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The presence of heterotrophic plate count (HPC) bacteria in drinking water distribution systems is usually not considered harmful to the general consumer. However, precautions must be taken regarding the immunocompromised. All water supply authorities in South Africa are lawfully required to provide consumers with high-quality drinking water that complies with South African-and international standards. This study mainly focused on the isolation, identification and characterization of HPC and other bacteria from biofilm-and bulk water samples from two sampling points located within the Potchefstroom drinking water distribution system. Based on five main objectives set out in this study, results indicated that the bulk water at the J.S. van der Merwe building was of ideal quality fit for lifetime consumption. Application of enrichment-and selective media allowed for the isolation of 12 different bacterial morphotypes. These were identified by way of biochemical-and molecular methods as Bacillus cereus, Bacillus subtilis, Brevundimonas spp., Clostridiaceae, Corynebacterium renale, Flavobacteriaceae, Kytococcus sedentarius, Leuconostoc lactic, Lysinibacillus sphaericus, Pseudomonas spp., Staphylococcus aureus and Staphylococcus capitis. The greatest diversity of bacteria was detected early autumn 2008, while the lowest diversity occurred during mid-winter 2007. Bacillus cereus, Kytococcus sedentarius and Staphylococcus capitis displayed potential pathogenic properties on blood agar. Kytococcus sedentarius could be classified as potentially the most pathogenic among the isolates. All isolates displayed multiple-resistant patterns towards tested antibiotics. Corynebacterium renale and Staphylococcus aureus were least resistant bacterial species and Lysinibacillus sphaericus the most resistant. All isolates were susceptible to ciprofloxacin (CIP) and streptomycin (S), but most were resistant to erythromycin (E). Transmission electron microscopy (TEM) allowed for detailed examination of Brevundimonas spp., Pseudomonas spp. and Staphylococcus spp. The capability of Brevundimonas spp. to produce slime and store nutrients within inclusion bodies, suggests the ability of this bacterium to form biofilm and persist in the drinking water for prolonged periods. Despite the inhibitory or toxic effect of copper against bacterial growth, scanning electron microscopy (SEM) revealed the presence of biofilms as well as diatoms on red-copper coupons. Biofilm activity was also observed on reverse-osmosis (RO) filters. Since corrosion was evident on red-copper coupons, it is recommended that prospective studies also look into the significance of microbial induced corrosion (MIC) within the Potchefstroom drinking water distribution system. Other prospects include determining minimum inhibitory concentrations of isolates against antibiotics and the application of culture independent methods such as SSCP and DGGE to investigate biofilm development. The use of diatoms as an index of the drinking water quality is also suggested. / Thesis (M.Sc. (Environmental Science))--North-West University, Potchefstroom Campus, 2010.

The presence of heterotrophic plate count (HPC) bacteria in drinking water distribution systems is usually not considered harmful to the general consumer. However, precautions must be taken regarding the immunocompromised. All water supply authorities in South Africa are lawfully required to provide consumers with high-quality drinking water that complies with South African-and international standards. This study mainly focused on the isolation, identification and characterization of HPC and other bacteria from biofilm-and bulk water samples from two sampling points located within the Potchefstroom drinking water distribution system. Based on five main objectives set out in this study, results indicated that the bulk water at the J.S. van der Merwe building was of ideal quality fit for lifetime consumption. Application of enrichment-and selective media allowed for the isolation of 12 different bacterial morphotypes. These were identified by way of biochemical-and molecular methods as Bacillus cereus, Bacillus subtilis, Brevundimonas spp., Clostridiaceae, Corynebacterium renale, Flavobacteriaceae, Kytococcus sedentarius, Leuconostoc lactic, Lysinibacillus sphaericus, Pseudomonas spp., Staphylococcus aureus and Staphylococcus capitis. The greatest diversity of bacteria was detected early autumn 2008, while the lowest diversity occurred during mid-winter 2007. Bacillus cereus, Kytococcus sedentarius and Staphylococcus capitis displayed potential pathogenic properties on blood agar. Kytococcus sedentarius could be classified as potentially the most pathogenic among the isolates. All isolates displayed multiple-resistant patterns towards tested antibiotics. Corynebacterium renale and Staphylococcus aureus were least resistant bacterial species and Lysinibacillus sphaericus the most resistant. All isolates were susceptible to ciprofloxacin (CIP) and streptomycin (S), but most were resistant to erythromycin (E). Transmission electron microscopy (TEM) allowed for detailed examination of Brevundimonas spp., Pseudomonas spp. and Staphylococcus spp. The capability of Brevundimonas spp. to produce slime and store nutrients within inclusion bodies, suggests the ability of this bacterium to form biofilm and persist in the drinking water for prolonged periods. Despite the inhibitory or toxic effect of copper against bacterial growth, scanning electron microscopy (SEM) revealed the presence of biofilms as well as diatoms on red-copper coupons. Biofilm activity was also observed on reverse-osmosis (RO) filters. Since corrosion was evident on red-copper coupons, it is recommended that prospective studies also look into the significance of microbial induced corrosion (MIC) within the Potchefstroom drinking water distribution system. Other prospects include determining minimum inhibitory concentrations of isolates against antibiotics and the application of culture independent methods such as SSCP and DGGE to investigate biofilm development. The use of diatoms as an index of the drinking water quality is also suggested. / Thesis (M.Sc. (Environmental Science))--North-West University, Potchefstroom Campus, 2010.

Water crises are predicted to be amongst the risks of highest concern for the next ten years, due to availability, accessibility, quality and management issues. Knowledge of the microbial communities indigenous to drinking water is essential for treatment and distribution process control, risk assessment and infrastructure design. Drinking water distribution systems (DWDSs) ideally should deliver to the consumer water of the same microbial quality as that leaving a treatment plant (“biologically stable” according to WHO). At the start of this Ph.D. program water microbiology comprised conventional culturedependent methods, and no studies were available on microbial communities from source to tap. A method combining 16S rRNA gene pyrosequencing with flow cytometry was developed to accurately detect, characterize, and enumerate the microorganisms found in a water sample. Studies were conducted in seven fullscale Dutch DWDSs which transport low-AOC water without disinfectant residuals, produced from fresh water applying conventional treatment. Full-scale studies were also conducted at the desalination plant and DWDS of KAUST, Saudi Arabia where drinking water is produced from seawater applying RO membrane treatment and then transported with chlorine residual. Furthermore, biological stability was evaluated in a wastewater reuse application in the Netherlands. When low-AOC water was distributed without disinfectant residuals, greater bacterial richness was detected in the networks, however, temporal and spatial variations in the bacterial community were insignificant and a substantial fraction of the microbiome was still shared between the treated and transported water. This shared fraction was lower in the system transporting water with chlorine residual, where the eukaryotic community changed with residence time. The core microbiome was characterized and dominant members varied between the two systems. Biofilm and deposit-associated communities were found to drive tap water microbiology regardless of water source and treatment scheme. Network flushing was found to be a simple method to assess water microbiology. Biological stability was not associated with safety. The biological stability concept needs to be revised and quantified. Further research is needed to understand microbial functions and processes, how water communities affect the human microbiome, and what the “drinking” water microbiome is like in undeveloped countries. / The research presented in this doctoral dissertation was financially supported by and conducted in collaboration with Delft University of Technology (TU Delft) and Evides Waterbedrijf in the Netherlands.