An Assessment of the Impact of Abattoir Effluents on River Illo, Ota, Nigeria
The aim of this research was to assess the impact of
abattoir effluents on River Illo in Ota, Nigeria. In order to achieve
this set objective seven sampling locations were chosen along the river
course. The choice of locations was to reflect the variations in concentrations
of the following important parameters of water quality issue: pH, conductivity,
total dissolved solids, total suspended solids, dissolved oxygen, biochemical
oxygen demand, chemical oxygen demand, ammonia and nitrate among others.
The choice of these parameters was based on their relative importance
in abattoir effluents composition. Results of analyses revealed impairment
in the quality of River Illo by the wash down from the abattoir activities.
Dissolved oxygen concentrations ranged between 0.01 and 4.6 mg L-1
while the highest concentrations of TSS and TS of 1026 and 1071.5 mg L-1,
respectively were obtained at the point of abattoir effluents discharge.
The BOD mean value of 312.9 mg L-1 obtained for the river water
is far above the highest permissible value of 30 mg L-1 allowed
by the Federal Environmental Protection Agency for discharge into receiving
water bodies in Nigeria. The mean value of 783 mg L-1 obtained
for the COD of the river body corroborates the pollution of the water
body. The current water quality status of River Illo from the discharge
of abattoir effluents therefore poses both environmental and health hazards
to users. In order to redress this and ensure public health safety, River
Illo needs adequate treatment before use.
Surface and groundwater pollution is a major problem beclouding most
developing nations. The source and nature of contamination however vary
from one nation to another. Aside, very few percentage of the population
in these nations has access to good and safe water while most surface
water is either contaminated by industrial effluents or sewerage. The
pollution can either be of point source or non-point source. Point sources
of pollution occur when pollutants are emitted directly into the water
body e.g., from industrial sewage or municipal wastewater pipes. A non-point
source delivers pollutants indirectly through environmental changes such
as pollution from urban run-off (TCEQ, 2002; Krantz and Kifferstein, 2005).
Major known sources of water pollution are municipal, industrial and agricultural.
The most polluting of them are sewage and industrial waste discharges
into rivers. Industrial effluents mostly contain heavy metals, acids,
hydrocarbons and atmospheric deposition (Alam et al., 2007). Agricultural
run-off is another major water pollutant as it contains nitrogen compounds
and phosphorus from fertilizers, pesticides, salts, poultry wastes and
wash down from abattoirs. Contaminants are usually of varied composition
ranging from simple organic substances to complex inorganic compounds
with varying degrees of toxicity. Pollution of surface water, the natural
habitat for aquatic animals could have consequential impact on man either
directly or indirectly since less than 1% of the world`s freshwater, about
0.007% of all water on earth is readily accessible for direct human use
(UNESCO, 2006; Krantz and Kifferstein, 2005). The pollution of surface
water body in any form is a critical issue in water resource management.
However, reports have it that large numbers of water bodies in developing
nations of the world are grossly polluted. The water quality situation
therefore becomes very critical in these countries and of great environmental
and public health concerns (World Bank, 1995; WHO/UNICEF, 2005; UNESCO,
In Nigeria, available reports cite gross contamination of most major
River bodies across the nation by discharge of industrial effluents, sewage
and agricultural wastes among others (World Bank, 1995). Contamination
of river body from abattoir wastes which is the main focus of this study
could constitute a significant environmental and health hazards (World
Bank, 1995; Coker et al., 2001; Nafarnda et al., 2006; Osibajo
and Adie, 2007). The location and operation of abattoirs are generally
unregulated, aside, they are usually located near water bodies where access
to water for processing is guaranteed. The animal blood is released untreated
into the flowing stream while the consumable parts of the slaughtered
animal are washed directly into the flowing water (Adelegan, 2002). Sangodoyin
and Agbawe (1992) identified improper management and supervision of abattoir
activities as a major source of risk to public health in South Western
Nigeria. Wastes from slaughterhouses typically contain fat, grease, hair,
feathers, flesh, manure, grit and undigested feed, blood, bones and process
water which is characterized with high organic level (Bull et al.,
1982; Coker et al., 2001; Nafarnda et al., 2006).
The total amount of waste produced per animal slaughtered is approximately
35% of its weight (World Bank, 1998). In an earlier study, Verheijen et
al. (1996) found out that, for every 1000 kg of carcass weight, a
slaughtered beef produces 5.5 kg of manure (excluding rumen contents or
stockyard manure) and 100 kg of paunch manure (partially digested food).
The weight of a matured cow varies with size, ranging from 400 kg for
thin, 550 kg for moderate to 750 kg for the extremely fat (Hammack and
Gill, 2002). Scahill (2003) gave more detailed statistics on both life
and dead weight of a cow in his study. A cow weighing 400 kg would have
its carcass weight reduced to about 200 kg after slaughter. Furthermore,
it looses about one-third in fat and bone after passing through the butcher.
Hence a 400 kg live weight animal will give about 140 kg of edible meat
which represents only 35% of its live weight. The remaining 65% are either
solid or liquid wastes. Corroborating the above findings, Gannon et
al. (2004) showed in their study that a slaughtered cow produced 13.6
kg of blood (with bovine blood density ranging between 0.01 and 0.15 g
cc-1). Moreover, the volume of water required for meat rendering
or processing ranged between 1.5 and 10 m3 t-1 of
product for hogs, 2.5 and 40 m3 t-1 of product for
cattle and 6 and 30 m3 t-1 of product for poultry.
The organic load from abattoirs could be very high. Tritt and Schuchardt
(1992) reported a COD level as high as 375000 mg L-1 for raw
bovine blood. Comparatively, in another study conducted by Mittal (2004),
on abattoirs in Québec, Canada, typical values for a range of parameters
in abattoirs wash down were given: TS concentrations (2333-8620 mg L-1);
TSS (736-2099 mg L-1); while average levels of nitrogen and
phosphorus were evaluated at 6 and 2.3 mg L-1, respectively.
Hence, abattoir effluents could increase levels of nitrogen, phosphorus,
total solids in receiving water body considerably. Excess nutrients cause
the water body to become choked with organic substances and organisms.
When organic matter exceeds the capacity of the micro-organisms in water
that break down and recycle the organic matter, it encourages rapid growth,
or blooms, of algae, leading to eutrophication. Equally, improper disposal
systems of wastes from slaughterhouses could lead to transmission of pathogens
to humans and cause zoonotic diseases such as Coli Bacillosis, Salmonellosis,
Brucellosis and Helminthes (Cadmus et al., 1999). Improper management
of abattoir wastes and subsequent disposal either directly or indirectly
into river bodies portends serious environmental and health hazards both
to aquatic life and humans. The current study therefore aimed at assessing
the water quality of River Illo and the impacts of abattoir effluents
on its quality.
MATERIALS AND METHODS
The Study Area
River Illo which is the focus of this study is located within River
Owo catchments area in Ota, Ogun State, Nigeria. The river drains 24 km
stretch of land along the boundary of Lagos and Ogun States. Ota town
lies between latitudes 60° 30 and 60° 50 N and longitudes 30°
02` and 30° 25` E, with a very close proximity to the city of Lagos.
It is the fourth largest city in Ogun State with an estimated population
of about 103,332. The Ota segment of River Illo where an abattoir is located
is the main thrust of the current study. The abattoir is a small-scale
business enterprise and it is managed by an Association of independent
butchers. The slaughtering area measures 150 m2 in size, fenced
with sandcrete blocks while the floor is made of concrete slab. An average
number of slaughtered animals per day are 15 cows, 20 sheep and goats.
Normal abattoir operations are carried out from Monday to Saturday. The
blood wash and the process water from the abattoir is channeled directly
into River Illo; about 10 m away from the slaughter slab (Fig.
Field Sampling and Laboratory Analysis
Field sampling was carried out at the tail end of the dry season in
March 2006. Seven water samples designated S1 to S7 were
collected from the sampling locations along the river course as shown
in Fig. 1. Sample S1 was collected at a distance
of 10 m upstream of S2, while S2 is the abattoir
effluent discharge point into the river body and it is designated 0 m
Samples S3 to S7 were taken downstream of S2
and at distances of 10, 20, 30, 50 and 100 m, respectively. The full description
of the sampling locations is shown in Table 1. At each
sampling location, water samples were collected in polyethylene bottles.
All bottles were previously washed with non-ionic detergent and finally
rinsed with deionized water prior to usage. Before the final water samplings
were done, the bottles were rinsed three times with the river water at
the points of collection.
||A sketch of studied area with sampling points
||Sampling location description
The sample bottles were labeled according to each sampling location.
Samples for microbiological analysis were collected in 500 mL sterilized
bottles with its mouth stoppered with foil and rubber band. All samples
were preserved at 4°C and transported to the laboratory.
The physico-chemical analyses of the various water quality parameters
were conducted following standard analytical methods (APHA, 1992). Results
of laboratory analysis were subjected to data evaluation by standard statistical
methods (Chapman, 1992) and results were compared with WHO and various
Nigerian water quality guidelines (FEPA, 1991; FMEnv, 2001; WHO, 2004;
RESULTS AND DISCUSSION
The pH of the River Illo is slightly acidic with pH values ranging
between 6.20 and 6.90. As known, pH is the indicator of acidic or alkaline
conditions of water status; hence the mean pH value of 6.64 obtained for
the river body is within the WHO pH tolerance level of drinking water
quality standards (Tables 2-4). The
TDS values ranged between 45.5 mg L-1 at S2 and
87.7 mg L-1 at S3. It is interesting to note that
the minimum value of 45.5 mg L-1 was obtained at S2,
the point of abattoir effluents discharge into the river body.
Figure 2 shows a noticeable decrease in TS levels downstream
of S2 indicating existence of a varying level of waste assimilation
capacity within the river body. Dissolved oxygen values obtained for S1
to S7 varied between 0.01 and 4.6 mg L-1 as shown
in Table 2. The DO is a measure of the degree of pollution
by organic matter, the destruction of organic substances as well as the
self purification capacity of the water body. The standard for sustaining
aquatic life is stipulated at 5 mg L-1 a concentration below
this value adversely affects aquatic biological life, while concentrations
below 2 mg L-1 may lead to death of most fishes (Chapman, 1992).
The DO level at S1, 10 m upstream of S2, of 4.6
mg L-1 was slightly below the level required for the sustenance
of most aquatic life, even though the sampling point was found to be the
most aerated sector of the river body. At S2 however, contamination
of the river body by the abattoir wash down is more evident. The obtained
DO value at this point stands at 0.01 mg L-1. This value is
500 times lower than the tolerance level necessary to support aquatic
life. Re-aeration of the river body picked up gradually at S4
and progressed till S5, 30 m away from S2. At S6,
deterioration in the oxygen saturation level could be noticed, with DO
concentration dropping to 0.39 mg L-1 before it picked up again
at S7 to 3.9 mg L-1. The obtained values for TSS,
BOD and COD as shown in Table 2 and Fig.
3, respectively corroborate this inference. The microbiological results,
presented in Table 5 indicate gross pollution of the water body at the
point of abattoir effluents discharge. At this point, the mean Faecal
Coliform count of 2.0x103 cfu/100 mL was obtained.
A zero count was recorded at S1 and from S3 to
S7, distances upstream and downstream from point of abattoir
effluent discharge. For other parameters such as NH4 and NO3
their values as shown
||Physico-chemical characteristics of River Illo
||Descriptive statistics of physico-chemical characteristics
of river Illo
||Various drinking water quality standards and effluent limitation
NS = Not Specified
||Trend of TS, BOD and COD levels in River Illo
in Table 2 are quite acceptable compared with WHO and Nigerian
interim water quality standards. For example, NH4 level aside from
the point of effluent discharge and at S6 ranged between 0.04 and
0.21 mg L-1, below the WHO tolerance level of 0.5 mg L-1
in surface water for drinking purposes. The highest value of 4.4 mg L-1
obtained at S2 is a direct effect of discharge of the abattoir effluents
on River Illo. However, concentrations of NH4+ downstream
of S2 would have indicated the fact that the river body is quite
safe in terms of ammonia pollution except at S6 where a relatively
low value of 0.52 mg L-1 was obtained. Figure 3 shows the trend in
NH4+ along the river course.
||Faecal Coliform counts in water samples
|*: WHO Standard 0 cfu/100 mL
||Trend of NH4, PO4, NO3 levels
in River Illo
Land and water pollution from abattoir activities
The conductivity levels in the surface water body ranged between 146 and 196
μS cm-1, most freshwaters values range between 10 and 1000 μS
cm-1 (Chapman, 1992).
The pollution of River Illo is much more pronounced at S2 indicative
of the impact of abattoir effluents discharge on the river body. This
is corroborated by high values of TSS and TS recorded in water samples
put at 1026 and 1071.5 mg L-1, respectively. A general trend
of increasing assimilation capacity could however be inferred from Fig.
2 and 3 along the river course downstream of S2.
Even though higher values of TS in surface waters are usually attributable
to the presence of silt and clay particles (Chapman, 1992), the observed
elevated value of 1071.5 mg L-1 of TS specific to S2
is not unconnected with the presence of high level of particulate matter
from the abattoir wash down (Fig. 4).
The mean DO concentration of 2.4 mg L-1 obtained for River
Illo is indicative of its level of contamination. Dissolved oxygen is
an important factor that determines the quality of water in lakes and
rivers hence, the higher its concentration, the better the water quality.
The drop in DO level from 4.6 mg L-1 at S1 to 0.01
mg L-1 at S2 defines the putrid condition of the
river at this point. The re-aeration of the river noticed at S3 could
not be sustained beyond S5. The sharp drop in the DO concentration
at S6 (0.39 mg L-1) from 3.7 mg L-1 at
S5 indicates additional source(s) of organic contamination
at this very segment other than the discharge of abattoir effluents at
S1. Biological respiration, including one induced by decomposition
processes, reduces DO concentrations. Hence, the visible depletion in
dissolved oxygen concentration at S6 is best associated with
wash down of organics from the solid waste accumulated near S6.
Observations on the field show an evidence of eutrophication process setting
in at this point. Eutrophication results when fresh water is artificially
supplemented with nutrients, it results in an abnormal increase in the
growth of water plants. Hence, the resulting eutrophication process could
produce problems such as bad tastes and odours as well as green scum algae.
The growth of macrophyte and other rooted plants decreases the amount
of oxygen in the water body (Chapman, 1992; Krantz and Kifferstein, 2005).
In small rivers like Illo, occurrence of pockets of high and low concentrations
of dissolved oxygen is likely, signifying different rates or cycles of
biological processes within the water body along its flow path.
The obtained values for TSS, BOD and COD as shown in Table
2 corroborate this inference. Both the BOD and COD are important water
quality parameters and are very essential in water quality assessment.
Therefore, the more organic material there is in the abattoir effluents,
the higher the BOD. They both indicate the level of organic pollution
in water quality assessment. River Illo from the results obtained is organically
polluted prior to the discharge of abattoir effluents as shown in Table
2. The absence of Faecal Coliform downstream of S2 is not
the true reflection of the microbiological status of River Illo. Filtration
method of microbiological analysis would have clearly indicated otherwise.
Results obtained in this study revealed that the quality of River Illo
has been impacted negatively by the activities of the abattoir. Analyzed
water samples for the following specific water quality parameters TSS,
DO, BOD and COD were above the Nigerian Regulatory Standards and WHO permissible
limits (FEPA, 1991; FMEnv, 2001; WHO, 2004; NSDWQ, 2007). The direct discharge
of abattoir effluents into River Illo raised the levels of these contaminants
at the point of discharge, even though there is a noted increased attenuation
in the levels of the parameters downstream.
In conclusion, the following recommendations are made so as to enhance
the quality of river Illo and as well protect the public health of the
people who depend on it as a source:
||Simple physical treatment of effluents from the abattoir could be
carried out by use of a retention pond. The use of retention ponds
for pre-treatment of abattoir effluents is an effective physical treatment
method in reducing BOD and COD levels (Sangodoyin and Agbawe, 1992).
||Waste management practice by waste reduction, re-use and recycling
should be encouraged when and where appropriate and essential. Entrepreneurs
dealing in animal wastes such as bones, manure and blood should be
encouraged through enabling government policies to convert abattoir
wastes to useful products.
||Abattoirs operators should be enlightened by both the State Environmental
Protection Agency and NGOs on impacts of wash down from abattoirs
on public health, the environment and the fragility of the ecosystem.
||Regular monitoring of activities of abattoirs by the State Environmental
Protection Agency and representatives of the municipal government
is recommended in order to enhance compliance with hygienic requirements
and sanitary regulations governing abattoir operation in the state.
||The research could be expanded to include treatability of abattoir
effluents by biological treatment process.
The authors are grateful to the management of Covenant University,
Ota, for providing the enabling environment for the conduct of this research.
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