Biodigest？o anaeróbia de dejetos de bovinos leiteiros submetidos a diferentes tempos de reten？？o hidráulica

continuous biodigestors filled with dairy cattle manure and operated at different hydraulic retention times, were used to determine the number of coliforms and the presence of helmints eggs and parasite larvae of ruminants and to analyze the total and volatile solid contents and the production and quality of the biogas produced. twenty days of the retention time were sufficient to reduce the number of coliforms and eggs of ruminant parasites. analysis of total and volatile solids and biogas production showed that the chinese biodigester was more efficient at a hydraulic retention time of twenty days. it should be pointed out, however, that twenty days of hydraulic retention time were not sufficient to prevent the survival of larvae of ruminant parasites.