PHYSICAL AND CHEMICAL ASPECTS OF WATER QUALITY
ASSESSMENT IN IMEKO, SOUTHWESTERN, NIGERIA.
IGE, O.O; BALE, R. B AND *OLASEHINDE, P. I
DEPARTMENT OF GEOLOGY AND MINERAL SCIENCES,
UNIVERSITY OF ILORIN, P.M.B 1515, ILORIN,
KWARA STATE, NIGERIA.
Email: vickyige2002@yahoo.com
*DEPARTMENT OF GEOLOGY,
FEDERAL UNIVERSITY OF TECHNOLOGY,
P.M.B 65, MINNA, NIGER STATE.
ABSTRACT
Imeko is a border town to Republic of Benin. The people of the town source
their water mainly from relatively deep handdug wells, few borehole and
streams. There is no public water supply (tap) while rain water is seasonal. This
study is on the hydrochemical evaluation of the water samples obtained from the
available various sources. A total of twenty - two water (22) samples (2 spring
water, 2 borehole water and 18 handdug wells) were subjected to various
physical and chemical analyses required for water quality evaluation.
The PH range from 6.9 – 7.6; Electrical conductivity range from 23.6 –
198.7µs/cm while color is generally clear. The hydrochemical characteristics of
the area, using the stiff pattern plots reveal that the cationic concentrations is in
the order of Mg> Ca> (Na + K) for the wells and boreholes and surface water
sources while the anionic concentration is in the order of HCO3>SO4>CL.
Statistical and graphical approaches of interpretation indicated two different, the
Mg – Ca - K + Na - HCO3 and the Ca - K + Na – S04., types of water present in
the study area.
The Mg-HCO3 type shows the predominant marine source of pollution while
the Ca-SO4 type water are from industrial sources. The aquifer is mainly
limestone but few locations are of Basement Complex rocks.
1
INTRODUCTION
The sources of water for any specific purpose are not as important as the
suitability of the water for that desired purpose. With increasing human
population, industrialization, urbanization and the consequent increase in
demand for water for both domestic and industrial uses, the attendant increase in
the implication of polluted water on man and the environment have been
severally studied (Hagerty and Pavoni, 1973; Coates, 1981; Christensen, 1989;
Cook, 1991; Denison and Sibergeld, 1991; Langer, 1995; Asiwaju-Bello and
Akande, 2000; Montgomery, 2000; Onipede and Bolaji, 2004; Seo, 2004 and
Kurian et al; 2005). Therefore, there is a need for thorough assessment of the
quality of water available for human consumption, agricultural and industrial
purposes.
The area of study, which is Imeko town, lies between longitude 20 44’ 22”
and 20 53’ 03”E and latitudes 70 22’ 08” and 70 30’ 05” N(Fig. 1). The town lacks
adequate supply of water as there was no pipe borne water supply system;
surface water is available only in the wet season. Hence the people result to rain
water, surface and groundwater for domestic and agricultural uses (Fig. 2). This
condition makes living in the town of Imeko a very difficult one during the dry
season. This is the basis for assessing the three water sources in terms of
2
physical and chemical quality seeing that routine boiling, cooling and filtering are
sufficient to take care of biological impurities.
The climate of the study area is tropical and the natural vegetation consists
of rain forests. The drainage is generally dendritic and the topography is
hummocky and undulating. The annual rainfall is about 1300mm and its
distribution is double-peaked within the hydrologic year. The first peak occurs in
the June-July while the second peak occurs in September – October. The two
wet seasons are normally separated by a drier August break, while the dry
season is defined by little or no rainfall between November and April.
GEOLOGY OF THE STUDY AREA
The geology of the study area is that of the Precambrian Basement
Complex and the Cretaceous –recent sedimentary rocks of southwestern Nigeria
(Jones and Hockey, 1964; Kogbe, 1975; Rahaman, 1975). The Basement
Complex rocks around the study area comprise of the migmatitic and granitic
gneisses, slightly migmatised to unmigmatised paraschists and metal igneous
dolerite dykes (Idowu and Ajayi, 1998). These rocks are characterized by
structural features such as foliation, lineations, folds and joints. The sedimentary
rocks are part of the layered rock sequence consistituting the Dahomey basin,
which extends from the western flank of the Niger Delta to the Volta river basin in
3
Ghana (Fig. 1). In the study area, the sedimentary rocks comprise of the
Abeokuta Formation. The Formation is essentially a succession of sands, clays,
shales and gravels (Idowu and Ajayi, 1998). The succession dips generally
southwards and increase in thickness from east to west (Jones and Hockey,
1964). The boreholes and wells sampled for this study were located in the
gneisses and Cretaceous – recent sedimentary rocks.
METHODOLOGY
The whole area under study was divided into four (4) segments namely; the
GEH, OKO, GEM and IGI (fig.3) and a minimum of four samples were taken per
segment. A total of twenty-two (22) water sample within and around Imeko town
were collected for analysis. The water sample comprise of eighteen (18)
handdugwells, two (2) boreholes and two (2) spring sources. No tap water was
analyzed. Prior to the collection of water samples, the prevailing environmental
condition of the town was studied. This was followed by the measurement of the
4
following physical parameters- Temperature, PH, and the electrical conductivity.
After these measurements, collection of water samples ensued using both glass
and plastic bottles, for anions and cations determination respectively. Two (2)
drops of concentrated nitric acid were added to each sample to prevent formation
of complexes (Schroll, 1976).
The field measurements and observations was followed by laboratory
assessment for the determination of concentration of Na+, K+, Ca2+, Mg2+, SO42-,
Cl-, CO32-, and HCO3-. Heavy elements were not analyzed because their sources
of generation such as industries and mines are not within the study area. All
analyses were carried out at the UNICEF laboratory using Gallenkamp Flame
Analyser- model FGA-330, UV-visible spectrometer-model Cam. Spec. M301
and titrimetrical methods for the determination of all ions. Field observations and
laboratory results of water samples analyzed have been compared with
recommendations of World Health Organization (WHO).
5
RESULTS AND DISCUSSION
Physical characteristics
The temperature of water samples ranges between 240C and 290C. Thus,
representing the average daily temperature of Imeko town which is (27.40C).
These values relatively keep ionization and dissolution at low level. The range of
measured PH is from 6.9 – 7.6. The mean value is 7.3 which show that the water
is neutral to slightly alkaline. The lowest value was measured at OKO B
(Borehole) while the highest value was measured at GEH A.
The electrical conductivity (EC) is a summarizing parameter reflecting the
total dissolved solids (TDS). The measured electrical conductivities of analysed
water samples range between 43.4µs/cm to 98.7µs/cm with a mean value of
61.3µs/cm. The highest value of EC was measured at GEH C while the lowest
value was measured at GEH A. Color varies from 5-45 Hazen Units indicating
generally clear water. Table 1represents the physical characteristics and other
properties measured on the field.
Chemical characteristics
The total cations and anions in water are generally regarded as “Total
mineralization” (Sim and Tischendorf, 1990). In this study, major cations (Na+, K+,
Ca2+ and Mg2+) and anions (Cl-, CO32-, SO2-4 and HCO3-) have been analyzed
using statistical and graphical methods (Piper, 1944)
6
The results of chemical analyses show that the calcium ion has
concentration values ranging between 1.5mg/l and 36.5mg/l. The measured
concentration for the Mg2+ ion ranges between 1.4mg/l and 33.2mg/l. Whereas,
the combined concentrations of Na+ and K+ range between 1.2mg/l and
10.40mg/l. The results of chloride (Cl-) ion concentration determined ranges
between 3.0mg/l and 8.5mg/l, with highest value at IGI C and least value at GEH
B for all samples. The concentration of SO42- decreases from 12.1mg/l at GEM B
to 3.20mg/l at OKO A while 5.9mg/l and 9.0mg/l were measured at OKOB and
IGI A for the two boreholes respectively. The bicarbonate is often formed from
the dissolution of carbon dioxide gas or dissolution of carbonates underground.
Bicarbonate (HC0-3) ion concentration values obtained show its dominance over
other anions with range of value between 8.0mg/l and 24mg/l. In majority of the
samples, the concentrations of nitrate (N0-3) ion range between4.4mg/l and
35.2mg/l. The concentrations of the chemical parameters are presented in Table
2. A summary of the predominant Cations and Anions has been made (Table 3)
after drawing the Piper trilinear diagram (Fig. 3). The twenty water samples show
a predominant Mg(HCO3) water.
7
DISCUSSIONS
PIPER’S TRILINEAR DIAGRAM: The diagram is used to show the
percentage composition of eigth (8) major ions. The piper’s trilinear diagram for
all water samples is presented in Figure 2. The result show magnesium and
calcuim (mg2+>ca2+) ions as dominant of the cations and bicarbonate (HCO3-) as
the dominant of the anions. The abundance of Mg2+ indicates fresh to weathered
Basement source while the concentration of bicarbonate measured is attributed
to probably the dissolution of carbon dioxide (CO2) and carbonate rocks. The
generally low concentration of ions makes the water samples good and safe for
drinking (Elueze, 2004). The presence of SO4-2 and Cl -1 indicate possibility of
industrial pollution in future although the concentration for now is not alarming.
There is therefore the need to make periodic check on the water quality because
water chemistry is a time dependent dynamic system (Olasehinde et al; 1998) at
least once per year or twice in a year to show the two seasons are represented.
The following are summarized:1)
Normal earth alkaline water type predominate at Imeko(Southwest
Nigeria). The Mg2+/HC03- water type is more dominant than Mg2+/SO4-2
type. Samples number 6, 11, 12 and 13 are Mg(HCO3)type waters while
samples 14, 15 and 17 are sulphatic water type respectively. Samples
2,3,4,7,9 and 18 are mixed type waters
8
2)
Three samples (5, 10 and 20) are earth alkaline water type with high
alkaline proportions.
3)
Samples 19 and 21 are purely alkaline water type containing Na+ +k+
and Cl- +S042- respectively.
This reflects that there are two water sources: - limestone and
weathered basement complex rocks.
CONCLUSION
The results of physical characteristics and concentration of eight chemical
parameters analyzed are well compared with the World Health Organization
(WHO) standard for drinking water (Table 4). The range and the mean values
indicated that there were no high concentrations of chemical components.
The graphical interpretations also show that the water within the town of
Imeko is Mg2+ + Ca2+ > HC03- water type. The sampled wells and boreholes
are generally deep (Table 1). This may have encouraged natural purification
of sampled water and preventing anthropogenic influence. Therefore, the
chemical components of water are essentially products of weathered regolith
and its interactions with the fresh Basement Complex rocks. Generally, water
from Sedimentary and Basement Complex areas are typically Mg- HCO3 type
with relatively low total dissolved solid.
9
REFERENCES
Asiwaju-Bello, Y. A. and Akande, O. O. (2004). Urban groundwater pollution:
Case study of a Disposal sites in Lagos metropolis. Journal of Water
Resources. 12, ISSN 0795-6495, 22-26.
Christensen. T. H (1989). Environmental aspect of sanitary landfill. In: Christensen
et al (eds). Sanitary Landfill: Processes, Technology and environmental impact.
Academic Press Ltd, London, 19-25.
Coates. D. R. (1981): Environmental geology. J. wiley, New York. 234p.
Cook. R. J. (1991): Municipal Solid Waste Incineration ash management: A state
Perspective. In: Hattemmer-Frey, H. A. and Travis. C. (eds). Health
Effects of municipal waste incineration. CRC Press, Boston, 265-273.
Dension. R. A. and Silbergerld. E .K (1991). Comprehensive Management of
Municipal Solid Waste Incineration: Understanding the risks.In:
Hattemerfrey, H. A. and Travis, C. (eds). Health effects
Of Municipal Waste Incineration. CRC Press, Boston, 275-293.
Hagerty. D. J. and Pavoni. J. L (1973). Geologic aspect of landfill refuse disposal.
Engineering. Geology. 7, 219-229.
Idowu, O. A. and Ajayi, O.(1998). Groundwater occurrence in southwestern Nigeria:
Comparison of two Geological environment. Journal of Water Resources. 9, ISSN
0795-6495, 33-40.
Jones. H. A. and Hockey, R. D. (1964). The Geology of part of southwestern Nigeria,
Geological survey of Nigeria bulletin, 31.
Kurian. J; Nagendran. R. and Palanivelu. P. (2005): Open Dumps to Sustainable
Landfill. Centre for Environmental Studies, Anna University,
Channai,India.www.serd.ait.ac.th/sidaSWM/project .
Langer. M. (1995). Engineering Geology and waste disposal. Scientific report and
10
recommendations of the IAEG commission.14, 32, 5-29.
Montgomery. W. M. (2000): Environmental Geology, 5th Edition, McGraw Hill,
546p.
Olasehinde, P.I, Virbka, P. and Esan, A. (1998). Preliminary results of Hydrogeological
investigation in Ilorin Area, Southwestern Nigeria- Quality of Hydrochemical
analysis. Water Resources , 9, 51-61.
Onipede, M. A. and Bolaji, B. O. (2004). Management and disposal of industrial
wastes in Nigeria. Nigerian Journal of Mechanical Engineering. 2, 1, 49-63.
Piper, A. M. (1944). A graphical procedure of chemical interpretation in water analysis.
Trans A. M. Geophysics union 25, 914-923.
Rahaman, M. A. (1976). A review of the Basement Geology of southwestern Nigeria.
In: Kogbe, C. A. (eds), Geology of Nigeria. Elizabeth publ., Lagos, 41-58.
Seo, S. (2004). Environmental impact of solid waste treatment methods in Korea.
Journal of Environmental Engineering. 130, 1, 81-89.
Schroll, E. (1976). Analytische Geochemie Band 11. Grunglagen and Anwendungen,
Ferdinand Enke verlag. Stuttgart, 294-306.
SON (1997). Nigeria industrial standard for natural mineral waters. NIS 345, 7P
WHO (1996).Guideline for drinking water quality.World Health Organization,
1, Recommendations, Geneva, 130p.
11
Table 1: Physical characteristics of analyzed water samples
COLOR
SAMPLE
WATER
Hazen
OC
LOCATION SOURCE unit
SWL(m)
PH
SPR A
SW
25.0
26.0
7.0
SPR B
SW
18.0
27.5
7.2
GEH A
DW
7.0
46.9
28.5
7.5
GEH B
DW
10.0
45.5
28.5
7.4
GEH C
DW
8.0
47.1
27.5
7.9
GEH D
DW
6.0
42.9
27.0
7.4
GEH E
DW
32.0
47.2
26.5
7.6
OKO A
DW
27.0
45.0
27.0
7.3
OKO B
BH
6.5
66.1
27.0
6.9
OKO C
DW
23.0
43.4
27.5
7.1
OKO D
DW
19.0
40.1
28.0
7.4
OKO E
DW
26.5
45.8
29.0
7.6
GEM A
DW
22.0
42.9
28.5
7.5
GEM B
DW
24.5
48.3
27.0
7.5
GEM C
DW
7.5
43.3
27.5
7.4
GEM D
DW
10.0
44.2
27.5
7.8
GEM E
DW
15.0
44.8
27.5
7.7
IGI A
BH
9.0
69.6
26.0
7.0
IGI B
DW
21.5
43.7
27.5
7.4
IGI C
DW
17.5
45.3
28.0
7.5
IGI D
DW
25.5
50.4
29.0
7.5
IGI E
DW
24.0
48.7
28.5
7.6
12
EC(µs/cm)
43.2
23.1
43.4
50.5
198.9
49.8
50.1
48.7
91.5
72.3
64.3
55.7
55.0
58.2
40.8
67.9
102.5
87.5
63.8
80.9
79.5
134.5
TDS(mg/l)
28.1
15.3
29.2
18.9
129.2
32.2
32.6
31.7
59.5
46.8
41.2
36.2
35.8
37.9
27.3
43.2
72.4
34.4
40.1
31.9
30.6
99.5
Table 2: Results of chemical analyses of water samples
Parameters
SPR SPR GEH GEH GEH GEH GEH
Mg/l
A
B
A
B
C
D
E
COLOR
104 33
33.0 33.5 33
33
34
BICARBONATE 9.2
12
7.3
13
10
17
8
CARBONATE
0
0
0
0
0
0
0
CHLORIDE
4.0
2.0
3.0
3.0
6.0
3
3.2
MANGANESE
0.1
0.04 0.07 0.11 0.13 0.10 0.11
IRON
0.31 0.04 0.10 0.3
0.2
0.25 0.14
SULPHATE
10.2 6.0
8.0
5.0
7.2
1.7
0.4
NITRATE
17.6 16.1 2.3
8.8
4.4
19.0 8.0
CALCIUM
HARDNESS
4.8
5.6
32
10
6.5
8.4
7.0
MAGNESSIUM 1.5
2.0
11.7 4.4
2.3
18
20.0
CALCIUM
1.9
2.2
12.8 4.0
2.6
4.2
8.0
TOTAL
HARDNESS
2.0
14
80
28
16
24
17
POTASSIUM
1.6
1.4
1.9
2.0
2.5
2.0
1.5
SODIUM
1.4
1.7
0
0
3.5
0
0
Results of chemical analyses of water samples contd.
Parameters
GEM GEM GEM GEM GEM IGI
Mg/l
A
B
C
D
E
A
COLOR
33.5
34
34
34
34
33.5
BICARBONATE 17.1
11.5 8
11
10
15
CARBONATE
0
0
0
0
0
0
CHLORIDE
7.0
3.5
2.5
6.1
3.5
2.5
MANGANESE
0.1
0.3
0.21 0.35 0.3
0.4
IRON
0.28
0.35 031
0.3
3
0.25
SULPHATE
10.0
12
10
10.5 10
9
NITRATE
13.0
22
15.7 15
15
17.6
CALCIUM
HARDNESS
5.2
6.9
91.2 10.3 25
10
MAGNESSIUM 1.9
2.4
33
17
22
2.4
CALCIUM
2.1
2.7
36.5 10
11
4.5
TOTAL
HARDNESS
13
17
228
15
84
20
POTASSIUM
1.6
1.2
2.3
2,4
3.2
1.8
SODIUM
8.8
0
0
0
0
0
13
OKO
A
34
6.5
0
3.5
0.05
0.12
3.2
8.8
OKO
B
33
14
0
2.5
0.03
0.18
5.3
13.2
OKO
C
33
12
0
6.0
0.2
0.2
4.8
35.2
OKO
D
35
17
0
3.0
0.04
0.21
5.0
11
OKO
E
35
25
0
4.0
0.07
.35
5.0
15.0
30
11.6
12
8.0
2.9
3.2
6.6
2.3
2.64
10.2
16
6.2
8.4
11
4
78
1.7
0
20
1.75
0
16
2.8
0
52
1.47
1.0
30
1.5
0
IGI
D
33
14.5
0
6
0.4
0.25
10
10
IGI
E
33
20
0
7.0
0.4
030
8.8
15
IGI
B
33.5
13
0
3
0.3
0.1
9
4.4
IGI
C
34
24
0
8.5
0.42
0.2
12.0
13.2
3.9
1.4
1.5
15
7.8
6.99 4.5
7.7 3.5
15
8
2.5
10
1.4
6.12
48
2.6
0
20
3
0
8
14
6.12
Table 3: Summary of water chemistry for Imeko
SAMPLE NO
DOMINANT CATION
DOMINANT ANION
1
none
none
2
None(slight Mg2+)
HCO3-
3
Mg2+
HCO-3 + SO-24
4
Mg2+
HCO-3 > SO-24
5
None
None-Slight SO-24
6
Mg2+
HCO3-
7
Mg2+
HCO3-
8
Mg2+
None
9
Mg2+
HCO3-
10
None(slight Mg2+)
HCO3-
11
Mg2+
HCO3-
12
Mg2+
HCO3-
13
Na+ +K+
None
14
Mg2+
None-Slight-SO-24
15
Mg2+
SO-24
16
Mg2+
SO-24
17
Mg2+
SO-24
18
None
HCO3-
19
Na+ +K+
SO-24
SO-24
20
21
Na+ +K+
SO-24
22
Mg2+
None
14
Table 4: Summary of the physio-chemical parameters of water
samples and Recommendations for water quality.
WHO STANDARD
ACCEPTABLE
PARAMETERS
RANGE
MAXIMUM PERMISSIBLE
MEAN
LEVEL
TEMPARATURE(oC) 26-29
27.4
-
-
PH
6.9-7.8
7.4
6.5
8.5
EC (µs/cm)
23.1-198 61.3
TDS (Mg/)l
15.3-129 41.4
500
1000
BICARBONATE
(Mg/)
CARBONATE (Mg/)
8.0-25.0
13.44
500
1000
-
-
-
120
CHLORIDE (Mg/)
2.0-8.5
4.22
-
250
MANGANESE (Mg/)
0.03-0.4
0.19
-
0.5
IRON (Mg/)
0.04-0.3
0.35
0.3
1.0
SULPHATE (Mg/)
0.4-12.0
7.41
200
400
NITRATE (Mg/)
2.3-35.2
13.65
0.3
10
MAGNESSIUM
(Mg/)
CALCIUM (Mg/)
1.4-18.0
9.20
-
-
1.9-91.2
6.63
75
200
POTASSIUM (Mg/)
1.2-3.2
2.53
-
-
SODIUM (Mg/)
0-6.12
1.30
-
200
1480
15
60
80
0
0
10
12
14 0 16 0
120
NIGERIA
0
10
0
8
60
ATLANTIC
OCEAN
0
100M
0
4
0
7 30
RE PUBLIC OF B ENIN
0
7 00
IMEKO
Ayetoro
Odeda
ABEOKUTA
Ijebu-Igbo
Alluvia Deposit
Costal Plains Sand
Ilaro Formation
Ewekoro Formation
Abeokuta Formation
Older Granite
Charnokitic Intrusive
Metasediment
Migmatitic - Gneiss
Complex
Geological Boundary
Inffered
Geological Boundary
Surveyed
International
Bondary
Ijebu-Ode
Falt Animal
Location of Imeko
0
Abigi
0
0
LEGEND
State Boundary
6 20
2 30
BASEMENT ROCK SEDIMENTARY ROCK
REPUBLI C O F
PEN IN
40
0
3 00
20km
0
30 30
4 00
ATLANTIC
OCEAN
Fig1: Location and Geological map of the study area
(Modified from Jones & Hockey 1964)
16
FIG. 2: A popular source of water supply in Imeko
17
0
400m
0
Ko n
go
R o
ad
**
**
**
**
GEH B
GEH D
gb
S
CC
et
GEM C
C
uta
Demarcation Line
GEH Sampled Point
ad
Ro
Spring
Minor Road
Round About
GEM B
OKO A
Hospital
Primary School
OKO B
Baba Yanki Road
ye R
oad
Sawmill
Denda Abida
Street
OK O E
GEH E
Mount of
Salvation Road
Market
i
Abi
O
Ro m o A
a d la b
I ya
A
a
b
ag
t re
k
eo
Ab
Co
ng
oR
oa
d
GEM A
OKO- Oke Ola
2 53’ 03” IGI - Igbo Ifa
7 30’ GEH- General Hospital
GEM D
d
a
N GEM - Gelete Market
Ro
Str
eet
A
SPRA
Od
am
uin
i
E
EH
G
A l h . O l o r u n O y in R o a d
EH
G
l
GEM E
Igbo Ifa Street
Ra
sh
Str eed A
ee
des
t
i na
H
ta
pi
s
o
GENERAL HOSPITAL ROAD
O
St sof a
ree
t
2 44’22”
OKO C
Motor Park
OKO D
Street
IGI A
IGI C
IGI D
Si na
Ad od ib o
Stre et
Araromi Street
Omo
Jasu
Street
o fa
Id o ad
R
B aba
A law o
St reet
1GI B
IGI E
Local Govt.
Secretariat Road
Oloruntele Road
Em
Ro i lan
a d du
Main Road
Custom Boundary
7 22’ 08”
Fig3: Sketch of Imeko Township Showing the sampling points
18
Fig.2:
Plotplots
of theofchemical
Nigeria. Nigeria
Fig.The
4: The
chemicalconstituents
constituentsfor
forImeko,
Imeko,SW,
Southwestern
19