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K. Kesava Rao got his B.Tech in chemical engineering from IIT Madras in 1977, and M.S. and Ph.D. in chemical engineering in 1979 and 1982, respectively from the University of Houston. He was a faculty member in the Department of Chemical Engineering, Indian Institute of Science from 1983-2021. His research interests are granular flow and defluoridation of drinking water.


Ingestion of excess fluoride through water, food, and air causes a disease called fluorosis. Many methods have been developed for defluoridation, or the removal of excess fluoride (F-) from drinking water. The health effects of fluorosis and some of the defluoridation methods are described. Defluoridation of reject water from a reverse osmosis (RO) unit located in a village in Karnataka was examined using column experiments involving the adsorbents activated alumina (AA) and a hybrid anion exchange resin embedded with hydrous zirconium oxide nanoparticles (HAIX-Zr). (developed by Prof. A. Sengupta’s group). A defluoridation unit was set up at the village using AA but it did not function well as the column developed leaks and the capacity was low. Subsequent experiments were done at the lab-scale using reject water and synthetic waters of various compositions. The feed composition strongly affected the adsorption capacity. The performance of HAIX-Zr was better than AA for synthetic fluoride water, but not for the reject. The cost of treated water was Rs. 0.3 – 1.0/L for AA and 0.2 – 11.5 for HAIX-Zr. Experiments on solar distillation and rainwater harvesting are also discussed. This work was done in collaboration with M.V.V.N. Samrat, R. Sankannavar, J.R. Mudakavi, and A. SenGupta.

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