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1. Scientific African 21 (2023) e01744
Contents lists available at ScienceDirect
Scientific African
journal homepage: www.elsevier.com/locate/sciaf
Evaluation of the physical, chemical, and biological
characteristics of surface water in urban settings and its
applicability to SDG 6: The case of Addis Ababa, Ethiopia
Thandile T. Gulea,∗
, Brook Lemmab
, Binyam Tesfaw Hailuc
a
African Centre of Excellence for Water Management, Addis Ababa University, Addis Ababa P.O. Box 1176, Ethiopia
b
College of Natural and Computer Sciences, Aquatic Sciences Section, Addis Ababa University, Addis Ababa P.O. Box 1176, Ethiopia
c
School of Earth Sciences, Addis Ababa University, Addis Ababa P.O. Box 1176, Ethiopia
a r t i c l e i n f o
Article history:
Received 30 March 2023
Revised 24 May 2023
Accepted 28 May 2023
Editor: DR B Gyampoh
Keywords:
Water quality
Water contamination
Physicochemical
Bacteriological
Addis Ababa
a b s t r a c t
In this study, an analysis of physicochemical and microbiological water quality parame-
ters was carried out to evaluate the water quality status of the city from the two major
reservoirs that supply drinking water to the city. Unlike most studies which only report
on the water quality from the source or final treated water, this study assessed the water
quality from the raw water source, the treatment plant as well as the treated water from
taps. The analysis was conducted in accordance with the American Public Health Associa-
tion’s recommended procedures. Silica varied between 8.85–15.1 mg/l for Legedadie reser-
voir which is less than the stipulated limit of 25 mg/l and 72.2 to 111.77 mg/L for Gefersa.
With the exception of turbidity, total phosphorus and dissolved oxygen which recorded
mean values of 252.4 NTU, 2.76 mg/l and 5.46 mg/l respectively, nitrate, nitrite, ammonia,
total soluble solids, total alkalinity, pH, electrical conductivity and temperature were dis-
covered to be within the WHO permitted range with mean values of 0.36 mg/l, 0.11 mg/l,
0.067 mg/l, 0.01 mg/l, 53.13 mg/l, 8.14 mg/l, 148.9 μS/cm and 18.57 °C respectively. To-
tal coliforms were found in all waters samples whilst faecal coliforms and Escherichia coli
were recorded in the range 20–3000 CFU/100 mL. Ammonia, turbidity, pH and electrical
conductivity were found to significantly influence microbial densities in the drinking wa-
ter. Filtered and treated water sample recorded a 0 CFU/100 mL for faecal coliforms value
which indicates that the water is in conformity to water quality standards. However, to-
tal coliforms in the range of 3000 to 5000 CFU/100 mL were found in all water samples
indicating contamination hence treatment is recommended before drinking it. In contem-
porary times of increased urbanization and water pollution, this research will assist in the
effort to provide safe water and sanitation for all city residents.
© 2023 The Author(s). Published by Elsevier B.V.
This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/)
Introduction
Water is a basic human resource that is necessary for numerous tasks, particularly in households. Nevertheless, in most
cases the quality of the water does not meet the generally accepted safety standards. In many developing countries, rapid
∗
Corresponding author.
E-mail address: thandiletanz@gmail.com (T.T. Gule).
https://doi.org/10.1016/j.sciaf.2023.e01744
2468-2276/© 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/)

2. T.T. Gule, B. Lemma and B.T. Hailu Scientific African 21 (2023) e01744
urbanization and population increase present significant challenges that have had a significant impact on the accessibility of
safe and clean water [1]. Water pollution from sewerage and agrochemicals is still a big issue in developing countries, where
90% of effluent is still discharged directly into waterways and lakes without any treatment [2,3]. Results from a study by
[4] showed that the concentrations of some heavy metal and physicochemical properties were slightly impaired as a result
of contamination from waste discharged from nearby beverage industries. In addition to feacal coliform concentrations in
waterbodies urban sprawl causes increased stormwater runoff. This is due to the fact that impervious cover prevents rain
from penetrating the soil; as a result, runoff is created and eventually gathers numerous pollutants and chemicals before
entering rivers, lakes, and streams within the basin [5]. Therefore, in many developing nations, water quality and the danger
of contracting waterborne infections are major public health problems. Hepatitis, typhoid fever, gastroenteritis, and other
less serious infections are among the illnesses and diseases that can be acquired from coming into contact with water that
has high fecal coliform counts [6]. Over a billion people, the majority of whom live in developing countries are estimated to
lack access to a dependable source of safe water [7]. Also, studies have revealed that consuming contaminated water results
in the deaths of over 5 million individuals, the majority of whom are also from underdeveloped nations [1].
The majority of African countries have emphasized ensuring access to adequate and high-quality water in order to
achieve Sustainable Development Goal 6. The goal 6 is aimed at ensuring availability and sustainable management of water
and sanitation for all. The Sustainable Development Goal 6 (SDG), adopted by the United Nations General Assembly for the
period 2015–2030, as a follow-up to the Millennium Development Goals (MDGs) for the period 2000–2015, include explicit
targets regarding the improvement of water quality worldwide and the increase in water-use efficiency and reduction in
water scarcity [8,9]. Safe drinking water can be defined as drinking water from an improved source which is located on the
premises, available when needed and free from contamination [10,11]. Ethiopia is still listed as one of the countries with
the least access to basic water services and sanitary facilities, as well as the highest incidence of water-borne diseases. For
instance only 6.3% of households have access to better sanitary facilities, while 66% of households have access to safe and
clean drinking water [12,13]. Ethiopia has 62.7% of its people relying on unimproved water sources [7]. The most common
and ubiquitous problem is the direct or indirect impairment of drinking water by industrial waste, other pollutants, or hu-
man or animal excrement. Acute and long-term impacts might result from microbial and chemical pollutants [14]. Research
by [15] also indicates that the presence of heavy metals such as lead, cadmium and chromium that come with effluents
from adjacent anthropogenic activities can result in significant contamination of surface water. Bacterial pollution is another
significant health risk associated with drinking contaminated water. This contamination may occur at the source, during
distribution, transportation, or owing to household handling, hygiene and sanitation practices [16]. Presence of bacteria no-
tably E. coli in water is a sign of pathogenic/faecal contamination [17]. There remains a pressing need for systematic water
quality monitoring strategies to assess drinking water safety and to track progress towards the Sustainable Development
Goals (SDG). Hence, determining the quality of drinking water is crucial to determining its safety.
According to Addis Ababa Water and Sewerage Authority (AAWSA), the city’s primary water utility organization, city res-
idents obtain domestic water from a variety of sources. These sources include bottled water, boreholes, tap connections, and
streams. Addis Ababa’s water resources are severely polluted as a result of rapid population increase, unchecked urbaniza-
tion, industrialization, and poor waste management methods, endangering human health and aquatic ecosystem function as
a whole. All types of waste released in the city are simply dumped into the rivers. Municipal solid and liquid wastes, toilet,
and open urination are the main sources of trash dumped into rivers and riverbanks. Additional sources of garbage include
construction sites, gas stations, garage operations, and densely populated areas. Addis Ababa is also host to more than 65%
of the country’s enterprises, and more than 90% of those businesses discharge untreated waste directly into the adjacent
Akaki River [18]. Each of them causes the spread of water-borne infections and lowers overall quality of life [19]. Therefore,
the Akaki river in particular has been a source of environmental contamination in the Addis Ababa waterways [20]. The
discharge of untreated pollutants to water can be a serious threat to access and quality of water [21]. Behavioral changes
are therefore required to ensure the attainment of water and sanitation goals by 2030.
Despite having sewer networks, Addis Ababa only has them in 7.5% of its built-up zones, which is a very tiny percentage.
Septic tanks are used in both residential and commercial spaces because only a portion of the city’s older neighborhoods
are connected to the municipal sewer system [22]. Most of the city’s roadside drains have a strong sewage odor, and most
waterways near the major industrial zones are heavily polluted. The city authority of Addis Ababa is currently making efforts
to manage and treat the river, including the recently completed massive river and riverbank development project [18]. But
nonetheless, these initiatives are very limited and do not fully address the city’s problem with water contamination. Water
treatment is usually a complex undertaking, often bound to fail if the objectives remain unclear, the raw water properties
not seriously examined and the treatment processes not adequately selected and applied. The removal or inactivation of
these pathogenic organisms is the primary target of any water treatment. Slow sand filtration and chlorination are thus the
two most widely used surface water treatment processes, which are sensitive and efficient enough to improve particularly
the microbiological water quality [23]. However with rapid urbanization, development and industrialization, sources of con-
tamination continue to diversify. Hence researchers are trying to overcome the resistance of the resistant pathogenic strains
from pharmaceuticals and agricultural input parameters by using nanotechnology [24]. However the surface water treatment
processes in the studied reservoirs still utilize the conventional slow sand filtration and chlorination processes.
The objective of this study was therefore to assess the water quality status of drinking water in Addis Ababa city, Ethiopia.
Although studies assessing the water quality have been done before, most of the them just focus on the water from the
lake and other points especially after treatment are ignored. However, contamination can happen at the water treatment
2

3. T.T. Gule, B. Lemma and B.T. Hailu Scientific African 21 (2023) e01744
Fig. 1. Map of the study area showing the water resources of Addis Ababa and the sampling sites circled in red.
plant due to unsuitable infrastructure as well as during the distribution into the taps where residents fetch their water
from. This study considered water samples from the lake, treatment plant as well as from the distribution taps, hence its
novelty. Water availability is not a matter of quantity alone; water quality can, in equal measure, determine how much is
available for particular uses. Degraded urban water resources have consequences for ecosystems, health, and water-reliant
livelihoods. This study is therefore important in ensuring water security in urban areas under escalating pressure of urban
expansion all around the globe. In an effort to ensure that Sustainable Development Goal 6 is met, this research will be
helpful in investigating access to adequate drinkable water and better sanitary facilities. This work contributes to target 6.1
of achieving universal and equitable access to safe and affordable water for all and target 6.3 of improving water quality by
reducing pollution, eliminating dumping release of hazardous chemicals and materials, halving the proportion of untreated
wastewater and sustainably increasing recycling and safe water reuse globally.
Methodology
Study area
This study was carried out in Addis Ababa city (Fig. 1) which is found in the central highlands of Ethiopia [25] and
covers an area of 540 km2. This city is divided into 10 administrative sub-cities. The boundaries of the watersheds for the
Awash and Abay rivers constitute the northern border of Addis Ababa, which is situated in the upper Awash Basin. Based
on the types of water resources and geographic locations, the city’s water supply sources can be divided into four groups.
The Gefersa Dam I, II, and III clusters, the Legedadi surface water subsystem, which consists of the Legedadi and Dire Dams,
the Akaki groundwater system, and the spring water sources at the base of Entoto Mountain constitute these clusters [26].
Field sampling procedure
Primary data on water quality was obtained from Legedadie and Gefersa Reservoirs. Parameters of interest included
those measured in the field, such as, electrical conductivity (EC), pH, temperature, and dissolved oxygen (DO). DO, water
temperature, pH, Oxygen, and conductivity we measured in situ using a Multimeter probe (model HQ40d, Germany) at all
sampling sites. Turbidity was estimated using a turbidity meter (T100 Oakaton, Singapore). This was done in four points of
each reservoir, raw water from the dam, clarified water, filtered water and treated water.
Moreover, water samples were taken from the Gefersa and Legedadie reservoirs in 2 liter plastic bottles under aseptic
conditions in order to prevent contamination of the water with other atmospheric bacteria. 12 water samples were collected
in each reservoir, amounting to a total of 24 water samples. The water source information, time, and date of collection were
written on the sample bottles’ caps, and they were then carried in a cooler box to the Addis Ababa University Limnology
3

4. T.T. Gule, B. Lemma and B.T. Hailu Scientific African 21 (2023) e01744
lab for analysis where they were stored in the fridge below 4 °C. The water samples were analyzed within three days of
collection from the field.
Microbiological analysis of water samples
The total coliform counts were determined using the conventional plate count method. Using distilled water, each water
sample was successively (10 folds) diluted. The diluted samples were added to standard plate count agar, MacConkey agar,
and Eosin Methylene Blue Agar and stirred with sterile pipette, to ensure that the inoculum was evenly distributed through-
out the agar. After being given time to set, the plates were put in an incubator for 24 h at 37 °C. A change in color to red
after the incubation time was regarded as proof of the presence of coliforms [27,28]. Deionized water served as the control
in each test batch. Following 48 h of incubation, the plates were examined for microbial growth, and the colonies that had
grown on the common plate count agar subsequently recorded. To measure faecal and total coliforms, the most probable
number approach was applied [29]. The established colonies on the various selective media were examined, sub-cultured
on new nutrient agar plates, and then incubated. Colonies were placed on an agar slant and kept at 44° for incubation. E.
coli was detected using the multiple tube fermentation method, where the presence of blue fluorescence signifies a positive
reaction for E. coli. After counting the generated colonies, the results were represented as CFU/ml.
Chemical analysis of water samples
The water samples were also evaluated in the laboratory for ammonia, nitrates, nitrites, total alkalinity, total phosphorus
(TP), total dissolved solids (TDS), total suspended solids (TSS), and soluble reactive Silica (SRSi). These parameters were
chosen because they are markers of the quality of drinking water, have been applied to relevant studies, and are available
in the secondary data from AAWSA. The samples used for nutrient assays were filtered using glass fiber filters (What man
GF/F) within 2 to 8 h, with the exception of total phosphorus (TP), which was quantified using an untreated water sample.
The total alkalinity was evaluated using the titration method. The total dissolved solids were determined by heating a pre-
filtered sample to a dry state and determining the weight of the dried residue per liter of sample. The water sample was
run through a pre-weighed filter to calculate TSS. Once there was no longer any weight change in the filter, the leftover
residue was dried in an oven at 103–105 °C. The TSS is represented by the filter’s weight [30]. The nitrate content of the
water samples was determined using the sodium salicylate technique [30,31]. Solvable reactive silica was measured using the
molybdosilicate technique [32,30]. Following persulfate digestion, total phosphorus was measured using a spectrophotometer
and an ascorbic acid method [33].
Data analysis
Data processing and analysis were performed using IBM SPSS software, version 23. The WHO and Ethiopian government
standard guidelines were compared to the mean values of the investigated physicochemical parameters and bacterial counts,
which were then presented as tables. Using the Kolmogorov-Smirnov test and the Levene test, respectively, the normality of
the data and homogeneity of variance for dependent variables within sampling sites were examined. The data was found to
be uniform and normally distributed. As a result, one-way ANOVA was carried out to establish differences in physicochemi-
cal sample means and to show significant differences in the measured parameters among the different sampling sites. Based
on the risk classification for thermotolerant coliforms, water samples were divided into various risk categories [34]. In every
instance, a p-value of 0.05 and a 95% confidence range were used to determine statistical significance. With the use of IBM
SPSS software, spearman "r" correlation tests were carried out to ascertain the effect of physicochemical variables on the
variation in microbial densities between the two reservoirs.
Water quality index
Using the arithmetic water quality index, the state of the water quality was assessed based on how appropriate the
water is for domestic consumption [35]. Hence, 15 parameters which include ammonia, SRP, total phosphorus, nitrate, silica,
nitrite, total dissolved solids, total alkalinity, pH, turbidity, conductivity, dissolved oxygen, temperature, total coliform, and
E. coli were taken into account in the current study to calculate the WQI. The water sample’s WQI was calculated in three
steps: (1) Each chemical characteristic was given a weight (wi) depending on how it was thought to affect primary health
and how important it was overall to the water’s quality for drinking, and the WHO limit; (2) Computing the unit weight
(Wi) of each parameter using the equation below:
Wi=k/si, where k = 1/(1/si)
3) A quality rating scale (qi) for each parameter was computed by dividing the concentration in each water sample by
its respective standard according to the guidelines laid down by WHO and then, the result was multiplied by 100 as shown
in the equation below: qi=(vi/si) ∗ 100, where vi is the parameter value taken on ground
Finally, for computing the WQI, the unit weight is multiplied by the quality rating scale (qi). The WQI values were
classified into different categories according to [36] (Table 1).
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5. T.T. Gule, B. Lemma and B.T. Hailu Scientific African 21 (2023) e01744
Table 1
Water quality scale for different in-
dices.
Water Quality WQI
Excellent 50
Good 50–100
Poor/Fair 100–200
Very Poor/Marginal 200–300
Unsuitable/Poor 300
Results and discussions
Bacteriological quality of the water samples
All sampling sites revealed total coliform bacteria, ranging from 3000 to 5000 CFU/100 mL with an average of 4000
CFU/100 mL. This shows that the water samples at these sites are of poor quality and can be harmful to people’s health. This
is in accordance with studies by [37–39], who found the waters of Nkolafamba, Cameroon, Portugal, and Nigeria respectively
to have a high bacterial load higher than the standard bacterial concentration level set by the World Health Organization
(WHO). A high total coliform count may not necessarily indicate the presence of pathogenic bacteria in the water, but
it does suggest improper chlorination, which suggests that the water is polluted with pathogenic bacteria. Treated water
from both reservoirs, and filtered water from Legedadie appeared free of contamination and the faecal coliform count was
zero which might be attributed to the water treatment process. Total coliform levels showed faecal and environmental
contaminations, which were most likely brought on by diffuse runoff pollution, poor catchment land management, human
activities and settlements, household sewage, livestock manure, and open defecation. The Escherichia coli count was between
20 and 3000 CFU/100 mL, with 1400 CFU/100 mL being the average. It is clear from the findings above that the bacterial
load is particularly concerning because both the raw water and the clarified water samples had very high coliform units for
E. coli. It can therefore be concluded that the water is not microbiologically safe for consumption without further treatment.
For filtered and treated water from both reservoirs, E. coli count was zero indicating that there is no evidence of recent
fecal contamination. Regarding the water sources, the highest value of total coliform counts and fecal coliforms counts were
recorded in the water samples collected directly from the reservoirs. The higher level of contamination is likely due to poor
protection and exposure to contamination by wastes from humans, animals, and the surrounding environment.
Physicochemical properties of the drinking water
Temperature varied between 17.6 °C to 19.6 °C. Microorganisms’ ability to grow and survive can be directly impacted
by temperature. It affects how effectively coagulants and disinfection chemicals function as well as the biological features
of the water [40]. In this research, the turbidity of all water samples was beyond the drinking water standards, with Leg-
edadie water samples recording very high turbidity values. According to research, turbidity of more than 1 NTU affects the
effectiveness of disinfection in water treatment plants [41]. Legedadie’s water samples had the greatest average turbidity
suggesting that it is dangerous to drink since the water is likely subjected to nearby polluting activities. However, all water
samples from Gefersa treatment plant and taps had an acceptable value of turbidity whilst raw water was above the stip-
ulated standard. High turbidity can be associated with excess amounts of suspended organic matter and microorganisms
such as bacteria. It could also be as a result of water coming into contact with surface runoffs [42]. Therefore, use of highly
turbid water can be a health risk since excessive turbidity stimulates growth of pathogenic bacteria and can protect them
from the effects of disinfectants [43,1]]. The pH range of water samples taken from the Legedadie reservoir was within WHO
and Ethiopian drinking water requirements, at 7.57 to 7.75. However for Gefersa, pH values of samples from clarified water,
filtered water and treated water were beyond the drinking water standards. This is an indication of higher alkalinity from
addition of lime and high doses of chlorine during treatment [44]. According to WHO water quality guidelines, electrical
conductivity below 400 μ/cm is deemed safe for human consumption, whereas electrical conductivity above 1500 μ/cm
may cause iron structures to corrode (WHO, 2017). Electrical conductivity ranged from 102 to 224 μ/cm which is within
the acceptable standards. This is in accordance with the study by [39] which reported that EC levels were within the max-
imal permissible limit of the WHO and in variance with the study by [45], which reported EC levels that exceeded WHO
and NSDWQ standard values. The dissolution of CO2 in water leads to alkalinity in natural waterways. Consequently cre-
ated carbonates and bicarbonates are dissociated to produce hydroxyl ions. Total alkalinity in the samples under analysis
ranged from 15 to 120 mg/L, which is desirable for household uses. The alkalinity value is essential to evaluate the dose of
disinfection in water treatment practices and defluoridation processes [41].
The water samples’ nitrate amounts ranged between 0.315 and 0.388 mg/L, which is substantially lower than the 50 mg/l
maximum suggested for drinking water [10]. The mean values of nitrite and ammonia were lower in the treated water
samples compared to values in other samples, which could indicate that at least the physical water purification system
was properly working [13]. This is also less than the maximum values of 10.8 mg/l and 12.9 mg/l from other Ethiopian
5

6. T.T. Gule, B. Lemma and B.T. Hailu Scientific African 21 (2023) e01744
Table 2
Physicochemical results for water samples of Legedadie and Gefersa Reservoirs and the WHO and Ethiopian government water quality stan-
dards.
Parameters Units Raw water
Clarified
water Filtered water Treated water
WHO
standard[48]
Ethiopian
standard [49]
Ammonia mg/l
Gefersa 0.085 0.036 0.044 0.019 1.5 1.5
Legedadie 0.223 0.048 0.042 0.037
Nitrate mg/l
Gefersa 0.382 0.345 0.388 0.338 50 50
Legedadie 0.370 0.315 0.388 0.365
Nitrite mg/l
Gefersa 0.157 0.199 0.247 0.028 3 3
Legedadie 0.133 0.033 0.031 0.026
SRP mg/l
Gefersa 3.754 1.342 3.067 2.198 120 –
Legedadie 0.191 0.217 0.226 0.203
Silica mg/l
Gefersa 111.77 131.77 132.58 72.2 25 –
Legedadie 15.1 13.6 14.15 8.85
TSS mg/l
Gerfesa 0.031 0.0091 0.005 0.002 50 50
Legedadie 0.0067 0.0073 0.0064 0.0068
Total
alkalinity
mg/l
Gefersa 15 50 45 120 500 200
Legedadie 45 45 45 60
TP mg/l
Gefersa 5.007 4.001 5.725 5.071 0.5 0.5
Legedadie 0.502 0.597 0.602 0.575
pH
Gefersa 7.97 8.53 8.93 9.06 6.5–8 6.5–8.5
Legedadie 7.57 7.75 7.61 7.73
Electrical
conductivity
μS/cm
Gefersa 102.6 221.7 223 224.7 400 1000
Legedadie 103.2 104.1 107.6 104.4
Turbidity NTU
Gefersa 16.68 2.79 2.68 3.17 5 5
Legedadie 630 578 456 330
Temperature °C
Gefersa 19.5 17.77 17.63 18.53 12–25 –
Legedadie 18.87 18.87 18.3 19.1
DO mg/l
Gefersa 6.35 3.37 5.15 6.12 5 5
Legedadie 5.46 5.67 6.1 5.47
source waters of Ziway town [46] and Bahir Dar town [47], respectively. The total phosphorus concentrations were above
the 0.5 mg/L stipulated standards by WHO and Ethiopian government, ranging from 0.502 to 5.7 mg/L. Table 2 shows the
results of the physicochemical parameters analysis.
Comparison of physicochemical parameters within the reservoirs
One way ANOVA test results indicated that there was no statistical difference between the two reservoirs for ammonia,
nitrate concentration, TSS, total alkalinity, DO and temperature. However, significant differences were noted for SRP, total
phosphorus, silica, nitrite, pH, turbidity and conductivity (Table 3).
Risk levels of drinking water with reference to bacteriological contamination
The risk level of the water was then determined according to [48] risk levels categories in terms of E. coli as shown
below:
Risk level In conformity Low risk Intermediate risk High risk Very high risk
No. of colonies 0 1–10 10–100 100–1000 1000
In the study, filtered and treated water samples were free of E. coli hence in conformity with safe water requirements.
Clarified water from Gefersa reservoir was in intermediate risk category whilst clarified water from Legedadie fell in the
high risk category. Raw water samples were found to be in the very high risk category as shown in Table 4.
6

7. T.T. Gule, B. Lemma and B.T. Hailu Scientific African 21 (2023) e01744
Table 3
One way Anova for the means of physiochemi-
cal parameters within the different reservoirs.
Parameters F p-value
Ammonia 0.768433 0.414417
SRP 20.73448 0.003877∗
TP 151.0466 1.77E-05∗
Nitrate 0.029969 0.868252
Silica 48.71709 0.00043∗
Nitrite 19.54006 0.004469∗
TSS 0.57268 0.477849
Total Alkalinity 0.150769 0.711205
pH 14.79167 0.008499∗
Turbidity 53.87511 0.000327∗
Conductivity 8.544427 0.026525∗
DO 0.379413 0.560543
Temperature 0.857214 0.39024
Table 4
Risk levels of drinking water with reference to E. coli contamination.
Categories Gefersa Risk category Legedadie Risk category
Raw 2330 Very high risk 3000 Very high risk
Clarified 20 Intermediate risk 250 High risk
Filtered 0 In conformity 0 In conformity
Treated 0 In conformity 0 In conformity
Table 5
Correlations between physicochemical parameters and bacterial density.
Microbiological variables
Physicochemical variables total coliforms faecal coliforms E. coli
Ammonia 0.786∗
0.708∗
0.748∗
SRP −0.429 −0.024 −0.19
Total phosphorus −0.571 −0.22 −0.419
Nitrate 0.108 0 −0.166
Silica −0.214 0.342 0.038
Nitrite −0.405 0.146 −0.051
Total soluble solids 0.357 0.586 0.621
Total Alkalinity 0.685 −0.585 −0.568
pH −0.714∗
−0.22 −0.381
Turbidity 0.738∗
0.22 0.495
Conductivity −0.69 −0.634 −0.786∗
Dissolved oxygen −0.048 −0.22 0.013
Temperature 0.180 0.233 0.472
Total coliform 1 0.634 0.736∗
E. coli 0.736∗
0.936∗∗
1
faecal coliform 0.634 1 0.936∗∗
∗
Correlation is significant at 0.05 level,.
∗∗
Correlation is significant at 0.01 level.
Assessment of the impact of physicochemical parameters on the variation of microbial densities
The Spearman’s r correlation test was used to correlate the densities of the isolated bacteria with physicochemical
characteristics. It turns out that parameters like ammonia and turbidity and the densities of total coliforms have very sig-
nificant (p 0.05) positive correlations. On the other side, there were notable negative relationships between pH and total
coliform count. The same observation was obtained between the density of E. coli and the electrical conductivity. Significant
(p0.05) and positive correlations were recorded on the one hand between fecal coliforms, E. coli content and ammonia
concentration (Table 5).
Water quality index results
The estimated WQI values in this investigation fell within the unsuitable/poor water category (Table 1). This is in cor-
relation to studies by [4] and [50] who also found that anthropogenic land uses such as industries and agriculture lower
the water quality index of the Ajali River in Enugu, Nigeria and Lake Tinishu Abaya Water, Ethiopia respectively. Total phos-
phorus, turbidity, dissolved oxygen, E. coli, silica, pH, and ammonia factors had a greater impact on the weighted arithmetic
7

8. T.T. Gule, B. Lemma and B.T. Hailu Scientific African 21 (2023) e01744
Table 6
Calculated water quality index values.
Parameters Units si 1/si Unit weight (wi) Water quality ratings (qi) Water quality index (WQI)
Gefersa Legedadie Gefersa Legedadie
Ammonia mg/l 1.5 0.67 0.182 1.267 2.467 0.23 0.448
SRP mg/l 120 0.008 0.002 1.832 0.169 0.004 0.0004
TP mg/l 0.5 2.00 0.545 1014.2 115 553.059 62.711
Nitrate mg/l 50 0.02 0.005 0.676 0.73 0.004 0.004
Silica mg/l 25 0.04 0.011 288.8 35.4 3.15 0.386
Nitrite mg/l 3 0.33 0.091 9.333 0.867 0.848 0.079
TSS mg/l 50 0.02 0.005 0.004 0.014 2.18E-05 7.42E-05
Total Alkalinity mg/l 500 0.002 0.001 24 12 0.013 0.007
pH 8 0.125 0.034 113.25 96.625 3.860 3.293
Turbidity NTU 5 0.2 0.055 63 6600 3.457 359.908
Conductivity μS/cm 400 0.003 0.001 56.168 26.1 0.038 0.018
DO mg/l 5 0.20 0.055 122.4 109.4 6.675 5.966
Temperature °C 25 0.04 0.011 74.12 76.4 0.808 0.833
Total coliform CFU 10,000 0 0 30 31.5 0.001 0.001
E. coli CFU 100 0.01 0.003 0 0 0.0009 0.0009
572.148 433.655
water quality index outcomes than other quality measures (Table 6). Thus, the analysis showed that both lakes’ surface
water requires some sort of treatment before use and that it is crucial to keep it free from the dangers of contamination.
Where, si=Standard value of i parameter [51]
k = 1/(1/si) qi=(vi/si) ∗ 100 vi= Parameter value taken on ground
Conclusions and recommendations
This study aimed to evaluate the water quality status of Addis Ababa drinking water by assessing the physicochemical
and microbiological water quality parameters. Standard methods from American Public Health Association were followed.
Water quality parameters such as turbidity, total phosphorus, dissolved oxygen and pH were found to be above the recom-
mended limits by WHO and Ethiopian standards. Other parameters such as nitrate, nitrite, ammonia, total soluble solids,
total alkalinity, pH, electrical conductivity and temperature were discovered to be within the WHO permitted range. The
samples were found to contain a high bacterial load, and consequently the WQI indicated that the water falls into the poor/
unsuitable category. From the findings of this research we can conclude that the supply networks and the sources both
contribute to the decline in water quality. Effective sewage disposal, drainage, and water treatment with improved nano
technologies, UV radiation or ozone are essential for supplying the people of Addis Ababa with safe drinking water. Public
health officials should frequently collect water samples from distribution taps as well so to assess the quality of the water
and educate the general public about water safety.
Total coliforms were found at every sampling location, which is a sign that Addis Ababa’s microbiological drinking water
quality does not meet national and International requirements. This work greatly contributes to the African Union Agenda
2063 because improving the water quality, public health is promoted through a reduction in waterborne diseases. Water
quality analysis can also inform policymakers and provide data for decision making related to infrastructure development
and environmental management. Additionally, improving water quality in urban areas is an important pillar for achiev-
ing sustainable development in Africa and tracking progress towards achievement of sustainable goal 6 designed to ensure
access to safe drinking water and sanitation to all by the year 2030. With the high levels of coliform bacteria present,
drinking water contamination in Addis Ababa city is clearly a threat to the general public’s health. The local administration,
health, and water departments should act right once to stop waste disposal and human activity around the water source
and reservoirs. They should also regularly inspect and maintain the distribution lines. Also, improving public awareness of
environmental sanitation and sanitary behaviors is crucial for lowering the burdens associated with water-related illnesses
on the community.
The topic of water quality is wide and encompasses many variables. This study was limited in that it concentrated on a
few particular parameters that are important in determining the quality of drinking water according to WHO guidelines. It
is recommended that further research should consider additional water quality parameters such as heavy metals parameters
like mercury, fluoride, calcium and sulfate and those in the area of pesticides, herbicides and related agricultural inputs. Also
measuring total metal content by using conventional analytical techniques may not necessarily provide a true indication of
the actual toxicity of these metals due to the speciation of heavy metal ions which ultimately determines their bioavailability
and toxicity [24,52]. We therefore recommend the use of electroanalytical techniques for evaluating and estimating the water
quality and determining the heavy metals contamination in the surface water. Studies such as those by [52] have used such
methods to assess the degree of pollution and implicitly the surface water quality, depending on the variation of climatic
parameters, and the impact of anthropogenic and industrial activity in the studied area. Its use is advantageous due to high
sensitivity, reduction in solvent and sample consumption, high-speed analysis, low operating cost and high scan rate in all
8

9. T.T. Gule, B. Lemma and B.T. Hailu Scientific African 21 (2023) e01744
cases [53,24]. Turbid and colored solutions, which are a problem with other methods, can also be easily analyzed with this
method and only small volumes of samples are necessary. The short analysis time also makes this technique very attractive
for routine determination of the analytes in different samples [53].
Data availability statement
All relevant data has been included in the manuscript, and if more data is required it will be made available on request.
Funding
This research was funded by the World Bank Group through the African centre of Excellence for Water Management,
Addis Ababa University, and Grant No. GSR/0140/13.
Declaration of Competing Interest
The authors of this paper declare that there is no conflict of interest and that the funding body had no influence on the
results and views presented in this paper.
CRediT authorship contribution statement
Thandile T. Gule: Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Validation, Visualization,
Writing – original draft, Writing – review editing. Brook Lemma: Conceptualization, Resources, Supervision, Writing –
review editing. Binyam Tesfaw Hailu: Conceptualization, Supervision, Writing – review editing.
Acknowledgments
This project was funded by World Bank under the Africa Center of Excellence for Water Management (ACEWM). We
acknowledge the Addis Ababa Water and Sewerage Authority (AAWSA) for their assistance in data collection.
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