ATTENUATION OF METHYLENE BLUE DYE DURING RIVER BANK FILTRATION

Abstract

Although several studies have focused on the removal of turbidity, organics and pathogens during riverbank filtration (RBF), no study has been carried out on the attenuation of dyes during RBF. This work investigates the removal of methylene blue (MB) during passage of surface water through sandy aquifers. Batch as well as column studies were carried out using natural aquifer materials collected from different river and lake bank fJtration sites in India. BET surface areas of the aquifer materials were 1.2-6.5 m2/g. Adsorption followed the pseudo second order kinetics and Langmuir isotherm suggesting monolayer adsorption. Column results showed adsorption of MB with a saturation capacity of 0.467-1 .234 mg/g for different aquifer materials. Retardation factors of the dye were found to be very high ranging from 430 to 987, likely due to its high hydrophobicity (octanol/watcr partition coeffic lent = 5.85). Results showed that BET surface area or the roughness played it very important role in the retardation of MB and a linear relationship (R2 = 0.786) between retardation factor and BET surface area has been found over the same range of grain sizes Results suggest that the breakthrough of MB in a RBF well in sandy aquifers will take several years. Thus RBF appears to be a promising technology of water abstraction for the attenuation of dyes.