title: Arsenic removal from drinking water by a household sand filter in Vietnam--effect of filter usage practices on arsenic removal efficiency and microbiological water quality.
abstract: Household sand filters are applied to treat arsenic- and iron-containing anoxic groundwater that is used as drinking water in rural areas of North Vietnam. These filters immobilize poisonous arsenic (As) via co-oxidation with Fe(II) and sorption to or co-precipitation with the formed Fe(III) (oxyhydr)oxides. However, information is lacking regarding the effect of the frequency and duration of filter use as well as of filter sand replacement on the residual As concentrations in the filtered water and on the presence of potentially pathogenic bacteria in the filtered and stored water. We therefore scrutinized a household sand filter with respect to As removal efficiency and the presence of fecal indicator bacteria in treated water as a function of filter operation before and after sand replacement. Quantification of As in the filtered water showed that periods of intense daily use followed by periods of non-use and even sand replacement did not significantly (p<0.05) affect As removal efficiency. The As concentration was reduced during filtration from 115.1 ± 3.4 μg L(-1) in the groundwater to 5.3 ± 0.7 μg L(-1) in the filtered water (95% removal). The first flush of water from the filter contained As concentrations below the drinking water limit and suggests that this water can be used without risk for human health. Colony forming units (CFUs) of coliform bacteria increased during filtration and storage from 5 ± 4 per 100mL in the groundwater to 5.1 ± 1.5 × 10(3) and 15 ± 1.4 × 10(3) per 100mL in the filtered water and in the water from the storage tank, respectively. After filter sand replacement, CFUs of Escherichia coli of <100 per 100mL were quantified. None of the samples contained CFUs of Enterococcus spp. No critical enrichment of fecal indicator bacteria belonging to E. coli or Enterococcus spp. was observed in the treated drinking water by qPCR targeting the 23S rRNA gene. The results demonstrate the efficient and reliable performance of household sand filters regarding As removal, but indicate a potential risk for human health arising from the enrichment of coliform bacteria during filtration and from E. coli cells that are introduced by sand replacement.
authors.affiliation: Geomicrobiology, Center for Applied Geosciences, University of Tübingen, Tübingen, Germany.
authors.forename: Katja Sonja
authors.initials: KS
authors.lastname: Nitzsche
authors.affiliation: Center for Environmental Technology and Sustainable Development (CETASD), Hanoi University, Viet Nam.
authors.forename: Vi Mai
authors.initials: VM
authors.lastname: Lan
authors.affiliation: Center for Environmental Technology and Sustainable Development (CETASD), Hanoi University, Viet Nam.
authors.forename: Pham Thi Kim
authors.initials: PT
authors.lastname: Trang
authors.affiliation: Center for Environmental Technology and Sustainable Development (CETASD), Hanoi University, Viet Nam.
authors.forename: Pham Hung
authors.initials: PH
authors.lastname: Viet
authors.affiliation: Eawag, Swiss Federal Institute of Aquatic Science and Technology, Dübendorf, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Berg
authors.affiliation: Eawag, Swiss Federal Institute of Aquatic Science and Technology, Dübendorf, Switzerland.
authors.forename: Andreas
authors.initials: A
authors.lastname: Voegelin
authors.affiliation: Environmental Geochemistry, University of Bayreuth, Bayreuth, Germany.
authors.forename: Britta
authors.initials: B
authors.lastname: Planer-Friedrich
authors.affiliation: Geomicrobiology, Center for Applied Geosciences, University of Tübingen, Tübingen, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Zahoransky
authors.affiliation: Geomicrobiology, Center for Applied Geosciences, University of Tübingen, Tübingen, Germany.
authors.forename: Stefanie-Katharina
authors.initials: SK
authors.lastname: Müller
authors.affiliation: Geomicrobiology, Center for Applied Geosciences, University of Tübingen, Tübingen, Germany.
authors.forename: James Martin
authors.initials: JM
authors.lastname: Byrne
authors.affiliation: Geomicrobiology, Center for Applied Geosciences, University of Tübingen, Tübingen, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Schröder
authors.affiliation: Geomicrobiology, Center for Applied Geosciences, University of Tübingen, Tübingen, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Behrens
authors.affiliation: Geomicrobiology, Center for Applied Geosciences, University of Tübingen, Tübingen, Germany. Electronic address: andreas.kappler@uni-tuebingen.de.
authors.forename: Andreas
authors.initials: A
authors.lastname: Kappler
mesh_terms: D001151:Arsenic / Q000032:analysis*; D060766:Drinking Water / Q000737:chemistry* / Q000382:microbiology; D005191:Family Characteristics; D060587:Groundwater; D012822:Silicon Dioxide / Q000737:chemistry; D014744:Vietnam; D014871:Water Microbiology; D014874:Water Pollutants, Chemical / Q000032:analysis*; D018508:Water Purification / Q000379:methods*; D060753:Water Quality / Q000592:standards
chemical_list: D060766:Drinking Water; D014874:Water Pollutants, Chemical; D012822:Silicon Dioxide; D001151:Arsenic
keywords: Arsenate; Arsenite; Fecal indicator bacteria; Groundwater; Iron minerals; Sorption