Coliform Sources and Mechanisms for Regrowth in Household Drinking Water in Limpopo, South Africa

Abstract

Resource-limited communities throughout the developing world face significant environmental health problems related to the myriad of coliform sources within those communities. This study comprehensively investigated contamination sources and the biological and chemical mechanisms sustaining them in two adjacent communities in rural Limpopo, South Africa. An 8-month study was conducted of household (n = 14) and source water quality, measurements of biofilm layers on the inside of household water storage containers and water transfer devices, and also hand-based coliforms and hand-washing effectiveness. A 7-day water container incubation experiment was also performed to determine the biological and chemical changes that occur in a household water storage container independent of human interference. Results indicate that household drinking water frequently becomes contaminated after collection but before consumption (197 versus 1,046 colony-forming units/100 mL; n = 266; p < 0.001). The most important contamination sources include biofilm layers on the inside of storage containers (1.85 ± 1.59 colony-forming units/cm2; n = 44), hands (5,097 ± 2,125 colony-forming units/hand; n = 48), and coliform regrowth resulting from high assimilable organic carbon (AOC) levels during storage. A maximum specific growth rate, μmax, of 0.072 ± 0.003 h−1 was determined for total coliform bacteria on AOC, and a high correlation between AOC concentrations and the growth potential of total coliform bacteria was observed. These results support the implementation of point-of-use water treatment and other interventions aimed at maintaining the safe water chain and preventing biological regrowth.

Modeling the Complexities of Water, Hygiene and Health in Limpopo, South Africa

“…Residents of Tshapasha and Tshibvumo get water from one of three di↵erent systems (Mellor et al , 2012b). The first source, referred to herein as "surface water" (SW), is a stream bisecting the communities.…”

“…contamination amount is based on field measurements previously reported (Mellor et al , 2012b), summarized in Chapter 2 and detailed in Appendix A.2. Likewise field measurements also found significant coliform bacteria associated with households"…”

“…If a household uses a "wide neck" storage container their water can be contaminated by water transfer devices and hands as detailed in Appendix A.2. During the storage period W Q i can increase or decrease daily as a result of bacteria regrowth or death which is a function of storage period, water source type and water container type (Mellor et al , 2012b).…”

“…The water chain model developed for this study was based on an 8-month investigation of community water quality and practices which was presented previously (Mellor et al , 2012b) and is summarized in Chapter 2. That study focused on 50 households within the communities and found significant monthly inter and intra-household water quality variability along with consistently higher levels of total coliform bacteria present at the household level compared to source water.…”

“…The myriad of pathogen sources within a typical developing-world community and the potential for biological regrowth (Mellor et al , 2012b) leads one to consider the fact that poor quality water is related to multiple technological, environmental and behavioral factors (Ezzati et al , 2005). It is this sort of thinking that has led some to suggest that a systems approach to enteric pathogen transmission would contextualize transmission and inform prevention and control e↵orts (Eisenberg et al , 2012).…”