International Journal of Basic Science and Technology May, Volume 9, Number 2, Pages 65 – 70 http://www.ijbst.fuotuoke.edu.ng/ 65 https://doi.org/10.5555/IXGR5401 ISSN 2488-8648 Article Information Abstract Article # 09008 Received: 4th Feb. 2023 1st Revision:19th April 2023 2nd Revision:3rd May 2023 Acceptance:19th May 2023 Available online: 21st May 2023. Key Words Underground water, Ozone generator, Pathogens, Oye Ekiti . *Corresponding Author: Kehinde, A.B.; kehinde.bolorunduro@fuoye.edu.ng Introduction Across the world, particularly in underdeveloped countries, water is a scarce resource. On average, 663 million people lack access to clean, drinkable water (Chitonge et al., 2020). Many rural communities in sub-Saharan Africa fall in this category, hence their heavy reliance on untreated sources such as streams, dams, boreholes, wells, and rivers to meet fundamental needs such as drinking, sanitation, and cooking and for their sustainable development (Odonkor and Addo, 2018). However, these untreated sources are contributing significantly to the global burden of disease, as a result of water-related infectious diseases such as cholera, dysentery, and typhoid (Varga, and Szigeti, 2016). These water-borne diseases are a result of the contamination of the water sources, due to anthropogenic influences, population growth, and urbanization ((Boczkaj and Fernandes, 2017, Ahmed and Hamid, 2018, Bayowa et al., 2014). The contamination thus leads to the growth and spread of pathogenic waterborne microorganisms. Escherichia coli is one of the major pathogens associated with waterborne diseases. Escherichia coli (E. coli) is a naturally occurring facultative anaerobic bacterium that populates the vast gastrointestinal tracts of endothermal mammals and is a significant component of the typical human colon (Nguyen et al., 2016, Thursby and Juge., 2017, Krieg et al., 1984). The mere presence of E. coli in water does not compulsorily imply the presence of disease-causing microbes. Nonetheless, it indicates the potential for faecal-borne pathogens like Salmonella and hepatitis A to exist (Price and Wildeboer, 2017, Brussow, 2005). This explains the use of E. coli as an indicator microorganism to analyse food and water samples to determine the levels of fecal contamination. In the past much of the treatment of these waters was done using chlorine (Cl2) compounds. However, chlorine is a very Efficacy of Ozone Bubbles in Disinfecting Underground Water in Okeijebu, Ikole Ekiti, Nigeria 1Bolorunduro, K.A.., 2Olayanju, K. O., 1Olayinka, A.J. and 1Fasuyi, A.L. 1Department of Civil Engineering, Federal University, Oye- Ekiti, Nigeria 2Department of Civil Engineering, Redeemer’s University, Ede, Nigeria The problem of potable water deficiency is becoming a global concern. The sixth of the sustainable development goals (SDG) calls for eradicating open defecation and ensuring that everyone has access to clean, affordable drinking water and to also promote sustainable freshwater supply and abstraction as well as to enhance water quality and water usage efficiency. The disinfecting process has been considered one of the most important vital steps in underground water treatment. Ozone (O3) is one of the disinfecting mechanisms used in groundwater to remove microorganisms, inorganic ions, and organic pollutants from underground water samples. This study is therefore focused on the assessment of the efficacy of ozone gas-based sterilization on underground water in a university community of Federal University Oye Ekiti, Ekiti State, Nigeria, and its environs where dependence on underground water is prominent because of lack of access to pipe borne water. O3 was diffused through water samples obtained by grabbed sampling method from different hand-dug wells (HDW1-HDW8) in the community for multiple durations (05, 10, 15, and 20 min), to determine the effectiveness of O3 in eliminating pathogens. Preliminary results showed that the E-coli levels in HDW1-HDW8 range between 28 and 55 cfu per 100ml of water sample. Upon exposure to ozone, the E-coli levels reduced drastically (0-8 cfu) at exposure times of 15- 20 minutes which conforms to the standard stipulated by the WHO (0-3cfu) and NSQDW (0-10cfu). It concluded that the high presence of E-coli in underground water sources in these communities requires proper treatment before consumption to forestall waterborne diseases and death and recommends the use of ozone for its treatment at an exposure rate of 20 minutes. . http://www.ijbst.fuotuoke.edu.ng/ International Journal of Basic Science and Technology May, Volume 9, Number 2, Pages 65 – 70 http://www.ijbst.fuotuoke.edu.ng/ 66 https://doi.org/10.5555/IXGR5401 ISSN 2488-8648 toxic substance with many storage and handling problems. It has been the usual choice as a microbiocide because it is relatively effective and has a reasonable cost. Many of these treatments have large problems in that the biocide concentration is heavily regulated due to their toxicity and some bacteria are immune to the current treatments, or that the allowable concentration of biocide is ineffective. Ozone (O3) is made up of three atoms of oxygen in an angular configuration. Ozone is a very strong oxidant; many times, stronger than oxygen (O2) and chlorine. In particular, two factors are responsible for the increased popularity of using ozone in these last years, they are - costs associated with ozone production considerably decreased in the last decade and ozone presents environmental advantages over chlorine. Ozonation is a prefered alternative in the treatment of water and wastewater containing organic matter and biological contaminants (Haung et al., 2016). Ozone is an unstable gas; therefore, its generation should be carried out in situ. The commercially available technology for ozone generation is based on the corona discharge process, which involves the application of a high-voltage discharge in a cooled/dried gaseous phase containing oxygen (O2 or air) (Rekhate and Srivastava, 2020). Ozone being a powerful oxidant (2.07 V) can degrade organic pollutants using two mechanisms: (1) direct electrophilic attack by molecular ozone; (2) indirect attack by OH- radicals produced through the ozone decomposition process. It was observed that raising the ozone concentration promotes the degradation rate of some pollutants but has no obvious effect on the degradation of some other pollutants. This may be because ozone molecules directly react with pollutants according to four categories: (i) The oxidation- reduction reaction such as the reactions between O3 and HO−2 mostly proceeds through the electron transfer process (Hoigné et al., 1983). (ii) The ozone reacts with pollution via cycloaddition reaction by forming a five-member ring ozonide structure (Beltran et al., 2005). (iii) Ozone being an electrophilic agent can attack the nucleophilic position of the organic substances and the group in the aromatic molecule, such as -OH−, -NO− 2 , and –Cl has a significant influence on the reactivity of the aromatic ring with ozone. (iv) Ozone demonstrates nucleophilic properties and nucleophilic reactions occur with molecules especially when the compound contains carbonyl or double and triple nitrogen carbon bonds (Wang and Chen, 2019). The benefits of ozonation in water and wastewater treatment plants include sludge reduction and removal of recalcitrant organic contaminants from water and wastewater. It is seen that ozonation leads to sludge solubilization, reducing overall biomass yield (Semblante et al., 2017). The ozone mass transfer is influenced by many factors, which can be divided into hydrodynamic and physicochemical effects. Ozone itself is unstable and can quickly decompose into molecular oxygen leading to a low utilization rate and can be dispensed in bubble-like form (Wang and Bai, 2017). The University community of Ikole is among the many communities in the developing world that depend on underground water. The study area is Oke-Ijebu, a representative community of Ikole Ekiti that houses the Federal University Oye Ekiti, Ekiti State, Nigeria (Ikole Campus) (Figure 1.1). Ekiti State is a state in southwestern Nigeria, bordered to the north by Kwara State, to the northeast by Kogi State, to the south and southeast by Ondo State, and the west by Osun State. The area is a Local Government Area whose headquarters are located in the town of Ikole. The geographical coordinates are Latitude: 7.78333, Longitude: 5.51667, 7o46’60’’ North, 5° 31′ 0″ East. It is endowed with numerous forest reserves and community forests. It has a landmass of 321.00 km² (123.94 sq mi) and a population of 168,436 as at the 2006 Nigeria Population Census. The people depend mostly on the natural environment for their livelihood; they are involved in subsistence Agriculture while others are the student’s population. The climate of Ikole Local Government Area is a Tropical savanna climate. The rainy season lasts from April to October while the dry season lasts from November to March. Commuters depend solely on underground water and their streams to access water for their different activities. This study, therefore, aims at studying the efficacy of the ozone bubbles in disinfecting underground water in Ikole Ekiti. http://www.ijbst.fuotuoke.edu.ng/ https://en.wikipedia.org/wiki/States_of_Nigeria https://en.wikipedia.org/wiki/South_West_(Nigeria) https://en.wikipedia.org/wiki/Nigeria https://en.wikipedia.org/wiki/Kwara_State https://en.wikipedia.org/wiki/Kogi_State https://en.wikipedia.org/wiki/Ondo_State https://en.wikipedia.org/wiki/Osun_State International Journal of Basic Science and Technology May, Volume 9, Number 2, Pages 65 – 70 http://www.ijbst.fuotuoke.edu.ng/ 67 https://doi.org/10.5555/IXGR5401 ISSN 2488-8648 Fig1: Map showing Ikole Ekiti Materials and Methods The main materials used were Eosin methylene blue agar, A giant autoclave, An ozone generator, and Portable PH meter. Water samples were collected from eight selected hand-dug wells in various residences at Oke-ijebu, Ikole-Ekiti in a 10-liter keg and was transported to the laboratory at a controlled temperature for analysis. The pH of the water sample was determined at the point of obtaining the sample using a portable pH meter calibrated with the use of distilled water. Microbial analysis was conducted using a pour plate method which was used to count possible microorganisms in the given sample by enumerating the whole range of colony-forming units (CFUs) inside and/or at the surface of the solid medium. It is generally used for enumerating bacteria presence. The pour plate method involves a number of simple processes like, sterilization of the bench with ethanol, washing of the petri dishes with soap and water then placing it on a sterilized bench. One (1) ml of each sample was pipetted into the Petri dishes using a micropipette and repeated the same for the eight samples while making provision for a control. The total amount of Eosin Methylene Blue agar (EMB) that would be enough for 8 samples was prepared and then placed inside a giant autoclave and left for 30 minutes. The conical flask was removed from the giant autoclave and left to cool up to 40⁰C. The neck of the conical flask was flamed and then poured inside the Petri dishes which 1ml of sample was pipetted in, then left to solidify. It was, inverted after it solidified, then placed in an incubator up to 37⁰C and left for 24 hours. Then dark-red spot was counted. The disinfection process involved the use of a 500mg ozone generator (FUKANG) that comes with an inbuilt Oxygenating tube and two Grey Diffuser stones. The ozone generator was connected to an ac supply at the standby mode of the generator. The switch was turned on to illuminate the LED of the selected timer while adjusting the disinfection time, (05, 10, 15, and 30 minutes). The oxygenating tube was connected to the oxygenating outlet connection on the side, then the diffuser stone was placed into the water container. The fine particles from the water was separated using filter paper and then poured into a labelled bottle. Plate 1: Hand dug well Plate 2: Ozone generator Results and Discussion: The results of the treatment process are presented under the following considerations (characterization of the water sample, effect of the treatment on the water samples). http://www.ijbst.fuotuoke.edu.ng/ International Journal of Basic Science and Technology May, Volume 9, Number 2, Pages 65 – 70 http://www.ijbst.fuotuoke.edu.ng/ 68 https://doi.org/10.5555/IXGR5401 ISSN 2488-8648 Characterization of the sample wells: Table 1: Initial Characterization of HDW1-8 parameters HDW1 HDW2 HDW3 HDW4 HDW5 HDW6 HDW7 HDW8 Standard (NSDWQ ) pH 6.6 6.3 7.3 6.6 6.1 6.5 6.7 7.1 6.5-8.5 E.coli (cfu)/100mL 40 35 33 28 38 32 55 41 10 Table.1 reveals the contaminant level of the underground water obtained from the different hand- dug wells (HDW) and their corresponding pH. From Table 4.1, the e-coli contamination level ranges between 28 cfu/100ml in HDW4 to 55 cfu/100ml in HDW7. This, compared to the standards stipulated by both World Health Organization (WHO) (0-3 cfu) and the National Standard for drinking water quality (NSDWQ) (0-10 cfu) shows heavy contamination which requires that the underground water should be subjected to a form of treatment to remove the e-coli. The table also reveals the pH values as obtained from the point of obtaining the samples to range between 6.1 in HDW5 to 7.3 in HDW3 which conforms to the stipulated standard by the WHO and NSDWQ . Table 2: 5 minutes treatment of water samples from HDW 1-8 Exposure time (mins) Parameter HD W1 HDW2 HDW3 HDW4 HDW5 HDW6 HDW7 HDW8 5mins Treatment Ecoli 25 14 12 10 21 12 35 25 E-coli Initial Ecoli 40 35 33 28 38 32 55 41 Table 2 shows the treatment of the water sample with ozone bubbles for 5 minutes. It further revealed that the treatment has a significant effect on the e-coli reduction but at the exposure time of 5 minutes, it was unable to treat it to the required standard. Table 3: 10 minutes treatment of water samples from HDW 1-8 Exposure time (mins) Parameter HD W1 HDW2 HDW3 HDW4 HDW5 HDW6 HDW7 HDW8 10mins Treatment (cfu) E.coli 10 5 3 2 9 3 19 10 E-coli Initial (cfu) E.coli 40 35 33 28 38 32 55 41 The Table.3 revealed the removal efficiency of the ozone bubbles at an exposure time of 10 minutes. Comparing with the initial contaminant level, it shows that e-coli levels in HDW1 and HDW8 have been significantly reduced from 40 cfu and 41 cfu to 10 cfu which satisfies the recommendation of the NSQDW but calls for further exposure time. Table 4. 15-minute treatment of water samples from HDW 1-8 Exposure time (mins) Parameter HDW1 HDW2 HDW3 HDW4 HDW5 HDW6 HDW7 HDW8 15mins Treatment (cfu) E.coli 2 0 0 0 1 0 8 2 E-coli Initial (cfu) E.coli 40 35 33 28 38 32 55 41 http://www.ijbst.fuotuoke.edu.ng/ International Journal of Basic Science and Technology May, Volume 9, Number 2, Pages 65 – 70 http://www.ijbst.fuotuoke.edu.ng/ 69 https://doi.org/10.5555/IXGR5401 ISSN 2488-8648 Table 4 reveals the removal rate of e-coli on exposure to ozone bubbles for 15 minutes. Comparing the initial contamination rate to the final, it can be deduced that the ozone bubble have removed a significant quantity from the water samples. HDW1 and HDW8 that was initially 40 and 41 cfu respectively now have a final value of 2 cfu. This can also be seen in hand dug wells 2,3,4 and 6 whose initial contamination was 35, 33, 28, and 38 cfu respectively that has been reduced to zero count. This is in adherence to WHO and NSQDW standards. The HDW7 with 8 cfu calls for an increase in the exposure time. Table 5: 20 minutes treatment of water samples from HDW 1-8 Exposure time (mins) Parameter HDW1 HDW2 HDW3 HDW4 HDW5 HDW6 HDW7 HDW8 20mins Treatment (cfu) E.coli 0 0 0 0 0 0 0 0 E-coli Initial (cfu) E.coli 40 35 33 28 38 32 55 41 Table .5 presents the treatment of the water samples at an exposure time of 20 mins. This reveals that the time is sufficient to conquer the contamination and reduce it to zero count which conforms to all standards for drinking water. It further revealed that the higher the exposure time, the more the reliability of its efficiency. Fig 2: Graph relating the performance of ozone bubbles on the water sample per time of exposure Figure 2 also shows the performance of the treatment method on the water samples per time of exposure. It demonstrates that within 20 minutes, all of the water samples from the eight wells had totally lost the e-coli infection. Conclusions Based on the strength of the results, the study has established the following facts in relation to the objectives of the research work: Oke-Ijebu hand-dug wells are unsafe for consumption because of the presence of E-coli. Exposure to ozonation treatment is capable of removing the pathogen contained in the samples extracted from the wells. Higher exposure time increases the efficiency of the ozonation treatment Recommendations Even though the research work has dealt extensively with the removal e-coli contaminants, some grey areas are yet to be worked on for example: Further studies should be carried out on the water samples to confirm the availability or not, of physic chemical contaminants. 25 10 2 0 14 5 0 0 12 3 0 0 10 2 0 0 21 9 1 0 12 3 0 0 35 19 8 0 25 10 2 0 0 5 10 15 20 25 30 35 40 5mins 10mins 15mins 20mins E c o li Treatment Time (Minutes) E Coli vs Treatment Time HDW1 HDW2 HDW3 HDW4 HDW5 HDW6 HDW7 HDW8 http://www.ijbst.fuotuoke.edu.ng/ International Journal of Basic Science and Technology May, Volume 9, Number 2, Pages 65 – 70 http://www.ijbst.fuotuoke.edu.ng/ 70 https://doi.org/10.5555/IXGR5401 ISSN 2488-8648 Adequate studies on the efficiency of the process to remove the physic-chemical contaminants provided they exist in the water samples. References. Ahmed, E. and Hamid, C. (2018). 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