A GLOBAL RECONNAISSANCE SURVEY OF PARTICULATES IN UNTREATED DRINKING WATER SOURCES: POTENTIAL RELATIONSHIPS TO WORLDWIDE METADATA

Waterborne illnesses can be caused by microbes, heavy metals, organic compounds, or suspended particulate matter. These are commonly present in untreated water in some combination, with particulate matter often being the substrate and transport vehicle for contaminants. Our group has addressed the role of particulates in drinking water by collecting baseline information on untreated drinking water sources in 25 countries. One aspect of the research is to explore correlations between particulates and regional land use, population density, ambient temperature, precipitation, elevation, soil type, bedrock, and waterborne microbial communities. Sampling for this global survey is done by trained NGO staff using 0.1 μm hollow-fiber membrane filters to assess local water sources. Filters are returned to Hope College where they are back-flushed to recover retained material. Particulate concentration, turbidity, and grain size distribution are being estimated by spectrophotometric measurements of re-suspended materials. Mineralogy is determined by PXRD and SEM-EDS analysis. Preliminary results from 120 different sources show that particulate concentration in water ranges from 90 to < 1 ppm, with (NTUs) ranging from 650 to < 1. In more than 60% of the sources, it is estimated that > 50% of the suspended load is agglomerates of particles < 100 nm diameter. Clays, feldspars, carbonates and quartz are commonly identified. Some samples contain metal oxides, sulfides, and other potentially ore-related phases. Population density in the vicinity of the sites ranges from over 17,000 people/sq. km. to 1 person /sq. km. ( mean = 922 (± 3088), median = 70 mode = 94). A negative correlation exists between suspended load concentration (turbidity) and population density. No consistent trends have emerged regarding bedrock geology and suspended load concentration, though waters with the highest levels are all located in volcanic terranes. This reconnaissance survey is still underway and relationships between particulate material in drinking water sources and other geographic characteristics are being investigated, including correlations to dissolved heavy metal concentrations. Another goal is to relate data from this study to the presence of microbes, and their potential effects on human health.