Evaluation of the presence of human pathogens in domestic (backyard) composts

To evaluate the presence of human pathogens in domestic (backyard) composts , 18 domestic composters were sampled in the area of Quebec City. An instit utional (cafeteria) composter was also sampled. The domestic composters wer e of several types including both commercial (Earth Machine, Soil saver, Gr een Cones, etc.) and artisanal units. The material composted by citizens we re representative and mainly constituted of yard and kitchen wastes. Temper atures recorded were below 34 degreesC, indicating that thermophilic temper atures were not reached even during the summer. However, the presence of Es cherichia coli and Salmonella spp. were well below the compost criteria of the Bureau de Normalisation du Quebec and the Canadian Council of Ministers of the Environment. There was just a single exception with a content of E. coli slightly higher than the criterion. Laboratory analysis also demonstra ted that the test of fecal coliform was giving overestimates of E.coli beca use of the interference of Klebsiella pneumoniae present in the domestic co mposts. In such composts, the test of E.coli should be preferred to prevent overestimation of the risk given by coliform analysis.