Sustainable Water Solutions: Evaluating Water Practices and Watermelon Rind-Mediated Ag/TiO2 Nanocomposite Modified Solar Disinfection Efficacy in Obunga Slum, Kisumu County
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Date
2024-11
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Kenyatta University
Abstract
Approximately 2 billion people worldwide lack access to safe drinking water, leading to 4
billion reported waterborne diarrheal diseases annually. The situation in Obunga slum,
located in Kisumu County, with its poor sanitation standards and lack of safe water,
highlights the urgent need for a sustainable scientific water treatment solution. Solar
disinfection (SODIS) of water, a point-of-use water treatment method that utilizes
ultraviolet (UV) radiation and the thermal effects of solar radiation to kill pathogens, is a
potential solution. However, its efficiency is influenced by weather conditions. The
incorporation of a visible light active photocatalyst has been proposed to enhance its
efficiency. This visible light active photocatalyst was synthesized using a green synthesis
method, using Citrullus lanatus (watermelon) rind extract (WMRE). This research, with its
potential to significantly improve water treatment, aimed to evaluate the water and
sanitation practices of Obunga slum residents, validate the application of SODIS in the
slum, and increase the effectiveness of SODIS by incorporating WMRE-synthesized silver/
titanium dioxide (Ag/TiO2) nanocomposite. The water and sanitation survey was done
using structured questionnaires randomly administered to individual household heads;
SODIS was performed on common ground sources within Obunga slum; synthesis of
Ag/TiO2 nanocomposite followed, and the effectiveness of SODIS modified with Ag/TiO2
nanocomposite was analysed. The green synthesis of Ag/TiO2 nanocomposite was done
using WMRE, and the operating conditions were optimized, while the control synthesis
was done using sodium borohydride (NaBH4). The Ag/TiO2 nanocomposite powders were
coated on 3-4 mm glass beads and incorporated into SODIS, and effectiveness
was assessed. The water and sanitation survey revealed that all Obunga slum residents
lacked access to improved sanitation facilities, which demands immediate attention and
action. Only 34.65% were accessing safe water sources, highlighting the pressing need for
improved sanitation. SODIS for the recommended 6 hours resulted in > 99.99% kill rate
for E. coli bacteria and only 82.36% kill rate for non-E. coli coliform bacteria, supporting
the need to incorporate a visible light-active photocatalyst. Synthesis of Ag/TiO2 using
WMRE was optimal at a reaction time of 45 minutes, temperature of 100 ℃, and pH 12
and yielded spherical Ag nanoparticles with an average diameter of 7.48 nm ± 4.06 nm
modified on the surface of TiO2 nanoparticles, yielding improved Ag nanoparticles
monodispersity. An absorption peak displayed the visible light activity of WMRE synthesized Ag/TiO2 at 425 nm and was comparable to the control's. SODIS modified with
Ag/TiO2 nanocomposite resulted in a > 99.99% E. coli and coliform bacteria kill rate
statistically similar to the > 99.98% kill rate achieved when treatment was performed
without modification, indicating no improved effectiveness upon modification. Ag/TiO2
nanocomposite is a widely studied and utilized anti-microbial agent; this lack of enhanced
efficiency was attributed to an interaction error between the glass beads and contaminated
water. Despite the lack of significant improvement in SODIS, the assessment of the water
and sanitation standards of Obunga slum and the successful synthesis of visible light active
Ag/TiO2 nanocomposite using WMRE provide hope for the future of water treatment.
Description
A Thesis Submitted in Partial Fulfilment of the Requirements for the Award of the Degree of Master of Science (Applied Analytical Chemistry) in the School of Pure and Applied Sciences, Kenyatta University November, 2024
Supervisors:
1.Erick Masika
2.Naumih Naoh