Evaluation of Performance of Sono 3-Kolshi Filter for Arsenic Removal from Groundwater Using Zero Valent Iron Through Laboratory and Field Studies
A.K. M. MUNIR and S. B. RASUL Sono Diagnostics Centre Environment Initiative, Kushtia, Bangladesh M. HABIBUDDOWLA 140 Northwood Road, Frankfort, KY 40601, USA M. ALAUDDINDepartment of Chemistry, Wagner College, Staten Island New York, USA, A. HUSSAM Department of Chemistry, George Mason University, Virginia, Fairfax, VA 220 30, USA and A.H. KHAN Department of Chemistry, University of Dhaka, Dhaka - 1000, Bangladesh Abstract A three-pitcher (locally known as ‘3-Kolshi’) water filtration system made from locally available materials was tested for its efficacy in removingarsenic, other trace metals and anions from the groundwater of Bangladesh and the disposal of the filtering materials after the breakthrough was studied. In this filter, the first Kolshi has cast iron turnings, and sand, the second Kolshi has wood charcoal and sand as the active ingredients. About 6000 L of groundwater containing 80 1900 µg/L of arsenic was filtered. The filtered water containedabout 10 µg/L As(total), no detectable As(III), and significantly reduced major, minor and trace
Technologies for Arsenic Removal from Drinking Water
metals. The filtration process was monitored for a year by measuring As (total), As(III), 23 other metals, 9 anions, pH, conductivity, temperature and flow rate. The complete conversion of Fe0 to nonmagnetic hydrous ferric oxide (HFO) asthe most active component for arsenic removal is indicative of an oxidizing environment sustained by continuous diffusion of air through the porous Kolshi. All parameters indicate that the water quality meets and exceeds USEPA, WHO, and Bangladesh standards. The effect of flow rate on arsenic removal has been studied separately for three tube wells with arsenic concentration of 166-212, 211-238and 1435-1642 µg/L (ppb) over a period of 4 months. The results -8 demonstrate that the optimum flow rate is about 7 L/hr for achieving an arsenic concentration down to the level of 7-13 ppb from the initial level of about 200 ppb. The optimum flow rate is 8.4 L/hr for achieving an arsenic concentration of about 20 ppb from the initial level of 1600 ppb. Any possibility of pathogenic contaminationduring the use of the system as a household utility can be removed with a 4-litre hot water cycle, once in a week. This contamination is not inherent to the system. Leaching experiment on solid wastes from 3-Kolshi filter, with rain water at pH 4 and 7, showed no release of arsenic above 16 µg/L of the leachate, which is the detection limit of ICP-AES method for arsenic. The release of other tracemetals was also not very significant. At its present capacity, five people can use the system for about five months at a consumption rate of 50 L/day. Regeneration of the system to its original efficiency can be achieved by changing the sand in the Kolshi. These low-cost units (ca. US $ 5.0- 6.0) are being used by people in the arsenic affected areas of Bangladesh in large numbers. Furtherstudies on the improvement of the design and the initial treatment of the filtering materials are in progress.
INTRODUCTION Recent measurements show that in many parts of the Ganges and Bhrahmmaputra basin more than 60% of the shallow and deep tubewell water contains arsenic above the WHO guideline value of 10 µg/L and more than 30% of the tubewells contains arsenic above the Bangladesh standard of50 µg/L (Chatterjee, et. al., 1995; Das et. al., 1995). It is estimated that of the 125 million people of Bangladesh, between 35-77 million are drinking groundwater containing more than 50 µg/L of arsenic. The contaminated water is widely handpumped from a depth of 30 - 200 feet using shallow tubewells. According to WHO estimate, there are about 2.5 million tubewells, although the unofficial...