IWA Publishing in conjunction with the International Water Association’s Young Water Professionals is happy to announce the newest post spotlighting the work of Young Water Professionals and showing how the work published in IWA Publishing Journals can be useful to those beginning their careers in the water sector.
Our 8th Young Water Professional's Spotlight Blog comes from Hemant Arora, who is currently studying for a PhD in water treatment and quality at the University of Waterloo, Canada. You can connect with Hemant on LinkedIn or Twitter (@hemantarora16).
Hemant was granted access to our entire journal portfolio for one month in order to select papers that relate to his research interests. He has discussed how his chosen papers relate to his work with the 1st IWA- YWP conference in Canada below. Thank you to Hemant for participating, we wish you the best of luck for the future!
Manganese: A cause of concern in drinking water
Hello! I am Hemant Arora, a Ph.D. student at the University of Waterloo in Canada. I was offered this wonderful opportunity to write a blog after the 1st IWA- YWP conference in Canada. I have also had the experience of working with IWA in The Hague, Netherlands where I worked on a project focusing on greenhouse gas (GHG) emissions reduction from water/wastewater utilities. I have always been fascinated by the natural processes involving microbes that can be used for water treatment. After working on slow sand filters (SSFs) in my Masters, I was very much intrigued and decided to explore the use of rapid sand filters (RSFs), commonly known as biofilters, in my Ph.D. I studied the use of biofilters for the removal of contaminants from drinking water, focusing on manganese.
As we are all aware, groundwater is a major source of water worldwide. Manganese is among various contaminants that are present in groundwater. Although humans need to consume a small amount of manganese to be healthy, too much manganese in drinking water can have adverse impacts, including causing neurological issues in infants and children, lower IQ, speech and memory difficulties, and behavioral changes (Dion et al., 2018). Manganese also creates aesthetic and operational problems in drinking water such as producing a metallic taste, brown color and stains in toilets and plumbing fixtures. Additionally, manganese has been associated with lead release in the distribution system. Lead itself is a neurotoxin, so along with manganese it can exacerbate adverse health conditions (Lane et al., 2020). Thus, it is imperative to reduce the manganese levels in drinking water below a threshold that means its impact is eliminated or minimized. Keeping that in mind, several guidelines have been issued regarding the acceptable manganese concentration in drinking water. The US Environmental Protection Agency (EPA) has a secondary standard of 0.05 mg/L, a standard established to address issues of aesthetics such as discoloration, rather than health concerns. Recently, Health Canada has enforced a stricter guideline for manganese with a maximum acceptable concentration (MAC) of 0.12 mg/L and an aesthetic objective (AO) of 0.02 mg/L (Health Canada, 2019). EU Directive has established a 0.05 mg/L as the maximum manganese concentration level in domestic water supplies.
Manganese (Mn) can be removed from drinking water by a range of physicochemical and biological processes depending on the water quality characteristics. The commonly used method includes oxidation and precipitation, sorption and catalytic oxidation, and biofiltration. A detailed description of these methods can be found in Tobiason et al. (2016). Among these different methods, biofiltration represents a green technology as it is environmentally friendly with little to no use of chemicals, no formation of disinfection by-products (DBPs) and low sludge/waste generation. Another important advantage of using biofiltration is its ability to simultaneously remove iron along with Mn which is commonly present in groundwater.
In biofiltration, filter media becomes biologically active due to the attachment of bacteria and other organisms to the surface of the media. Different mechanism contributes to Mn removal in biofilters namely homogenous, heterogeneous and biological oxidation removal. The dominant mechanism depends on the process condition such as influent water characteristics, pH, redox potential, temperature, etc., and is currently a black box where future research is required. As a starting point, I would recommend reading papers from Bruins et al. (2015) and (2014) where authors tried to determine the dominant mechanism of Mn removal in biofilters at different stages of filter operation and the role of water quality parameters affecting Mn removal. In these papers, it was also highlighted that microbiology plays a crucial role in the removal of Mn especially during the start-up of biofilters. With the advancement of microbial techniques such as next-generation sequencing (NGS) and 16S rRNA gene amplicon sequencing, several microorganisms like Pseudomonas sp., Crenothix, Gallionella, Leptothrix sp., and Hydrogenophaga sp., which are capable of biological Mn oxidation, have been identified in drinking water biofilters.
In another interesting paper by Burger et al. (2008), it was highlighted that the presence of these microorganisms depends on several factors, most notably influent water characteristics. Rather than a single species of microorganism, it is a microbial consortium that is responsible for biological Mn oxidation. In another study carried out by Breda et al. (2017), it was observed that filter media used in the biofiltration process can also result in significant differences between these microbial communities. Furthermore, it is important to highlight here that the presence of these microorganisms is not a guarantee of Mn biological oxidation as most of these organisms are heterotrophic and organotrophic, thus not requiring Mn for their growth. This leaves us with the fundamental question of why these microorganisms oxidize Mn?
To sum up, Mn in higher concentration in drinking water can have an adverse impact, therefore potential solutions to eliminate or minimize its concentration in drinking water should be studied. Biofiltration represents one such alternative. Despite certain knowledge gaps, there has been widespread use of biofilters for Mn removal, even though the applicability of biofilters is quite site-specific as I tried to highlight above and requires further research.
I hope you have enjoyed reading this blog and, in the future, if you see the water coming out of your faucets is brown or tastes metallic, it is because of manganese.
Looking forward to meeting many of you in the future conferences/workshops organised by IWA.
Until then, take care!
Hemant Arora
Ph.D. Candidate
Department of Civil and Environmental Engineering, University of Waterloo
Contact: h5arora [at] uwaterloo.ca
List of Scientific Papers highlighted from IWA Publishing:
Breda, I. L., Ramsay, L., & Roslev, P. (2017). Manganese oxidation and bacterial diversity on different filter media coatings during the start-up of drinking water biofilters. Journal of Water Supply: Research and Technology - AQUA, 66(8), 641–650. https://doi.org/10.2166/aqua.2017.084
Bruins, J. H., Vries, D., Petrusevski, B., Slokar, Y. M., & Kennedy, M. D. (2014). Assessment of manganese removal from over 100 groundwater treatment plants. Journal of Water Supply: Research and Technology - AQUA, 63(4), 268–280. https://doi.org/10.2166/aqua.2013.086
Bruins, J.H., Petrusevski, B., Slokar, Y.M., Slokar, Huysma, K., Y.M.Jorris, K., Kruithof, J.C, Kennedy, M.D. (2015). Biological and physicochemical formation of Birnessite during the ripening of manganese removal filters. Water Research, 69C: 154-161
Burger, M. S., Krentz, C. A., Mercer, S. S., & Gagnon, G. A. (2008). Manganese removal and occurrence of manganese-oxidizing bacteria in full-scale biofilters. Journal of Water Supply: Research and Technology - AQUA, 57(5), 351–359. https://doi.org/10.2166/aqua.2008.050
Lane, K., Trueman, B. F., Locsin, J., Gagnon, G.A. (2020). Inorganic contaminants in Canadian First Nation community water systems. J Water Health 1 October 2020; 18 (5): 728–740. https://doi.org/10.2166/wh.2020.185
Bibliography
Dion, L.-A., Saint-Amour, D., Sauvé, S., Barbeau, B., Mergler, D., & Bouchard, M. F. (2018). Changes in water manganese levels and longitudinal assessment of intellectual function in children exposed through drinking water. Neurotoxicology, 64, 118–125. https://doi.org/10.1016/j.neuro.2017.08.015
Health Canada (2019). https://www.canada.ca/en/health-canada/services/publications/healthy-living/guidelines-canadian-drinking-water-quality-guideline-technical-document-manganese.html
Tobiason, J. E., Bazilio, A., Goodwill, J., Mai, X., & Nguyen, C. (2016). Manganese Removal from Drinking Water Sources. In Current Pollution Reports (Vol. 2, Issue 3, pp. 168–177). Springer. https://doi.org/10.1007/s40726-016-0036-2