Regrowth and survival of indicator microorganisms on the surfaces of household containers used for the storage of drinking water in rural communities of South Africa

Abstract

The present study covered two rural communities of South Africa: Ncera and Ntselamanzi villages. Raw water from Ncera river is used by the community of Ncera village for drinking, while the community of Ntselamanzi receives their drinking water from Alice purification system. Treated water is supplied to the community by a public standpipe system. In rural communities of South Africa, many households use polyethylene (PE) and galvanized steel (GS) containers for the storage of their drinking water. To investigate the regrowth and survival of indicator microorganisms on the surface of household containers during the storage of drinking water, PE and GS slides were suspended in the appropriate household containers for a period of 48 h. This period of 48 h was chosen as the study period because results from the questionnaire indicated that the largest percentage (62%) of households store their water for that length of time. The experiment was performed to test drinking water as it is collected and stored by rural communities. No disinfection of household containers or slides was done during the study period. Attached coliphages (F-RNA (FP) and somatic phage (SP), coliform bacteria (total coliform (TC), presumptive Escherichia coli (EC), Salmonella (Sal) and Clostridium perfringens (CP) were measured during the study period. With the exception of CP , attached indicator microorganisms consisted of TC, presumptive E. coli and Salmonella, somatic and F-RNA coliphages, although the yield (average count) for the last four groups (EC: <1–3 cfu cm −2, Sal: <1–15 cfu cm −2, FP: <1–7 pfu cm −2, SP:<1–7 pfu cm −2) was lower than that of TC (3–183 cfu cm −2). However, the lowest yield of indicator microorganisms was noted for presumptive E. coli. Whereas the occurrence and survival of TC was noted on the surface of household containers during the entire period of the experimental study, other indicator microorganisms occurred from time to time. The regrowth of indicator microorganisms occurred 48 h after the exposure of slides to both types of test waters. This length of time mostly resulted in the regrowth of TC (with an increase in bacterial counts) while the persistence of other indicator organism groups on the surface of the slides was apparent. A comparison between PE and GS containers showed that more TC (average count) regrew on PE than on GS containers (for river water, PE: from 36 to 55 cfu cm −2, GS: from 25 to 26 cfu cm −2; for standpipe water, PE: from 147 to 183 cfu cm −2, GS from 3 to 4 cfu cm −2). This study revealed that both types of household containers supported the growth and survival of indicator microorganisms due to the bad quality of the intake water before storage. The storage of drinking water for 48 h mainly resulted in the regrowth of TC. Nevertheless, the persistence of other indicator microorganisms was observed on the surface of household containers.