Heterotrophic microflora involved in the simultaneous process of metal bioleaching and sewage sludge digestion

Until now, some microbiological studies have made it possible to highlight the role and identification of certain chimiolithotroph microorganisms dire ctly involved in the simultaneous sewage sludge digestion and metal leachin g (SSDML process). Moreover, some other studies have established the perfor mance of the SSDML process for the destruction of pathogens. However, until now no study has been carried out to define the equilibrium of the heterot rophic microbial populations during the sludge acidification occurring duri ng the operation of the SSDML process. Hence, the SSDML process was studied in batch and continuous mode employing different types of sludges (Communa ute Urbaine de Quebec (CUQ)-East primary sludge, Beauceville secondary slud ge, and mixture of primary and secondary Valcartier sludge). The equilibriu m of heterotrophic microbial populations was investigated along with sludge acidification and solids degradation. The results obtained during the SSDM L process on different sludges showed a decrease followed by the destructio n of a majority of heterotrophic bacterial species found in fresh sludges. The isolation and characterization of different microbial species showed th at only two types of microorganisms persisted: the yeast Blastoschizomyces capitatus and an unidentified fungus.