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Determination of Water Quality Index (WQI) of Selected Rivers in
Ezeagu Local Government Area of Enugu State, Nigeria
Okoye, N.H., Anarado, I.L
*
., Anarado, C.J.O., Muobike, C.M., Okonkwo, N.A., Ikeh ,O.A.,
Onukwube, N.D., Izuka, E.C.
Department of Pure and Industrial Chemistry, Nnamdi Azikiwe University, Anambra State
*Corresponding author
DOI : https://doi.org/10.51583/IJLTEMAS.2024.130521
Received: 18 May 2024; Accepted: 29 May 2024; Published: 22 June 2024
Abstract: Assessment of water quality of Ajali, Karawa and Nnam rivers in Enugu State, Nigeria, was determined over a 10
year-span, in order to ascertain the level of deterioration of the water over time. Water samples were collected in 2013 and 2023
from the aforementioned rivers. For these 2years, the samples were collected in April and July to represent early rainy season and
peak rainy season respectively. The physicochemical parameters such as pH, electrical conductivity, total hardness, total
suspended solids, total dissolved solids, alkalinity, dissolved oxygen, biochemical oxygen demand, calcium, magnesium,
sulphate, nitrate and chloride were determined using standard methods. The water quality indicator ranges were found to be as
follows: pH: 4.10–9.23, electrical conductivity (μs/cm): 6.88-53.30, total hardness (mg/L): 4.00-220.00, total suspended solids
(mg/L): 0.002-91.00, total dissolved solids (mg/L): 0.08-9.52, alkalinity (mg/L): 10.00-31.50, dissolved oxygen (mg/L): 0.25-
36.80, biochemical oxygen demand (mg/L): 0.05-73.60, calcium(mg/L): 0.31-9.40, magnesium (mg/L): 0.003-0.68, sulphate
(mg/L): 119.35-425.65, nitrate (mg/L): 0.07-36.80, chloride (mg/L): 3.60-30.00. The WQI values of the three rivers were as
follows: 72.93, 78.93 and 66.17 in April 2013; 47.34,85.79 and 75.81 in July 2013, while 425.3, 194.1 and 242.0 in April 2023;
70.68, 50.61 and 62.95 in July 2023 for Ajali, Karawa and Nnam rivers respectively. Ajali and Karawa river water were only
suitable for drinking in July 2013 and July 2023 respectively. All the April samples show high level of deterioration and as such
is very poor and unfit for human consumption. Generally, there was an increasing trend in the pollution level of the rivers over
the period. The need for appropriate treatment cannot be over-emphasized,
Keywords: Ajali, Karawa, Nnam, physicochemical properties, water quality index, rivers
I. Introduction
A river is a naturally occurring surface water with defined banks. It is essential for setting national development goals as well as
those of the entire world because it touches on every aspect of the ecosystem and human endeavour while promoting national and
human wealth, civilization and educational attainment. (UN-waters, 2016; Smith et al., 2019). In most cases, it provides drinkable
water in areas where groundwater resources are insufficient or non-existent (Seiyaboh et al., 2017). Surprisingly, the
indiscriminate discharge of sewage and industrial waste, along with a multitude of human activities that impact its
physicochemical and microbiological quality, are polluting this vital natural resource for human progress. (Chauhan and Singh,
2010). One of the most basic human rights—access to clean water has been undermined by the global decline in river water
quality. This problem continues to be a major focus of the UN water campaign, especially in the world’s poorer nations (Ibrahim
et al., 2015). The global degradation of freshwater quality is a threat to the world’s economy and health (Barbosa et al., 2016;
Nwabor et al., 2016; Otene and Nnadi, 2019; Zakir et al., 2020; Bhutiani et al., 2021), particularly in developing nations like
Nigeria where policies and laws are rarely implemented (Iloba, 2021). Therefore, it is crucial to make sure that this limited
resource is used appropriately, accepted, and upholds water quality requirements while maintaining its primary usage. Two
reliable indices that offer helpful information on water quality are the comprehensive pollution index and the water quality index
(WQI). The Water Quality Index (WQI) is a numerical value that lacks units and represents the overall quality of water by
categorizing it based on its suitability for residential use.
(Tyagi et al. 2013). The objective of water quality index is to turn complex water quality data into information that is
understandable and used by the public (Thakor et al, 2011). Many researchers have worked on water quality index of many rivers
in and outside the country, but with limited knowledge on the extent of degradation over time. This study aims to assess the water
quality of Ajali, Karawa and Nnam rivers in Enugu State, Nigeria, over a 10 year-span, in order to ascertain the level of
deterioration.
II. Matrerials and Method
Study Area
Ajali, Karawa and Nnam Rivers are located in Ezeagu Local Government Area of Enugu State. It shares boundary with Udi Local
Government Area, Oji Local Government Area and Uzo-Uwani Local Government Area.
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Fig 1: Map showing the sampled rivers in study area.
Sample collection:
Clean and sterilized air-tight plastic bottles were used to collect the samples. Equal volumes of the samples were collected from
different points of the river to ensure good representation of the entire body of the water. For these 2 years (interval of 10 years),
the samples were collected in April and July to represent early and peak of rainy season.
Sample Analysis
Total hardness as well as calcium and magnesium were measured using ethylenediaminetetraacetic acid (EDTA) titrimetric
method (Smith 1999). pH was determined with pH meter (model 3510). Chloride (Cl
-
) was determined by Mohr’s Argentometric
method using silver nitrate (Eaton et al. 2005). total dissolved solids (TDS) and electrical conductivity (EC) were done using
Hanna multimeter with replaceable electrodes (Hanna HI 9811-5 multi-meter). Phosphate (PO
4
3−
) was measured colorimetric
ally using the ascorbic acid method (Murphy and Riley 1962; Edwards et al. 1965). Nitrate (NO
3
−
) concentration was determined
using cadmium reduction method (Eaton et al. 2005). All other parameters were analysed using standard methods (APHA 2012).
Water Quality Index method
The water quality index (WQI) was evaluated by using the weighted arithmetic water quality index method (Egun and Oboh
2021; Egun and Ogiesoba-Eguakun 2018; Oboh and Agbala 2017; Tyagi et al., 2013). The reference standard used for the
computation was the World Health Organisation standard for drinking water quality (WHO, 2017). The WQI was computed from
Eq. (1):


(1)
Where, qn = Quality rating of n
th
water quality parameter. Wn= Unit weight of n
th
water quality parameter
Quality rating (qn)
The quality rating (qn) is calculated using the expression given in Equation (2).
󰇳
󰇛


󰇜
󰇛


󰇜
󰇴
 (2)
Where, Vn = Estimated value of n
th
water quality parameter at a given sample location.
Vid = Ideal value for n
th
parameter in pure water. (Vid = 0 for all parameters except pH (with a value of 7.0) and dissolved
oxygen (with a value of 14.6 mg/L) Sn = Standard permissible value of n
th
water quality parameter.
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Unit weight
The unit weight (Wn) is calculated using the expression given in Equation (3).
(3)
Where, Sn = Standard permissible value of n
th
water quality parameter. k = Constant of proportionality and it is calculated by
using the expression given in Equation (4).
󰇩
󰇪
 (4).
WQI values are categorized into five classes based on the weighted arithmetic water quality index method (Tyagi et al. 2013) as
follows: 0–25 (excellent water quality), 26–50 (good water quality), 51–75 (poor water quality), 76–100 (very poor water
quality), and > 100 (water unsuitable for drinking).
III. Results and Discussions
A summary of the values of some physicochemical properties of the various rivers are presented in Tables 1, 2 & 3. The mean pH
values range from 4.90 - 9.12, 4.15 - 9.23 and 4.10 – 8.92 for Ajali, Karawa and Nnam respectively. Showing a slight deviation
from the stipulated limit by the World Health Organization (WHO, 2017). The higher pH values recorded in Ajali River can be
attributed to washing of clothes in the river and processing of tapioca and cassava (Okoye et al. 2009; Ogbu et al. 2016). Iloba,
et al., (2021), recorded a minimum pH value of 5.3. Otokune for and Obiukwu (2005) and Ekhaise and Anyasi (2005) reported an
alkaline pH range of 8.3 to 8.5 in river water in Niger Delta, South-eastern Nigeria and 8.8 to 9.1 in Ikpoba River, Nigeria,
respectively. The highest concentration of electrical conductivity (53.30 μS/cm) was obtained during the early rainfall from Ajali
River. Karawa river recorded lowest value for electrical conductivity (6.88 μS/cm) in April 2013 and highest (13.4 μS/cm) in
April 2023. This is lower than the values obtained by Alum and Okoye (2020) who reported electrical conductivity value in the
range of 88.00 to 225.00 μS/cm for the same Karawa river. Parameters like electrical conductivity, total hardness and nitrate
though within the permissible limit by WHO, show an increase in concentration in April and July 2023 when compared with
values obtained in April and July 2013. In general, the mean values range for parameters like electrical conductivity (μs/cm), total
hardness (mg/L), total suspended solids (mg/L), total dissolved solids (mg/L), alkalinity (mg/L), calcium(mg/L), magnesium
(mg/L), sulphate (mg/L), nitrate (mg/L) and chloride (mg/L) were within the permissible limit (WHO, 2017). Higher values for
TSS, TDS & Cl
-
have been reported for river water from Ajali (Nwerem et al., 2023). Also, Alum and Okoye (2020) reported
higher values for some parameters (EC, TDS, TH, magnesium, chloride, nitrate) for water sample from Ajali and Karawa river.
Table 1. Physicochemical parameters of Ajali river
Parameter
2013
2023
WHO
April
July
April
July
pH
8.77
4.90
8.485
9.12
6.5-8.5
Electrical Conductivity (μs/cm)
21.60
24.20
53.3
31.9
250
Total Hardness (mg/L)
40.0
36.00
65
140
300
TSS (mg/L)
80.0
91.00
0.006
15.91
250
TDS (mg/L)
20.0
43.00
26.6
0.08
500
Alkalinity (mg/L)
31.5
10.00
ND
ND
120
DO (mg/L)
0.25
11.00
36.8
8.2
5
BOD (mg/L)
0.05
1.10
73.6
0.1
5
Ca
2+
(mg/L)
5.40
1.54
0.385
0.56
75
Mg
2+
(mg/L)
ND
0.32
0.085
0.45
30
SO
4
2-
(mg/L)
164.4
329.20
164.55
119.35
500
NO
3
-
(mg/L)
1.106
1.46
3.402
31.20
50
Cl
-
(mg/L)
3.60
21.00
4.998
4.99
250
ND = Not Detected
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Table 2. Physicochemical parameters of Karawa river
Parameter
2013
2023
WHO
April
July
April
July
pH
9.23
4.15
8.56
9.05
6.5-8.5
Electrical Conductivity (μs/cm)
6.88
11.81
13.4
12.08
250
Total Hardness (mg/L)
4.0
30.00
65
185
300
TSS (mg/L)
0.9
4.50
0.002
0.11
250
TDS (mg/L)
9.1
4.70
6.71
6.01
500
Alkalinity (mg/L)
21.5
10.00
ND
ND
120
DO (mg/L)
0.30
3.50
12.80
8.90
5
BOD (mg/L)
0.05
1.57
25.60
0.30
5
Ca
2+
(mg/L)
5.31
ND
0.342
0.84
75
Mg
2+
(mg/L)
ND
0.09
0.009
0.68
30
SO
4
2+
(mg/L)
425.65
288.10
267.54
147.90
500
NO
3
-
(mg/L)
1.07
10.41
4.108
31.7
50
Cl
-
(mg/L)
12.00
30.00
14.995
ND
250
ND = Not Detected
Table 3 showing physicochemical parameters of Nnam river
Parameter
2013
2023
WHO
April
July
April
July
pH
8.26
4.10
8.08
8.92
6.5-8.5
Electrical Conductivity (μs/cm)
7.83
12.08
17.82
19.03
250
Total Hardness (mg/L)
40.0
32.00
50
220.00
300
TSS (mg/L)
0.90
1.50
0.002
0.009
250
TDS (mg/L)
9.10
6.50
8.91
9.52
500
Alkalinity (mg/L)
20.0
12.00
ND
ND
120
DO (mg/L)
0.25
6.20
18.40
8.60
5
BOD (mg/L)
0.05
1.38
36.800
0.30
5
Ca
2+
(mg/L)
9.40
0.31
0.510
0.55
75
Mg
2+
(mg/L)
ND
0.05
0.003
0.35
30
SO
4
2+
(mg/L)
329.5
123.5
144.15
148.17
500
NO
3
-
(mg/L)
0.07
9.67
3.48
36.8
50
Cl
-
(mg/L)
7.2
17.00
4.998
9.99
250
ND = Not Detected
For a water source to be considered suitable for drinking and other domestic purposes, its WQI value must be less than 50. The
WQI values obtained in this study are shown in Table 4. The elevated WQI values for April obtained in all the rivers indicate that
the water quality at the various study locations in the first year is of very poor quality and deteriorated after 10years, therefore, is
unsuitable for human consumption and possibly domestic use. For July samples, only Ajali river shows some level of
deterioration after 10years. This could be as a result of agricultural activities around it. Generally, this water status report
unambiguously revealed that this body of water is being affected by anthropogenic activities in and around the river.
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Table 4. WQI values for various samples
River
Month
WQI
Water quality
Ajali
April
72.93
Poor for drinking
July
47.34
Good for drinking
April
425.33
Unsuitable for drinking
July
70.68
Poor for drinking
Karawa
April
78.93
Very poor for drinking
July
85.79
Very poor for drinking
April
194.16
Unsuitable for drinking
July
50.61
Poor for drinking
Nnam
April
66.17
Poor for drinking
July
75.81
Very poor for drinking
April
242.08
Unsuitable for drinking
July
62.95
Poor for drinking
IV. Conclusion
The results presented in this study highlight the general quality of water from Ajali, Karawa and Nnam rivers in Ezeagu local
government of Enugu state, Nigeria. The various significant physicochemical factors that have an
impact on the overall quality of river water were identified. A comparison of the physicochemical water parameters with their
respective permissible limits indicated that all but pH, DO and BOD were within the allowed permissible limits.
In the first year (2013), the water quality, as indicated by the WQI values (˂50), showed that only water from Ajali in July was
good for drinking. All the April samples very poor and deteriorated after 10 years as a result of pollution. The implication of the
results of this study is that water from the aforementioned rivers are currently unsuitable for drinking. Remediation strategies
need to be urgently put in place for continued use of this water source.
One way to achieve this is to stop untreated wastewater from entering the rivers.
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