Fluoride in the drinking water of Nagaur tehsil of Nagaur District, Rajasthan, India

State-of-the-art of research progress on adsorptive removal of fluoride-contaminated water using biochar-based materials: Practical feasibility through reusability and column transport studies

Fluoride (F^-) is one of the essential elements found in soil and water released from geogenic sources and several anthropogenic activities. Fluoride causes fluorosis, dental and skeletal growth problems, teeth mottling, and neurological damage due to prolonged consumption, affecting millions worldwide. Adsorption is an extensively implemented technique in water and wastewater treatment for fluoride, with significant potential due to efficiency, cost-effectiveness, ease of operation, and reusability. This review highlights the current state of knowledge for fluoride adsorption using biochar-based materials and the limitations of biochar for fluoride-contaminated groundwater and industrial wastewater treatment. Biochar materials have shown significant adsorption capacities for fluoride under the influence of low pH, biochar dose, initial concentration, temperature, and co-existing ions. Modified biochar possesses various functional groups (-OH, -CC, -C-O, -CONH, -C-OH, X-OH), in which enhanced hydroxyl (-OH) groups onto the surface plays a significant role in fluoride adsorption via electrostatic attraction and ion exchange. Regeneration and reusability of biochar sorbents need to be performed to a greater extent to improve removal efficiency and reusability in field conditions. Furthermore, the present investigation identifies the limitations of biochar materials in treating fluoride-contaminated drinking groundwater and industrial effluents. The fluoride removal using biochar-based materials at an industrial scale for understanding the practical feasibility is yet to be documented. This review work recommend the feasibility of biochar-based materials in column studies for fluoride remediation in the future.

Industrial Utilization of Capacitive Deionization Technology for the Removal of Fluoride and Toxic Metal Ions (As3+/5+ and Pb2+)

Capacitive deionization (CDI) is an emerging desalination technology, particularly useful for removing ionic and polarizable species from water. In this context, the desalination performance of fluoride and other toxic species (lead and arsenic) present in brackish water at an industrial scale of a few kilo liters using a CDI prototype built by InnoDI Private Limited is demonstrated. The prototype is highly efficient in removing ionic contaminants from water, including toxic and heavy metal ions. It can remove fluoride ions below the World Health Organization (WHO) limit (1.5 ppm) at an initial concentration of 7 ppm in the input feed water. The fluoride removal efficiency of the electrodes (at a feed concentration of 6 ppm) deteriorates by ≈4-6% in the presence of bicarbonate and phosphate ions at concentrations of 100 ppm each. The removal efficiency depends on flow rate, initial total dissolved solids, and other co-ions present in the feed water. Interestingly, toxic species (As3+/5+ and Pb2+) are also removed efficiently (removal efficiency > 90%) by this technology. The electrodes are characterized extensively before and after adsorption to understand the mechanism of adsorption at the electrode.

Vitamin C and E supplementation can ameliorate NaF mediated testicular and spermatozoal DNA damages in adult Wistar rats

OBJECTIVE

Present study was designed to explore the efficacy of vitamin C and E (VC&VE) against fluoride mediated testicular, epididymal and spermatozoal anomalies.

MATERIALS AND METHODS

Thirty two adult Wistar rats were divided into four groups. Group-I was control; Group-II received sodium fluoride (NaF) at 15 mg/kg/day dose; Group-III was provided with VC (200 mg/kg/day) and VE (400 mg/kg/day) plus NaF; Group-IV received only VC&VE. Structural integrity and oxidative stress markers (superoxide dismutase, catalase, malondialdehyde and protein carbonyl) of testis and epididymis were assessed. Spermatozoal parameters (count, motility, viability and hypo-osmotic swelling) were evaluated. Testicular functional maker enzymes (acid phosphatase, alkaline phosphatase and lactate dehydrogenase) were also assessed. Integrity of testicular and spermatozoal DNA were evaluated. Testicular fluoride content was measured.

RESULT

Fluoride induced structural changes and alterations of oxidative stress markers were observed in testis and epididymis. Spermatozoal potentials were altered and reduced activities of testicular functional marker enzymes were observed. Fluoride caused testicular and spermatozoal DNA damages. VC&VE supplementation resulted in protectionfrom all fluoride mediated alterations and helped in attenuating testicular fluoride accumulation.

CONCLUSION

Antioxidant properties of VC&VE ameliorated fluoride mediated reproductive damages but only supplementation did not exhibit any notable effect compared to control rats.

Bioaccumulation of Fluoride in Plants and Its Microbially Assisted Remediation: A Review of Biological Processes and Technological Performance

Fluoride is widely found in soil–water systems due to anthropogenic and geogenic activities that affect millions worldwide. Fluoride ingestion results in chronic and acute toxicity, including skeletal and dental fluorosis, neurological damage, and bone softening in humans. Therefore, this review paper summarizes biological processes for fluoride remediation, i.e., bioaccumulation in plants and microbially assisted systems. Bioremediation approaches for fluoride removal have recently gained prominence in removing fluoride ions. Plants are vulnerable to fluoride accumulation in soil, and their growth and development can be negatively affected, even with low fluoride content in the soil. The microbial bioremediation processes involve bioaccumulation, biotransformation, and biosorption. Bacterial, fungal, and algal biomass are ecologically efficient bioremediators. Most bioremediation techniques are laboratory-scale based on contaminated solutions; however, treatment of fluoride-contaminated wastewater at an industrial scale is yet to be investigated. Therefore, this review recommends the practical applicability and sustainability of microbial bioremediation of fluoride in different environments.

Fluoride and nitrate in groundwater of rural habitations of semiarid region of northern Rajasthan, India: a hydrogeochemical, multivariate statistical, and human health risk assessment perspective

In arid and semiarid regions, groundwater is required for the drinking, agriculture, and industrial activities due to scarcity of surface water. Groundwater contaminated with high concentrations of fluoride and nitrate can severely affect human health in these regions. Twenty-eight groundwater samples from rural habitations of Jhunjhunu district, Rajasthan, India, were collected in March 2018 and subjected to analysis for water quality parameters. Fluoride and nitrate concentrations in groundwater varied from 0 to 5.74 mg/L and 10.22-519.64 mg/L, respectively. Nitrate content of about 86% samples and fluoride content of about 54% exceeded the permissible limit of Bureau of Indian Standards (IS:10,500) as well as World Health Organization standards. All groundwater samples belonged to poor to unfit drinking water quality index. Principle component analysis elucidates the anthropogenic contribution to high nitrate concentrations observed in this area. Noncarcinogenic human health risk evaluated from high nitrate and fluoride in drinking water for children, men, and women points to the fact that noncarcinogenic risk is exceeding the allowable limit to human health. The predominating hydrochemical facies in the area is Na⁺-HCO₃^--Cl^- followed by Na⁺-Mg²⁺-HCO₃^--Cl^-. The Gibbs plot and bivariate ionic cross-plots suggest the noncarbonate weathering (rock dominance), evaporation dominance, and ion exchange process to be the predominating geochemical mechanisms governing the evolution of groundwater hydrogeochemistry. Giggenbach diagram shows the immature character, i.e., incomplete equilibration of the groundwater.

Review on Health Impacts from Domestic Coal Burning: Emphasis on Endemic Fluorosis in Guizhou Province, Southwest China

Endemic fluorosis in Guizhou Province, Southwest China was firstly reported by Lyth in 1946 and was extensively concerned since the early 1980s. Initially, the pathological cause of endemic fluorosis in Guizhou Province was instinctively ascribed to the drinking water. However, increasing evidences pointed that the major exposure route of fluorine for the local residents is via the roasted foodstuffs, especially the roasted pepper and corn. Source of fluorine in roasted foodstuffs was once blamed on the local coal and subsequently imputed to clay mixed in the coal. In fact, both are probably the source. Geogenic fluorine concentration in soil and clay is indeed high in Guizhou Province, but is not likely to be the direct cause for endemic fluorosis. The real culprit for endemic fluorosis in Guizhou Province is the unhealthy lifestyle of the local residents, who usually roasted their foodstuffs using local coal or briquettes (a mixture of coal and clay), resulting in the elevated fluorine in roasted foodstuffs. Nowadays, endemic fluorosis in Guizhou Province has substantially mitigated. Nevertheless, millions of confirmed cases of dental fluorosis remain left. In addition to endemic fluorosis, other health problems associated with domestic coal burning may also exist, because of the enrichment of toxic/harmful elements in the local coal. It is necessary to determine how serious the situation is and find out the possible solution. As people in other developing countries may suffer from similar health issues, same health issues around the world deserve more attention.

Groundwater fluoride contamination, probable release, and containment mechanisms: a review on Indian context

Fluoride contamination in the groundwater has got great attention in last few decades due to their toxicity, persistent capacity and accumulation in human bodies. There are several sources of fluoride in the environment and different pathways to enter in the drinking water resources, which is responsible for potential effect on human health. Presence of high concentration of fluoride ion in groundwater is a major issue and it makes the water unsuitable for drinking purpose. Availability of fluoride in groundwater indicates various geochemical processes and subsurface contamination of a particular area. Fluoride-bearing aquifers, geological factors, rate of weathering, ion-exchange reaction, residence time and leaching of subsurface contaminants are major responsible factors for availability of fluoride in groundwater. In India, several studies have reported that the groundwater of several states are contaminated with high fluoride. The undesirable level of fluoride in groundwater is one of the most natural groundwater quality problem, which affects large portion of arid and semiarid regions of India. Rajasthan, Andhra Pradesh, Telangana, Tamil Nadu, Gujarat, and West Bengal are the relatively high-fluoride-contaminated states in India. Chronic ingestion of high doses of fluoride-rich water leads to fluorosis on human and animal. Over 66 million Indian populations are at risk due to excess fluoride-contaminated water. Therefore, groundwater contamination subject to undesirable level of fluoride needs urgent attention to understand the role of geochemistry, hydrogeology and climatic factors along with anthropogenic inputs in fluoride pollution.

Origin and assessment of groundwater pollution and associated health risk: a case study in an industrial park, northwest China

Groundwater quality which relates closely to human health has become as important as its quantity due to the demand for safe water. In the present study, an entropy-weighted fuzzy water quality index (WQI) has been proposed for performing groundwater quality assessment in and around an industrial park, northwest China, where domestic water requirements are solely met by groundwater. The human health risk was assessed with the model recommended by the United States Environmental Protection Agency. In addition, the sources of major ions and main contaminants were also analyzed. The study shows that groundwater in the study area has been contaminated conjunctively by natural processes and industrial and agricultural activities. Nitrate, manganese (Mn), fluoride, total dissolved solids, total hardness and sulfate are major contaminants influencing groundwater quality. Nitrate and heavy metals such as Mn are mainly affected by human agricultural activities and industrial production, while other contaminants are mainly originated from mineral weathering and water-rock interactions. The results of water quality assessment suggest that half of the groundwater samples collected are of medium quality thus require pretreatment before human consumption. The mean health risk caused by the consumption of contaminated groundwater in the area is 8.42 × 10(-5) per year which surpasses the maximum acceptable level (5 × 10(-5) per year) recommended by the International Commission on Radiologic Protection. The entropy-weighted fuzzy WQI proposed in this study can not only assign proper weights to parameters but also treat uncertainties associated with water quality classification. This study will be of interest to international environmentalists and hydrogeologists. It will also be useful in regional groundwater management and protection.