The purpose of the present study was to evaluate the chemical alterations in the substrate with time of the vermicomposting involving different combinations of urban sewage sludge (USS) and sugarcane bagasse (SB), besides it's quality as organic fertilizer. The vermicomposts were obtained from the treatments T1= 150 kg of USS; T2 = 121.6 kg of USS + 97.30 kg of SB; T3 = 59 kg of USS + 97.30 kg of SB; T4 = 35.5 kg of USS + 97.30 kg of SB; T5= 23.10 kg of USS + 97.30 kg of SB. For the vermicomposting process, Red-California earthworm (Eisenia fetida) was utilized. Chemical characteristics determined in the vermicomposts indicate that it can be used as organic fertilizer, mainly with regard to organic matter content, pH, C/N ratio, nitrogen and phosphorus levels. Heavy metal concentration of the vermicomposts was below the acceptable values recommended by international legislation. Increase of the proportion of USS as substrate increased the final concentration of N, Ca and Mg, and reduced that of K.
urban sewage sludge; biosolids; vermicomposts; earthworms
