Abstract
The contamination of groundwater sources by pathogenic bacteria poses a public health concern to communities who depend totally on this water supply. In the present study, potentially low-cost filter materials coated with silver nanoparticles were developed for the disinfection of groundwater. Silver nanoparticles were deposited on zeolite, sand, fibreglass, anion and cation resin substrates in various concentrations (0.01 mM, 0.03 mM, 0.05 mM and 0.1 mM) of AgNO3. These substrates were characterised by SEM, EDS, TEM, particle size distribution and XRD analyses. In the first phase, the five substrates coated with various concentrations of AgNO3 were tested against E. coli spiked in synthetic water to determine the best loading concentration that could remove pathogenic bacteria completely from test water. The results revealed that all filters were able to decrease the concentration of E. coli from synthetic water, with a higher removal efficiency achieved at 0.1 mM (21–100%) and a lower efficiency at 0.01 mM (7–50%) concentrations. The cation resin-silver nanoparticle filter was found to remove this pathogenic bacterium at the highest rate, namely 100%. In the second phase, only the best performing concentration of 0.1 mM was considered and tested against presumptive E. coli, S. typhimurium, S. dysenteriae and V. cholerae from groundwater. The results revealed the highest bacteria removal efficiency by the Ag/cation resin filter with complete (100%) removal of all targeted bacteria and the lowest by the Ag/zeolite filter with an 8% to 67% removal rate. This study therefore suggests that the filter system with Ag/cation resin substrate can be used as a potential alternative cost-effective filter for the disinfection of groundwater and production of safe drinking water.
Highlights
The World Health Organisation (WHO) has indicated that approximately 1.8 million deaths and61.9 million disability-adjusted life years (DALYs) worldwide are attributable to unsafe water, sanitation and poor hygiene
The amount of silver ions eluted from Ag/zeolite, Ag/sand, Ag/fibreglass and Ag/anion resin exceeded by far the recommended limit set by the World Health Organisation and US Environmental Protection Agency (USEPA), which is less than 0.10 mg/l in drinking water used for human consumption
scanning electron microscope (SEM), energydispersive spectroscopy (EDS), Transmission electron microscope (TEM), Particle Size Distribution and X-ray diffraction (XRD) analyses, which confirmed the presences of silver loading on the substrates
Summary
The World Health Organisation (WHO) has indicated that approximately 1.8 million deaths and61.9 million disability-adjusted life years (DALYs) worldwide are attributable to unsafe water, sanitation and poor hygiene. Consumption of groundwater and surface water sources contaminated with pathogenic bacteria such as Escherichia coli O157:H7, Salmonella typhimurium, Shigella dysenteriae and Vibrio cholera continues to be one the major causes of diarrheal diseases and gastrointestinal infections [2,3,4,5,6]. This implies that safe drinking water plays a significant role in human health and well-being. Tremendous progress has been made to date, the 2010 updated report by the WHO and the United Nations Children’s Fund (UNICEF) has indicated that 884 million people in the world still lack access to drinking water from improved sources
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