Modelling Water Flow and Escherichia coli Transport in Unsaturated Soils Under Drip Irrigation

Abstract

The HYDRUS‐2D/3D model was used to simulate the wetting patterns and distributions of E. coli in unsaturated sandy and sandy loam soils under surface drip irrigation with sewage effluent. The simulated wetting dimensions of soil volume and distributions of E. coli in soil were compared with data obtained from laboratory experiments. The relatively lower values of normalized root mean square error (NRMSE) and relatively larger index of agreement (d) values indicated good performance of the model. Our simulations confirmed that soil texture greatly influenced the adsorption characteristics and played an important role in the migration of E. coli cells. E. coli was transported further in the sandy soil than in the sandy loam soil, while its concentration decreased considerably with distance from the point source in both soil types. In the sandy loam soil, E. coli was mostly concentrated in a substantially smaller volume 5 cm from the soil surface. An increasing application rate of water‐suspended bacteria accelerated water flux and enhanced the E. coli transport rate, thus resulting in a larger distribution with a higher E. coli concentration in both soil types. In the proximity of the point source, an extremely high concentration of E. coli was recorded under simulated and observed conditions, and the value increased with an increasing input concentration. Copyright © 2017 John Wiley & Sons, Ltd.

Increasing Crop Productivity in an Eco‐Friendly Manner by Improving Sprinkler and Micro‐Irrigation Design and Management: A Review of 20 Years' Research at the IWHR, China

“…Reducing the bacterial concentration in the sewage effluent during wastewater treatment is important to decrease the risk of soil pathogenic contamination caused by irrigation with sewage effluent. The laboratory experiments were then successfully used to develop a model of water and E. coli transport in soil (Wen et al, ). The model was adequately verified by the experimental data, and it has strengthened our understanding of E. coli transport in unsaturated soil.…”

“…The new approaches to describing the system‐dependent upper boundary conditions were established for different soils with and without ponded areas around the emitter (Li et al, ) and verified by laboratory observations (Li et al, ). The model has been successfully used in subsequent research (Wang et al, ; Wen et al, ).The continuous efforts contributed to the testing of a non‐deterministic approach to using artificial neural networks (ANNs) for modelling nitrate distribution under drip fertigation testing (Li et al ., ). In selecting the initial soil water content, initial nitrate concentration in soil, emitter discharge rate, input concentration of the fertilizer, applied volume and final soil water content as the input parameters, the model predicted the nitrate concentrations in the soil after fertigation with an acceptably high accuracy.…”