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Water 2015, 7(3), 836-854; doi:10.3390/w7030836

Soil and Waste Matrix Affects Spatial Heterogeneity of Bacteria Filtration during Unsaturated Flow

1
Boreal Ecosystems Research Initiative, Memorial University of Newfoundland, 20 University Drive, Corner Brook, NL A2H 5G4, Canada
2
University of Leeds, School of Geography, Leeds LS2 9JT, UK
3
Conestoga-Rovers and Associates, 651 Colby Drive, Waterloo, ON N2V 1C2, Canada
4
School of Environmental Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada
*
Author to whom correspondence should be addressed.
Academic Editor: Miklas Scholz
Received: 10 December 2014 / Revised: 12 January 2015 / Accepted: 3 February 2015 / Published: 27 February 2015
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Abstract

Discontinuous flows resulting from discrete natural rain events induce temporal and spatial variability in the transport of bacteria from organic waste through soils in which the degree of saturation varies. Transport and continuity of associated pathways are dependent on structure and stability of the soil under conditions of variable moisture and ionic strength of the soil solution. Lysimeters containing undisturbed monoliths of clay, clay loam or sandy loam soils were used to investigate transport and pathway continuity for bacteria and hydrophobic fluorescent microspheres. Biosolids, to which the microspheres were added, were surface applied and followed by serial irrigation events. Microspheres, Escherichia coli, Enterococcus spp., Salmonella spp. and Clostridium perfringens were enumerated in drainage collected from 64 distinct collection areas through funnels installed in a grid pattern at the lower boundary of the monoliths. Bacteria-dependent filtration coefficients along pathways of increasing water flux were independent of flow volume, suggesting: (1) tracer or colloid dependent retention; and (2) transport depended on the total volume of contiguous pores accessible for bacteria transport. Management decisions, in this case resulting from the form of organic waste, induced changes in tortuosity and continuity of pores and modified the effective capacity of soil to retain bacteria. Surface application of liquid municipal biosolids had a negative impact on transport pathway continuity, relative to the solid municipal biosolids, enhancing retention under less favourable electrostatic conditions consistent with an initial increase in straining within inactive pores and subsequent by limited re-suspension from reactivated pores. View Full-Text
Keywords: unsaturated flow; pathway continuity; soil; bacteria; microspheres; land-application; organic waste unsaturated flow; pathway continuity; soil; bacteria; microspheres; land-application; organic waste
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Unc, A.; Niemi, J.; Goss, M.J. Soil and Waste Matrix Affects Spatial Heterogeneity of Bacteria Filtration during Unsaturated Flow. Water 2015, 7, 836-854.

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