Batch and Column adsorption studies for simultaneous removal of Iron. Arsenc and Fluoride by Wooden Charcoal and river sand used as filter media in Indigenous Household Iron filter Units of Rural and semi-Urban Assam(India) : Author

Abstract

Groundwater is the major source of domestic water for people living in rural and semi-urban area of Assam D a northeastern hilly province of India. However, it contains excessive amounts of fluoride (F-), arsenic [As(III)] and iron [Fe(II)] D much higher than the permissible limits of drinking water. The rural and semi-urban population of Assam use different variants of indigenous household iron filter units D developed over last few generations using locally available materials such as community prepared wooden charcoal (CPWC) and river sand (RS) to reduce concentration of Fe(II) from the groundwater. No efforts are being made by the rural and semi-urban population to reduce concentrations of FD and As(III) from the groundwater before using it. Research efforts of past few decades have yielded many techniques and methods to remove Fe(II), FD and As(III) from groundwater in developing countries including India which have been tested for community level use especially in rural area. However, none of the techniques and methods developed has found application in rural and semi-urban areas of Assam; and people are still dependant on different variants of indigenous household iron filtrer units. There are very scanty scientific study available showing the effectiveness of the filter units in reducing Fe(II) as well as FD and As(III) from groundwater. The Government of India has launched DWater Technology InitiativeD as well as DWAR for WaterD to promote research and development activities to provide safe drinking water at affordable cost and in adequate quantity using appropriate science and technological interventions. The focus of work is directed towards assessing the potential of CPWC and RS D media used in the indigenous household filter units for removal of Fe(II), F- and As(III) through kinetics (batch mode), equilibrium (batch mode) and column (continuous mode) studies from mono-, binary- and ternary-metal ion systems comprising of Fe(II), FD and As(III) ions. The ultimate aim of this work is to design an improved filter unit for simultaneous removal of Fe(II), As(III) and FD. The procured CPWC and RS were processed to the required size ranges which were termed as processed wooden charcoal (PWC) and processed sand (PS). Potential of PWC and PS for metal uptake were evaluated through various batch and continuous mode column studies from mono- [comprising of either Fe(II), or F-, or As(III)], binary- [comprising of Fe(II)+As(III) and Fe(II)+FD] and ternary- [comprising of Fe(II)+FD+As(III)] metal ion systems using synthetic water samples in the laboratory. The effects of variation in different parameters such as pH, shaking speed, contact time, adsorbent dose and initial metal concentrations were investigated through batch studies. Continuous mode column studies were carried out using 3 cm internal diameter PVC columns to investigate the impact of bed depths and flow rates on metal adsorption by PWC and PS beds from mono-, binary- and ternary-metal ion systems to generate breakthrough profiles with bed depths of 5, 10 and 15 cm operated at flow rates of 1.5, 2.5 and 3.5 mL/min. The column data were used to carry out bed depth service time (BDST) analysis. Co-precipitation experiments were conducted with binary- and terna....