Grantee Research Project Results
Process Engineering to Optimize Biosand Filtration for Point-of-use Applications in the Developing WorldEPA Grant Number: F5A20163
Title: Process Engineering to Optimize Biosand Filtration for Point-of-use Applications in the Developing World
Investigators: Elliott, Mark
Institution: University of North Carolina at Chapel Hill
EPA Project Officer: Packard, Benjamin H
Project Period: September 1, 2005 through August 1, 2006
Project Amount: $101,172
RFA: STAR Graduate Fellowships (2005) RFA Text | Recipients Lists
Research Category: Academic Fellowships
More than 1 billion people in the developing world lack access to safe, reliable sources of drinking water. The biosand filter (BSF) is a point of use (POU) drinking water treatment technology that allows people to improve the quality of their water by treating it in the home. The BSF is a biologically active, intermittently operated, household-scale version of a slow sand filter (SSF) that has been shown to be economically sustainable in many developing country settings. Conventional, large-scale SSFs have been used to treat drinking water for over 150 years but the operating parameters and performance of the BSF differ significantly from those of the conventional SSF. There are over 50,000 BSFs in use in the developing world today and there is an abundance of anecdotal evidence on the ability of the BSF to improve health. Notwithstanding what appears to be successful implementation, there has been little systematic, process engineering research to substantiate the effectiveness of the BSF or to optimize its design. Additionally, unlike other POU devices, epidemiologic field studies on the health impact of the BSF are completely absent from the literature. Until systematic laboratory and field research are conducted on the BSF, international aid organizations, NGOs and governmental institutions will remain reluctant to endorse the technology. We intend to conduct the laboratory and field research necessary to evaluate the efficacy of the BSF in reducing the concentration of enteric microorganisms and reducing the incidence of diarrheal disease.
The major objectives of the laboratory study are:
- to characterize the performance of the BSF for removing enteric bacteria and viruses
- to determine the operating parameters that control filter performance
- to isolate the mechanisms of microbial reduction and
- to make recommendations on filter operation and design modifications.
In parallel with the laboratory work, another student in our research group will be conducting an epidemiologic study to determine the effect of the BSF on diarrheal incidence.
Both full-scale and column experiments will be conducted in the laboratory. Operational parameters such as elevation head, sand type and size, standing water depth, and filter pause time will be evaluated based on their effects on microbial reduction. Investigation of the mechanisms of microbial attenuation will be conducted at column scale. Filter mechanisms will be investigated initially by monitoring dissolved oxygen and other parameters throughout the column and then by controlling for oxidative phosphorylation and protease activity. Recommendations for operational and design changes will be weighed in light of practical considerations for operation of the filter in the home. The field work will consist of a baseline determination of fecal indicator concentration and diarrheal incidence followed by a randomized longitudinal prospective cohort study. The field study will last roughly one year and take place in a community near Bonao, Dominican Republic.
We anticipate that future laboratory results will verify our preliminary findings that the BSF is capable of removing approximately 99% of enteric bacteria and roughly 90% of enteric viruses as currently configured. We hope that by understanding the operating conditions and mechanisms we will be able to modify the design and operation of the filter to achieve 99.9% reduction of enteric bacteria and 99% reduction of enteric viruses. We expect that the field study will establish the efficacy of the BSF for reducing the diarrheal disease incidence in developing country settings.