Arsenic removal with zero-valent iron filters in Burkina Faso: Field and laboratory insights

Anja Bretzler*, Julien Nikiema, Franck Lalanne, Lisa Hoffmann, Jagannath Biswakarma, Luc Siebenaller, David Demange, Mario Schirmer, Stephan J. Hug

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

47 Citations (Scopus)

Abstract

Groundwater contaminated with geogenic arsenic (As) is frequently used as drinking water in Burkina Faso, despite adverse health effects. This study focused on testing low-cost filter systems based on zero-valent iron (ZVI), which have not yet been explored in West Africa for As removal. The active ZVI bed was constructed using small-sized iron nails, embedded between sand layers. Household filters were tested for nine months in a remote village relying on tube well water with As concentrations of 400–1350 μg/L. Daily filtered volumes were 40–60 L, with flow rates of ~10 L/h. In parallel, downscaled laboratory filter columns were run to find the best set-up for optimal As removal, with special attention given to the influence of input pH, flow rate and water/nail contact time. Arsenic removal efficiencies in the field were 60–80% in the first six months of operation. The laboratory experiments revealed that trapped air in the nail layer greatly lowered As removal due to preferential flow and decreased water/nail contact time. Measures taken to avoid trapped air led to a partial improvement in the field filters, but effluent As remained >50 μg/L. Similar structural modifications were however very successful in the laboratory columns, where As removal efficiencies were consistently >95% and effluent concentrations frequently <10 μg/L, despite inflow As >1000 μg/L. A constantly saturated nail bed and careful flow control is necessary for optimal As removal. Slow flow and longer pauses between filtrations are important for sufficient contact times and for transformation of brown amorphous Fe-hydroxides to dense magnetite with incorporated As(V). This preliminary study has shown that nail-based filters have the potential to achieve As removal >90% in a field context if conditions (filter bed saturation, flow rate, pauses between filtrations) are well controlled.

Original languageEnglish
Article number139466
JournalScience of The Total Environment
Volume737
DOIs
Publication statusPublished - 1 Oct 2020

Bibliographical note

Funding Information:
Many thanks to the team of the NGO “Le Soleil dans la Main”, especially Adèle Ouédraogo and Didier Kienou for the organization and support of the field trials. Thank you to Moustapha Ouédraogo (2iE) for assembling the filter buckets and to the villagers of Souriyala for their collaboration and cooperation. We are grateful to Thomas Rüttimann (Eawag) for ICP-MS analysis and technical support. We gratefully acknowledge Carsten Bahr of GEH Wasserchemie GmbH & Co. KG in Osnabrück for supplying GEH free of charge for research purposes. Thanks also to Guillaume Clair (Eawag) for helpful discussions and to all people that transported water samples from Ouagadougou to Switzerland. Funding for this study was provided by the Swiss Agency for Development and Cooperation (SDC) through the “Programme 3E” (contract no. 81016359 ) and the Information Management System on Geogenic Contaminants , GAP (contract no. 81025383 ).

Funding Information:
Many thanks to the team of the NGO ?Le Soleil dans la Main?, especially Ad?le Ou?draogo and Didier Kienou for the organization and support of the field trials. Thank you to Moustapha Ou?draogo (2iE) for assembling the filter buckets and to the villagers of Souriyala for their collaboration and cooperation. We are grateful to Thomas R?ttimann (Eawag) for ICP-MS analysis and technical support. We gratefully acknowledge Carsten Bahr of GEH Wasserchemie GmbH & Co. KG in Osnabr?ck for supplying GEH free of charge for research purposes. Thanks also to Guillaume Clair (Eawag) for helpful discussions and to all people that transported water samples from Ouagadougou to Switzerland. Funding for this study was provided by the Swiss Agency for Development and Cooperation (SDC) through the ?Programme 3E? (contract no. 81016359) and the Information Management System on Geogenic Contaminants, GAP (contract no. 81025383).

Publisher Copyright:
© 2020 The Authors

Keywords

  • Arsenic
  • Burkina Faso
  • Drinking water treatment
  • Filtration
  • Groundwater
  • Zero-valent iron

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