EFFECTIVENESS OF MODIFIED BIOSAND FILTERS (BY INCORPORATING BAMBOO ACTIVATED CHARCOAL, DIATOMITE, BONE CHAR, AND STEEL WOOL) IN REMOVAL OF FLUORIDE, AND E. coli FROM WATER.

Abstract

The Rift Valley contains the most significant sources of fluoride exposure. People in the Rift Valley have been confirmed to drink water containing up to 33mg/L of fluoride. The WHO has set the maximum allowable limit for fluoride in potable water at 1.5 mg/L. For millions of Kenyans, drinking water with a high fluoride content is a health risk such as dental fluorosis and skeletal fluorosis. Several studies on defluoridation have been conducted, and the majority of them concentrate on separate treatments for flouride, even though mixed contamination is common. Among Point of Use water treatment systems, the domestic Biosand filter (BSF) is a low-cost technology that has been implemented in Kenya. Several studies have shown that the BSF can reduce the turbidity and microbial contaminants effectively however, limited studies have focused on removal of fluoride. Various low-cost materials like bamboo activated charcoal, bone char, diatomite and steel wool were investigated to assess their capacity to remove fluorides from water by batch adsorption studies. Experiment was also conducted to determine the effect of the modified filter on bacteria reduction using E. coli as an indicator. The specifications of the standard Biosand filter were reduced, and four modified filters and one standard filter were designed. The 5 filters were replicated four times to produce a total of 20 filters. The filters were subjected to trials in the laboratory where 1.5, 2.26 and 3.0 mg/L initial fluoride concentration were subjected to 30 minutes, 60 minutes and 90-minutes contact time in order to reduce fluoride concentration to the recommended level of below 1.5 mg/L. E. coli was cultured and serially diluted into sterile saline deionised water and passed through modified Biosand filters. Data obtained was analysed using descriptive statistics, t-test and Analysis of Variance (ANOVA). The bamboo activated charcoal, diatomite, bone char and steel wool modified filters performed significantly better (p<0.05) than the standard filter, removing over 90% of fluoride after 24 hours and treating the water to below the WHO fluoride limit of 1.5mg/L. This study also indicated that the standard Biosand filter removed the highest amount of E. coli bacteria with removal rate of 96%. Bamboo activated charcoal, diatomite, bone char and iron oxide (Fe0) removed 90, 85, 81 and 70% respectively. This study's findings indicate that the modified filters are effective in removing both fluoride and E. coli from water. The bone char modified biosand filter proved to be the most effective in removing fluoride, while the standard biosand filter was found to be the most effective in removing E. coli. The study recommends that bone char modified filters can be built with locally accessible materials (sand, gravel, coarse sand and bone char) and applied in communities that are exposed to both fluoride and E. coli pollution but cannot afford expensive fluoride and E .coli reduction approaches.