Particle fractionation controls Escherichia coli release from solid manure

Abstract

Bacteria transport through soil is a complex process particularly when the cells are released from solid manures and co-transported with particles. This study focuses on understanding of the Escherichia coli release from different particle fractions (0.25-, 0.5-, 1-, and 2-mm) of solid manure and evaluating different influent boundary conditions during cell release from manure and when a solid manure is applied to the soil. The 0.25-mm and 2-mm particle sizes resulted a greater cell release compared to 0.5-mm and 1-mm fractions (p < 0.05). The shape and magnitude of the cell release curves (CRCs) from the original manure bulk were mainly influenced by the two 0.25-mm and 2-mm fractions, respectively. The arithmetic mean for normalizing the CRCs and the time variable- based normalized CRCs for the manure-treated soil were the robust variables in evaluation of the experimental data. However, a single maximum bacteria concentration could provide the realistic dataset for the modeling process. Evaluation of the root-mean-squared-error and Akaike criterion showed that the two- and three-parametric models are recommended for simulating the cell release from solid manure in comparison with one parametric models. This study also suggests considering separate microbial release evaluations, with regards to influent concentration, for manure and manure-treated soils to propose best management practices for controlling bacteria pollution. Further research will reveal the key roles of different woody components and soluble material ratios for the various solid manures in bacteria release.