Although all the advantages of the use of ETE silts? s in agriculture, some problems must be taken in consideration. As Nuvolari (2003) one of the problems is related to the possible presence of elements potentially toxics (EPT) in the silt. The toxicidade of the potentially polluting elements can give for the effect right-handers to the plant, causing death or the loss of productivity, or provoke indirect effect for the accumulation in the alimentary chain, causing diverse problems to the health human being. Another problem becomes related it the presence of pathogenic organisms gifts in the silt that can contaminate ingested foods raw being able to affect the health human being. A last problem becomes related with the possible nitrogen presence, in the nitrate form that, when not absorbed immediately for the plants or when in great amounts in the silt, can contaminate freticos sheets, having it the high mobility of nitrates in the water and the ground. The used silt in the agriculture, also called biosslido, is classified in two types according to norm of the CETESB, considering, according to Jordo et. al (1995): it classe: biosslidos of unrestricted use. Objective the reduction of the amount of patogncios including analysis of fecais coliformes, Salmonella sp., virus, helmintos and protozorios.
For this reduction technologies of advanced reduction of pathogenic must be used as the compostagem, thermal drying, thermal treatment, termoflica aerobic digestion, irradiation and pasteurizao; b classe: objective to only assure that the amount of pathogenic organisms will meet for levels not comprometedores of the public health and the environment reduced, becoming necessary the analysis of fecais coliformes. For attainment of this composition, the job of technologies is considered as the aerobic digestion, drying, compostagem and stabilization with whitewash.