Abstract
The microbial contamination in a spring water distribution system in the Western Cape, South Africa was investigated. Sampling at various points from the spring and throughout the bottling system started in February and continued until November 2004. The number of culturable cells was determined using the heterotrophic plate count (HPC) and total microbial counts were evaluated by flow cytometric analysis (FCM). Heterotrophic plate counts in the final bottled water ranged from 1.34 x 108 cfu/ml (week 1) to 5 x 104 cfu/ml (week 46). In comparison, the total cell counts (FCM) ranged from 2.09 x 108microorganisms/ml (week 1) to 5.70 x 107 microorganisms/ml (week 46).The higher FCM counts indicated that the flow cytometry technique was able to detect viable but non-culturable organisms in the water and was thus more reliable for the routine quantitative enumeration of microbial populations in water samples. 16S ribosomal ribonucleic acid (rRNA) of the bacterial species present was amplified with PCR and phylogenetic trees were constructed using the neighbour-joining algorithm. The sequenced isolates from the various water samples belonged to the major groups Bacillus sp, and Enterobacteriaceaeand included Shigella boydii, Serratia sp., Enterobacter asburiae and Pseudomonas sp. Key words: Bacterial contamination, flow cytometry, heterotrophic plate count, molecular typing, spring water distribution system.
Highlights
Natural spring water is obtained directly from underground water sources and is collected under conditions that maintain its natural chemical composition and microbiological purity
The spring water system sampled was experiencing problems with bacterial contamination and the high counts could be ascribed to the fact that the 0.35 μm filter of line two was contaminated, clogged or faulty or that a biofilm was present in the distribution system which periodically sloughed off and served as a continuous source of contamination
In spring water distribution systems filters must be backwashed on a regular basis to maintain the integrity of the filter system, as non-fixed pore filters enlarge in pore size after high water volumes have passed through them, resulting in the release of trapped contaminants into the filtered water (Pall Filters, 2004)
Summary
Natural spring water is obtained directly from underground water sources and is collected under conditions that maintain its natural chemical composition and microbiological purity. Natural bottled water can only be subjected to certain treatment processes such as the separation from unstable constituents by decantation and or filtration, aeration, and by any process that will ensure that the natural mineral content is not modified, such as ultraviolet irradiation and ozonation (South Africa Department of Health, 2004). It is essential to assess the microbial contamination risk or the level of pollution at the location of the spring (Leclerc and Moreau, 2002). Coliforms are present in large quantities in soil, and if found in water they usually present a significant health risk. The water source should be routinely tested for faecal contamination and coliforms are used as indicator organisms in bottled water analysis (Ryan, 2004)
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