Final report of Deep
aquifer Data BAse and Preliminary Deep Aquifer Map. (Local
Government Division, GoB March 2006)
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. An overview of the arsenic problem in
Bangladesh written by the webmaster can be found here.
Will you
Help?
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 frquent flyer
coupons gratefully accepted:
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 hae 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.
For
Bangladesh there is now a NATIONAL
WATER POLICY. There
are various annexes with instructions on how to fulfil various parts of
the policy. The various file are listed in this
directory. Professor Dipankar Chakraborti who has
worked for 18 years on these
problems recently (2005) outlined
his strategies for
mitigation of
the arsenic problems
in West Bengal and
Bangladesh. It may be downloaded in full but this
webmaster will quote from various parts of it in due course. In the opinion of this webmaster there is
no conflict between these various options for getting pure
water.
This webmaster
believes, first
and foremost, that it is important to make the villagers fully aware of
the
problem and involve them in the solution. It is vital to
gain their confidence. In this connection it is
important that, according to a recent study, villagers seem to
be more willing to pay for running water than for arsenic free
water. Thus, any solution which leads toward running water
is to be preferred (see the second
and third phases of the DCH program on dugwells below).
It is important to listen to women in the villages as well as to
men. Women do most of the water carrying.
At the WHO conference and at the
5th International Arsenic
Conference in San Diego in
July 2002 several different methods were discussed as appropriate
for different places. The Bangladesh Arsenic Mitigation Water
Supply Project recommended the first three of these.
Purifying
the water by simple inexpensive means available to each
household. Many argue that
this last of the four recommended solutions, can only be a short
term solution but the proponents are more
optimistic.
Several groups (in Kushtia in Bangaldesh for example, and in Nepal,
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. It also leaves a lot of sludge that must be
disposed. There
has
been a mixed experience. Dipenkar Chakraborti, Meera Smith
and John McArthur all find that systems have stopped working in many
placesin West Bengal (presumably because of clogging by
iron). Not only is it a waste of resources but it is a
tragedy of false
hopes. (See comments below)
Many experts and groups have stopped recommending small scale
purification. Nonethess, if there is local backup these
seem successful (see below).
Drilling
deep wells (150+ m) where arsenic contamination is at present
smaller. This is being urged by UNICEF and Columbia
University scientists. But this solution may not be available
everwhere. There have been some problems so that
continued monitoring (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) and regular
monitoring for bacterial contamination.
Rainwater collection and
storage. Again the long storage time needed suggests the
need for careful attention to sanitation.
The number of people supplied by
each system varies and the total number of Bangaldeshis 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.
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.
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 "havecollected
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
mnufacturing defect that has now been corrected and the group has
relaced 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. Dr.
Susan Murcott of MIT has been developing a cheap and simple system,
the KANSHAN filter for
use in
Nepal. Columbia
University also reportsucessful
use of such devices, but when arsenic free
water supplies were available, villagers preferred to get the arsenic
free water. 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.
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 abandonded 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."
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 there exist
ARS that work on all waters in Bangladesh and which they are; 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.
Although the situation is far from
clear, Dr S-Amiri of OCETA has a small
report discussing both iron and phosphate as possible system
cloggers. A recent
addition to the list of on line articles discusses a simple
stainless steel filter. The following
interchange where the
STATESMAN exagerrated the implications of a suggestion that the
iron/arsenic interaction might be reversed, illustrates the problem. It
is important NOT to blindly install devices which have not been tested.
In 1978the Government Of
Bangladesh instituted a program called ETV-AM (Environment
Technology Verification-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 is 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 ETV-AM program. In February 2004 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), Sidko and
MAGC/ALCAN. Unfortunately only scanty details are
available in aposterand a pdf file of
some tables, so that this webmaster is unclear under
what conditions OCETA claim they will work. Dr Hussam
of SONO claims that some of the data in that poster
are meaningless. Nor has this webmaster been able
to find an independent expert who understands enough to inform
him. Therefore this webmaster awaits the
complete report. It was ora;;y stated at the American Chemical
Society meeting in March 2006, that the report has just been
released. But as of mid-May 2006 the webmaster has been unable to
get a copy. Perhaps the Grainger Challenge Prize
will stimulate both a well designed system and full,
publicly
available, well documented, systems.
The webmaster was also promised, January 2006, details of
the SIDKO and
MAGC/ALCAN systems which will be posted as soon as
available.
The pessimistic concusions of Chakriborti and
McArthur are also challenged in West Bengal by Arup Sengupta of Lehigh
University and his colleagues in Bengal Engineering
College. Their
detailed paper of the results of followup on over 150 medium sized
systems seems convincing. 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. Anyone
interested should call Dr Anriban Gupta at Bengal College.
In Bangladesh,
This webmaster
makes 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. ector, School of Environmental Studies,
Jadavpur University”.
Well
switching
Left. a well painted green(water safe) and,
right, one marked red(arsenic content is toxic).
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 respone to the general advertiseent of the
problem. The team of Columbia University 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.
There are two thoughts that may enable continued use
of tube wells. John McArthur has
reinterpreted the data of Harvey et al. to suggest that continuous
pumpling (especially for irrigation) is flushing (removing) the arsenic
from the shallow aquifer in many places. This optimistic, highly
speculative, but but
exciting thought is discussed in his paper in press. Another long shot arises from the
belief that the arsenic is liberated when iron oxides are reduced in
the anoxic ground layers just beelow the survface, liberating the
attached arsenic. This suggestes to Professor Harvey and
others that the aquifer might be purified by inserting oxidizing
agents. A small trial with some nitrates reduced the arsenic
levels for a week, and a more massive trial will gtake place in January
2006.
A report by APSU (November 2004) entitled "not
just red or green?" discusses this issue in a very clear way and
makes several important recommendations.
Use of Deep Wells
The information from well water
surveys such
as that of the British
Geological Survey
and Mott MacDonald shows that deep wells,
greater than 150 meters in depth, are free of arsenic. This
seems to be confirmed by more detailed studies from an MIT/BUET
(and others) group and a Columbia
University group. Dhaka and the
southern part
of Bangladesh (where salt water enters the shallow aquifer) are
mostly free of arsenic. But this may not be true
everywhere. Although about twice the price of a
shallow well, deep wells could be used and are
cheaper ($100) than most other alternatives. ($200 for a
renovated and $300 for a
new dug well) For a village
based unit this comes to around $1 per person.
Dr Colin Davis of UNICEF was
recommending their use at the 5th International Arsenic Conference in
San Diego in July 2002, and the Columbia
University scientists are recommending them as the cornerstone of a
major program. It was reported
in
the New Nation on December 28th 2004 that the World
Bank is spending $44 million to install deep tubewells in
appropriate arsenic contaminated
areas.
Since it it is one of the cheapest methods, it is
hard not to support the idea. Although the
1992 WHO
conference and BAMWP
only conditionally recommend them, BAMWP has provided 300 deep
tube wells in coastal areas. It is reported
that the World Bank is financing many such wells. But there are
potential
problems that should be considerd in any implementation:
- if such wells are dug
carelessly, and not properly grouted, there is a possibility of
"shunting" the aquifers and
allowing water from the higher aquifer to contaminate the lower
aquifer.
- it is unsure whether the lower acquirer is a
"closed"
acquifer from a hydrogeologic point of view or whether it is as easily
recharged as the upper aquifer.
- It is unclear whether, in
a longer term, pumping from
these wells would increase the
arsenic level.
However, these can
be checked by
frequent (once a year) measure of the arsenic levels. If
arsenic levels are rising, other solutions must immediately be
found. Since money would be saved by using this cheaper
method, the money could be set aside for such eventualities in
what, we all hope, would be a limited number of locations. Without such a
committment in advance, the webmaster is dubious about using deep
tubewells as a panacea. They are, however, one of a set of
possible solutions, available in appropriate places with appropriate
precautions. We
have attached some opinions
of experts in 2002 and of Dr
Dipankar Chakraborti in 2005. The Phase 1
report of June 2004by
the Arsenic Policy Support Unit (APSU) "Risk Assessment of Arsenic Mitigation
Options (RAAMO)" finds little arsenic and almost no bacteria
in a selected group of deep tube wells. Nominally they were
selected randomly but that means little since it is strongly believed
that the quality of deep wells is very dependent on
geography. Nonetheless this is
highly encouraging and suggests that some of the caution in the use of
deep tube wells may not be justified. Indeed this reviewer
would emphasize that at the worst, a deep tubewell would produce
arsenic-free water for 10-20 years, and might do so for well over 100
years. Since the cost is lower than other alternates, t it
would in most cases be well worth a try.
See also the
Bangladesh government reports:- Ground
Water Task Force, July, 2002Full Final report of
Deep
aquifer Data base and Preliminary Deep Aquifer Map. (Local
Government Division, GoB March 2006) Contents , Chapters1&2
, Chapter3 , Chapter4 , Chapter5.1-5.4 Chapter5.4-5.44
, Chapter5.5
, Chapter 6
,
Chapter7Con , Chapter8Ref ,
Chapter9Appendices
In
the past (50 years ago) many of
the villagers drank from "holy" ponds where the water was protected
from
animals and cattle. Many of these were unsanitary. It was to prevent
water borne diarrheal diseases that the tube wells were suggested.
A return to surface waters must therefore be done with full regard to
better sanitation than before. In particular this webmaster
recommends rigid adherence to WHO standards. Waters
should
be tested for coliform bacteria, not just once but regularly and in
particular at the worst period
-
the end of the dry season. Disinfectants , lime or chloride should be used
regularly - every 3 months or whenever trouble is
suspected.
Indeed in the USA Some wells are chlorinated daily. Tests
should be made before the disinfection, not only just afterwards,
to be
representatative of the worst time. Also in the rainy
season when the ground is water logged and the ability to filter
bacteria is lost. Public
confidence was lost when water from the
tube wells were found to contain arsenic. It was lost again when
the Arsenic Removal Systems were not successful in many places.
Confidence once lost is hard to regain. For that
reason, among others, this webmaster recommends that in order to inspire public
confidence these measurements must be available for public
inspection
(for example the measurements of the dugwells installed by DCH are in a
directory
on this website.) As of May 2006 this webmaster knows of no
completely satisfactory protocl for coliform avoidance and testing in
Bangladesh. The successes and failures are discussed
further below. Tests must
be made for coliform bacteria frequently - how frequently is a
matter still under discussion. Unfortunately it is
not yet clear that any of the organizations installing surface water
systems are yet completely satisfactory. This is discussed
further below when the individual systems are discussed.
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 fine paper using such a procedure has been presented APSU, "Risk Assessment of Arsenic Mitigation
Options (RAAMO)". Not surprizingly,the Phase
1
(June 2004) report finds that the risks of improper use of
surface waters outweighs the risk of badly installed deep tube wells.
But the data on the wells and ponds surveyed is
still is in its infancy (see below under individual systems) so that
the webmaster warns against simplistic use of the numbers so
far available.
Use
of Dug Wells
Before the (cheap and
simple)
tube well was
introduced, many
villages dug wells to obtain surface water. However,
many, if not most, were NOT carefully installed, dug, covered,
and chemically
treated, and they were full of bacteria. Sucessful
projects involving sanitary
dugwells exist in other countries, and some that may be successful have
been reported but not yet in the detail to convince the skeptics that
no coliform bacteria exist.
Large Dug wells
Dr Chakraborti discusses dugwells in
his 2005 list of mitigation stategies. He has a large
dugwell/pond system in his ASHRAM which he descibes: "It is almost 3 years my model
village people are drinking dug-well water. In my opinion my dug-well
water is nectar, complete balanced cations and anions, arsenic
8-18 microgram/l and iron ~100 microgram/l. Please find herewith the
photograph of my dugwell. I have two ponds near my dugwell with two
cement storage tanks 20 ft X 20 ft X 5 ft. The tank is two storied.
Between upper and lower tank people can rest in summer, as
it is cold. Note my dugwell is 12 ft diameter with depth ~ 50 ft. It is a complete concrete structure. After
two years of laboratory testing villagers are now allowed to drink the
dug well water. To keep dugwell safe from bacterial contamination
normally I make through cleaning twice a year and removing the sand and
treating with KMNO4/bleaching powder and NaOCl. Almost 2-3 days I
do not use the dugwell (but stored water in tank serves the need). Most important fact
even after cleaning everyday at night I put 2 drops of NaOCl per
5 liters of water. I know the water level and a simple calculation will
deecide how much NaOCl to be added. If you do it regularly
bacteria contamination is not there. From my dugwell 800 people can
drink water. Here are
pictures"
Dr Chakraborti
reports on
tests of 483
dugwells in West Bengal confirming that most are arsenic free.
No measurements of coliform bacteria are available to this webmaster,
but Dr Chakriborti recommended disinfection with chlorine once a
month.
Project
Well in West Bengal, directed by Dr
MeeraSmith, has
published details on about 40
sanitary dugwells in West Bengal; again the detailed lsiting on
the coliform measurements and the timeing thereof is not avalaible to
this webmaster.
Smaller
Dugwells
Initially both BRAC and the Grameen Bank
installed many wells that did not follow WHO guidelines - some were
uncovered for example. But they claim to have been
been
installing dug
wells with
filtration.
However, the webmasters have no up to date report on their sucesses,
failures, and costs in spite of diligent enquiry. WE INVITE AND SOLICIT ANY AND ALL SUCH
INFORMATION. All we have are oral reports that 250 have
been abandoned
as being unsanitary - presumably because sanitary procedures (see
below) have not
been followed.
The Arsenic Policy Support Unit (APSU), a Bangladesh Government group, reported
in June 2004, and final a year later, that 1,524 dugwells had been dug by 6
groups: BAMWSP, DPHE-Unicef, DPHE-Danida, World Vision, WATSAN,
and Asia Arsenic Network. They studied 351 wells in 6
clusters "chosen at random." T "Risk Assessment of Arsenic Mitigation
Options (RAAMO)", on the bacteriological contamination is not encouraging - showing that 94% have
bacterial contamination .
Although arsenic
levels were low in most dugwells, a few had levels up to
100ppb. As
far as can be discovered from
the RAAMO report APSU measured
some wells paid for by UNICEF but never
measured wells those paid for by UNICEF but dug by DCH. They
missed for example, any wells dug by Dhaka Community Hospital although
their results were ncorrectly claimed to be representative of DCH wells
(in Siridjikan in Table 3.2 of the
June 2004
RAAMO report.
Although
they claim to be a representaive sample, that claim, therefore is not
substantiated, Nor is it clear whether the claim to be
random has a useful meaning, RAAMO have not put their
detailed numbers
on the web, and have made no comment on the measurements of the 48
wells dug by DCH for UNICEF that have been available on this site for
over two years. They seem to
consider all
dugwells as equal, although some follow WHO guidelines and some do
not. This is not appropriate It
seems that many, if not most, of the wells were
badly sited, were not constructed using WHO guidelines, or did not use
disinfectant (lime).
But that
does not mean that the wells not discussed in RAAMO are all
satisfactory. Dhaka
Community Hospital (DCH), has
supervised the
installation of several hundred dugwells. Three phases of a
"pilot" project of 66 dugwells in the PABNA area in which the webmaster
was proud to
have assisted are reported here. (2nd phase (in html)
and (msword);
third phase in MSWORD)
A detailed paper has been
submitted to a journal. Initial measurements
showed
that they were
free of arsenic and bacteria
as shown
here in EXCEL.
But later masurements
showed high levels of colifor bacteria. The
capital cost for arsenic free
water in the kitchen works out at less
than $70 per family or $5 per person. This
webmaster cannot resist
showing pictures
from his visit
(in February 2004) to several villages in the PABNA area.Starting in the second phase (2003) water
is pumped to a small storage tank from which there
is piping
to individual houses.(also
msword file) (layout
of the piping). Measurement
of 48 wells supervised by DCH in 2003-2004 for
UNICEF in Sirajdikhan Upazila also showed few bacteria (and
little
arsenic) in the initial testing,; moreover some of these
measurements were confirmed by independent testing by IDDRB. But later
masurements of some of the PABNA wells showed high levels of coliform
bacteria. The webmaster speculatesat
the initial tests were made just after chemical treatement with lime,
and the bacteria increased thereafter. Another suggestion, made
in.another
report on the APSU website, is that the PABNA
wells themselves were cracked so that during the rainy period water
went staright into the well from the surface without
filtration. Studies are being
undertaken to study this so that public confidence can be
restored. It may well
turn out that the cost of maintaining bacteria free wells is too large
for a small well with few users. This
obviously puts additional emphasis on pipeline systems where more
people can be served from a single, somewhat larger,
dugwell. Meanwhile wells are being chlorinated every 3
months.
As noted above some early attempts to provide pure water
did NOT pay attention to sanitary procedures.
In the past many wells were too close to latrines and
animals were not kept
away. A
modern
dug well (following WHO
has suggested guidelines
for modern dugwells. They must be covered to prevent entry of
animals and refuse but is
aerated to allow oxidization. Water
is taken out by a connected tube well and pump,
making them as easy to use as a tube well. They are located at a
distance from
latrines including past latrines with their buried organic waste if
possible. DCH
and Chakribortiave developed written instructions for correct
intallation. Grameen Bank now has a similar
list. The
wells must of course be tested for
arsenic, manganese and other heavy metals, initially and perhaps every 2 years.
But tests must
be made for coliform bacteria more frequently - how frequently is a
matter still under discussion. Dr Khaliquzzaman of the World Bank
also has
a short
report
on dugwell test and maintenance with similar warnings to those in the
DCH report noted above.
Reports on dugwells are listed in
this directory
including many
more pictures of dugwells in Bangladesh The
dugwells, with pipeline, are a further step in matching the
history of the water supply
in the small English village in which Richard Wilson lived from
1953-1955. For
several centuries, a village well existed from which everyone drew
water
in a bucket. In the 1930s, the well was covered and a windmill
installed to pump water to a storage tank with water supply to one tap
in each cottage. The cottages were "modernized" by installing
staicases to the upper floors to replace the ladder. In the 1940s
a small petrol (gasoline) engine supplemented the windmill when the
wind died down, and a bathroom was installed in the cottage in which
Richard Wilson lived. In the 1960s, the main water supply pipe to
the city of Oxford was brought within 1/2 mile and the village
connected to main water.
In 1998 it was a
puzzle to many geologists, and even some hydrogeologists,
why
the surface wells were free of arsenic. For they seemed to be sample
the
same water as the shallower tube wells, and in many locations shallow
tube wells showed concentrations of arsenic concentrations increaing
with time. Why does this not happen in dugwells? This
question, asked 6 years ago has never been satisfactorily answered.
There are several possible answers. Firstly, over
centuries people
used dugwells, mostly unsanitary, but no arsenic problems were ever
reported. Secondly the experience of DCH, Meera Smith and
Dipenkar Chakraborti suggest a difference. They
claim that the shallow dug wells were likely
to be less polluted than shallow tube wells because, being wider (often
over a meter diameter) they allowed access of oxygen and so would
oxidize dissolved ferrous iron and that would scavenge arsenic from the
water.Also the top of the aquifer is the
freshest,
youngest
water, which has been most recently recharged by flood
(rain) water, and so the
least likely to be polluted by iron reduction. On coming to
the surface in a dug well the water oxidizes and deposits
arsenic, by co-precipitation with FeOOH or sorption onto existing
FeOOH in the sediment.
This argument may not apply to a small dugwell where water is
continually coming in from the side and aeration may not be complete.
The dug wells generally sample water that is
shallower than the shallow
tube wells. Dug wells are dug until the water table is hit, plus a bit
more. Those dug in December, when the water table is high,
sometimes went dry in a dry year. They were often a bit shallower
than those dug
in May at the end of dry season. Shallow tube wells are sunk
until
the first good clean aquifer sand in found, then are made 20 foot
deeper
to accommodate the screen, Much of the pipe comes in 20
feet
lengths, so that "shallow" tube wells may be 20 to 30 meters deep (5-7
pipe
lengths, including screen).
Rainwater
Harvesting
Household
tanks with
a capacity of 3200 litres. Photo courtesy of UNICEF-Bangladesh.
For
anyone
unfamiliar with the cycle of monsoon rain and long dry season, it is
puzzling why there
is a problem in Bangladesh at all. One of the web masters
lived
in an English village where rain water harvesting and storage was
usual.
But storage was only needed for several weeks. In
Bangladesh water must be stored for several (none!) months.
The size of the tank must be increased tenfold, and it becomes
difficult, although vitally important, to keep the water pure
during storage. Nonetheless it is a solution for many communities
where other alternates are not available. Particularly in
southern Bangladesh, where there is frequent flooding, it is almost
impossible to make a sanitary surface well, because it is not possible
to keep the latrines at a distance from the wells.
Rainwater harvesting is being advocated by UNICEF as reported by Dr
Colin Davis at the
5th International Arsenic Conference in San Diego in July 2002.
As of February 2004, 1000 new rainwater harvesting
units
were being installed by UNICEF and DCH
Simple
storage of rainwater
is not as simple a
solution as it may appear from the above description. In some high-iron
waters little or no arsenic is found. Everyone who has looked for
microbiological contamination of such stored waters has found gross
contamination - water containers act as incubators in the house,
especially when they are uncovered or do not have taps. After 12 hours,
fecal coliforms can be more than 10,000/100ml, or even 'TNTC' (too
numerous to
count). The Phase 2
report of May 2005 by
the Arsenic Policy Support Unit (APSU) "Risk Assessment of Arsenic Mitigation
Options (RAAMO)" tests 42 rainwater
harvesting systems. While less than half were contaminated by
coliform bacteria in the
monsoon period, this increased markedly during the dry
season. Again,
measurement
and regular disinfection seems essential.
Pond
Sand
Filters
It seems logical to collect
river water in a pond, and then filter it naturally. Again this
has been done for centries. Then it can be filtered as it goes
into a second pond by sand or soil. A pond sand filter can purify
water for several hundred people so that the overall cost (per
person) is about the
same as a deep tube well, but it probably needs more careful
maintenance. The webmaster photographed one
system in 2004. At first it was not bacteria free but
it was improved and is bacteria free now. The Phase 2
report of May 2005 by
the Arsenic Policy Support Unit (APSU) "Risk Assessment of Arsenic Mitigation
Options (RAAMO)" tests 42 Pond Sand
Filter systems and found that 95% had bacteria both in the monsoon and
in the dry seasons. They attribute this to inadequate maintenance
and poor filter depth. Again no indication was given that
disinfectant (lime) was used as recommended by DCH in all their
projects.
The
abstract of a comparative field study on the effectiveness of arsenic
removal from groundwater by household sand filters is available on the ACS
website.
In
India, the
Jal-TARA Slow
Sand
Filter isa
common water purification systems comprise of chlorination, coagulation
and sand filtration techniques. Of all these techniques, sand
filtration offers a chemical- free, reliable and economical treatment.
Jal-TARA Slow Sand Filter is designed to treat drinking water using
slow sand filtration technique as per the specifications of World
Health Organisation (WHO). Jal-TARA filter is a biological filter
merged with advanced technique of fabric protection to improve and
simplify the traditional process of slow sand filtration. Two type of
filtration act together to improve the quality of water: It consists of a gravel filter to
remove turbidity, and sand
bed filters to completely remove pathogenic bacteria from raw water.
Large Scale Arsenic
Removal Systems
There
are several
arsenic removal methods, which are appropriate for a large scale (small
town) or a medium (village) scale. They are particularly appropriate
for countries which have developed a central water supply and can
therefore use the economy
of scale. Those must be tested in the field , and attempts
must
be made to manufacture equipment locally to make them affordable. The
web masters
have not done so and merely list them below. A
list of larger scale technologies.
In Bangladesh,
UNICEF
have helped the Department of Public Health Engineering (DPHE), Government of Bangladesh, to
install over 40 community-based
arsenic removal plants in different parts of Bangladesh, and they are running well with the
active participation of the community. Each plant can produce approximately
3,600 liters of filtered water every 15 hours. The arsenic contained in the
treated water is below 0.01 mg/L, which is below the WHO and the new EPA
guidelines. The
communities each employ one caretaker for each plant. They are paying salary to the caretaker, the
electric bill, incidental expenses,
and generating funds to purchase the chemicals in the
future. This experience is very promising for
communitoes of 10,000 people or more where people are willing to walk
to the central purification system to collect their water.
Again the webmasters have no up to date report of the success of these
purification methods.
The
long
term future
In 1998 there was a confusing controversy by some
over enthusiastic people (e.g.
see the article by
Bridge and
Husain)
that the problem is a barrage on the Ganges river.
However this seems to be reliably repudiated (by Dr McArthur from UCL
among others).
TIn the longer term (50 year time scale) a national
water policy was promulgated in 2004 to replace the previous one
which
produced the arsenic problem. It emphasized use of surface
waters. Yet many more people are turning deep tube wells
than surface waters. Many hyrdrologists see no
problem with this. The long term, will presumably use water piped
from a central system of some sort, and the village size piped systems
being pioneered by DCH seem to be a step in this direction.T.
Improving the Diet
An important issue for coping with arsenic
exposure is the
effect of diet. A general issue can be stated: there
is frequently more than one cause of a cancer or a lesion. For
example lung cancer can be caused by cigarette smoking or asbestos or
both together, in a synergistic way such that the
risks multiply (rather than add) when both are present.
In the USA it has been
found that people who have a good diet of fresh fruitand
vegetables (5 servings per day) have half the risk of many
cancers, including lung cancers caused by
cigarettes, as those without
a good diet. By analogy, one might expect that
the lung cancer risk from arsenic will be less among those
with
a good diet, but this is not yet supported by direct data.
Indeed,
there are anecdotal indications from Bangladesh that a good
diet reduces skin lesions also. Clearly, it is a good
approach for many reasons, but epidemiological
studies to confirm this are highly desirable.
There are several specific chemicals that
have been suggested that would either (i) help to prevent arsenic
lesions by rapid removal of arsenic from the body or (ii) help to cure
arsenic
lesions. Encouragement of methylation of the arsenic probably
accelerates
methylation, but the methylation has been suggested as a cause of
internal
cancers.
The
specific chemical that has come to the mind of many health experts is
selenium.
It was noted in the 1930s that effects of excess selenium can be
counteracted by adding arsenic to the diet because As and Se combine.
Does the inverse take place? It is reported that
areas
with high incidence of arsenical lesions have low selenium
in the water. Some victims have low selenium levels.
Does adding
selenium to the diet really help, either to prevent the lesions from
forming
(likely), or to treat them afterwards (less likely)? We have,
with help from others, compiled a list of
referencesand
a
recent
paper on the subject.
Professor Zuberiof Rajshashi University has suggested methionine to reduce the
arsenic
lesions. Dr OGB
Nambiar
has suggested that ferrous sulphate, after conversion to sulfide by
bacteria in the colon, absorbs arsenic and assists safe excretion.
The evidence for these remains indirect, and there may be (as suggested
above) competing adverse effects. Only good epidemiology can tell.
UNU/BUET meeting
Discussion of
technologies in May 2001, primarily
in the context of Bangladesh,
in the following talks
which can be downloaded:
Central
Electrochemical Research Institute (CECRI), Karaikudi, India with the
sponsorship of Department of Science and Technology (DST),New Delhi,
India has developed a Domestic
2A capacity Electro Arsenic Purifier for Drinking Water,
which can treat 2L of drinking water per one hour. This unit will
reduce the arsenic level from 3ppm to 20ppb (WHO standard). This can
also be operated with the use of Solar Energy. The Novelty of the
Arsenic Purifier is this will removal both arsenite and atsenate with high
effieiency (reduce to 10ppb level). CECRI also developed a Community
model Electro Arsenic Purifier for Drinking water, which can treat 40L
of drinking water per one hour.The cost of the one 2A Arsenic Purifier
is Rs.6,000. The cost of treatment of water is 3paise.Those who are all
interested may contact:
Dr.S.VASUDEVAN Electroinorganic
Chemicals Division Central Electrochemical Research
Institute Karaikudi – 630 006 Phone: 91 4565 227550 – 227559; Fax: 91 4565 227779Mobile: 9442552441 Email: svdevan_2000 @ yahoo.com, vasudevan65 @ gmail.com
SONO
Filter, a modification of the 3 jar Kalshi filter, developed by
Dr Hussam in USA and extensively used in Bangladesh particularly near
Kushtia. As noted above it has been approved by the Government of
Bangladesh. It costs approximately $30.
Contact: Dr. A.K.M.Munir, COURT PARA,
KUSHTIA, BANGLADESH.
Tel:071-61335,61909
Mob:0171-275041
Fax:088-071-61235
e-mail:akmmunir2003@yahoo.com
We link here to several pdf files about using the filter. Paper by Khan et al. abut the
filter
MAGC/ALCAN We have limited information about
this system. However it has been approved by the Government of
Bangladesh, Mr M. Saber Afzal claims that it is the cheapest
system with acost of Taka
1,950 ($32,50) which includes everything.
Paul Friot, of Friot Corporation, Ayer, MA, USA http://www.friot.com
has US patent 6,368,510 B2 for a "Method and
Apparatus for the Removal of Arsenic from Water" using a two stage
process: manganese greensand oxidizer to convert arsenite to
arsenate, followed by an anion exchange resin. Arup K.
SenGupta, of Lehigh University has
developed and collegaues at Bengal Engineering College in Howrah, West
Bengal, have installed alumina filter systems for $1250 for 300 housholds or $1 per person Their
detailed paper of the results of followup on over 150 medium sized
systems seems convincing.
Dr Ashok Gadgil from
Lawrence Berkeley Labs is developing a
filter with coal ash
Susan Murcott at MIT has
developed a
sand filter called the KANSHAN filter
Australians are develpong a solar
energy operated
distillation
unitwhich
will remove
arsenic
and many other pollutants.
Recommendations for water supply in arsenic mitigation: a
case
study from Bangladesh. B. Hoque, AA Mahmood, M. Quamruzzaman et al.
Public
Health (2000), 114, 488-494
A
Simple Household Device to Remove Arsenic from Groundwater and Two
Years Performance Report of Arsenic Removal Plant for Treating Ground
Water with Community Participation. School of
Environmental Studies, Jadavpur University,
Calcutta-700032, India
Ferric Oxydioxide and Settling by Dr. Richard
Anstiss of New Zealand and Professor Mustaque Ahmed (being tested
in Bangladesh) procedure presented by
Dr. Anstiss at Remediation Conference at DCH, Dhaka, Dec. 14 1998
A Swedish Group with a new water
purification
technology called membrane distillation. It is able to remove all
arsenic
3 and 5 completely. It has been tested at Sandia National
Laboratory, Texas University in El Paso, and in Sweden. It costs
roughly what all advanced systems cost but has three advantages: 1 Removes arsenic completely, 2 Requires very little
maintenance
or component replacement, 3 If waste heat is available,
the
cost of the water is very low indeed So far we only have a description in
Swedish
.
At the 5th International Arsenic Conference in San Diego,
the
purification systems successfully used in Vietnam (particularly in
Hanoi) were described.
HYDRO-Solutions
and Purification This arsenic removal system was designed to remove
arsenic from Alaskan mining wastes. It is claimed by its' proponents to
be the most inexpensive (both capital & recurrent costs) process
for
commercial, industrial, and municipal arsenic removal. They also have a
selenium removal methodology."
