REVISTA INGENIO
Located in Quito
Determinación del Índice de Calidad del Agua para Evaluar la
Calidad del Agua del Río Monjas Ubicado en Quito
Suly Rodríguez1 1 Universidad Central del Ecuador UCE, Quito-Ecuador,
Oldrin Bonilla1 1 Universidad Central del Ecuador UCE, Quito-Ecuador,
1 1 Universidad Central del Ecuador UCE, Quito-Ecuador,
Gissella Duque1 1 Universidad Central del Ecuador UCE, Quito-Ecuador,
José Lara1 1 Universidad Central del Ecuador UCE, Quito-Ecuador,
Stalyn Pilaguano1 1 Universidad Central del Ecuador UCE, Quito-Ecuador,
Montserrat Rodríguez2 2 Universidad de Madrid UAM, Madrid-España,
Darwin Caina1 1 Universidad Central del Ecuador UCE, Quito-Ecuador,
https://doi.org/10.29166/ingenio.v7i2.6737 pISSN 2588-0829
2024 Universidad Central del Ecuador eISSN 2697-3243
CC BY-NC 4.0 —Licencia Creative Commons Reconocimiento-NoComercial 4.0 Internacional vicedecanat.ng@uce.edu.ec
, (), -, . -
The study of water quality is important over time because it is an essential element for human beings, it
has been vital for their survival, territorial expansion, and socioeconomic development. The water of the
Monjas river present contamination issues, mainly due to human activities such as agriculture, animal
husbandry, and gray water discharges that alter their chemical, biological, and physical properties. The
purpose of this research is to evaluate whether the water conditions are suitable for agricultural use,
applying the Water Quality Index (WQI) methodology, which requires a study in the laboratory for fecal
coliforms, dissolved oxygen, pH, biological demand for oxygen, nitrates, phosphates, dissolved solids,
turbidity, and temperature. Samples were taken at six sampling points along the riverbed. Results were
de Ministerio de Ambiente), and FAO (The Food and Agriculture Organization of the United Nations)
environmental regulations. Higher values were obtained for fecal coliforms, and biochemical oxygen
demand that exceeded the maximum permissible limits with respect to the rest of the parameters exam-
ined. In this study, the WQI ranged from 26 to 50, classifying the water quality of the Monjas river as
unsuitable. It implies that it is not appropriate for agricultural use due to the contamination that it could
cause to the crops. The main reasons for this could rely on the presence of fecal matter of human, and
animal origin, fertilizers, pesticides, and household waste.
El estudio de la calidad del agua es importante a lo largo del tiempo debido a que es un elemento indis-
pensable para el ser humano, pues ha sido vital para su supervivencia, expansión territorial y desarrollo
socioeconómico. El agua del río Monjas presentan problemas de contaminación principalmente por
actividades humanas como la agricultura, la crianza de animales y las descargas de aguas grises que
alteran sus propiedades químicas, biológicas y físicas. El propósito de esta investigación es evaluar si
las condiciones del agua son óptimas para uso agrícola, aplicando la metodología del Índice de Calidad
de Agua (ICA) que requiere un estudio de laboratorio de coliformes fecales, oxígeno disuelto, pH, de-
manda biológica de oxígeno, nitratos, fosfatos, sólidos disueltos, turbidez y temperatura. Se tomaron
muestras en seis puntos de muestreo a lo largo del cauce cuyos resultados fueron comparados con los
resultados con la normativa ambiental TULSMA y la FAO. Se obtuvieron valores más altos para los
coliformes fecales y la demanda bioquímica de oxígeno, que superaron los límites máximos permisibles
uso agrícola por la contaminación que podría ocasionar en los cultivos. Los motivos principales de este
resultado podrían explicarse por la presencia de materia fecal de origen humano y animal, fertilizantes,
plaguicidas y residuos domiciliarios.
article history
Received: 18/09/2023
Received aer review: 02/11/2023
Accepted: 10/04/2024
Published: 15/06/2024
key words
M Water Quality Index, FAO, contami-
nation, Monjas river, water
palabras clave
Sistema meteorológico, Asistente del ho-
gar, Raspberry Pi, IoT.
45
Determination of the WQI Index to Evaluate the Water Quality of the Monjas River located in Quito
From what was mentioned above, there is not any
project in Quito city. It has an area of 4,235.2 km2,
national population. It is estimated that by 2022,
the population will grow to 2.8 million people, and
important basin in the city is the Guayllabamba
basin, formed by the Machángara, Monjas, and San
within the Distrito Metropolitano de Quito (DMQ).
contamination, being Monjas river one of the
water supply for the city. According to a study by
Campaña et al. [8], it has been determined that the
critical contamination the rivers in Quito has caused
that the water is not suitable for agricultural use,
In the last years, there has been a population
growth in the sectors of Pomasqui and San Antonio
de Pichincha. This has caused an increase in
waste generated that is thrown into streams and
state streams such as rivers. It turns them into an
infectious focus, generating major environmental
and health problems. Poor territorial planning has
the risk of landslides due to both the instability of
the soil and the growth of the Monjas river caused
by the rains. These problems have slowed down the
economic development in the neighborhoods in that
sector [8].
1.1 Locations of study
This study took place in the Monjas River located
in the city of Quito, during the month of December
2021. It covers an approximate area of 17.61
hectares, with an altitude of 2,342 meters [8]. It
empties from the Guayllabamba river and runs
throughout the city of Quito crossing sectors such
as San Antonio, Pomasqui, Cotocollao, Carcelén,
Cochabamba, La Pampa, and El Condado [15], as
depicted in Figura 1.
1. INTRODUCTION
The water is strongly related to the development
their settlements near areas with abundant water,
since it was the key to their survival, territorial
expansion, and socioeconomic development [1].
Moreover, since ancient times, it has been relevant
to acquire knowledge on monitoring, and control
of water quality for agricultural use, and human
consumption. To evaluate the status of water, there
the parameters that are analyzed and how they are
calculated [2].
Water resources both in Ecuador and around the
world satisfy several basic needs for all human
beings. This is the reason because water is exposed
to strict control measures. Moreover, according to
comes from hydraulic sources. Therefore, adequate,
and sustainable water management is of the utmost
importance.
The population growth together with the dizzying
pace of social, technological, and industrial
advances, have generated a critical need for
freshwater for various activities worldwide [1].
Therefore, the design of methods and mechanisms
to evaluate water quality is necessary nowadays.
The Water Quality Index (WQI) is one of these
tools to evaluate it. It is a tool for assessing the state
of water resources. R. K. Horton [4] was one of
into a single value some physical, chemical, and
biological factors.
The WQI is an elementary instrument in the
development of public policies, production activities,
and the evaluation of water resources. Fernández
and Solano [5] state that the WQI is represented by
values. In Ecuador, the use of the WQI method has
the Sangay National Park in 2013 [6], and other for
the determination and evaluation of the quality of
the water in the Chibunga river in 2014 [7].
46
Rodríguez S., et al.
2. METHODS
taking surface water samples. They are San José de
Morán (1), and Pomasquí (2), located in the parishes
of Calderón. Quishuar (3), and La Pampa(4), located
in the parishes of Pomasqui. Chaguar (5) and, La
Providencia (6), located in the parishes of San
Antonio. Table 1 shows the Universal Transverse
Mercator (UTM) coordinates for the selected places
or sampling points.
Table 1.
UTM coordinates of sampling locations
At point 1, the passage of a stream whose purpose
into the Monjas river, carrying with it residues from
agricultural activity. A large amount of organic
fertilizer was witnessed in the vicinity of the river,
belonging to the owners of crops, but also crops on
the banks of the hydrographic basin. In addition, the
inhabitants of the sector expressed concern since the
At point 2, there are many green areas contaminated
by plastic waste such as bags and bottles. In its
surroundings there are tourist sites, mainly the
“Granja del Tío Mario” whose crops have an
irrigation system that depends directly on the
Monjas river. In addition, at this point the breeding
of horses, goats, sheep, and cattle predominates, so
large tracts of land and the banks of the river are
heavily contaminated by excrement.
At point 3, the river is similarly contaminated by
plastic waste, tires, and glass. In addition, there
Figure 1.
Map of strategic points for water samples collection
47
Determination of the WQI Index to Evaluate the Water Quality of the Monjas River located in Quito
are agricultural and livestock activities in its
surroundings. The same ones that generate organic
waste such as animal excrements.
At point 4, there is a large amount of domestic waste,
mainly organic, such as fruit peels, vegetables, and
animal excrement, which generate a fetid odor that
causes discomfort among its residents.
At point 5, it was evidenced that part of its waters is
used for crops, Moreover, on the banks of the river
domestic, waste from anthropogenic activities was
found.
the generation of waste and contamination such as
Textile Vicuña, the Ruins of Catequilla, housing
complexes and several quarries of stone material
were found. At this point, the river separates a rural
area from an urban one, where land for agriculture,
nurseries and residences can be found. On the other
hand, on the riverbank, a large amount of construction
debris and plastic waste was visualized. In addition,
its smell resembles decomposing sludge. However,
even though it corresponds to a dry territory, some
native vegetation grows around it.
In this research, the water quality of the Monjas
river has been evaluated through the application
of the WQI index and the analysis of the following
parameters: fecal coliforms, dissolved oxygen (DO),
5),
nitrates, phosphates, dissolved solids, turbidity and
change of temperature. This evaluation will allow to
compare the results of each parameter with the FAO
Discharge of the Ministry of the Environment of
Ecuador in order to know the current state of the
river and to determine if its waters are suitable for
agriculture and irrigation of crops.
To calculate the WQI, the methodology proposed
by Brown (1970) is used, which is based on a
weights assigned to each evaluated parameter to
evaluate the water; This function is expressed
mathematically as follows:
Which:
Subi= variable subscript i,
Wi= subscript weighted weight i.
To determine the Subi values of each parameter, the
curves developed by NSF International Consumer
and by Fernández and Solano [5] were used. While
to classify the WQI, the ranges shown in Tables 2,
and Table 3 were used. The Wi values are standard
values and were taking from [32].
Table 2.
Relative weights for each WQI parameter
Table 3.
Qualitative classication “WQI
The methods used to analyze the water from the
Monjas river are detailed below:
2.1 Determination of nitrates by colorimetry
and cadmium reduction (APHA 4500 -E)
The APHA 4500 -E is an analytical chemical
method that uses cadmium granules processed
with copper sulfate and wrapped in a glass column
to reduce nitrate (NO3-) to nitrite (NO2-) (National
Environmental Methods Index, n.d.). The materials
used in this procedure were: a reduction column
with enough Cu-Cd granules to reach 18.5 cm in
length, and a colorimetric equipment (543 nm) or a
48
Rodríguez S., et al.
The main instruments required are a reduction column
and a colorimetric equipment, spectrophotometer or
The procedure begins with the treatment of the
sample, adjusting the pH to a value between 7 and
phosphoric acid and 10 g of sulfonamide) is added,
which colors a false red to the analyte, and 15
minutes after reduction, the absorbance is measured
at 543 nm using distilled water as blank [21].
Standard nitrate reagents are prepared, diluting
volumes of 0.5; 1.0; 2.0; 5.0, and 100 milliliters
100 ml. Finally, the calculation of the nitrate
concentration is obtained by means of a calibration
curve, by plotting the absorbance of the standards
as a function of the nitrate concentration (National
Environmental Methods Index, n.d.). Sample
standard curve. It is important to consider that there
are certain interferences in the result of the method,
of samples, oil and grease that coats the column,
among others [11].
In this method, ammonium molybdate together with
antimony and potassium tartrate react in an acid
medium with orthophosphate to form compounds
that are reduced to molybdenum blue, intensely
colored by ascorbic acid [27].
The materials used in this procedure were: acid-
washed glassware and colorimetric equipment
photometer (880 nm) [11].
The procedure begins with a treatment that consists
of pipetting 50 ml into a sterilized test tube with 0.05
ml of phenolphthalein indicator. If it turns red, a 5N
sulfuric acid solution is added dropwise to remove
the color [27]. After treatment, 8 ml of a combination
of reagents is added (50 ml of 5N sulfuric acid, 5
ml of 0.009M potassium antimony tartrate solution,
15 ml of 0.03M ammonium molybdate tetrahydrate
solution and 30 ml of 0.1M acid solution) and mix
thoroughly (American Public Health Association,
n.d.). It is necessary to correct the turbidity of
the sample in the case of highly colored water.
In the measurement and calculation process, the
individual calibration curves were prepared from a
series of standards. Next, the absorbance is plotted
as a function of the phosphorus concentration,
obtaining a linear graph (American Public Health
Association, n.d.). At least one phosphorus standard
is tested with each set of samples. Finally, the
amount of phosphates is acquired by stoichiometry
after calculating phosphorus, as shown in equation
(2).
2.3 Determination of total dissolved solids
2540 - C)
Wilder and Costa [29] indicated that to obtain real
data for the TDS parameter, the MEAGP - 37 APHA
2540 C method is used, which allows determining
values with a minimum error, thus avoiding human
errors when handling equipment and materials or
imprecision. of these. The materials to determine
In this methodology, it begins by heating the
residue-free evaporation dish at 180 °C ± 2 °C for 1
hour in an oven and then inserting it into a desiccator
until further use. With an analytical balance, the
weight of the evaporation plate or better known as a
crucible is recorded. Subsequently, the appropriate
sample volume was chosen with the purpose of
obtaining the amount of dry residue that is in the
range between 2.5 and 200 mg.
Using a magnetic stirrer, the sample was
2O
and continue suction for 3 minutes immediately
a respective evaporation plate that was previously
measured by its weight on the analytical balance
49
Determination of the WQI Index to Evaluate the Water Quality of the Monjas River located in Quito
and by means of the steam bath, evaporate all the
liquid. Dry in the oven at 180 ± 2< °C for one hour.
Finally, place in a desiccator until reaching room
temperature and weigh the dried sample for further
analysis [29]. Once the weight of the dry sample is
obtained, the TDS is calculated with the following
equation (3):
The MEAG -53 APHA 2130 – A method is carried
out by comparing the intensity of the light scattered
that scattered by a reference standard solution under
the same conditions [20]. This methodology is
based on the fact that if the sample presents a higher
intensity of scattered light, it has high turbidity
values.
Within the methodology, the authors Zhihui et al.
[31] indicate that turbidity be determined in situ
to avoid any type of interference and, if this is not
possible, samples should be stored for no more than
24 hours in a dark environment.
To start with the turbidity measurement, the
turbidimeter was calibrated following the
manufacturer’s or laboratory personnel’s
instructions. In this methodology there are two
types of measurements: To measure turbidity of
less than 40 NTU (Nephelometric Turbidity Unit),
so that the air bubbles disappear, once these bubbles
are no longer observed, the water is added to the
turbidimeter tube. Then immerse the tube in an
ultrasonic bath for approximately 1 to 2 seconds to
completely remove bubbles. Finally, the turbidity
value measured by the apparatus is observed. To
measure a turbidity of less than 40 NTU, the sample
is diluted with distilled water until it reaches a value
of 30 or 40 NTU and the turbidity of the original
sample is calculated based on the dilution factor,
added to a volume of sample and this manifested a
turbidity of 30 NTU, then the original sample was
180 NTU [20].
MEAG-15 (APHA 4500 B)
The MEAG-15 APHA 4500 method is based on
the process of determining the activity of hydrogen
ions in an aqueous solution by measuring with
a potentiometer that uses a reference electrode
together with a standard hydrogen electrode. The
pH of the sample is determined by extrapolation
[11].
In view of the problem of their use and the potential
for contamination of the hydrogen electrode,
electrodes made of glass are often used. The pH
presents a strong linear relationship with the
electromotive force (emf) originated in the electrode
system, this linear relationship can be described by
drawing the mean of the electromotive force against
values [31].
First, the potentiometric equipment is calibrated
following the manufacturer’s instructions, removing
the electrodes from the storage solution. Establish the
equilibrium between the two electrodes by stirring
the sample in order to ensure the homogeneity of
the solution; Stir slowly to decrease carbon dioxide
samples or those with high ionic strength, condition
the electrodes after the cleaning process, introducing
them into the sample for 1 min. Dry, immerse in a
fresh portion, and read the pH. When working with
to equilibrate the electrodes by immersing between
three or four sample portions [31].
08 (APHA 5210 - D)
The MEAG-08 APHA 5210 D method is based
on respirometric procedures, which directly
microorganisms existing in an environment rich in
air or oxygen found in a closed container at constant
temperature and agitation (American Public Health
Association, n.d.).
According to Guzman and Perea [17], respirometry
measures oxygen consumption continuously
50
Rodríguez S., et al.
over time. They are useful for evaluating the
amounts of toxic compounds on the oxygen uptake
reaction of a test wastewater or organic chemical.
To start the measurement, the equipment is calibrated
following the manufacturer’s instructions. Next, the
sample is prepared, which goes through a process
of homogenization, pH adjustment, dechlorination
(total elimination of chlorine). If the sample
contains toxic substances, a treatment will have to
be carried out to eliminate said substances and make
an adjustment. of temperature, it should be at 1°C.
Then, a solution of the sample is carried out with
distilled water, adding adequate quantity that brings
prepared sample goes through nutrient and mineral
addition processes for a subsequent inhibition of
20°C or another suitable temperature [13].
2.7 Determination of fecal coliforms 9215
enzyme substrate
The MEAG-60 APHA 9215 E method is based
on the use of bacteria and their respective color
fermentation of lactose, which produces and forms
in the degree of generation and maintenance of
metallic luminosity among coliform strains. On the
other hand, the dissimilarity in the choice of the
correct indicator is not considered critical to change
its importance for public health [30].
size: The sample selection criteria will be governed
by the number of bacteria needed, the sample size
will be limited only by the level of proliferation
of other contaminants of non-coliform origin and
turbidity in Water. For regulatory purposes, 100 ml
or undiluted, depending on the desired bacterial
density. “When less than 10 mL of sample (diluted
10 ml of sterile dilution water to the funnel prior to
dilution. This increase in the volume of water helps
the uniform dispersion of the bacterial suspension
sample on the previously sterilized high porosity
plate. Carefully place the necessary funnel over
in the corresponding place. Under partial vacuum
proceed to wash the inside of the funnel with
approximately 30 ml, thus avoiding losses and
alterations. Alternatively, rinse the funnel with
a stream of sterile dilution water from a squeeze
bottle. Contamination produced by entrainment
is eliminated thanks to rinsing. At the end of the
vacuum, and the funnel is unlocked and removed
with sterile tongs and placed in the middle, it is
done with rotating movements and circular so that
no trace of air remains inside [30].
or other optical device, preferably with a
optimum display of brightness. The typical set of
coliform bacteria is a deep pink color that has a
metallic-like surface sheen. Count both typical and
atypical coliform colonies. Occasionally, typical
bright colonies may be produced by non-coliform
organisms and atypical colonies (deep pink
check all typical and atypical coliform colony types.
Depending on the need and the type of sample,
laboratories can incorporate stricter measures that
allow the evaluation of water quality [30].
Finally, the following equation (4) is applied to
51
Determination of the WQI Index to Evaluate the Water Quality of the Monjas River located in Quito
to the WQI value. This same process is carried out
for the six sampling points.
The following example details the WQI
•
for example, fecal coliforms (FC), which has a
value of W
=
shown in Table 2.
•
For the calculation of the value of Sub
i
, there are
two possible resolution cases:
Case 1: In the biochemical oxygen demand
process (BOD5), the Sub3
from Figure 3. First, the value of the measure
-
ment of the parameter is located on the “x” axis
of the graph., BOD5=28ppm, it is interpolated
with the “y” axis obtaining the value of the sub-
script of the parameter, Sub3=5.46.
Case 2: The value of Subi
Figure 4. Regarding fecal coliforms (FC), there
-
terpolation is not carried out, since it meets the
conditions proposed by the author that are locat-
ed in the notes section at the bottom of the im-
age, which indicate that for a FC value greater
than 105, the Subi result corresponds to 3.
•
Then, the following multiplication is performed:
W1*Sub1(0.15*3), whose result was 0.45.
• The process is repeated for the remaining 8 wa-
ter quality parameters from point 1.
•
Once the products (W1*Sub1) for the nine pa-
-
ly obtaining the sum of all the values resulting
from said operation, as indicated below:
Finally, the value obtained from the WQI is
proposed in Table 3. In this case, point 1 located in
Calderón has unsuitable water quality.
2.8 Determination of dissolved oxygen by
using a membrane electrode (4500-O-G)
According to laboratory analysis, for the respective
continuous analysis of Dissolved Oxygen (DO),
membrane electrodes are very useful, which are
used in cultures of various bacteria, including the
BOD5 test and are excellent for evaluating and
determine water with polluting loads, as well as
are used, which must be sensitive to the type of
oxygen, either galvanic or polarographic, which are
made up of two solid metal electrodes. This type of
permeability of the membrane [11].
The procedure begins with the respective calibration
chloride, making sure that the marker indicates
zero in DO. For the measurement of DO, the
water samples are placed in beakers and, by using
the membrane electrodes, the level of Dissolved
Oxygen that the problem water has is determined,
providing the appropriate amount of sample on the
surface of the membrane, so as not to exceed the
margin of error [11].
For the calculation of the WQI index, Equation
1 is required, corresponding to the methodology
described by Sánchez (2018). The Wi components
that correspond to the weight units for each water
in Table 2.
The Subi parameter is obtained from the standard
graphs described in Figures 2. Interpolating the
abscissa axis that corresponds to the concentration
of the parameter, with the ordinate axis that indicates
the value.
Subsequently, the product Wi* Subi is obtained for
fecal coliforms, pH, BOD5, nitrates, phosphates,
temperature, turbidity, total dissolved solids, and
nine parameters analyzed, whose result corresponds
52
Rodríguez S., et al.
Figure 2.
Evaluation of water quality according
to the parameters of WQI
Figure 3.
Evaluation of for BOD5 parameter
according to WQI
53
Determination of the WQI Index to Evaluate the Water Quality of the Monjas River located in Quito
Figure 4.
Evaluation of for the parameter Fecal
Coliforms according to WQI
3. RESULTS
In this research project, an analysis of the quality
of the water samples from the Monjas river was
carried out. The laboratory parameters measured in
the water samples taken from the 6 sampling points
are presented in Table 4.
Within the fecal coliforms found in the collected
samples, the mean was 1.10E+06 ± DE 1.49E+06
NMP/100 ml. There is an extreme value at point 5
corresponding to Chaguar with a quantity of fecal
coliforms that reaches 4.14E+06 NMP/100 ml. On
the other hand, at point 2 the lowest levels were found
with 456 900 NMP/100 ml. In relation to dissolved
oxygen, the lowest saturation percentage was
detected at point 2 as well, and the highest at point 6
laboratory parameter presented a mean of 41.95 ±
SD 19.49. In relation to pH, the mean was 7.82 ±
SD 0.06. The value with the highest frequency was
a pH of 7.87, which corresponds to the sample from
point 2, followed by a pH of 7.86 from point 2, and
a pH of 7.85 from points 3 and 4. In general, the
values pH values were found in a range of 7.71 to
7.87, within accepted limits of normality (between
6.5 and 8.4) [9].
Regarding the biochemical oxygen demand, the
lowest value was found at point 6 (San Antonio).
between 20 mg/l and 35 mg/l with a mean of 28.67
± SD 5.28 g/dl. In relation to nitrates, the mean
of the measured values was less than 0.3 mg/l at
all sampling points; the mean level of phosphates
mg/l. With measured values of 5.57 mg/l and 7.27
mg/l, respectively, the lowest phosphate levels were
measured at point 6, and the highest at point 1. The
mean dissolved solids measured in the samples was
273.17 ± SD 16.19 mg/l. The lowest value was
determined at point 6, and the maximum value at
point 1 with 250 mg/l and 296 mg/l respectively.
Furthermore, turbidity varied between < 5 NTU and
6 NTU in the samples obtained. The sampling point
with the highest turbidity was point 2 with a value
of 6 NTU, while the one with the lowest turbidity
was found at points 1, 4, 5 and 6 with an NTU value
of less than 5. Finally, the mean temperature at the
sampling points was 18.31 ± SD 0.83 ºC. The range
of this parameter oscillated between 17.8ºC and 20
ºC; the lowest corresponded to point 4, while the
Next, the physical-chemical parameters measured
Ministry of the Environment of Ecuador (MAE)
and the Food and Agriculture Organization of the
United Nations (FAO) (Table 5) are compared
within of environmental quality standards and
water use for anthropological activities. The values
corresponding to fecal coliforms exceeded the
maximum recommended limit, in addition, the
dissolved oxygen saturation percentage was lower
than stipulated. The rest of the parameters were
adjusted to the limits considered for its consumption
as a water resource for irrigation.
Table 5.
Table 4.
Determination of laboratory parameters for WQI
54
Rodríguez S., et al.
- No data.
the Environment of Ecuador (2).
Table 6 (Exhibit Table 6) shows the WQI result
values for the study in the Monjas river. The mean
of the WQI is 42 with a range between 36.38 and
49.09. The lowest value of WQI corresponded to
point 4, while the highest was found at point 6.
According to the obtained values in this study, the
water quality is unsuitable.
The results obtained from each parameter were
compared with the Environmental Quality and
of the Environment of Ecuador and the FAO for
agricultural use, where it was determined that the
waters of the Monjas river are not suitable for
irrigating crops without a previous treatment. Since
the analyzes of the laboratory samples and the
values obtained from the WQI index were between
26 and 50, which corresponds to an unsuitable water
quality. It could cause contamination in the crops
due to water contaminated by fecal matter from
human and animal origin, fertilizers, pesticides, and
household waste.
According to the data obtained, the average pH is
7.82. This value is accepted in the water regulation
index for agricultural and irrigation purposes.
However, it is important to mention that point 2
turned out to be the maximum pH value with 7.87,
which tends to be closer to becoming a basic pH.
According to Caho and López [2], the progressive
increase of this parameter throughout the sampled
points is due to mine drainage, wastewater
discharges, and atmospheric sedimentation caused
by industries located near the Monjas river.
Point 6 had a value of 20 ºC, being the maximum of
the sampled points, this increase in temperature is
attributed to the residual water from the production
processes of the “Vicuña” textile company. In
addition, a strong smell of drainage was detected
which, according to Valencia et al. [28], generally
In addition, it enhances the development of
microorganisms.
The BOD5 varies between 20 mg/L and 31 mg/L,
Discharge. Park and Lee [14] states that BOD5 is
an indicator of the organic matter contained, this
includes solids from anthropogenic activity, the
plant and animal kingdom. The Monjas river has
point 3. This leads to the river presenting pollution
problems related to anthropogenic, livestock and
agricultural activity that takes place near the river.
In the case of dissolved oxygen (DO), Rubio et al.
[25] pointed out that the levels of this parameter
depend on the time it is exposed to in the sun, since
plants capture CO2 during the day, converting it into
oxygen. On the other hand, authors such as Hernández
et al. [18] report that the DO depends on the depth,
that is, that at a greater depth its concentration
decreases and in turn the environmental conditions
temperatures there will be lower concentrations.
In the results of the DO analysis (Table 5) it was
Table 5.
Comparison of the minimum and maximum water quality limits dened by the FAO and the MAE
55
Determination of the WQI Index to Evaluate the Water Quality of the Monjas River located in Quito
observed that the lowest percentage of saturation
In general, the DO values at the six points were
below the permissible limit, which is greater than
regulations. The low DO content in the cause is due
to anthropic activities (deforestation, agriculture,
sports, among others) practiced on the banks of the
Monjas river [2]. Therefore, when analyzing this
parameter, it is inferred that there is no natural life
along the river, and it is not suitable for agricultural
use.
Regarding the phosphate parameter, the results
show that its concentration has a negative trend as
the sampling points go north, which means that in
the most populated areas such as point 1, point 2, and
point 3 show a higher concentration of phosphates.
Although none of the six sampling points exceeded
the permissible limit (Table 5). According to Aldana
and Zacarias [24] the presence of chemicals such as
detergents and fertilizers. In addition to anthropic
activities such as agriculture and domestic and/
or industrial discharges, they contribute to the
existence of phosphates in the Monjas river. In
addition, as stated by Caho and López [2], the
growth of plant organisms is considerably lower
when dissolved oxygen has low concentrations,
consequently, phosphorus levels increase in the
water as evidenced in Table 4.
Total dissolved solids values range from 250 mg/L
to 296 mg/L, with the points with the highest
concentration of this parameter being points 1
and point 4. Based on Gutiérrez [6], the high
concentrations of dissolved solids are caused due
to the transport of anthropogenic pollutants caused
mainly by the existing erosion on the banks of the
Monjas river and the dumping of solid waste.
Turbidity, according to Clesceri, Greenberg and
Trussell (1992), refers to the low transparency
present in water due to the presence of suspended
particles. When referring to this factor in
agricultural activities and irrigation, it is compared
with the permissible limit of freshwater turbidity,
which, according to the Standard for Environmental
value corresponding to anthropogenic activities
with a maximum permissible limit of 100 NTU,
so when analyzing the values obtained from the
6 sampling points, an average of 5.25 NTU was
obtained, being within the permissible range.
The presence of Nitrates in the Monjas river is
constant (<0.3 mg/L) this value is within the
permissible limits of the Environmental Quality and
is that according to Litter et al. (2009). It is more
compared to surface waters, varying according to
For fecal coliforms (FC), ecuadorian legislation
shows that the permitted value of FC in agricultural
activities is between 0 and 600 NMP/1000ml of
water [9]. In this investigation, a general mean
of 1.10E+06 ± SD 1.49E+06 NMP/100 ml was
observed, a minimum value of 456 900 NMP/100
ml at point 2 and at point 5 had a maximum range
of 4.14E+06 MPN/100 ml. These values exceed the
limits established by the TULSMA environmental
regulations. This is due to the fact that in several
points of the Monjas river agricultural activities
and the raising of horses, goats, sheep, and cattle
predominate where there are large tracts of land and
on the banks of the river it is heavily contaminated
by their fecal matter [2]. In addition, there is
inhabitants of the populations settled on its banks,
which directly contribute these microbiological
contaminants, which means that their waters cannot
be used in agricultural activities [10].
For fecal coliforms (FC), ecuadorian legislation
shows that the permitted value of FC in agricultural
activities is between 0 and 600 NMP/1000ml of
water [9]. In this investigation, a general mean
of 1.10E+06 ± SD 1.49E+06 NMP/100 ml was
observed, a minimum value of 456 900 NMP/100
ml at point 2 and, at point 5 has a maximum range
of 4.14E+06 MPN/100 ml. These values exceed the
limits established by the TULSMA environmental
regulations. This is due to the fact that in several
points of the Monjas river agricultural activities
and the raising of horses, goats, sheep, and cattle
predominate where there are large tracts of land and
on the banks of the river it is heavily contaminated
by their fecal matter [2].
and latrines of the inhabitants of the populations
settled on its banks, which directly contribute these
microbiological contaminants, which means that
their waters cannot be used in agricultural activities
[10].
56
Rodríguez S., et al.
4. CONCLUSIONS
The study of water quality in rivers is of the utmost
importance because the necessary water resources
are taken from their tributaries to carry out various
productive activities. In addition, the WQI is more
instrument in decision-making in order to avoid
threats to aquatic life or its use.
The Monjas river presented an average WQI of 42,
which represents a deplorable quality of its waters.
It is important to indicate that from these data there
was a slight downward trend in the upper parts of
the tributary and according to what was observed,
its level of contamination is due to everything to
activities such as: agriculture, livestock, industry,
and domestic activities that generate solid waste on
the banks of the river.
The measured quantities of fecal coliforms and
BOD5 exceed the permissible limits established
by the “FAO” environmental legislation and the
Discharge: Water Resources of the Ministry
of the Environment of Ecuador”. Waters with
high BOD5 values present reduced levels of DO,
since the percentage of oxygen decreases when
it is assimilated by bacteria, endangering the
sustainability of aquatic life. On the other hand,
coliform bacteria cause diseases, with symptoms
such as gastrointestinal upset and among others
In general terms and according to the results of this
study, its waters are not optimal for agricultural use
and human consumption.
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Rodríguez S., et al.
Appendix
Table 6.
WQI index of each sampling
point of the Monjas River
