The occurrence of intestinal parasites in swine slurry and their removal in activated sludge plants

Thirteen intensive pig farms and two activated sludge treatment plants for pig slurry in north-western Spain were studied from April 2005 to June 2006 in order to evaluate the presence of enteric pathogens (Cryptosporidium, Giardia and helminths) and the efficiency with which they were removed. These parasites were present on 53%, 7% and 38% of the farms studied, respectively, with concentrations of 104–105 oocysts per litre (/L) for Cryptosporidium, 103 cysts/L for Giardia and 102–103 eggs/L for helminths. The overall removal of parasites in the pig slurry treatment plants ranged from 86.7% to over 99.99%. The results revealed a constant reduction at each stage of the treatment system, with activated sludge processes being the most effective treatment in reducing pathogens in pig slurry, 78–81% for Cryptosporidium oocysts and over 99.9% for helminth eggs. A heat drying procedure for sludge removed 4.3 log units of Cryptosporidium oocysts, demonstrating the excellent effectiveness of this treatment for reducing pathogens in sludge intended to be applied to land.