A simple and effective arsenic filter based on composite iron matrix: Development and deployment studies for groundwater of Bangladesh

Abstract

Drinking groundwater contaminated with naturally occurring arsenic is a worldwide public health issue. This work describes the research, development and distribution of a filter used by thousands of people in Bangladesh to obtain arsenic-free safe water. The filter removes arsenic species primarily by surface complexation reactions: = FeOH + H₂AsO₄ ⁻ → = FeHAsO₄ ⁻ + H₂O (K = 10²⁴) and = FeOH + HAsO₄ ²⁻ → = FeAsO₄ ^{2 −} + H₂O (K = 10²⁹) on a specially manufactured composite iron matrix (CIM). The filter water meets WHO and Bangladesh standards, has no breakthrough, works without any chemical treatment (pre- or post-), without regeneration, and without producing toxic wastes. It costs about $40/5 years and produce 20–30 L/hour for daily drinking and cooking need of 1–2 families. The spent material is completely non toxic-solid self contained iron-arsenate cement that does not leach in rainwater. Approved by the Bangladesh Government, about 30,000 SONO filters were deployed all over Bangladesh and continue to provide more than a billion liters of safe drinking water. This innovative filter was also recognized by the National Academy of Engineering – Grainger Challenge Prize for sustainability with the highest award for its affordability, reliability, ease of maintenance, social acceptability, and environmental friendliness, which met or exceeded the local government's guidelines for arsenic removal.

Keywords:

• Arsenic filter
• composite iron matrix
• Grainger challenge prize
• groundwater
• Sono filter

Acknowledgment

The authors deeply appreciate the workers of SDC/ MSUK, Bangladesh for their unwavering support. We also acknowledge assistance from Prof. A. H. Khan and Prof. A. Barkat, Dhaka University, Bangladesh; Prof. M. Alauddin, Wagner College, NY, USA; and Dr. S. S. Newaz, Polyorganix Inc., USA. The authors acknowledge Dr. Shahamat. U. Khan for his critical constructive suggestions during the development of this filter.

Notes

^a Flow rate 20–30 L/hour, Other water chemistry parameters are similar to that in Table 4. Consumption: 60–180 L/day. As (total) was measured by ASV on a thin film gold electrode validated by IAEA interlaboratory comparison studies at SDC/MSUK, Kushtia Bangladesh and with Graphite Furnace AA at GMU Chemistry Department. Iron was measured spectrophotometrically at SDC/MSUK. Cost per liter decreases as more water is filtered.

^a Bangladesh standard values are given as maximum desirable concentration with maximum permissible concentration in parentheses.

^b SONO filters. ICP multielement measurements of Cu, Zn, Pb, Cd, Se, Ag, Sb, Cr, Mo, and Ni show concentrations below the USEPA, and WHO limits at all times. All other measurements show average of semi-continuous measurement of more than 394,000 L of groundwater filtered by us and ETVAM in at least eight different water chemistries in different regions of Bangladesh. Water chemistry parameters were recoded for 23 metals, 9 anions, E _h , pH, Temp, dissolved oxygen, conductivity, and turbidity for hundreds of samples. All prescribed parameters passed the drinking water standards of WHO and Bangladesh.

^c One tubewell at Bheramara was found to contain As (total) 4000 μ g/L. The filtered water had 7 μ g/L. This well was later capped by the Government.

^d In some wells As(III) concentrations exceeded 90% of the As(total).