Effectiveness of Thermal Sanitization of Piggery Slurry Using Heat Exchangers

Livestock agriculture dominated by pig rearing is responsible for the production large volumes of wastes. Across the European Union there are over 151 million pigs that produce 300 million tonnes of slurry annually. Furthermore, intensive production linked to certain regions, leads to zones of nutrient excess where available land for land spreading is insufficient. However, even if the environmental problems that affect these zones have been long recognised and largely dealt with, the concern now lies equally with sanitary aspects. Questions are now asked on the relationship between land spreading of animal manures and the faecal contamination of groundwater (and sometimes bathing water) and the outbreaks of specific disease or general ill health. Over 150 zoonoses have been isolated from livestock slurries with a variable prevalence, but often not negligible. These include the bacteria Campylobacter sp, Escherichia coli O157:H7 and Salmonella sp ; the viruses enterovirus and hepatitus E; the protozoa Cryptosporidium parvum and Giardia lamblia ; and the helminths Ascaris suum and Taenia solium (Levasseur, 2007). Pathogens are today considered to be a rising barrier to recycling manures to land for crop nutrition. Furthermore, within the context of a growing demand of water quality for domestic use, it is becoming necessary (a) to find methods for sanitisation that are economically acceptable, (b) to establish effective regulations and (c) to establish and manage the hygienic risks. Within these definitions, the work presented here is set out to establish the effectiveness of sanitation of continuous thermal treatments based on the use of heat exchangers. The specific germs studied were the classic indicators (E. coli and enterococci), coliforms, aero-anaerobic flora and the bacteriophages F+ specific and somatic.