TREATMENT DURATION AND ADSORPTION CAPACITY OF CRUSHED BRICKS IN THE REMOVAL OF FLUORIDE FROM DRINKING WATER

Abstract

BACKGROUND: Fluorosis, a serious bone disease related to consumption of water with excessive fluoride is a public health problem in the rift valley region of Ethiopia. Defluoridation of drinking water is one of the common fluorosis prevention strategies; however most of the defluoridation methods used in fluorosis prevention programs are inappropriate technologies to be used in poor developing countries. Hence, this study was conducted to determine the treatment duration of a low cost crushed brick fluoride filter media made with sand filter and the fluoride adsorption capacity of the crushed bricks material per unit weight.

METHODS AND MATERIALS: Crushed materials made from ordinary bricks were incorporated as part of filtration column in experimental sand filter together with sand, charcoal and gravel in a 200 liter barrel. Fluoridated water samples with known concentration of 8mg/L were poured in to the filter unit in batch system. The filtrate of each batch were collected after two hours of contact time and analyzed for fluoride concentration. To determine the adsorption capacity of bricks, 2 gm of washed dried and crushed bricks material was mixed with 100ml of water sample that had fluoride concentration of 8mg/L and stirred for two hours in polyethylene bottle, centrifuged, and the residual fluoride was analyzed using standard methods. ANOVA, student T-test and correlation coefficient was done to see the significance of the outputs of linear model made for percent fluoride reduction and cumulative volume of water filtered

RESULTS: During the filter run about 300 liters of 8-ppm fluoride water was defluoridated up to the safe fluoride limit. The residual fluoride was observed to increase beyond the permissible upper limit (1.5mg/L) after 300 liters of fluoridated water was filtered. It was also observed that one-gram of crushed brick material can adsorb 0.365 to 0.372 milligram of fluoride from water with fluoride concentration of 8 mg/L.

CONCLUSION: this study showed that this experimental filter is effective for a duration of 30-40 days and have a capacity of filtering 300 liters of water with fluoride concentration of 8 mg/l to below 1.5mg/l within 30 minutes. The crushed bricks material has high fluoride adsorption capacity (91.76%) per unit weight. We recommend further large-scale studies to evaluate the utility of the technology in conventional water treatment systems and test the technology in the community to determine the affordability and applicability.