Defluoridation by Microbes: A Potential Remediation Technique

Rapid development of human civilization with increase in human population has contributed to the accumulation of hazardous pollutants in the environment. Fluorine a highly reactive element, is ubiquitously found in the world environment, mostly as inorganic compounds of fluoride. Fluoride is beneficial in trace amounts to the human body, but is extremely toxic beyond threshold limits of 1–1.5 mg/L in drinking water, as established by health organizations. Unfortunately, due to modern industrial activities, agricultural technologies, domestic facilities and rampant urbanization, its presence in all components of the ecosystem has increased to alarming levels. With the contamination of soil, water and air, its effects on plants and humans are extremely adverse. Several damaging effects on the physical and biochemical processes of plants and animals have been documented, the most common being dental and skeletal fluorosis in humans. Asian and African countries are the most affected, with India and China enumerating 66 million and 45 million people suffering from fluorosis respectively. Defluoridation is the attenuation or removal of fluoride from water, deeming it safe for consumption. In the past, various physiochemical and electrochemical methods for remediation or removal of fluoride from contaminated samples have been successfully applied. However, most of these methods requiring sophisticated equipment, laborious procedures, expensive construction and time, proved to be impractical and universally inapplicable. In the past few decades, the role of microorganisms in bioremediation ignited hope in their ability to defluoridate water as well. In this chapter, we provide a comprehensive understanding of the biological means of defluoridation, including the use of microorganisms for bioremediation approaches of biosorption and bioaccumulation to attenuate environmental pollutants. The role of microbial immobilization for defluoridation, metabolic engineering and omics approach for improvements in fluoride-resistant microbes, have been illustrated. This chapter documents the various findings of microorganisms, their consortia, defluoridation rates and mechanisms involved in bioremediation of fluoride. We present the current challenges faced in defluoridation and bioremediation of environmental pollutants, along with some future perspectives.