Water quality at points-of-use in the Galapagos Islands

- The Galapagos Islands have poor drinking water quality despite improvement efforts.
- Clean finished water at the DWTP is contaminated during distribution or storage.
- Lack of human-specific fecal bacteria implicate other sources of contamination.
- Detected E. coli appears to be associated with environmental contamination.
- HF183 markers have similar prevalence in Galapagos as other populations.

Piped drinking water is often considered a gold standard for protecting public health but research is needed to explicitly evaluate the effect of centralized treatment systems on water quality in developing world settings. This study examined the effect of a new drinking water treatment plant (DWTP) on microbial drinking water quality at the point-of-use on San Cristobal Island, Galapagos using fecal indicator bacteria total coliforms and Escherichia coli. Samples were collected during six collection periods before and after operation of the DWTP began from the freshwater sources (n = 4), the finished water (n = 6), and 50 sites throughout the distribution system (n = 287). This study found that there was a significant decrease in contamination by total coliforms (two orders of magnitude) and E. coli (one order of magnitude) after DWTP operation began (p < 0.001). However, during at least one post-construction collection cycle, total coliforms and E. coli were still found at 66% and 28% of points-of-use (n = 50), respectively. During the final collection period, conventional methods were augmented with human-specific Bacteroides assays - validated herein - with the goal of elucidating possible microbial contamination sources.Results show that E. coli contamination was not predictive of contamination by human wastes and suggests that observed indicator bacteria contamination may have environmental origins. Together these findings highlight the necessity of a holistic approach to drinking water infrastructure improvements in order to deliver high quality water through to the point-of-use.