Table of Contents
Background
The provision of safe and contaminant-free drinking water to the general public has been a serious challenge for governments throughout the world particularly during the 20th and 21st centuries because of increased urbanization, industrialization, and population growth. The US government has emphasized regulation and implementations related to the transport of a variety of contaminants in drinking water due to anthropogenic activities. US clean water act and Safe drinking water act along with their amendments are considered major regulatory outcomes set by the government. In this regard, US Environmental Protection Agency (EPA) being the main governing body, has been continuously working on the implementation of these acts by setting up the permissible levels of various environmental contaminants in drinking waterranging from inorganics, organics, disinfectants, radionuclides and microorganisms along with physicochemical parameters.
For this purpose, EPA has classified contaminants into two main categories comprising national primary drinking water regulations (NPDWR) which contain a list of 90 essential contaminants with serious public health concerns. EPA has set the maximum contaminant levels (MCLs) of these contaminants with aim of protecting public health by limiting the contaminant levels in drinking water. Another category includes national secondary drinking water regulations (NSDWR) containing guidelines of 15 non-enforceable parameters with only cosmetic or aesthetic effects on humans at certain levels however, their elevated and chronic exposure may result in some documented health implications.
Iron (Fe) occurs as the second most abundant earth crust metal with broad applications to humans. Its occurrence in drinking water has remained a serious public health concern globally and scientists have been investigating its chemical and biological impacts on the ecosystem and humans. Fe has vital significance to the human body and plays key biological roles in various metabolic processes and is a key element of blood hemoglobin that supplies oxygen to the whole body. Both, deficiency and elevated Fe levels in the human body may result in serious health implications. Naturally, Fe occurs in two ionic forms in drinking water which include soluble bivalent ferrous iron (FeII) and insoluble trivalent ferric iron (FeIII) forms. Inside the underground aquifers where no oxygen is available, Fe exists in a ferrous state, and water containing the soluble form is colorless odorless, and clear in appearance. However, when it comes out and is exposed to air, the atmospheric oxygen interacts with bivalent Fe and oxidizes it to ferrous which is insoluble in water resulting in its reddish brown or cloudy appearance giving it an unpleasant texture and metallic taste and making it not suitable for drinking.
Following the recommendations of SDWA, USEPA and WHO have set the MCL of 0.3 mg/L in drinking water to be safe for drinking. Although Fe lies under NSDWR guidelines set by EPA for having cosmetic and aesthetic effects on humans upon consumption through drinking water, there is strong evidence that long-term exposure to Fe through drinking water may result in serious health implications among exposed populations and demand serious measures in terms of treating water and making it free from Fe before consumption. It has also been suggested that the levels of Fe inside the underground aquifers and surface water reservoirs mostly lie in low concentrations and within the EPA permissible levels. However, these levels may get exceedingly high during water supply through the corroded pipes. The United States (US) drinking water supply systems provide one of the safest drinking water in the world to the public throughout the country.
According to the center for disease control (CDC), these water systems utilize surface and groundwater reservoirs to supply to households after following recommended treatment strategies. The surface water sources include lakes, streams, and rivers whereas, the groundwater comprises underground water stored in pores, rocks, and in the form of aquifers. Fe contamination of these water sources mainly occurs through either natural or anthropogenic sources. Naturally, Fe contamination of drinking water occurs through underground geogenic processes, changes in pH during chemical weathering, and microbial actions that involve Fe-consuming bacteria.
The surface water usually gets enriched with elevated Fe levels due to atmospheric deposition, surface runoff, percolation of Fe-containing water into the soil pores, industrial activities involving Fe and steel processing, and malfunctioning of water treatment plants fail to completely remove Fe before its supply to the households. Most importantly, the corrosion of water supply pipes and tanks contributes a major proportion of elevated Fe levels in drinking water even after its proper treatment and requires regular monitoring of the water system to ensure a safe drinking water supply in the US. This exceeding concentration of Fe in the water demands serious interventions involving state-of-the-art treatment technologies for the efficient removal of Fe from drinking water. The recommended Fe removal strategies will be described in the following sections.
Findings from previously conducted research suggest that the Fe levels in the US groundwater range from <0.001- 30 mg/L depending on the geographical areas. Notably, the Southern and Midwest states often exceed the USEPA-recommended MCLs (0.3 mg/L) (DeSimone et al. 2009). Certain types of bacteria utilize Fe in their metabolism and growth, this results in the formation of clogs in the supply pipelines and makes the drinking water aesthetically unfair for drinking as well as gives it a metallic taste (Michalakos et al. 1997). Fe possesses a high metabolic significance for the human body and is vital for hemoglobin and myoglobin to perform proper functioning along with its key role in important hormones and vitamin synthesis. Its recommended daily dose in humans varies between age groups and gender as well as ethnicities. In general, the daily Fe requirement for the human body ranges from 1-2 mg with dietary requirements ranging from 7-35 mg/day with an average of 16 mg/day (DeZuane 1997).
Water containing elevated Fe levels for a prolonged duration upon consumption by humans may result in impaired blood circulation by the hematopoiesis phenomenon. Moreover, excessive Fe consumption is also responsible for numerous health issues such as knee and joint pain, fatigue, and eye disorders (Alimohammadi et al. 2017). Whereas, low Fe levels give rise to the condition of blood deficiency called anemia (Kumar et al. 2022). Importantly, Fe also works synergistically to infer a disease risk in humans. For example, consumption of water with high Mn and Fe was found positively correlated with reduced infant weight at birth (Grazuleviciene et al. 2009). Further, higher levels of Fe along with Cu have been consistently reported in literature giving the water an unpleasant taste and smell (Shi and Taylor 2007). Excessive intake of both of these elements has been mainly associated with neurodegenerative disorders, arteriosclerosis, diabetes risks, and aging problems (Brewer 2010).
Detection Methods and Removal Strategies
Various detection methods have been proposed to quantify Fe in drinking water based on affordability, desired results, and financial costs. Volumetric and gravimetric methods are relatively cheaper and provide estimated information on testing water for iron results. In case, more accurate information is desired, this can be achieved through spectrophotometric methods mainly atomic absorption spectrophotometer (AAS) with various detection systems such as flame, electrothermal, and hydride generation. More recently, Inductively coupled plasma integrated with Mass spectrometry (ICPMS) has been considered a state-of-the-art detection approach for the quantification of Fe and other metals with low detection limits however it has limitations related to expensive per sample measurements cost.
Once detected in the drinking water supply, the main challenge to the authorities and treatment plants arises in terms of its efficient removal. Numerous strategies/techniques have been reported so far for effective Fe removal from drinking water. The adopted approach for Fe removal mainly depends on its available form in drinking water. If the water contains a dissolved ferrous form of Fe, oxidation-based techniques are usually preferred that oxidize ferrous into an undissolved ferric form which can be collected using various filter types. Scientists have described numerous removal techniques for Fe removal. These techniques either comprise conventional methods mainly oxidation-precipitation-filtration, electrocoagulation, aeration or sequestration, etc., or advanced strategies including biological, membrane technology, and Nanotechnology.
Among these, the nanotechnology-based approach has been recently adopted and has high efficiency of up to 99% removal of Fe from drinking water. This includes the use of carbon nanotubes (CNTs) and nanomaterials including nanoparticles, nanotubes, and nanocomposites have been effectively applied in recent times for effective Fe removal. However, applying the modern approaches at a wide scale will be a serious challenge for the US government and developing a cost-effective treatment system. (Chaturvedi and Dave 2012) and (Khatri et al. 2017) have described various treatment approaches in their review that summarizes conventional and modern methods for effective Fe removal from drinking water. Apart from conventional, chemical, and filtration-based methods, biological treatment has also been proven a very effective strategy for Fe-removal and more importantly its cost-effectiveness makes it a reliable and applicable approach. However, there are a few controversies related to mechanisms of biological removal which are not completely understood so far.
In this method, a trickling filter containing a thin film coat of specific bacterial strain is used and water is allowed to pass through the filter. The bacterial film oxidizes the dissolved ferrous into ferric and eliminates Fe from the drinking water in a highly efficient way. Future research and approaches should focus on the integration of conventional and modern technologies in a cost-effective way. Use of Gold and silver nanoparticles can replace conventional oxidizing agents used in various methods for Fe removal. Further, graphene and carbon-based nanomaterials can be more effective in membrane technology-based approaches. However, this further has some limitations related to difficulty in recovering from an aqueous system. Therefore, keeping the introduction of a variety of contaminants into the environment in view, that is still unregulated, the scientists must keep various biological and chemical aspects in view while developing a modern treatment strategy for Fe and other contaminants removal.
Public Perspective
Following frequently asked questions (FAQs) try to address some general public concerns in the US, especially the NYC region.
The United States government provides Worlds best drinking water to its residents. Drinking water directly from the tap is safe as EPA along with local authorities makes sure to deliver safe and non-contaminated drinking water. However, to be on the safe side, drinking water should regularly be monitored to check for any unregulated contamination.
Fe, which is an essential mineral for the human body usually does not affect human health up to certain levels. However, consuming water with high Fe for a prolonged period may cause serious health impacts.
USEPA and WHO have set MCL of 0.3 mg/L for Fe in drinking water
Low Fe levels in humans give rise to the medical condition of blood deficiency (anemia). Whereas, a high Fe level may cause a range of health implications. These impacts can be worse when some other metals such as Cu and Mg also exist at high levels.
Various natural and anthropogenic sources have been described in section 1 causing elevated Fe levels in drinking water. Briefly, these sources include geogenic, industrial, domestic, and malfunctioned water treatment systems.
Generally, Fe bacteria do not have any health impact however, it makes water aesthetically unpleasant and also provides a substrate for other harmful microbes that can affect human health.
If your drinking water smells like cucumber, sewage, or rotten eggs, Fe can be present in it because of the presence of Fe/Sulpher-eating bacteria.
Rust is an oxidized form of Fe. Drinking water with rust in it usually does not cause any adverse health effects unless consumed for a longer period.
In case of high levels of dissolved Fe in drinking water, it will require oxidation-based treatment strategies mainly aeration, chlorine, hydrogen peroxide, or ozone that oxidize dissolved Fe into undissolved Ferric iron which can easily be trapped in filters.
Fe in drinking water occurs mostly in dissolved form. Boiling the water can only kill harmful bacteria from water but can not remove Fe. Fe-removal can be effectively done through chemical or biological methods.
Conclusion
Contamination of Fe in drinking water can occur through various natural and anthropogenic sources. Although Fe is beneficial to human health in many ways. However, its elevated exposure for a prolonged period may raise health risk concerns. These effects are either associated with low or high Fe exposure in humans, especially through drinking water. Although, EPA ensures the delivery of Fe-free drinking water to US residents after properly treating and testing the drinking water and keeping it under permissible limits of 0.3 mg/L.
However, there exists a risk of Fe contamination when water is being supplied through different pipe systems making the internal linings of pipes rusty and clogged due to Fe and Cu deposition along with the coating of Fe-consuming bacteria. This raises a need of adopting modern treatment technologies along with regular monitoring of household drinking water to ensure a safe supply to the US residents.
References
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Chaturvedi S, Dave PN. 2012. Removal of iron for safe drinking water. Desalination. 303:1-11.
DeSimone LA, Hamilton PA, Gilliom RJ. 2009. The quality of our nation’s waters—quality of water from domestic wells in principal aquifers of the united states, 1991–2004—overview of major findings. US Geological Survey.
DeZuane J. 1997. Handbook of drinking water quality. John Wiley & Sons.
Grazuleviciene R, Nadisauskiene R, Buinauskiene J, Grazulevicius T. 2009. Effects of elevated levels of manganese and iron in drinking water on birth outcomes. Polish Journal of Environmental Studies. 18(5).
Khatri N, Tyagi S, Rawtani D. 2017. Recent strategies for the removal of iron from water: A review. Journal of Water Process Engineering. 19:291-304.
Kumar SB, Arnipalli SR, Mehta P, Carrau S, Ziouzenkova O. 2022. Iron deficiency anemia: Efficacy and limitations of nutritional and comprehensive mitigation strategies. Nutrients. 14(14):2976.
Michalakos GD, Nieva JM, Vayenas D, Lyberatos G. 1997. Removal of iron from potable water using a trickling filter. Water research. 31(5):991-996.
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- Yasir A. Rehman, Ph.D.
Dr. Rehman was born in Rawalpindi, Pakistan. He completed his MSc from PMAS – Arid Agriculture University Rawalpindi in 2011 where his thesis comprised a health risk assessment of subjects living in the vicinity of wastewater channels in urban settings and its relationship with the incidence of Malaria.
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OTHER RESEARCH ON WATER CONTAMINANTS BY DR. YASIR
