Zero-Valent Iron Sand Filtration Can Reduce Human and Plant Pathogenic Bacteria While Increasing Plant Growth Promoting Bacteria in Reclaimed Water

Abstract

The increasing use of reclaimed water for irrigation in areas lacking access to advanced wastewater treatment and reclaimed water distribution systems calls for an examination of irrigation-site-based treatment technologies that can improve the quality of this alternative water source. To address this need, we investigated the impact of zero-valent iron (ZVI)-sand filtration on the bacterial community structure and functional potential of conventionally treated reclaimed water utilized in downstream applications. Over a 2-month period, reclaimed water was collected from a tertiary wastewater treatment plant in the Mid-Atlantic, U.S. and trucked to our greenhouse facility. The water was stored in rain barrels and then filtered through one ZVI-sand filter every 5 days. Filtrate was then subjected to enumeration, phylotyping, shiga toxin screening, and antimicrobial susceptibility testing of Escherichia coli. Aliquots of filtrate were also DNA extracted, and purified DNA was subjected to 16S rRNA gene sequencing and metagenomic shotgun sequencing. The genera Dechloromonas, Desulfotomaculum, Leptonema, and Thermomonas, which contain denitrifying and sulfate reducing species, commonly used in bioremediation, and known to increase the inherent reactivity of ZVI, were significantly more relatively abundant in ZVI-sand filtered reclaimed water compared to reclaimed water. The concentration of E. coli in ZVI-sand filtered reclaimed water was significantly lower compared to that of reclaimed water, and cefoxitin-and tetracycline-resistant E. coli were undetectable after ZVI-sand filtration. ZVI-sand filtration reduced the occurrence of human as well as plant pathogenic genera (Aeromonas, Mycobacterium, Shewanella, Acidovorax, Agrobacterium, and Clavibacter) but increased the proportion of Azospira, a nitrogen fixing bacterial genera, in the microbial community. Our exploratory functional

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).…”

“…According to Naseri et al (2017), in testing a Fe 0 system, the main interest should be to check whether the designed system generated enough contaminant scavengers for efficient water treatment, regardless from the redox properties or even the chemical nature of the pollutants. It is recalled that Fe 0 filters also remove pathogens (You et al, 2005;Bradley et al, 2011;Tepong-Tsindé et al, 2019;Kulkarni et al, 2020) and many other species without redox properties (Richardson and Nicklow 2002;Henderson and Demond 2007;Ullah et al, 2020).…”