Absorption potential of heavy metals and organochlorine compost (PCDD and PCDF) in Brassica juncea using compost and bio-sludge from an Eucalyptus kraft bleached pulp mill

Bleached kraft pulp mill sludge can have traces of heavy metals and organochorine composts. Although most mills use ECF (elemental chorine free) bleaching sequences, organochlorine composts are still present in pulp and in effluent due to the use of chlorine dioxide in the bleaching stages. The present work evaluated the absorption potential of heavy metals and organochlorine composts (PCDD and PCDF) by Brassica juncea when bio-sludge of an activated sludge plant and compost prepared from bio-sludge mixed with Eucalyptus bark of a bleached kraft pulp mill and soil were used. The plants were cultivated in 0.63 dm3 vessel in greenhouses during 65 days. The following parameters were monitored in the substrate and in the plants: Fe, Mn, Pb, Ni, Cu, Zn, Cr, Cl, Organic Carbon and AOX (adsorbable organic halogen). The heavy metal content in the soil after compost application was within the Brazilian legal standards for compost application. Traces of PCDD e PCDF were found in the substrate in concentration smaller than 0.5 ng I-TEQ/kg (ppt). These values were lower than the highest quality criteria of 17 ng I-TEQ/kg from Canada and Germany.