Influence of storage containers on the physicochemical and microbiological (biofilm formation) indices of drinking water sources

Abstract

Effect of surfaces of earthenware pots, glass, plastic and stainless steel containers on the physicochemical and bacteriological (biofilm formation) quality of borehole and atmospheric water stored for twelve days were determined using standard analytical and bacteriological techniques. Susceptibility of the bacterial isolates to different antibiotics was also determined using standard Kirby-Bauer agar disc diffusion procedures. The physicochemical parameters determined for borehole water sample were within WHO permissible standard while rain water sample recorded slightly higher values for NO3 - , and NO2 (10.2 mgL -1 and 0.045 mgL -1 respectively) than WHO standards of 10 mgL -1 and 0.02 mgL -1 respectively. Biofilm bacterial communities from stored borehole water consisted of nine genera including Pseudomonas, Micrococcus, Klebsiella, Bacillus, Staphylococcus, Escherichia, Proteus, Serratia, and Enterobacter. The recovery rate of the various bacterial genera were 40% in earthenware pot, 80% in plastic, 70% in stainless steel and 60% of the genera were isolated from glass container for stored borehole water. Fewer bacterial genera were isolated from stored atmospheric water and these included Pseudomonas, Bacillus, Staphylococcus, Streptococcus and Yersinia. The isolates were recovered at the rates of 40%, 80%, 60% and 40% in earthenware pot, plastic, stainless steel and glass containers respectively. While Escherichia coli, Yersinia sp and Pseudomonas aeruginosa exhibited remarkable sensitivity to Septrin (30 μg), Ampicillin (30 μg), Augmentin (30 μg) and Nalidixic acid (10 μg) as evinced by clear zones of inhibition, Enterobacter sp, Klebsiella sp and Proteus sp were moderately sensitive to some of the tested antibiotics. Amongst the gram positive bacteria, Micrococcus sp was most sensitive to the various antibiotics. Although Staphylococcus aureus showed resistance to most of the tested antibiotics, it was sensitive to Erythromycin (30 μg) and Chloramphenicol (30 μg). It could be deduced from the above results that the physicochemical and bacteriological quality of stored water are affected by both the source of the water and type of storage vessel. Although the effect of the vessels are not definitive, the levels of pH, Mg 2+ , NO2 - , NO3 - and hardness are enhanced in water stored in earthenware pots. The isolation of antibiotic resistant bacteria from stored water is of public health concern, thus, drinking water should not be held in containers for more than a day or two.