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Zero-valent iron sand filtration can reduce human and plant pathogenic bacteria while increasing plant growth promoting bacteria in reclaimed water



Prachi Kulkarni, Nathanael David Olson, Joseph N. Paulson, Emmanuel F. Mongodin, Mihai Pop, Amy R. Sapkota


The increasing use of reclaimed water for irrigation in areas that lack 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 two-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 ZVI-sand filtered every five 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. Denitrifying and sulfate reducing bacteria (Dechloromonas, Desulfotomaculum, Leptonema and Thermomonas), commonly used in bioremediation, and known to increase the inherent reactivity of ZVI, were significantly more 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 reclaimed water, and the ZVI-sand filter was able to eliminate cefoxitin- and tetracycline-resistant E. coli. ZVI-sand filtration reduced the occurrence of human as well as plant pathogenic genera (Aeromonas, Mycobacterium, Shewanella, Acidovorax, Agrobacterium, Clavibacter) but increased the occurrence of nitrogen-fixing bacterial genera (Azospira). Our exploratory functional analysis showed a modest non-significant increase in open reading frames for genes associated with iron uptake, oxidative stress and defense and repair mechanisms after ZVI-sand f
Frontiers in Microbiology


zero-valent iron, reclaimed water, point-of-use treatment, small-scale agriculture, metagenomics, whole genome sequencing, 16S rRNA gene sequencing, shotgun sequencing


Kulkarni, P. , Olson, N. , Paulson, J. , Mongodin, E. , Pop, M. and Sapkota, A. (2020), Zero-valent iron sand filtration can reduce human and plant pathogenic bacteria while increasing plant growth promoting bacteria in reclaimed water, Frontiers in Microbiology, [online], (Accessed March 1, 2024)
Created November 2, 2020, Updated January 31, 2024