Bacterial pathogen fate in slaughterhouse-residual biopiles.

摘要

Managed biopiles were used to dispose of slaughterhouse-residuals to reduce the risk from zoonoses. Three cells were constructed to simulate a natural environment yet allow for real-time analysis of physical, biological, chemical, and hydrological biopile parameters. Evaluation of these systems was a main objective. The fate of pathogen indicator bacteria (e.g. Escherichia coli, Streptococcus fecalis) was another main objective. The indicators were enumerated using membrane-filtration and PetriFilm(TM) methods.;In biopile effluent, exponentially decreasing populations of indicator bacteria were observed. The behaviour of inoculated nalidixic acid resistant E. coli suggested that inactivation was the primary process in the biopiles. Large (>15 mm) and intense precipitation events generated nearly 90% of indicator loads from the biopiles, which was consistent with transport via preferential flow. However, total loads constituted 0.01% of initial indicator levels. Indicator retention in biopile and soil samples also suggested their persistence in, but not migration from, the media. This inferred that tertiary methods and biopiling phases should be employed to mitigate risk. Though the Gram-negative indicators (e.g. E. coli) shared behavioural correlations, they exhibited different fates in all media versus Gram-positive S. fecalis. It was speculated that S. fecalis re-grew in the biopiles. This negated the use of (widely adopted) fecal coliform:streptococcal ratios to predict pathogen fate. In retrospect, properly managed biopiles proved suitable for slaughterhouse-residual degradation and safe for on-farm implementation.;Trends between cells for temperature, effluent, soil water content, and periodic and total derived effluent mimicked one another closely. In two experiments in 2006 and 2007, biopile temperatures peaked at 70.5°C and 68.1°C and remained >55°C for 21-28 and 22-29 days, respectively. Biopile volume reductions approximated 65%, and turning did not produce unpleasant odors. This indicated efficient waste degradation. Approximately 75% of the disparity between input and output cell water levels was attributed to microbial evaporation and incorporation. Low levels of common water quality parameters were detected in effluent, which indicated minimal effects of the biopiles on water quality. Though few trends were observed for soil media, high and variable levels of nutrients were measured in the biopiles. Microbial activity and immobilization were credited for this occurrence.