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BUET-UNU
International Workshop
on Technologies for Arsenic Removal from Drinking Water
TECHNOLOGY
FOR ARSENIC REMOVAL
(Saturday,
May 05, 2001)
Arsenic Mitigation Component,
Danida SPS for Water Supply and Sanitation,
Dhaka, Bangladesh
Anisur Rahman Sarkar and Omar Twabur Rahman
Abstract
Two well-known methods of iron removal were tried to see their effectiveness
in removing arsenic. One of these was in-situ sedimentation and the other was
conventional iron removal technique. The analysis of the preliminary results
revealed that both the methods are capable of bringing down arsenic level to
Bangladesh standard when the raw water concentration is of the order of
0.1mg/l. The higher values could however, be reduced to halves of their
originals. The former contamination level accounts for 50% of the total
contaminated tube wells in most of the arsenic problem area. The promotion of
these methods can bring a good range of coverage in arsenic mitigation in the
country. The methods being chemical free are likely to be well accepted by the
people. The methods may, however, be further improved for wider range of
effectiveness and need to be field-tested for acceptability by the target
group before mass scale promotion.
Development of Low-cost Technologies
for Removal of Arsenic from Groundwater
M. Ashraf Ali, A.B.M. Badruzzaman, M.A. Jalil, M. Delwar Hossain,
M. M. Hussainuzzaman, M. Badruzzaman, O.I. Mohammad, N. Akter
Department of Civil Engineering,
Bangladesh University of Engineering and Technology, Dhaka 1000, Bangladesh
Abstract
Performance of three alternate arsenic removal technologies was evaluated in
the laboratory. These were: (i) removal system based on alum and iron
coagulation; (ii) removal system based on sorptive filtration using iron
coated sand filter, and (iii) removal system based on sorptive filtration
using gravel bed containing iron sludge. Based on laboratory performance, two
technologies, ferric chloride coagulation, and sorptive filtration through
iron-coated sand, were selected for the development of household arsenic
removal units. The ferric chloride based unit is similar in design to the
bucket treatment unit developed by DPHE-Danida. It involves precipitation of
arsenic by adding a packet of coagulants to 25 liters of tubewell water and
subsequent filtration of the water through a sand filter. The unit based on
iron-coated sand has a pre-treatment system for removal of excess iron. This
consists of a bucket where water is poured and stirred for sometime to
accelerate precipitation of iron. The water then flows through a sand filter
where the excess iron is filtered out. Finally the water is passed through the
iron-coated sand filter. Field-testing of 15 ferric chloride based units at
Adda village in Barura thana of Comilla district showed very good arsenic
removal efficiency. Arsenic concentrations in the treated water were found to
be mostly below 20 ppb; while maximum arsenic concentration in the tubewell
water was about 400 ppb. For some of these units, presence of fecal coliform
was detected in the treated water. However, continued use of bleaching powder,
along with the coagulant, for a period of about 15 days eliminated fecal
coliform. This type of unit appeared to be widely accepted and in great demand
at the village. The cost of chemical for treatment by this unit is about Tk.
0.10 per liter of water. Field-testing also showed good arsenic removal with
the iron-coated sand unit.
Naved Ahmed Chowdhury
ITDG, House 32, Road 13A, Dhanmondi R/A,
Dhaka-1209, Bangladesh
Abstract
This paper reviews the results and conclusions from a DFID funded project
‘Rapid Assessment of Household Level Arsenic Removal Technologies’,
carried out in association with the Bangladesh Arsenic Mitigation Water Supply
Project. Nine technologies were assessed under this project. The project
comprised two phases. Phase I sought to identify whether the nine technologies
removed arsenic to below the Bangladesh Guideline Standard of 0.05 mg/L, under
idealised field-operating conditions. Phase II looked at arsenic removal under
householder operation and considered the treatment of other water chemistry
parameters, bacteriological contamination and the opinions of the householders
who used the technologies. This paper considers the priorities in adoption of
technologies, which are most effective in the treatment of groundwater and
most acceptable to the potential users. It is argued that before a technology
should be adopted it should be assessed against a given set of criteria (in
the form of questions). These are: Does it work? Does it create any further
chemical/biological problems? Is it acceptable to potential users? If not, why
not? The issue of cost should only be brought into consideration if the
technologies pass the preceding criteria. Five of the nine technologies (Alcan
enhanced activated alumina, BUET activated alumina, Sono 3-kolshi, Stevens
Institute technology and the Tetrahedron) comfortably passed the arsenic
removal test. Two others (DPHE/Danida 2-bucket system and GARNET) passed the
arsenic removal test under certain conditions and two (Ardash filter and
passive sedimentation) failed the test. The performance of the seven that were
further assessed was variable, with most requiring some modification to design
or use or a change of attitudes to hygiene by the users. The main concerns,
particularly for the lower cost technologies, related to apparently high
levels of faecal contamination, low flow rates, the use of chemical reagents,
long waiting times within the filtration process and the maintenance of the
technologies.
An Overview of Arsenic Removal Technologies in Bangladesh and India
M. Feroze Ahmed
Department of Civil Engineering
Bangladesh University of Engineering & Technology, Dhaka-1000, Bangladesh
Abstract
In the context of prevalence of high concentrations of arsenic in tubewell
water, a wide range of technologies has been tried for the removal of arsenic
from drinking water. The most common technologies utilized the conventional
processes of oxidation, co-precipitation and adsorption onto coagulated flocs,
adsorption onto sorptive media, ion exchange and membrane techniques for
arsenic removal. The conventional technologies have been scaled down to meet
the requirements of households and communities and suit the rural environment.
Some technologies utilized indigenous materials for arsenic removal. This
paper presents a short review of the technologies used for arsenic removal in
Bangladesh and India.
Safe Water Technology for Arsenic Removal
Richard Johnston
Consultant to UNICEF and WHO
and
Han Heijnen
WHO Environmental Health Advisor, Bangladesh
Abstract
Arsenic contamination of drinking water has been reported from many parts of
world. In some arsenic affected areas, substitution of drinking water source
by a safe and easily available one may not be possible during part or all of
the year, or may be very expensive. Arsenic removal may be a more appropriate
water supply option in these situations. This paper describes some safe water
technologies for arsenic removal.
Coagulation is the most common arsenic removal technology. As many Bangladesh
waters contain arsenite, oxidation with chlorine or permanganate is required
first. Coagulation with ferric chloride works best at pH below 8. Alum has a
narrower effective range, from pH 6-8. Ion exchange resins are commercially
produced synthetic materials that can remove some compounds from water. These
resins only remove arsenate. Activated alumina, like ion exchange resins, is
commercially available in coarse grains. Activated alumina beds usually have
much longer run times than ion exchange resins, typically several tens of
thousands of beds can be treated before arsenic breakthrough. Activated
alumina works best in slightly acidic waters (pH 5.5 to 6). Membrane methods
for arsenic removal include reverse osmosis and nanofiltration. Currently
available membranes are more expensive than other arsenic removal options, and
are more appropriate in municipal settings, where very low arsenic levels are
required. Other techniques exist for arsenic removal, but are less well
documented. When arsenic-rich water also contains high levels of dissolved
iron, iron removal will also remove much of the arsenic. Introduction of zero-valent
iron filings in three-pitcher filters to treat water in the home is showing
great promise. Many new materials are being tested for arsenic removal, from
low-tech iron-coated sand and greensand to specially engineered synthetic
resins.
In all cases, technologies should meet several basic technical criteria. The
biggest challenges ahead lie however in applying the technologies described in
poor, rural settings, and in enabling those communities to choose safe sources
of water for drinking and cooking.
Approaches for Removal of Arsenic from Tubewell Water for Drinking Purpose
M. D. Hussain, M. A. Haque, M. M. Islam and M .A. Hossen
Deapartment of Farm Power and Machinery,
Bangladesh Agricultural University
Mymensingh-2202
Abstract
Removal of arsenic from tubewell water is possible by passing it through wood
charcoal, by chemical treatment, by sedimentation method or by removing the
layer floating on arsenic bearing water. It was found that when arsenic water
was treated with calcium oxide, it produced arsenic-free water. In this method
more than 90 percent removal of arsenic was achieved by adding 0.10% (by
weight) calcium oxide to arsenic-contaminated water. After 10 hrs the water
becomes arsenic-free. In another experiment, arsenic-bearing water was passed
through wood charcoal at different flow rates and it was found that up to 98%
removal was possible. If arsenic water (0.45 mg/L) is kept in a big tank
(about 3000-liter capacity) for about 9 days, arsenic concentration level is
reduced in the top layers to acceptable level (0.05 mg/L). When
arsenic-bearing water comes in contact with free air, a thin layer is formed
which is nothing but an arsenic compound and its concentration was about 0.7
mg/L. In this way arsenic level can be reduced to acceptable level by repeated
removal of the floating layer. Any of the methods mentioned above can be used
to produce arsenic-free water and it can be recommended for use in rural areas
of Bangladesh.
Comparative Studies for Selection of Technologies
for Arsenic Removal from Drinking Water
J. C. Saha
Development Design Consultants Limited
DDC Centre, 47 Mohakhali C/A, Dhaka-1212, Bangladesh
K. Dikshit and M. Bandyopadhyay
Department of Civil Engineering
Indian Institute of Technology, Kharagpur-721302, India
Abstract
This paper present the possible alternative removal options for the
development of safe drinking water supply in the arsenic-affected areas. Each
alternative option was studied in the Environmental Engineering Laboratory at
Indian Institute of Technology (IIT) Kharagpur, India. In this paper
conventional precipitation (Alum and Iron salt) and adsorption (With various
types of adsorbent) method were used for arsenic removal. Various parameters
such as, coagulant dose, pH, anions concentration and reaction time were
studied to establish optimum conditions. Iron salt as a coagulant and Hydrous
Granular Ferric Oxide as a fixed bed adsorbent were found to be effective
options for arsenic removal.
Apyron Arsenic Treatment Unit – Reliable Technology for Arsenic Safe Water
Kiron Senapati
4030-F Pleasantdale Road
Atlanta, Georgia 30340, USA
Iftekhar Alam
ATAZ Bangladesh
67 Naya Paltan, Dhaka-1000, Bangladesh
Abstract
Apyron Technologies Inc. has developed Arsenic Treatment Unit (ATU) in which
Aqua-Bind™ media is used for ground water arsenic reduction. These prototype
units are field tested both in Bangladesh and in India. The results of
laboratory testing of the treated water have proven the effectiveness of the
arsenic removal technology. The test results of the treated water have been
consistently below 10 ppb of arsenic. This highly effective arsenic treatment
system is user friendly and is easily adaptable in the rural settings of
Bangladesh. The spent media is non-hazardous to the environment and does not
pose any risk to the users.
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