International Journal of Aquaculture, 2013, Vol.3, No.15, 79
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84
http://ija.sophiapublisher.com
80
ensure its quality. This study is therefore aimed at
assessing the physico-chemical quality of the river in
comparison with national and international standards.
1
Results and Discussion
The results of the physico-chemical parameters of
River Ogun are shown in Table 1. Some selected
national and international water quality standard
guidelines are shown in Table 2. The Comparison of
hardness values is shown in Table 3. Water
temperature is one of the most important physical
characteristics of aquatic systems (Deas and Lowny, 2000).
It is one of the most important regulators of life
processes in aquatic ecosystems (FOEN, 2011). It has
direct and indirect effects on nearly all aspects of
stream ecology. Temperature also influences the rate
of photosynthesis by algae and aquatic plants. As
water temperature rises, the rate of photosynthesis
increases thereby providing adequate amounts of
nutrients (Boulton, 2012). Water temperature ranged
between 26.9 ± 1.1
(
June, 2012) and 32.1± 0.5
(
April,
2012).
This was found to be within the permissible
limit of the WHO but exceeded the maximum
permissible limit of FEPA. This result is similar to
Fafioye et al., (2005) who reported a range of 26.5
℃
-31.5
℃
in Omi water body, Ago iwoye, Ogun state,
Nigeria. Dissolved oxygen is one of the most
important parameters in aquatic systems (Manora
online, 2012). When the temperature of water
increases, a portion of oxygen converts from the liquid
state to a gaseous state. Thus the ability of water to
maintain oxygen in dissolved state decreases with
increasing temperature. As a result, colder water can
potentially contain more dissolved oxygen than warm
water (AWQA, 2012). Dissolved oxygen ranged
between 2.8±1.95 (January, 2012) and 7.7±0.50 (May,
2012).
This value exceeded the maximum permissible
limit of the standards. The dissolved oxygen values
for the first four months were observed to be critically
low. This could be as a result of human activities on
the water and low water volume which is
characteristic of the dry season. Conductivity is a
measurement of the ability of an aqueous solution to
carry an electrical current (Manora online, 2012).
Conductivity measurements are used routinely in
many industrial and environmental applications as a
fast, inexpensive and reliable way of measuring the
ionic content in a solution (Gray, 2005). Conductivity
ranged between 99.0±7.84 (February, 2012)
and
180.5
±6.64 (December, 2011). This value fell within
the permissible limit of NAFDAC, SON, NSDW,
WHO, EU and USEPA but exceeded the maximum
permissible limit of FEPA. Total dissolved solid (TDS)
is a measurement of inorganic salts, organic matter
and other dissolved materials in water (U.S.
Environmental Protection Agency, Office of Water,
1986).
TDS concentrations are used to evaluate the
quality of freshwater systems (Manora-online, 2012).
Total dissolved solids ranged between 48.8±3.68
(
February, 2012) and 90.8±3.35 (December, 2011).
This value fell within the permissible limit of the
standards. Transparency is how easily light can pass
through a substance. In other words, when the water is
murky or cloudy and contains a lot of particles, the
light cannot penetrate as deeply into the water column
which hence limits primary productivity. Transparency
ranged between 0.2±0.08 (May, 2012) and 0.7±0.07
(
December, 2011). The trend in transparency values
showed that the first three months was constant after
which it began deteriorating gradually and then shoots
up again in June, 2012. The reduction in water
transparency could be as a result of the human
activities around the river such as locust bean
processing, ferrying, refuse disposal etc. and run offs
from land erosion while the increase could be as a
result of more water influx which is characteristic of
the wet season. Alkalinity is a measure of the
acid-neutralizing capacity of water. In most natural
waters, it is due to the presence of carbonate (CO
3
-
),
bicarbonate (HCO
3
-
),
and hydroxyl (OH
-
)
anions.
However, borates, phosphates, silicates, and other
bases also contribute to alkalinity if present (Wilson,
2010).
Alkalinity ranged between 4.4±0.38 (January,
2012)
and 17.8±0.25 (April, 2012). This value fell
within the permissible limit of the standards. Hardness
is most commonly associated with the ability of water
to precipitate soap. As hardness increases, more soap
is needed to achieve the same level of cleaning due to
the interactions of the hardness ions with the soap.
Chemically, hardness is often defined as the sum of
polyvalent cation concentrations dissolved in the
water (Wilson, 2010). In fresh waters, the principal
hardness-causing ions are Calcium and Magnesium;
Strontium, Iron, Barium and Manganese ions also
contribute (USEPA, 1976). Hardness ranged between
45.5
±4.79 (January, 2012) and 105.0±46.74 (April,
2012).
This value exceeded the maximum permissible
limit of the standards excluding NSDW. The trend in the
hardness values showed that River was moderately soft
then soft then moderately soft then slightly hard and