Berkeley Lab

Confronting the unmet need of safe drinking water using a low-cost defluorination method

By Cheryl Tajon

Dr. Katya Cherukumilli is the CEO and Founder of the non-profit agency, Global Water Labs, and is a Postdoctoral Fellow at University of Washington.  She delivered a scientifically compelling and aspirational presentation on developing low-cost technologies to provide safe drinking water across the globe.  The audience was challenged with the connotation the term “fluoride” provokes.  From her comprehensive view, “fluoride” exposes the fact that an excess of it (>1.5 mg F/L) leads to irreversibly crippling bone and enamel deformations.  Over 200 million people are at risk of these irreversible conditions due to unsafe water.  People of the Rift Valley and East India constitute >40% of the global population exposed to these harmful levels.  Current defluorination methods are costly or harbor an infrastructure that has been difficult to initiate in low-income settings.  Activated alumina, a conventional adsorbent of fluoride, is ca. 50 times more costly than an inexpensive alternative called bauxite ore.  Dr. Cherukumilli’s work focuses on bauxite’s characterization and its application in a low-cost defluorination method to generate safe drinking water.    

Bauxite can be mined in the USA, Guinea, Ghana, and India.    Bauxite from different regions share a similar intrinsic affinity for fluoride adsorption at an optimal pH of 5.5 to 6.0.  When conditions become too basic or acidic, fluoride removal becomes inefficient.  X-ray fluorescence showed that bauxite contains 20% Al, along with Fe, Si, Ti, and Ca, while scanning electron microscopy revealed its heterogeneous structure.  X-ray diffraction confirmed bauxite’s mineral phase of Gibbsite, Al(OH)3, where Fexchanges with OHduring the adsorption process.  Interestingly, a component found in bauxite from India is calcite, CaCO3.  With an equilibrium pH of 8.1, the performance of this grade of bauxite is hindered as an adsorbant.  Dr. Cherukumilli sought ways to improve its implementation and coupled milder methods to achieve optimal fluoride adsorption.  By heating the temperature to 100 – 200˚C instead of 300˚C, fluoride adsorption was facilitated when bauxite contained the calcite additive.  Furthermore, thermogravimetric analysis/mass spectrometry (TGA/MS) showed that loss of mass upon heating originated from water, which increased bauxite’s surface area and consequently improved fluoride adsorption.

Dr. Cherukumilli’s work of transferring technology in three separate pilots brought her to Tanzania, Kenya, and India to build and test column filters containing bauxite.  Her eye is toward independently scaling up to the real world, but also keeping in mind that harmful inorganic chemical contaminants beyond fluoride need consideration.  Her talk was thought-provoking and highlights how one can use science to improve the quality of life across the globe.  She brings a rigorous and scientific voice to global challenges that we all need to hear and confront with justified urgency.