Global Survey of Suspended Load Mineralogy and Heavy Metal Content in Rural Drinking Water Sources Using Point-of-Use Water Filter Kits

Waterborne illnesses continue to be a major global health concern. One strategy for providing clean drinking water is point-of-use water filters. Hope College has partnered with a privately-owned outdoor product company to test the efficacy of hollow-fiber membrane filters in removing bacteria, protozoa, cysts, and other water-borne microbes from rural drinking water sources. This global water-quality survey is testing water from 30 different countries. Field collection is performed by NGOs which deliver water filter kits to sites, collect and process water samples, and return the filters to Hope College for genetic analysis of microbial populations.

In addition to collecting microbial information, field kits also include polyurethane foam filters (PFFs) for capture of heavy metals. Returned PFFs will be processed and analyzed with ICP-OES for the presence of heavy metals sequestered from water. Several different protocols for the analysis of metals retained by PFFs are currently being developed and tested. These include digestion, rinsing and ashing procedures.

Returned filters also offer a unique opportunity to assess the suspended load (TSS) concentration and mineralogy of drinking water sources. Through a systematic backflush procedure, suspended load particles filtered from water can be retrieved, and the TSS load estimated by spectrophotometric measurement of the re-suspended materials. Mineralogy can be determined by a combination of PXRD and SEM analysis. Re-suspension absorbance can be correlated to model suspensions based on the composition of bedrock and substrate materials at the sampling localities or by the mineralogy of retrieved particulate matter.

Filters from many countries have been returned for analysis, including Solomon Islands, Fiji, Mexico, Liberia, India, Indonesia, Peru, Costa Rica, Haiti, Kenya, Ecuador and Senegal. Preliminary results show a range of TSS, with large differences between surface and groundwater. Minerals retrieved correlate somewhat to bedrock composition, but are not representative of the geologic substrate in all source localities.

This survey is still underway and data will be used to evaluate rural human health in the context of inorganic suspended load, the presence of heavy-metal contamination and overall microbial content of drinking water sources.