Contribuição ao estudo da eliminação de organismos patogênicos na compostagem de lixo urbano.

Abstract

The problem of solid waste in Brazilis characterized by the high total dayly production, by the disposal of hospitalar waste with domestic waste and by the inadequate disposltion of these wastes in open áreas, exposing humankind and environment to the contamination by pathogenic organisms. Composting is a solid waste biologic, aerobic and controlled treatment process, that through microorganisms work, mineralizes the organic fraction of the material under termophilic temperatures (45 - 65°C) in two diferent phases: biodegradation and maturation. Through composting, a low costing process, makes possible to obtain the wastes' sanitization further than the organic matter degradation, by eliminating pathogens, without environmental damage. The compost, final product of composting, being an humified material, can be utilized in agriculture as a soil's conditioner, but it must be estabilized and bacteriologlcally safe. The fecal contamination's grade of a compost may be appraised through microbiological indicators (fecal coliforms and fecal streptococci), besides pathogenic microorganisms (viruses, bactéria, helmints). Among pathogens, the genus Salmonella presents a high correlation with indicators of fecal contamination and these bactéria are ethiologic agent of dhiorrea, disease responsible for 30,4% of total children's deaths in Brazil's northeast (Carvalho et alii, 1990). The present work's objectives were to verify temperature's and thermic stratifying inside composting piles Influence on pathogens éllmination and the property of sistematic . use of Salmonella. as fecal indicator during composting. In this order, it was accompanied, along eleven months, eith aerated staticpiles and seven windrows, through measurements of density, temperature, analysis of pH, humidity, volatile solids and fecal coliforms, fecal streptococci and Salmonella dle-off. Results showed that temperature i s the most important factor affecting pathogens elimination, but this elimination's efficience depends on various operational factors (type of aeration, aeration tube*s position, control temperature, characteristics of material) and composting material's conditions (excess of humidity or drying, compactness, pH variations, nutrients' availability) . The utilization of Salmonella didn't present enough advantages to justify its use in routine's monitoring of pathogenic die-off in composting. It was also observed that remaining microorganisms can be presented at the process' end. Because this, the maturation becomes into a very important phase when anothers lethal effects will be suffered by these microorganisms.