INTRODUCTION
Humans, animals, and
plants all depend on water; without it, life cannot exist. An adequate supply
of clean water is a basic requirement for a community's socioeconomic growth.
High-quality drinking water is also essential to everyone's health and welfare.
Acceptable water quality is defined as the absence of bacteria of fecal origin
that can cause human diarrhoea and other
life-threatening diseases (like typhoid fever), chemicals (like heavy metals)
or other substances that can harm human health, and when the water does not
taste or smell unpleasant (Agbede et al., 2017).
In majority of developing nations, rainwater harvesting is a common
practice. Rainwater harvesting is defined as the process of directly collecting
rainfall for domestic uses, irrigation or refilling groundwater storage (Lade
and Oloke, 2013). The technique of gathering
rainwater and storing it for use at a later time on the surface, below ground,
in the soil, or in reservoirs is known as rainwater harvesting. Rainwater
harvesting also refers to the practice of using surface runoff from rainfall to
be used for irrigation in farms and houses (ABS 2010, ADWG 2004).
In many parts of the
world, collected rainwater is a significant source of water for domestic use.
Rooftop water is collected and stored in concrete surface tanks, concrete
subsurface tanks, or other types of water storage containers. Rooftop rainwater
collection has the potential to create water of exceptional quality if the
rooftop is clean, impermeable, and made of non-toxic materials (Lee et al., 2010). There is a growing interest in
rainwater harvesting as a substitute for surface and ground water due to the
rising scarcity of potable water in various parts of the world. As a substitute
source of potable and non-potable water resources, rainwater harvesting has
gained more attention globally (Hatibu et al.,
2006; Ghisi and Ferreira, 2007). In Nigeria,
rainwater harvesting is practiced by about 80% households (Lade and Oloke, 2013).
This strategy reduces
water demand while encouraging energy and water conservation. It also
stimulates climate change adaption measures. Rainwater is the main water supply
for residents in some rural areas in Nigeria, who utilize it for drinking and
other domestic needs (Grandet et al., 2010).
Even though using rainwater has some prospective advantages over other sources,
it is generally disregarded as a source of drinkable water due to worries about
the water quality (Dobrowsky et al., 2014).
Heavy metals, nutrients, and pathogens can all be present in substantial
amounts in rainwater (Khayan et al., 2019;
Hassan, 2023; Bełcik et al., 2024).
Dust, insect and bird feces, and even small animals present on
rooftops hold a variety of germs, including human pathogens (Ahmeda et al., 2012; Ahmed et al., 2014). During rainfall,
pathogen-carrying material such as feces and other objects can be washed into
rainwater harvesting tanks, reducing the quality of the water (Pachepsky et al., 2011). The presence of bacteria,
viruses, and parasites, many of which potentially cause waterborne diseases,
has been associated with rainwater harvesting (Ahmed
et al., 2012b; Ahmed et al., 2014). Kanzler
et al., 2008; Hageskal et al., 2009) had that
the existence of organisms in rainwater itself, atmospheric deposition of
organisms, and the introduction of contaminants during the extraction and
processing of harvested rainwater are possible sources of microbial
contamination of rainwater this view was also asserted by (Ahmed et al.,
2012a; Kaushik et al., 2014; Schets et al., 2010).
Escherichia coli (E. coli) is a
facultative anaerobic bacterium that lives in the large intestines of
warm-blooded mammals and is a significant member of the typical flora of the
human colon (Thursby, 2017). Thus, the presence of E.
coli in food or water often indicates recent faecal
contamination or inadequate sanitary conditions in food or water processing
plants (Odonkor and Ampofo,
2013). As a result, the population of E. coli is greatly influenced by faecal contamination, inadequate sanitation practices, and
poor storage conditions (Agensi et al., 2019; Kayembe et al., 2018). The presence of E. coli
in water does not automatically indicate the presence of pathogenic bacteria.
However, it provides evidence of the potential presence of faecal-borne
bacteria (Price and Wildeboer, 2017; Brussow, 2005). This explains why food and water samples
are examined for E. coli in order to determine the levels of fecal
contamination (Price and Wildeboer, 2017). Most E.
coli strains are harmless, but some, such as serotype O157:H7, can cause
serious food poisoning in humans, and are occasionally responsible for product
recalls (Hudault et al., 2011; Vogt and Dippold, 2015). The relationship between rainwater
harvesting and the increase in E. coli related diseases in Otuoke community is currently not present in existing
literature. This study is limited to Azikel road, hospital Road and Federal University West
Campus, Otuoke in Ogbia
Local Government of Bayelsa State.
Study Area
Otuoke community is located at 4°42'23.418"N and 6°19'44.472E. Otuoke community is a suburban area located within the Ogbia Local Government Area of Bayelsa
State, Nigeria. The majority of its residents are engaged in agricultural and
fishing activities. The wet season is warm and
overcast. The wet season usually starts from March to October, with a dip in
August. The dry season is hot and partly cloudy. Over the course of the year,
the temperature typically varies from 22°C to 34°C and is rarely below 18°C or
above 40°C.
Table 1: location of the sample sites
|
Location site
|
GPS Reading
|
|
Federal University Otuoke
|
4o48’3.294” N 6o18’54.67788”
E
|
|
Hospital Road
|
4o47’31.96212” N 6o19’1.92612”
E
|
|
Azikiel Road
|
4o47’30.75612” N 6o19’8.24988”
E
|
Sample Collection
Samples used for the research work were rain
water collected from three (3) different locations in Otuoke
community namely Azikel Road, Hospital Road and Federal
University Otuoke West Campus. The
water samples were collected from rain water reservoirs, and a control gotten
directly from the rain. They were collected into sterile sample bottles, and
transported to the laboratory for analysis.
Preparation of Nutrient Agar (NA):
28 grams of the medium was dissolved in
1000ml of distilled water. It was heated, to dissolve the powder. Sterilization
was done by autoclaving at 121°C for 15 minutes and the medium was dispensed
into sterile Petri dishes and left to solidify, for inoculation.
Preparation of Manitol
Salt Agar (MSA):
111.02 grams of the Mannitol
Salt Agar was suspended in 1000 ml of distilled water (contained in a conical
flask), the medium was heated, to dissolve completely. The resulting suspension
was sterilized by autoclaving using an autoclave, at 15 lbs pressure (121°C) for 15 minutes. It was allowed to cool
to 50°C and poured into sterile Petri dishes, to solidify.
Preparation of Salmonella Shigella
Agar (SSA):
63grams of the medium was added into one
liter (1000ml) of distilled water. The medium was properly mixed, and heated
with frequent agitation and boiled for one minute. At
the end, the medium was aseptically poured into sterile Petri dishes, and
allowed to solidify.
Preparation of Eosin Methylene Blue (EMB)
Agar:
36grams of the medium was suspended in 1000
ml distilled water, and mixed until the suspension was uniform. It was further
heated to boiling to dissolve the medium completely, and sterilized by
autoclaving at 15 lbs pressure (121°C) for 15
minutes. The medium was allowed to cool to 45-50°C and agitated in order to
oxidize the methylene blue, and to suspend the flocculent precipitate. It was
then poured into sterile Petri dishes. The plates were allowed to solidify, and
warm to room temperature, before inoculation.
Preparation of Simmons Citrate Agar (for
Citrate Test):
Simmons Citrate Agar is an agar medium used
for the differentiation of Enterobacteriaceae based
on the utilization of citrate as the sole source of carbon. 5.0
ml of the suspended medium was dispensed into 12-mm test tubes, and autoclaved
at 121°C under 15 psi pressure (for 15 minutes). The
tubes were Left to cool in slanted position.
Preparation of Tryptophan Broth, MR/VP Broth
5.0 ml of the suspended medium was dispensed
into 12-mm test tubes, and autoclaved at 121°C under 15 psi pressure (for 15
minutes).
Procedure for the enumeration of bacteria in
the water samples:
The process involved Serial Dilution,
Inoculation, Incubation, Subculturing, Isolation,
Monitoring, and Identification.
Serial Dilution:
10 fold serial dilution was used for the
enumeration process. 10 12ml test tubes containing 9ml each of distilled water
for each of the samples were sterilized using autoclave at 121°C psi for 15
minutes.
Enumeration and
Isolation of Total Bacteria
The samples were serially diluted using 10 fold
serial dilution, and 0.1ml of each diluted sample from 10−5 diluent was
plated onto the nutrient agar, and spread on the surface, using the spread
plate technique. The plates were incubated at 37°C for 24-48 hours.
Procedure for
Biochemical Characterization
MR
TEST: Using organisms taken from a 24 hour old
pure cultures, using a sterile wire loop, each bacteria isolate was inoculated
into the prepared Methyl Red broth. The tubes were incubated at 37°C, for 24
hours. Following 24 hours of incubation, 2 to 3
drops of methyl red indicator was added to the tubes, and observed for red colouration immediately.
VP TEST: Using organisms taken from a 24 hour old pure cultures, using a
sterile wire loop, each bacteria isolate was inoculated into the prepared Voges-Proskauer broth. The tubes were incubated at 37°C,
for 24 hours. Following 24 hours of incubation, 1ml each of Barrett's reagents
A & B was added to the tubes. The tube was shaken gently, and allowed to
stand for 15-30 minutes.
INDOLE
TEST: The 24 hour old isolates were added to the
Tryptophan broth prepared in the test tubes and sterilized, with the help of a
sterile wire loop, with a control tube and incubated for 24 hours. After
that, 1ml of Kovac's indole
reagent was added to all the tubes, including the control. The tubes were
agitated gently, and results recorded after 10-15 minutes.
Citrate Test and
Oxidase Test were also carried in tubes to observe for the presence or absence of
blue colouration.
Catalase Test was done to
observe for the presence or absence of bubbles.
While Coagulase Test was
done to observe for the clumping or agglutination of the mixture over the
period of 10-15 seconds.
Gram's
Reaction: A thin smear of the isolates from 24hours
old pure cultures were made on clean glass slides, and allowed to air dry. The
slides were heat fixed, by passing them through a Bunsen burner flame. Following
the fixation process, the slides were covered with crystal violet, for 1minute,
and washed with distilled water after that. They
were covered with Gram's Iodine for another 1minute, and washed off again with
distilled water. Decolonization with 95% ethanol was done for
10 seconds, followed by counter staining with saffranin
for 40 second. The slides were allowed to air dry and
observed under the microscope, using oil immersion lens.
After 48 hours of incubation, distinct
colonies suspected (using culturing characteristics) to be E. coli, Staph. aureus, Psuedomonas, Salmonella etc were sub-cultured onto
other special media.
EMB was used for E. coli, SSA was
used for Salmonella, MSA was used for Staph. aureus.
Three (3) of the samples were positive for E. coli with Azikel
Road sample having the highest microbial load, followed by Hospital Road
Federal University Otuoke (FUO), carrying the lowest.
For Salmonella, all of the samples had Negative results. However,
other opportunistic pathogens such as Psuedomonas aeruginosa, Staphylococcus aureus,
and yeast were present in all of the samples, including the control sample
(though in insignificant number, for the control sample). For
these other bacteria isolates, Hospital Road sample had the highest levels of
Staph and Psuedomonas, followed by Azikel Road sample, FUO still had the least microbial load. The
control sample had few (insignificant) colonies of Psuedomonas aeruginosa, Staph. aureus, and yeast, which could be as a result of
condensation from suspended dust in the air.
Purple colonies with green metallic sheen,
(on EMB,) colourless colonies with hemolysis on SSA,
Yellow colonies with fermentation on MSA, and light green-blue colonies on NA
were further sub-cultured back onto Nutrient Agar at 37°C for 24 hours, for
biochemical characterization.
DISCUSSION
The rainwater
samples were taken from three locations namely Azikiel
road, Hospital Road and within the Federal University Otuoke
premises. The highest bacteria load was at Azikiel
road and it is followed by the samples gotten from Hospital Road. The control sample
had insignificant bacteria load recorded.
The micro-organisms that were detected include E. coli, Salmonella, Pseudomonas and Staphylococcus
aureus. The Gram's reaction indicates the Gram
staining characteristics of the organisms. All three organisms are
Gram-negative. Three
(3) of the samples were positive for E.
coli with Azikel road sample having the highest
microbial load, followed by Hospital Road, and samples from within the school
premises, carried the lowest. For Salmonella, all of the samples had negative
results.
However,
other opportunistic pathogens such as Psuedomonas aeruginosa, Staphylococcus aureus,
and yeast were present in all of the samples, including the control sample
(though in insignificant number, for the control sample). For these other
bacteria isolates, Hospital Road sample had the highest levels of Staphylococcus aureus
and Psuedomonas,
followed by samples from Azikel Road sample, and
within the university premises still had the least microbial load. The Control
sample had few (insignificant) colonies of
Psuedomonas aeruginosa,
Staphylococcus aureus, and yeast, which could be
as a result of condensation from suspended dust in the air. A study by Ahmed et al., (2010) showed a list of pathogens that were isolated from
rain water harvesting which includes Salmonella
spp, G. lamblia and L. pneumophila. Rainwater tanks can face contamination as debris is washed into them from
the roof and gutters during rain events. The main contributors to pathogen
presence are expected to be fecal materials from birds, lizards, and possums
that have access to the roof. Salmonella spp. has previously been detected in roof-harvested
rainwater cisterns and in tanks as reported by Simmons et al., (2001).
CONCLUSION
This study focused on rainwater harvesting for domestic use in Otuoke community and it also looks at its role in the
prevalence of Escherichia coli related diseases and other water borne
pathogenic microorganisms. Escherichia coli is generally employed
as an indicator of faecal pollution by warm-blooded
animals and there is a general high frequency of detection of these indicator
organisms in rain water samples gotten from rooftops resulting in the
contamination of the rainwater with the faecal matter
from animals, amongst others, that might be deposited on the rooftops or in the
gutter systems. Escherichia coli, a
member of faecal coliforms has a significant place in
water microbiology as an indicator of faecal
pollution and a pathogen in drinking water. As a pathogen, it causes a variety
of diseases ranging from urinary tract
infections, sepsis, meningitis and bacteraemia to diarrhoea. Escherichia coli poses a health
risk to rainwater from rooftop end-users in Otuoke
and other communities with similar environmental characteristics, especially
when used for drinking, washing kitchen utensils, cleaning of the home, garden
hosing, washing laundry by hand, or when accidentally consumed by human beings.
This study results show the presence of different pathogenic bacteria in the
rainwater samples gotten from the study area which indicates a strong
relationship between rainwater consumption within the study area and the
occurrence of E. coli related diseases. Hence, a comprehensive approach for safe and effective rainwater
utilization should be implemented. Community
workshops and awareness campaigns should be organized to educate residents
about the benefits and potential risks associated with rainwater harvesting. Regular testing for microbial
contaminants and treatment of such, especially Escherichia coli, will ensure that the harvested rainwater remains
a safe and reliable source for domestic use.
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