without wastewater
contamination are shown in Table 3.
DISCUSSION
The mean total bacterial count and fungi/yeast were high
for samples from the two studied abattoirs (Figures 1 and
2). Going by international standard, any water
contaminated to this level is neither good for domestic
use nor is it supposed to be discharged directly into the
environment without treatment. Clostridium welchii (C.
perfringens), a common cause of gas gangrene and food
poisoning as well as bowel disease called necrotizing
colitis (Revis, 2004), was isolated from the wastewaters.
Ogunseitan (2002) reported that animal excrement can
be positive to tests on chemical indicators which will
focus on compounds that would complement information
based on indicators of pathogenic microorganisms
present in feacal materials. The pH of the wastewaters
was acidic, ranging from 4.3 to 5.1. However, a pH near
7.0 (neutral) plays a part in determining both the
qualitative and quantitative abundance of microflora
(Federov et al., 1993, Edward, 1990). It could be inferred
then, that more hydrogen ion became available; lowering
Organism Agege abattoir Odo abattoir
Bacteria Bacillus sp. Bacillus sp.
Clostridium welchii (C. perfringes) Clostridium welchii (C. perfringes)
Pseudomonas aeruginosa Pseudomonas aeruginosa
Micrococcus luteus Micrococcus luteus
Vibrio sp. Vibrio sp.
Lactobacillus plantarum Lactobacillus plantarum
Fungi Aspergillus niger Aspergillus niger
Mucor sp. Mucor sp.
Saccarhomyces sp. Saccarhomyces sp.
Penicillium sp. Penicillium sp.
Fusarium sp.

the pH value of contaminated soil and affecting the
pattern of microbial population. This can be corroborated
by the report of Nazina et al., (2002) that abundance and
activity of microflora in soil strata are controlled by the
availability of water, nutrients, pH, concentration of metal
ions, hydrodynamic communication with the ground sur-
face, the lithology of bearing rocks, and so on.
Total bacterial population obtained from the contamina-
ted abattoir soil was more than that in the soil without
wastewater contamination. This could be regarded as
destabilization of the soil ecological balance arising from
contamination. Environmental stresses brought about by
the contamination could be adduced for the reduction in
microbial species diversity but increasing the population
of few surviving species. Previous reports have proposed
extensive microbial diversity (including species richness
and species evenness) with population estimated bet-
ween approximately 4x103 to 104 species per g of uncon-
taminated soil (Borneman et al., 1996). A possible
explanation on what transpired leading to the change in
population pattern is that the organisms in the waste-
water and organisms autochthonous to the soil engaged
in competition and other negative microbial interactions
such as antibiosis, after the water was discharged into
the soil. Guided by the law of survival of the fittest
(Madigan et al., 2003), those that were not able to survive
the new conditions were probably excluded.
Similar to a previous study (Laukova et al., 2002), less
diversity of bacteria but increase in population of survi-
ving species was observed in this study. Higher popula-
tion of bacteria observed in the contaminated soil (Figure
1) possibly had more of bacteria that were able to
withstand acidic conditions. Changes in the ecology of
soil have been observed by different authors but one
germane question is how long such changes can persist.
We believe the duration depends on many factors but in
agreement with Hill et al. (1996), the type, quantity or
concentration of the contaminant and the level of toxicity
are very important. High level of contamination of the
abattoir wastewater as revealed in this study, further
confirmed the dangers associated with discharging
untreated wastewater to the environment, thus the need
for adequate treatment to ensure decontamination. We
use some of the words of Ogunseitan (2003) to submit
that sustainability in food production (in this case – meat
production) should be given priority of place since it
intertwines with public health and economic development.
Another related question (outside this study) is the
relationship of wastewater contamination to soil fertility.
This area is recommended for further studies.
ACKNOWLEDGEMENTS
The authors are grateful to Prof. Poju Akinyanju of the
Department of Microbiology, Adekunle Ajasin University,
Akungba-Akoko, Ondo State, Nigeria and Prof. Henry
Fadamiro, Department of Entomology and Plant Patholo-
Adesemoye et al. 1967
gy, Auburn University, USA, for their helpful criticisms of
the initial manuscript.
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