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 variablebased 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 threeparametric 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.

Time since faecal deposition influences mobilisation of culturable E. coli and intestinal enterococci from deer, goose and dairy cow faeces

“…The faecal structure will also dictate the speed at which infiltrating water can make contact with resident cells, in turn facilitating their wash-out [11]. The proportion of finer and larger fractions of organic matter that characterises each faecal matrix may also explain differences in mobilisation potential, as has been reported in studies exploring E. coli release from specific fractions of faeces (0.25, 0.5, 1.0, 2.0 mm faecal components) [34]. FIB mobilisation will be influenced by the degree of erodibility associated with the faecal source [11] and observations of faecal disruption during the DESPRAL test identified that dairy faeces more readily disaggregated relative to the goose and deer faeces.…”

“…We did not determine how FIB mobilisation varied over the duration of the 'event'. Over longer experimental timeframes and using different measures of mobilisation there are reports of a faster, or in some cases more irregular, initial FIB release from faeces followed by a slower steady-state FIB release [34,37]. Despite a smaller mass of faeces being used in assessing FIB mobilisation from goose faeces, the ratio of faecal mass to rainwater was consistent with that used to determine FIB concentrations released from dairy cow and deer faeces, and thus the difference in faecal mass should not impact on comparing the concentrations of FIB mobilised across different treatments.…”