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Designing a Scalable and Affordable Fluoride Removal (SAFR) Process for Groundwater Remediation in India

  • Author(s): Cherukumilli, Aruna Kirani Katyayani
  • Advisor(s): Gadgil, Ashok J
  • et al.
Abstract

Globally, 200 million people are at risk of adverse health effects from drinking groundwater contaminated with geogenic fluoride concentrations exceeding the World Health Organization’s maximum contaminant limit (WHO-MCL = 1.5 mg F−/L). Although many defluoridation technologies have been demonstrated to work in lab, most have proven inappropriate for developing countries because they are cost-prohibitive, require skilled labor, or are difficult to scale. Activated alumina (AA) column filters are widely used by the upper middle class but production of AA remains costly in terms of money, energy, and greenhouse gas emissions. Eliminating these energy-intensive steps in refining bauxite, a ubiquitous aluminum-rich ore ($30/tonne), to AA ($1500/tonne), has the potential to reduce the annual per-capita material cost of treated water significantly.

The purpose of this dissertation is to ascertain the use of bauxite as a potentially inexpensive defluoridation technology through experimental studies characterizing globally diverse bauxite ores and tradeoffs associated with mild processing steps to enhance fluoride removal performance. Chapter 1 presents an overview of fluoride as a geogenic groundwater contaminant worldwide and in India, the health effects of excess fluoride consumption, and existing treatment technologies. Chapter 2 establishes proof of concept that mildly processed bauxite can effectively remediate field-relevant fluoride concentrations to below the WHO-MCL in synthetic and real groundwater matrices at comparable kinetics and significantly lower cost than AA. This chapter also characterizes intrinsic features of globally diverse bauxite ores (from Guinea, Ghana, USA, and India) to identify factors predicting bauxite’s performance. Chapter 3 utilizes insights on underlying molecular mechanisms and proposes thermal activation and groundwater pH adjustment as two processing methods to optimize the fluoride removal performance of bauxite. Chapter 4 discusses some remaining practical challenges and unknowns for implementing our scalable and affordable fluoride removal (SAFR) process in the field. Chapter 5 concludes this dissertation by discussing the implications of the research findings and by suggesting additional future studies needed before field implementation of the proposed SAFR groundwater treatment technology.

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