Escherichia coli transport through soil columns amended with nano-zeolite and cow manure

Manure application or wastewater use as irrigation water introduces agriculture as one of the main culprits of spreading antibiotic-resistant pathogens to the environment that threatens human health. Therefore, urgent measures are needed to control the fate of antibiotic-resistant enteropathogens of agricultural origin in the environment. This study aimed to evaluate the effect of different amounts of nano-zeolite on the transport of nalidixic acid-resistant Escherichia coli strain (E. coli NAR) through disturbed soil columns amended with cow manure. Soil mixtures were prepared by adding nano-zeolite (0, 5, and 15%), with/without 5% cow manure to a loam soil. Mixtures were incubated for 60 days and then poured into polyvinyl chloride cylinders (3.6 × 15 cm) for the leaching experiment. After establishing a steady-state unsaturated flow condition, a pulse (0.1 pore volume) of E. coli NAR suspension (10⁶ CFU mL⁻¹) was added on top of the soil columns. The leaching experiment was followed until 5 pore volume. Nano-zeolite application increased the filtration coefficient (λ_f), and relative adsorption index (S_R), and decreased the maximum depth (Z_max) of E. coli NAR transport in all treatments. Meanwhile, cow manure application increased E. coli NAR transport through soil columns compared to the controls. The average (C_av) and cumulative (C_cum) cell density of E. coli NAR for the columns containing 5% and 15% nano-zeolite were about 2.3 and 10-fold less than the control respectively. Therefore, the nano-zeolite application can improve soil adsorption parameters, even in manure-amended soils, and consequently reduce the risk of groundwater contamination by fecal bacteria.