Bacteriological characterization of wastewater samples obtained from a primary treatment system on a small scale swine farm

This study was carried out in order to quantify enteric bacteria and identify the presence of Salmonella spp., Escherichia coli, Clostridium perfringens and Erysipelothix rhusiopathiae in the liquid fraction of excreta generated from a small scale swine farm by means of a primary treatment system, consisting of the separation of solids and the sedimentation of liquids. Samples were collected at the following stages of the treatment: collection basin (CB), liquid obtained from a solids separator (SLF) and liquid from the sedimentation basin (SB). In each sample, enteric bacteria (cfu/g wet weight) and E. coli were quantified, Salmonella spp. was isolated and typified, and C. perfringens, and E. rhusiopathiae were isolated. No significant differences (p > 0.05) were found in the enteric bacteria and E. coli population levels at any treatment stage. S. choleraesuis was found in 20% of CB samples analyzed, 40% of SLF samples and 30% of SB samples. C. perfringens was isolated from SLF and SB. E. rhusiopathiae was not isolated (below the minimum detection limit). Results suggest that primary treatment does not reduce the amount of enteric bacteria, or eliminate Salmonella spp., E. coli and C. perfringens. Therefore, it is necessary to apply additional treatments to allow safe use of the liquid obtained in the farm.