Providing
Pure Water
Distinction
between
different Countries.
It
is
important to
distinguish the problems in most of the world, where high
arsenic
levels are rare, from the problems in Bangladesh and
Bengal. In most of the world, once arsenic has
been
discovered in drinking water, the most important
action is to
provide pure water to those who have been drinking
from the
wells. This was the action taken, for example, in
Taiwan, in
Chile, and in Inner Mongolia (as soon as the problem was
understood). In the developed countries
(in which we
include Chile and Taiwan) provision of pure water is
simple, and
not overly expensive. In the United States of America,
only a few
water supplies have levels of arsenic above 50 ppb, and even
the number
with levels above the standard of 10 ppb should be easily
manageable. In our listing of remediation
technologies we
must distinguish methods appropriate for the U.S.A. (and
large cities)
and those
appropriate for villages in Bangladesh West Bengal and
Southeast Asia
generally. We concentrate on the latter
and
Bangladesh in particular.
A tubewell such as
that shown above is
simple to drill and seems to get pure water.
BUT one
quarter of the wells drilled in Bangladesh tap an aquifer
containing
too much arsenic. This page outlines the
different
ways that people are using to address the problem and
provide arsenic
free pure water to all the people in the world,
particularly in SEAsia
and Bangladesh. This is a massive
effort. There is of course no exact
number, but as of
the year 2000 there were 70 million people drinking water
with arsenic
above the "old" US EPA standard of 50 parts per billion,
and 35 million
drinking water with levels above the new US EPA and WHO
recommended
standard of 10 parts per billion.
WHO has an excellent discussion of the scientific issues
involved on
their website at http://www.who.int/water_sanitation_health/dwq/wsh0306/en/index5.html.
The number of people supplied by
each system varies and the total number of Bangladeshis
is
therefore not certain. It is probably less than 10% of
the number
of Bangladeshis who need pure water. This
depends
upon the nature of the supply systems. It would be
useful if
there was a continuous monitoring of the number of systems
needed.
This
webmaster believes that in
all cases it is necessary to monitor the solution.
Is
it indeed
providing arsenic free water, bacteria free water a
year
later? Measurement
is therefore an
essential part of
any
remediation method.
In the view of
this
webmaster, the most important
feature is that the villagers must be fully involved with the
decision
(a so-called buy in) and be responsible for continued
maintenance and
monitoring. There must, of course, be
organizations with
expertize to advice and help when requested. A
decision
between these alternatives should include a discussion of the
available
follow-up
Eventually
each technology should be subjected to a
risk assessment - comparing risks and benefits of the
various
options. Even in developed countries such risk
assessments
are rare and can be misunderstood. Since the
major risk is
not of death, a measure must be found of sickness.
Two measures
are in use for this "Quality Adjusted Life Years " lost
(QALYs) and
"Disability Adjusted Life Years" lost (DALYs). See
for example
page 12 of "Risk
Benefit
Analysis"
A paper using such a procedure has been presented to
APSU, "Risk
Assessment
of
Arsenic Mitigation
Options (RAAMO)". The report finds
that the risks of improper use of
surface waters outweighs the risk of badly installed deep
tube wells.
A more complete report was presented to the Arsenic Policy Support
Unit (APSU), now defunct, in 2006 by MF
Ahmed,
G.Howard, D.
Deere S.G
Mahmud, and SKJ Shamsuddin.
It must be noted that the bacteria concentration numbers in
the APSU
reports for
dugwells is very pessimistic, because a collection of wells
was used,
some built according to WHO standards and some not, and it
appears
that none used chlorination. Moreover the
coefficients
relating the bacteria concentrations to risk came under very
heavy
criticism by Professor Allan Smith in the March 2009
conference
in Bangkok and maybe overestimates.
Well
switching
Left. a
well painted green(water
safe) and,
right, one marked red(arsenic content is toxic).
This is in many ways
the simplest,
cheapest and most effective method of remediation.
It is
important to
understand the causes
of the availability of arsenic in the tube wells and the
extent to
which the problems can be avoided by careful choice of
wells.
John
McArthur of University College, London, emphasizes
that 75% of the
shallow wells are doing what was intended - providing pure
water. The
general view is that 33% of the people in Bangladesh
villages have
switched wells in response to the general advertisement of
the
problem. The team of Columbia Uiversity and
University of Dhaka
scientists find that in Ariahazar Upazilla, where they
have been
working, 68% of people have switched wells. This
well switching
is the cause of the biggest number of persons now drinking
arsenic free
water who were not before. Yet in a Government of
Bangaldesh
survey, this still leaves 1400 villages without any well
that is free
of arsenic. Obviously, these villages are priority
villages for
the pilot projects for the various technologies discussed
below. This issue was discussed by the Arsenic
Policy
Support Unit (APSU) now defunct in a report
"not just red or green".
Various
remediation Systems
\
Small (Household) Scale Arsenic Removal
Use of
deeper wells
Surface
waters
Sanitary dugwells
River Sand Filters
Pond Sand Filters
Rainwater
collection and Storage
Large
Scale arsenic filtration
- Purifying
the water by simple inexpensive means available to each
household. Many
argue that
this last of the four solutions recommended in 2003 by
the Bangladesh
government, can only be a short
term solution but
the proponents
are more
optimistic.
Several groups (in Kushtia in Bangladesh for example,
claim lasting
success. Others have not had such good
experience. It
was widely recommended in 1978 as an emergency measure
but is
hard to
implement and maintain. An important facet
of many of the
early systems is that after a period of use there was
and is a
"breakthrough". The filtering action ceases,
and even some
of the arsenic previously trapped comes
back. There
has
been a mixed experience. Dipenkar
Chakraborti, Meera Smith
and John McArthur all find that many systems have
stopped working in
many
places in West
Bengal . The reasons are
unclear. Maybe it is because of the
break
through that is not understood by villagers,
maybe
because of clogging by
iron. Not only is it a waste of
resources but it is a
tragedy of false
hopes. As discussed further below, there
is one system, the
SONO filter, for which "breakthrough" has not been
observed. For this system there is
also local
backup In Kushtia.
- Drilling
deep wells (150+ m) where arsenic contamination is at
present
smaller. This is being urged by UNICEF and
Columbia
University scientists. It will
probably be fine for
75% of locations in Bangaldesh. But this solution
may not be
available
everywhere. There have been some problems so
that
continued monitoring (yearly arsenic measurement) is
recommended by all
experts.
- Encouraging
a return to well constructed and sanitary,
surface (dug) wells,
in which arsenic contamination
tends
to be smaller than in the tube wells - even
those on the
surface. This, as
noted
below, is an option that is being studied by Professor
Chakraborti,
Dr Meera Smith , Dhaka
Community Hospital (DCH), with some scientists in
Harvard
University. But they must be installed with care.
This
webmaster urges
strict attention to WHO
guidelines (which includes use of
disinfectants).
Chlorination was not at first used in Bangaldesh, although
widely used
in most other countries, but recent work
by DCH suggests that chlorination at least every two
weeks is
essential - especially in the monsoon period.
The necessary
monitoring ( measurement of bacterial contamination) is
uncertain but
once a year may be fine provided chlorination is used, and
provided it
is done at a time of expected maximum
pollution. In
2009 this is being studied further
- Rainwater collection and
storage. Again the long storage time needed
from the time
of heavy rain to the end of the dry season suggests the
need for careful attention to sanitation.
Small
(Household) Scale Arsenic Removal
At
the first
International Conference on Arsenic in drinking water,
held in
Dhaka in February 1998 simple methods for each household to
filter the
water were suggested as an immediate short term
solution. They
have in common a series
of
containers.
Water is poured into the top container and
filters through
sand and iron chips to the bottom container where the water
is now
free of arsenic. It was hoped that these methods
would be
easily used by villagers, would use local
materials, and be
affordable. Several groups claim
lasting success.
Here is a 2001
report of several systems by an independent company,
WR Akins.
Guy
Howard of the Bangladesh
Arsenic Policy Support Unit
pointed
out that there were, in August 2005, 100,000 household
arsenic
removal units in
Bangladesh.
Dr
Abul Hussam of George Mason University, with his brothers in
Kushtia
and Dhaka,
designed and market the
SONO/MSUK
filter.
21,000 SONO filters have
been distributed throughout Bangladesh by May
2006. They
are marketed from their base in Kushtia. 400,000 people
drink
water from these filters from may parts of Bangladesh as shown
in the map..
PDF files of
photographs and other details of the SONO filter can be downloaded.
Professor Abul
Barkat of
the University of Dhaka comments that they "have collected
data for last four years (that's how long some of these
filters are
running). More than a billion liters of water has been
consumed
from these filters. The filter has been optimized to
last for
seven years minimum at a cost of $35.00"
The system is continuously being modified
and updated. The importance of the back up that
is provided
for the SONO filter is the example of a dozen filters that
were
supplied in the village of Eurian in eastern Bangladesh
where Dr
Chakriborti of Kolkata and DCH are working. The
tests, in
2005, of
these filters in the field by DCH were far from
satisfactory. Dr Hussam believes this was due to
a
manufacturing defect that has now been corrected and the
group has
replaced the filters at no charge. The test results of the
replacement
filters are excellent. This emphasizes the importance
for this
method, of
expert back up. The need for expert back up probably
applies for all
mitigation methods! A recent independent report on
the SONO
filter shows that this filter is playing a major role in
reducing the
Bangaldesh arsenic problem. Additional data on the tests on
the SONO
filter installed by BAMWSP-DPHE in Hagijang, Chandpurhas can
be found here.
Furthermore, the water quality test report on the SONO
filter installed
by the BAMWSP-DPHE in Gojaria, Munishijang can
be found here.
The SONO filter by
itself does not grow
bacteria as shown in tests
by
Village Education Resource Center (VERC),
In other
locations problems
arose. According to the 6th report by
the Jadavpur
University team, 80% of Arsenic Removal Systems (ARS) in
West Bengal
are not functional. Not only is it a waste
of several millions of dollars but also it is a tragedy of
false hopes.
It was noted as early as 1998 that the systems then proposed
all had a
problem of "breakthrough"
After a certain time, the
filtering
action ceases, and even some of the arsenic previously
trapped comes
back. The
existence of
the "breakthrough" was a primary reason that the filters
were proposed,
as stated on this site at the time, solely as a short term
solution. A possible reason for the
failures is
explained in
this note from Professor
McArthur.
"Do they know the water is Fe-rich? If not, find a way
to tell
them. It
might change their view of the matter, because, unless Fe is
removed
before the As plant, it messes up a good deal of the removal
technology
currently available: and, as an Fe-removal plant aerates and
precipitates FeOOH, it removes most of the As. This is
standard (old)
technology. If they fund someone who does not know the water
is Fe-rich
(and most don't) they
may
put a
big sum into methods doomed to fail.
Attached is a good example: a year old and doomed to follow
20 or so
other clones now abandoned that litter my field area in West
Bengal.
Raw feed
is 900, output 300 and climbing, blocked by Fe most of the
time: a
disaster." Another reason may be
that
villagers
found them too complex to use.
In this connection it is very encouraging
that the
SONO filter has so far
experienced no breakthrough.
Whether the break though will come in 7 years, 20 years or
not within a
lifetime is unknown. But this gives a user, and
those
recommending their use, enormous confidence. It
seems clear
that the reliability and
effectiveness of Arsenic Removal Systems depends upon the
water
chemistry, and probably on the maintenance. It
is also
unclear whether laboratory experience is predictive of
performance in
the field. It is unclear to this webmaster whether the
SONO or
other filters work on all waters in Bangladesh; and
if a particular ARS only works on some waters how to decide
whether it
will work on a particular village water and how to explain
all of this
to the villagers affected.
In 1978 t
he Government Of
Bangladesh instituted a program now called BETV-SAM
(Bangaldesh Environment
Technology Verification-Support to Arsenic Mitigation) to
verify the
claims
regarding the efficacy of Arsenic Removal Technologies
and
appointed BCSIR ( Bangladesh
Council
of
Scientific and Industrial
Research) to carry out this program. BCSIR is
being assisted by OCETA (Ontario Center for Environmental
Technology
Advancement) of Canada. This program was supported by
CIDA and BAMWSP (Bangladesh
Arsenic
Mitigation Water Supply Project
financed by the World Bank).
Under
the current GOB regulations, no
arsenic removal technology may be deployed in Bangladesh
unless it is
cleared by the BETV-SAM program. In February 2004 the first four
technologies were approved for
"provisional" use and are now being sold -READ-F, SONO
45-25 (the system noted above designed by Dr Hussam for
which he
has been awarded the Grainger challenge prize ), Sidko and
MAGC/ALCAN.
For three years the webmasters unsuccessfully tried
to obtain a
copy of the report but now the
report
of
BETV-SAM has now been posted on the BAMWSP website and
is copied
here.
It is noteworthy that
releases of
the test results failed to note the important fact that only
the
SONO filter had no 'breakthrough". In Nepal, the KANSHAN filter
has been
deployed by Susan Murcott but the webmasters have no test
data thereon.
A new
system,
Electrochemical Arsenic Removal (ECAR)
has been developed at Lawrence
Berkeley
Laborotary is is now being tried in the field both in
India and in Bangladesh. This webmaster has no
opinion yet
on the relative advantages and disadvantages.
Medium (community) Scale
Arsenic Removal
The pessimistic
conclusions of Chakriborti and
McArthur are also challenged in West Bengal by Arup Sengupta
of Lehigh
University , John E, Lee M. Blaney,
Owen E.
Boyd, Arun K. Deb,
and
the
nonprofit organization Water For
People and
colleagues in Bengal Engineering
College. Their
detailed paper of the results of follow up on over 150
(now 200) medium sized
systems seems convincing. As of June 2011
their Tagiore-SenGupta Foundation was awarded the first
prioze of $50,000 in the Reed-Elzevier environmental
challenge for this fine work.in West Bengal. The cost is
about $1,200 for a unit which purifies water for 300
families or about
1200 people. This works out at $1 per
person. We are delighted that the Silver award of
the Grainger Challenge Prize of $200,000 has been awarded to
this
details of
the award can be accessed here. Anyone
interested should call Dr Anriban Gupta at Bengal
College. As of June 2011 their Tagiore-SenGupta Foundation
was awarded the first prioze of $50,000 in the Reed-Elzevier
environmental challenge for this fine work.in West Bengal.
In 2006 this webmaster
made a tentative conclusion: it is vital to have
a village
community that is committed to follow up maintenance and
hopefully a
nearby institution for expert backup information and
advice. In 2011 he is more sure of this than
ever.
Subterranean Arsenic
Removal
In some places it may
be possible to remove the arsenic by oxidiation of the
aquifer. This is the aim of the Subterranean Arsenic
Removal (SAR)
technology proposed by Mukherjee of Kolkata,
India. They cliam" This technology can
transform the way arsenic is removed from groundwater in
Ganges,
Brahmaputra and Mekong delta where the arsenic is of
arsenopyrite
origin, saving millions of lives. This includes affected areas
of
India, Bangladesh, Cambodia, Nepal, Vietnam and Thailand. The
technology is about to be implemented in Cambodia and Burkina
Faso with
the help of Royal University of Phnom Penh and ‘Friends in
Action
International’ respectively, subject to proper research. The
technology
is scalable from a production capacity of 10,000 litres/day
(USD 4,000)
to 1,00,000 litres/day (USD 20,000) for each plant, catering
to the
drinking water needs of 2000 to 20000 people, depending on the
soil
& water conditions."
A couple of years ago Harvey
tried expeiments along these lines with limited success
Various
Charitable organizations are helping to bring pure water to
Bangladesh
and SE Asia. This webmaster
suggests
that you
financially support one or all (any currency) and airline
frequent
flyer
coupons gratefully accepted:
