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Safe Drinking Water: Effect of Granular Activated Carbon Bed Characteristics on Iron Removal from Water

Md. Golam Rasul
Department of Chemical Engineering, Bangladesh University of Engineering and Technology (BUET), Dhaka-1000, Bangladesh.

Imtiaz Ahmed
Department of Chemical Engineering, Bangladesh University of Engineering and Technology (BUET), Dhaka-1000, Bangladesh.

Md. Iqbal Hossain
Department of Chemical Engineering, Bangladesh University of Engineering and Technology (BUET), Dhaka-1000, Bangladesh.

Abstract/ Executive Summary:

Tuning the characteristics of granular activated carbon bed (GAC-bed) in household water-filters would be a technique to maintain iron at the required-level in drinking water. In the present study the individual effects of the depth of GAC-bed and the size and porosity of GAC particles on the iron removing capacity are investigated experimentally. A spectrophotometer is used to measure iron-content in water. It is observed that iron removing capacity increases monotonically with the increase in bed-depth regardless of the size of GAC particles. It is also observed that the iron removing capacity decreases drastically with the increase in the size of GAC particles for any fixed bed-depth. Finally the porosity of GAC particles is found to affect the iron removing capacity. The higher the GAC porosity the higher is the iron removing capacity over the considered porosity-range. It is believed that the observations of present study would be useful in adjusting GAC-bed characteristics at the time of designing household water-filters to maintain iron at the required-level.

Keywords: Safe drinking water; Water-filters; Iron content; Activated carbon; Bangladesh

Location: Department of Chemical Engineering, Bangladesh University of Engineering and Technology (BUET), Dhaka-1000, Bangladesh.

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: Drinking water

Objectives:

Hence the main objective of this study is to investigate the effect of GAC-bed characteristics on the removal of iron from water. Particularly the individual effects of the depth of GAC-bed and the size and porosity of GAC particles are investigated in this study.

Methodology:

The schematic of experimental setup used to determine iron removing capacities at various conditions. The setup consists of a feed reservoir having 40 L volume, three columns made of acrylic and having 60 cm length and 6 cm diameter, and a drain tank having 10 L volume. There is a regulating valve below the underneath of feed reservoir to control the discharge flow rate. The feed reservoir is charged with water obtained mixing equal-volume of drinking waters from three different sources. The iron-content of mixed water is 0.693 mg/L. Iron-content in water is measured employing a scanning spectrophotometer.18 Prior to the scanning in spectrophotometer for iron content, the water sample is mixed with Ferro Ver Iron Reagent (1, 10 phenanthroline) which recovers total soluble ferrous and ferric iron, as well as complex iron compounds and many insoluble iron forms. Each column, which is to be charged with GAC particles for removing iron from water, is also accompanied with a pair of flow-regulating valves. The bottom of each column is equipped with a polymeric screen with 0.10 cm mesh size to prevent the GAC particles from leaving the bed. The activated carbon is collected from local supplier. The collected activated carbon is grinded using a small laboratory scale ball-mill grinder. An ASTM sieve analysis is subsequently performed to obtain GAC particles of the average sizes of 0.120, 0.155, 0.204, 0.287 and 0.406 cm. To remove foreign dirt from GAC particles, the particles are washed carefully with distilled water. The washed particles are finally dried in an oven at 102^oC for 24 hrs to eliminate moisture. In the course of the operation in experimental setup, the feed-water is discharged from the reservoir through the columns filled with GAC particles, keeping the valves associated with the columns open. The water samples are then collected simultaneously from the outlet of each column right after a fixed time of two minutes counted from the moment at which water starts to appear in the outlet of each column. The iron-contents in the collected water samples are measured in the scanning spectrophotometer as described earlier.19 The difference in iron-content between the feed-water and collected sample-water is taken as the measure of the iron removing capacity at the respective condition. The iron removing capacity at ith condition is defined mathematically. The arithmetic mean of the iron removing capacities of three columns under an identical condition is used as the average iron removing capacity for the same condition.

Source of Information: Chemical Engineering Research Bulletin 18(2015) 1-5 EISSN: 2072-9510

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Iron in drinking water is to perform a number of crucial biological functions in human body. It is therefore always required to be present at the right proportions in drinking water. A GAC-bed is mostly used in household water-filters to refine water to be used for drinking purpose. Hence the individual effects of GAC-bed characteristics (i.e. bed-depth and the size and porosity of GAC particles) on iron removing capacity are studied experimentally in the present research. An increase in the depth of GAC-bed is found to increase the iron removing capacity substantially over the entire range of bed-depth considered. However the size of GAC particles exhibits a substantial reverse effect. It is observed for different fixed bed-depths that the higher the size of GAC particles the lower is the iron removing capacity. Finally the increase in the porosity of GAC particles is also found to increase the iron removing capacity remarkably. All these experimental observations prove the feasibility of tuning GAC-bed characteristics in household water-filters as a technique to control iron content in drinking water. The results presented here can subsequently be utilized for the development and validation of proper mathematical model to represent the influences of GAC-bed characteristics on iron removing capacity at various conditions.

Knowledge Management: Journal