Accounting for the Three-Dimensional Distribution of Escherichia coli Concentrations in Pond Water in Simulations of the Microbial Quality of Water Withdrawn for Irrigation

Abstract

Evaluating the microbial quality of irrigation water is essential for the prevention of foodborne illnesses. Generic Escherichia coli (E. coli) is used as an indicator organism to estimate the microbial quality of irrigation water. Monitoring E. coli concentrations in irrigation water sources is commonly performed using water samples taken from a single depth. Vertical gradients of E. coli concentrations are typically not measured or are ignored; however, E. coli concentrations in water bodies can be expected to have horizontal and vertical gradients. The objective of this work was to research 3D distributions of E. coli concentrations in an irrigation pond in Maryland and to estimate the dynamics of E. coli concentrations at the water intake during the irrigation event using hydrodynamic modeling in silico. The study pond is about 22 m wide and 200 m long, with an average depth of 1.5 m. Three transects sampled at 50-cm depth intervals, along with intensive nearshore sampling, were used to develop the initial concentration distribution for the application of the environmental fluid dynamic code (EFDC) model. An eight-hour irrigation event was simulated using on-site data on the wind speed and direction. Substantial vertical and horizontal variations in E. coli concentrations translated into temporally varying concentrations at the intake. Additional simulations showed that the E. coli concentrations at the intake reflect the 3D distribution of E. coli in the limited pond section close to the intake. The 3D sampling revealed E. coli concentration hot spots at different depths across the pond. Measured and simulated 3D E. coli concentrations provide improved insights into the expected microbial water quality of irrigation water compared with 1D or 2D representations of the spatial variability of the indicator concentration.

Applicability of the WASP Model in an Assessment of the Impact of Anthropogenic Pollution on Water Quality—Dunajec River Case Study

“…It should be emphasized that human contact with coli bacteria is also dangerous in an indirect form, for example in the case of agricultural irrigation (bacteria entering food). For this purpose, among others, the risk of coliform bacteria was modeled in waters used for this purpose [58]. Most often, the presence of coliform bacteria indicates that the intake is susceptible to microbial contamination.…”

Persistent Patterns of E. coli Concentrations in Two Irrigation Ponds from 3 Years of Monitoring

“…Additionally, the use of drone-based imagery may be an appropriate source of data on spatial variation of major microbial habitat-affecting parameters such as chlorophyll-a, suspended solids, and dissolved organic matter concentrations (Pyo et al, 2016;Kutser et al, 2020). The existence of areas in the ponds with persistently lower E. coli concentrations makes these areas attractive for the placement of the irrigation water intake (Stocker et al, 2020). As irrigation progresses, water from different parts of the pond flows towards the intake and one may expect changes in microbial water quality at different times during the same irrigation event if substantial spatial heterogeneity of concentrations is observed.…”

Difficulties in the Modeling of E. coli Spreading from Various Sources in a Coastal Marine Area

“…The reliability of the obtained results depends mainly on the accuracy of the model used, its adaptation to the expected results, consideration of spatial and temporal dimensionality, and the amount and quality of the input data used for modeling. Models for the spread of microorganisms in different waterways (rivers, lakes, seas, and oceans), which have been used over the last 10 years, are presented in supplementary material , Section S1, Table S1 [ 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ].…”