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Project: Remediation technologies for the removal of arsenic from water and wastewater

Objective

Produce a review of critically evaluated methods used for the removal of arsenic from water and wastewater.

 Remarks: another IUPAC project, complementary to this one, is coordinated within CHEMRAWN > see project 2003-050-1-021

Description
Arsenic currently threatens millions of people in West Bengal, Bangladesh and Thailand, as a result of their exposure to contaminated groundwater (where concentrations may reach 0.06 mg/L to 1.86 mg/L, a value far in excess of the WHO Maximum Permissible Levels). Major problems have also been identified in some areas in the USA and China and south America (1,2 ).

The WHO and USEPA recommended limit for arsenic in drinking water is currently 10 μg/L (3). It is not so much the difficulty of removing arsenic from water, as the extremely low levels to which it must be reduced to ensure safety, that presents the challenge to water treatment initiatives, especially in developing countries where the issues of cost and expertise often make 'high-tech' solutions impractical.

Arsenic may be released into natural waters from a variety of hosts, most commonly either iron oxides, organic matter or sulphides. Elevated concentrations of dissolved arsenic may be expected under conditions where these phases are unstable, or where arsenic is weekly bound (i.e. adsorbed) to the host phase. Arsenic speciation in waters is complex (4); fundamentally, it is a function of both pH, and Eh, as arsenic occurs naturally in two common oxidation states (III and V).

In considering arsenic removal from water, the principal processes of interest are those involving adsorption to particle surfaces, those defined as precipitation reactions and those involving filtration process (e.g. reverse osmosis or electrodialysis) (5).

We propose that a critical review of these processes and technologies will be carried out and will include an evaluation of their appropriateness to different situations.Each process would be reviewed on a case-by-case basis with a literature review, compendium of the data available and critical analysis. Draft publication will be provided on the web and final publication as an IUPAC volume.

References:
(1) www.epa.gov/safewater/ars/arsenic_finalrule.html
(2) Caussy D.H 2003 The arsenic catastrophe in India and Bangladesh- can it be solved? Special seminar report. LSHTM August 2003.
(3) Smedley,P.L Kinniburgh DG. 2002. A review of the source, behaviour and distribution of arsenic in natural waters. Appl. Geochem. 17(5): 517-568.
(4) Feguson, J.F.; Gavis, J. Water Res. 1972, 6, 1259.
(5) USEPA. 2000. Technologies and costs for removal of arsenic from drinking water. EPA 815-R-00-028.
Progress

This project was presented at a poster session at the IUPAC Congress/GA July 2005
>view pdf - 137KB<

The task group met in Bath, UK, on 5 Jan 2005. At the meeting the group specifically identified the need for a simplified and practical guide which condenses the available literature in a form that will allow informed decisions to be taken. We aim to produce a scientifically sound report that will at the same time inform and advise non-specialists on key aspects of arsenic remediation technologies. The report should ideally help people in arsenic affected areas by providing a practical and easy to follow guide similar to the WHO guide for infectious agents in water. The project will consider outcomes of remediation technologies in the wider context of overall water quality (e.g. microbiological contamination) rather than just arsenic contamination.

The following contributions and tasks have been agreed, and tentatively, a first draft should be available by April 2005, and the final document by September 2005.

1. Introduction
Lead: Nick Priest in consultation with Harry Caussy
To provide a brief historic overview and comment on the nature/form of arsenic and its changing economic significance to society.
2. Arsenic pollution sources
Lead: Hemda Garelick and Huw Jones
Arsenic pollution sources divided into point sources (industrial, mining) and diffuse sources (geochemical, water supply) categories: a) natural water (wells, hot springs), b) industrial (end of pipe), and c) mining/industrial (diffuse - either from past or current mining activities)

3. Chemical behaviour
Lead: Eva Valsami Jones
Processes of transformation of arsenic in the environment and their effect on arsenic toxicity (speciation).
Factors affecting natural immobilisation
(e.g. iron, other metals, pH, organic matter, hardness chemical biological, climatic, geographical, jungle, river, lake, volcanic)
Soil/water

4. Testing for As on site
Lead: Jörg Feldmann
Field test kits evaluation in terms of sensitivity, reliability, applicability and cost.

5. Remediation technologies and disposal of residues
Lead: Jean-Claude Bollinger and Pornsawan Visoottiviseth.
These will be divided according to type of water treated - potable water, irrigation water, environmental water, and wastewater,

6. Case studies
Lead: Hemda Garelick and Agnieszka Dybowska will be collecting them from each group member. A decision will have to be made whether these should be included in the various chapters or should form a separate chapter.

7. Summary recommendations
A decision making system will be provided, supported by information flow from the above aspects.

This project was presented at a poster session at the IUPAC Congress/GA July 2005
>view pdf - 137KB<

Remarks: another IUPAC project, complementary to this one, is coordinated within CHEMRAWN > see project 2003-050-1-021