Kanchan Arsenic Filters and the Future of Fe0-Based Filtration Systems for Single Household Drinking Water Supply

Abstract

Biological and chemical contamination of natural water bodies is a global health risk for more than one billion people, mostly living in low-income countries. Innovative, affordable, and efficient decentralized solutions for safe drinking water supply are urgently needed. Metallic iron (Fe0)-based filtration systems have been described as such an appropriate solution. This communication focuses on the Kanchan arsenic filter (KAF), presented in the early 2000s and widely assessed during the past decade. The KAF contains iron nails as the Fe0 source and is primarily designed to remove As from polluted tube well waters. Recent independent works assessing their performance have all reported on a high degree of variability in efficiency depending mostly on the following factors: (1) the current operating conditions, (2) the design, and (3) the groundwater chemistry. This communication shows that the major problems of the KAF are two-fold: (1) a design mistake as the Fe0 units disturb the operation and functionality of the biosand filter, and (2) the use of poorly characterized iron nails of unknown reactivity. This assertion is supported by the evidence that the very successful community filter designed by the Indian Institute of Technology Bombay works with iron nails and has been efficient for many years. Replacing iron nails by more reactive Fe0 materials (e.g., iron fillings and steel wool) should be tested in a new generation KAF. It is concluded that a methodological or systematic approach in introducing and monitoring the efficiency of KAF should be used to test and disseminate the next generation KAF worldwide. Moreover, better characterization of the Fe0 materials including their intrinsic reactivity is required.

Universal Access to Safe Drinking Water: Escaping the Traps of Non-Frugal Technologies

“…Attempts to improve the efficiency of SSF by reinforcing biological activities [81,82] 2000 Fe 0 amended BSFs for the As and pathogen removal in Bangladesh [83] 2006 Development of Kanchan Arsenic filters in Nepal [84] 2007 Development of SONO Arsenic filters in Bangladesh [85] 2008 Development of IITB Arsenic filters in West Bengal (India) [37,40] 2010 Fe 0 amended BSFs for the As, pathogen, and U removal in rural Canada [39] 2012 Efficiency of Kanchan Arsenic filters disproved [86] 2012 Adoption of SSFs for the water supply in rural Switzerland [87] >2012 Implementation of several aggregate-amended SSFs for rural water supply [52,88] 2016 Development of the modular SSF/biochar filters for rural water supply [35,89] 2019 Domestic steel wool-based water filter operating for one year [43,68] Before presenting the technologies and discussing their costs, it is important to recall the key points related to clean water provision. Cities in developed countries are supplied with drinking water provided via conventional centralized water treatment systems.…”

Metallic Iron for Environmental Remediation: The Fallacy of the Electron Efficiency Concept

“…These applications have been discussed in earlier papers (Naseri et al, 2017;Antia, 2020, Huang et al, 2021a, thus, a detailed review is beyond the scope of the present paper. In summary, typical applications of Fe0-based remediation systems documented in literature include: i) decentralized safe drinking water provision in low-income settings (Huang et al, 2021b;Mueller et al, 2021), ii) industrial wastewater treatment systems (Li et al, 2019;Kulkarni et al, 2020), iii) recovery of heavy metals from industrial effluents (Vollprecht et al, 2018;Calabrò et al, 2021;Noubactep, 2021), iv) urban stormwater treatment (Rahman et al, 2013;Tian et al, 2019), v) treatment of drainage water from agroecosystems (Das et al, 2017;Lanet et al, 2021), vi) subsurface permeable reactive barriers (PRBs) for remediation of contaminated groundwater (Thakur et al, 2020;Njaramba et al, 2021, Wang et al, 2022, and vii) treatment of domestic wastewater (Wakatsuki et al, 1993;Latrach et al, 2018).…”

The key role of contact time in elucidating the mechanisms of enhanced decontamination by Fe0/MnO2/sand systems

“…Research during the past two decades has rediscovered filtration systems based on metallic iron (Fe 0 ) as an affordable, applicable, and efficient water treatment technology for decentralized water supply (e.g. households and small communities) 3 , 7 , 9 – 13 . Such Fe 0 filters are only sustainable upon admixing Fe 0 with other aggregates like granular activated carbon, biochar, gravel, magnetite (Fe 3 O 4 ), manganese oxides (MnO x ), pyrite (FeS 2 ), and sand 10 , 14 , 15 .…”