posted on 2014-08-22, 13:04authored byAnna Valentinova Piterina, John Bartlett, Tony J. Pembroke
The degradation of sludge solids in an insulated reactor during Autothermal
Thermophilic Aerobic Digestion (ATAD) processing results in auto-heating, thermal
treatment and total solids reduction, however, the ability to eliminate pathogenic organisms
has not been analysed under large scale process conditions. We evaluated the ATAD
process over a period of one year in a two stage, full scale Irish ATAD plant established in
Killarney and treating mixed primary and secondary sludge, by examining the sludge
microbiologically at various stages during and following ATAD processing to determine its
ability to eliminate indicator organisms. Salmonella spp. (pathogen) and fecal-coliform
(indicator) densities were well below the limits used to validate class A biosolids in the final
product. Enteric pathogens present at inlet were deactivated during the ATAD process and
were not detected in the final product using both traditional microbial culture and molecular
phylogenetic techniques. A high DNase activity was detected in the bulk sludge during the
thermophilic digestion stage which may be responsible for the rapid turn over of DNA from
lysed cells and the removal of mobile DNA. These results offer assurance for the safe use of
ATAD sludge as a soil supplement following processing.
History
Publication
International Journal of Environmental Research and Public Health;7, pp. 3422-3441