DSpace at VNU: Response to comment on "Arsenic removal from groundwater by household sand filters: Comparative field study, model calculations, and health benefits"

Environ. Sci. Technol. 2007, 41, 1053

Response to Comment on “Arsenic Removal
from Groundwater by Household Sand Filters:
Comparative Field Study, Model Calculations,
and Health Benefits”
We appreciate the comments made by Blaney and co-authors
(1) highlighting their important contribution in providing
thousands of people in West Bengal with drinking water that
is treated for arsenic removal in community-based activated
alumina units. Operation and performance of these units
are documented in a publication published by Sarkar et al.
(2).
The primary comment of subject (1) refers to a remark
made in the introduction of our recent article (3). We therein
state: “There is an urgent need for simple and efficient As
removal techniques on the household level. Ion exchange,
activated alumina, reverse osmosis, membrane filtration,
modified coagulation/filtration, and enhanced lime softening
are water treatment technologies for As removal recommended by the USEPA. However, none of these technologies
are currently applied on a broad scale in developing countries
because they require sophisticated technical systems and
are therefore unpractical in low income regions.” Correspondingly, our work focused on the performance and
applicability of point-of-use sand filters for arsenic removal
that are constructed, operated, and maintained by each
individual family on their private home premises. This is a
considerably different situation which cannot be compared
to the community based approach referred to in the comment
(1).
We evaluated sand filters in Vietnam where millions of
people are using arsenic-burdened groundwater for daily

drinking water needs (4, 5). People in this area prefer to have
a drinking water supply in their own houses. We showed
that household sand filters, which use locally available sand
and operate without chemicals, can achieve average arsenic
removal rates of 80% in groundwater. Additionally, analyses
of hair samples verified that people consuming this sandfiltered water lowered their arsenic body burden to physiologically safe levels. The concentration of dissolved iron in
groundwater is the decisive factor for the removal of arsenic.
The easily observable removal of iron from the pumped water
makes the effect of a sand filter immediately recognizable
even to people who are not aware of the arsenic problem.
Regarding the use of activated alumina (AA), Blaney et al.
in their comment do not mention that (i) the AA units are
periodically regenerated with 175 L of 4% NaOH and 150 L
of 1% HCl (2), (ii) AA must eventually be replaced after a
certain lifetime, and, (iii) monitoring of arsenic levels in the
unit outlet is applied (2). Hence, unlike the sand filters
described in our publication (3), AA requires chemicals and
presumably demands well-trained people to properly conduct such maintenance. Besides, 10% of iron seems to pass
the AA unit while the household sand filters remove g99%.
The second issue addressed by Blaney et al. probably arises
from misreading of the section entitled “Model Calculations”

10.1021/es062798d CCC: $37.00
Published on Web 12/30/2006

 2007 American Chemical Society

in our paper. We have exclusively modeled passive coprecipitation (but not sand filters) of arsenic to freshly precipitated HFO using sorption constants derived from laboratory
experiments (6), but we did by no means state that “birnessite
might be responsible for greater arsenic removal with sand

filters than with coprecipitation.” In fact, the particular
paragraphs compare coprecipitation efficiencies determined
in real groundwater in the field with coprecipitation experiments performed in the laboratory in artificial groundwater.
Concerning the third point, we generally agree that
community-based arsenic removal providing drinking water
for some 100 families has the advantage of concentrating
arsenic-burdened sludge in one confined place, where its
disposal can better be secured than in individual households.

Literature Cited
(1) Blaney, L.; Sarkar, S.; SenGupta, A. K. Comment on “Arsenic
Removal from Groundwater by Household Sand Filters:
Comparative Field Study, Model Calculations, and Health
Benefits”. Environ. Sci. Technol. 2007, 41, 1051-1052.
(2) Sarkar, S.; Gupta, A.; Biswas, R. K.; Deb, A. K.; Greenleaf, J. E.;
SenGupta, A. K. Well-head arsenic removal units in remote
villages of Indian subcontinent: Field results and performance
evaluation. Water Res. 2005, 39 (10), 2196-2006.
(3) Berg, M.; Luzi, S.; Trang, P. T. K.; Viet, P. H.; Giger, W.; Stu
¨ ben,
D. Arsenic Removal from Groundwater by Household Sand
Filters: Comparative Field Study, Model Calculations, and
Health Benefits. Environ. Sci. Technol. 2006, 40, 5567-5573.
(4) Berg, M.; Tran, H. C.; Nguyen, T. C.; Pham, H. V.; Schertenleib,
R.; Giger, W. Arsenic Contamination of Groundwater and
Drinking Water in Vietnam: A Human Health Threat. Environ.
Sci. Technol. 2001, 35, 2621-2626.
(5) Trang, P. T. K.; Berg, M.; Viet, P. V.; Mui, N. V.; van der Meer,
J. R. Bacterial Bioassay for Rapid and Accurate Analysis of
Arsenic in Highly Variable Groundwater Samples. Environ. Sci.

Technol. 2005, 39, 7625-7630.
(6) Roberts, L. C.; Hug, S. J.; Ruettimann, T.; Billah, M.; Khan, A.
W.; Rahman, M. T. Arsenic removal with iron(II) and iron(III)
waters with high silicate and phosphate concentrations.
Environ. Sci. Technol. 2004, 38, 307-315.

Michael Berg,* Samuel Luzi, and Walter Giger
Eawag, Swiss Federal Institute of Aquatic Science and
Technology
Ueberlandstrasse 133, 8600 Du
¨ bendorf, Switzerland

Pham Thi Kim Trang and Pham Hung Viet
Center for Environmental Technology and Sustainable
Development (CETASD)
Hanoi University of Science
334 Nguyen Trai, Hanoi, Vietnam

Doris Stu1 ben
Institute for Mineralogy and Geochemistry
University of Karlsruhe
Kaiserstrasse 12, D-76128 Karlsruhe, Germany
ES062798D

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