Enteric Pathogen Survival in Sewage Sludge-Amended Agricultural Soil
Biosolids represent the solid fraction of sewage and potentially contain a number of human and animal pathogens. This report describes a series of field trials in which sewage sludge that had been subjected to selected treatment methods was land applied and subsequent pathogen survival assessed.
Nymbers of Escherichia coli in biosolids-amended soils decayed to the background population in field soil within 40-60 days of sludge application. E. Coli O157, Listeria and Salmonella all showed significant decay when introduced to two different soil types in inoculated sludge and were undetectable or at background values within 50-150 days following sludge addition. E.coli numbers in unamended soils were highly dynamic and fluctuated between 1and 6 log10 100 g-1 ds during all field trials.
Clostridium and Campylobacter did not decay to a significant extent when introduced to both soils with sludge.
Sludge application consistently increased protozoa numbers in field soil, with raw sludge having a larger effect than anaerobically digested sludge, presumably due to greater availability of substrates in the unstabilised sludge. Protozoa numbers in biosolids-amended soils remained between 0.5 and 1 log above those of the control in field soil.
A laboratory incubation study provided evidence for the direct effect of soil protozoa activty and other ecological processes on E.coli decay in sludge-amended soil.
|UKWIR Reference 11/SL/06/8||Published Date 29/09/2011|
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