The Source of Arsenic in Bangladesh’s Drinking Water

Seth H. Frisbie, Better Life Laboratories, Inc., 293 George Rd., East Calais, VT 05650, USA, Tel: 802-456-7054, Fax: 802-456-7054, Email: shf3@cornell.edu
Donald M. Maynard, The Johnson Company, Inc., 100 State St., Montpelier, VT 05602, USA, Tel: 802-229-4600, Fax: 802-229-5876, Email DMM@jcomail.com
Erika J. Mitchell, Better Life Laboratories, Inc., 293 George Rd., East Calais, VT 05650, USA, Tel: 802-456-7054, Fax 802-456-7054, Email: em63@cornell.edu  
Richard Ortega, Laboratoire de Chimie Nucléaire Analytique et Bioenvironnementale,CNRS UMR 5084, Université de Bordeaux 1, 33175 Gradignan, France, Tel: (33) 557 12 09 07, Fax: (33) 557 12 09 00, Email ortega@cenbg.in2p3.fr
Bibudhendra Sarkar, Department of Structural Biology and Biochemistry, The Hospital for Sick Children and Department of Biochemistry, University of Toronto, Toronto, Ontario M5G 1X8, Canada, Tel: 416- 813-5921, Fax: 416-813-5379, Email bsarkar@sickkids.on.ca

The life expectancy in Bangladesh during the mid-1960s was only 46 years.  Many premature deaths resulted from drinking surface water that was contaminated with bacteria causing diarrhea, cholera, typhoid, and other life-threatening diseases.  Aid agencies, the Bangladesh government, and private individuals began installing approximately 10,000,000 tubewells to prevent these deaths by providing access to microbially safe groundwater for drinking.  By 1995 Bangladesh had 120,000,000 people, approximately 97% of Bangladeshis drank tubewell water, and the life expectancy had increased to 55 years.  Regrettably, this new source of drinking water was not tested for toxic metals.  In 1993 chronic arsenic poisoning attributed to groundwater ingestion was first diagnosed.  Currently, there are 2 major hypotheses about the source of this arsenic in Bangladesh’s tubewell water.  According to the first hypothesis, arsenic is initially associated with a poorly soluble pyrite mineral (FeAsS or FeS₂) that is underwater in a reducing environment.  This arsenic is released when the pyrite is aerated by lowering the water table during groundwater pumping.  According to the second hypothesis, arsenic is released into groundwater by the reductive dissolution of non-pyrite minerals and by the anion exchange of sorbed arsenate or sorbed arsenite.  The arsenic, sulfide, sulfate, total sulfur, oxidation-reduction potential, ferrous iron, total iron, manganese, pH, chloride, and phosphate measurements from our 2 national-scale surveys of tubewell water in Bangladesh do not support the “pyrite oxidation” hypothesis.  In contrast, these measurements strongly support the “reductive dissolution and anion exchange” hypothesis, which was initially proposed by our team in 1997.  An evaluation of these 2 hypotheses using the results from our 2 national-scale surveys will be given.

Use of Native Organic-Rich Soil for Passive Removal of Arsenic from Groundwater

P. James Linton, Blasland Bouck and Lee, Inc., 3350 Buschwood Park Drive, Suite 100, Tampa, FL 33618, Tel: 813-933-0697 ext. 19, Fax: 813-932-9514, Email: pjl@bbl-inc.com
Susan Tobin, Task Remediation, Inc., 501 South Boulevard, Tampa, FL 33606, Tel: 813-254-8838, Fax: 813-254-8484, Email: susant@taskenvironmental.com

In 1996, the State of Florida enacted the Lake Apopka Restoration Act to accelerate the restoration of the Lake Apopka Basin through acquisition of agricultural lands impacting the Lake.  One 120-acre parcel in this acquisition was historically used for horticultural purposes that included a muck mining area, structures and disposal areas.  Groundwater in an area associated with historic burn disposal was found to contain dissolved arsenic above State of Florida guidelines; however, sandy soil in this area, both above and below the water table, did not contain significant concentrations of arsenic. 

Studies conducted by the University of Florida (Ma, et al., 1997, 1998 and 1999) have suggested that arsenic has an affinity for soil with a high organic content and reduced pH.  A bench-scale test was conducted to determine if the native organic-rich soil (muck) could be used to passively remove arsenic from the groundwater.  Results for this test were presented to the Florida Department of Environmental Protection, application of the method as the selected remedial alternative was approved, and the remedial action has been implemented at the time of preparation of this abstract. 

The groundwater plume was delineated, the sandy soil within the plume area was excavated, and the excavation was backfilled with native muck soil.  Subsequent groundwater sampling has show a significant reduction in arsenic concentrations in the groundwater with time since treatment.

This poster presents the methodology and results of the bench-scale test, describes remedial implementation, and provides a discussion of effectiveness of the alternative under field conditions.

Arsenic Remediation of Groundwater with Calcium Peroxide Background

Frank C. Sessa, FMC Corporation, 1735 Market St, Philadelphia, PA, 19103, Tel: 215-299-5993, Email: frank_sessa@fmc.com
Philip A. Block, PhD, FMC Corporation, 1735 Market St, Philadelphia, PA, 19103, Tel: 215-299-6645 Email: philip_block@fmc.com
Lonnie D. Norman, FMC Corporation, 1735 Market St, Philadelphia, PA, 19103, Tel: 215-299-6477, Email: lonnie_norman@fmc.com
Michael J. Kirby, PG, CPG, Shaw Environmental, Inc., 4400 College Blvd., Suite 350, Overland Park, KS 66211, Tel: 913-317-2627 Email: michael.kirby@shawgrp.com

The treatment of arsenic chemistry in the environment involves redox transformations, precipitation reaction and adsorption onto particulates and surfaces. In oxidized environments (ORP > 100mV), As (V is favored over As(III) and exists primarily as arsenic acids. Under reducing conditions (ORP <100 mV), As (III) is favored, typically as arsenious acids. Oxidation of As (III) to As (V) decreased arsenic toxicity and mobility.

As(V) adsorbs to surfaces more readily than As (III) and additionally can substituted for and incorporate into phosphate-containing minerals. As (V) has a strong affinity for the minerals hydroxyapatite (Ca₅(PO₄)₃) and ferric hydroxide.  The strategy for removal of As is to first oxidize As to its +5 state, then remove the As (V) from solution via adsorption and precipitation reactions. Chemical oxidants including Potassium permanganate, calcium peroxide, and calcium hydroxide in concert with ferrous iron were evaluated. The results of the laboratory studies indicated that arsenic removal from groundwater is best facilitated by treatment with 0.55% calcium peroxide and 2000 mg/L Fe (II).

Subsequent to the laboratory tests and prior to the on site pilot test leaching tests were performed on composites of soil and ground water that were treated with the aforementioned treatment.  The purpose of these tests is to provide an indication of the stability of the treated soil (i.e. will As and P be re-released from the soils as groundwater migrates through?)

Top