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Article From News From Bangladesh archives

Low-cost method developed to treat arsenic water

AAFS-50 shows 100 per cent success rate

Naimul Haq

At last a solution has been found to the problem of arsenic contamination of tubewell water across the country.

"A relatively cheap but most effective method has been approved after successful trial under the Rapid Assessment programme of the government," a highly placed source said.

The simple technology uses a process of arsenic removal known as 'adsorption to enhanced activated alumina' (AAFS-50) introduced in Bangladesh by Alcan Chemicals.

The technology uses two large plastic containers containing activated alumina (small grains like desert sand). Contaminated water while passing through the containers undergo chemical reaction which involves removal of all soluble arsenic molecules in the water no matter how high is the concentration.

The activated alumina grains attract the arsenic molecules like magnet and binds them together, never breaking the molecular bonding.

Regular tests carried out in BUET laboratory and Intronics Technology Centre and by WS Atkins, a UK based consulting firm in Bangladesh have shown 100 per cent success in arsenic removal to well below the permissible level in Bangladesh.

The treated water also meets the drinking water quality parameters of WHO Guide Line Value (1984 & 1996) as well as the Bangladesh Standard for Drinking Water. Tests under the Rapid Assessment Programme confirmed this.

After months of evaluation, experts concluded that 'one load of the media or the filter material' is able to treat at least 80,000 litres of arsenic contaminated tubewell water to well below the Bangladesh limit of 50 parts per billion (ppb). That is more than seven family's daily requirement of water for drinking and cooking for one year.

"Alcan's method is very simple, easy to install, operate and maintain. It almost completely removes arsenic at a rate faster than any other chemical options available in Bangladesh now," claimed Saber Afzal, Chief Executive Officer of MAGC Technologies which owns Alcan Chemicals.

"Based on current estimates, the cost of our main unit (Alcan) is about Tk 10,000 which carries a warranty of five years (containers) and a projected useful life of 20 years. One load of the media (AAFS-50) will cost Tk 12,400 excluding local import duty, VAT and other official levies," said Afzal.

"To make the best Arsenic Removal Technology available and affordable countrywide, we have also designed and introduced a single-family unit (Alcan-2), some of which are already in use. The initial cost of the unit is Tk 2,000 only (unit plus media), which guarantees 10,950 litres of treated water based on one family (4 - 5 members) requiring 30 litres of treated water for drinking and cooking daily, for one year. The replacement cost of the AAFS-50 is Tk 1,200 only for further delivery of 10,950 litres of processed water," Afzal added.

The first tank is placed directly under the tube's neck and is connected with the second tank by a pipe and a flow meter that records the number of litres of water processed. Requiring no power source, this 'Low - Tech' system is locally manufactured and readily available. Due to its excellent flow rate of 300 litres/hr, one unit can serve a community of up to 100 families.

To operate the system, tubewell water is simply pumped in to the first tank where it goes through the 'media' or filter to the bottom and on to the second tank through the connecting pipe and flow meter. Once in the second tank, the water again passes through the media to the top where a faucet delivers almost completely arsenic free water.

The system's ingenious design also provides a 'by pass channel' through which the users can pump as much untreated water as they need for their washing, bathing and other day-to-day needs.

Out of nine options under review of the Technical Advisory Group (TAG), all of which use techniques involving chemical reactions, Alcan Chemicals' method topped the list in terms of efficiency and user preference. The method was recommended by the Advisory Group and approved by the Project Steering Committee of Bangladesh Arsenic Mitigation Water Supply Project.

While reviewing the technology, experts came up with the question of disposing of the sludge. In response, Alcan scientists said AAFS-50 does not need to be regenerated. It is certified for drinking water safety and the spent media is approved by US environment protection agency for land flling.The spent media remains a robust material (not sludge) that can alternatively be used for brick building, glass making, cement manufacturing etc.

"Two of our units are in operation in Sonargaon under BRAC since April 20 last year and many other units have been installed for BRAC in Sonargaon and Jhikorgacha

under the UNICEF project. For Rotary, our units are operating in Sonargaon, Bandar thana, Munshiganj and for Grameen in Kochua", one scientist said.

A member of the TAG requesting anonymity said,"Now that we have a solution in hand, we no longer have an excuse to delay mitigation. We have no time to waste and we should go on with the job of saving lives. There is a proven technology which can be immediately implemented countrywide to get emergency mitigation. Side by side, we can continue other efforts of screening, testing, patient identification, awareness building and search for alternative source of safe water." (The Daily Star)

Copyright 1998 Global Amitech


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