Leaching of heavy metals (Cu, Mn, Zn, Ni, Pb and As) after six months application of raw and composted recycled paper mill sludge

摘要

Sludge from paper mill with recycled paper feedstock (RPMS) is a waste from secondary process of paper making, generated at final stage of paper production after biological treatment. Land application of RPMS could provide substantial benefit to plantgrowth and contributes to increase in organic matter that may result in chemical and physical changes in soil. Nevertheless, the potential for groundwater contamination from land application of RPMS is an important concern. Therefore, the objective of this study is to evaluate the cumulative amount of heavy metals (Cu, Mn, Zn, Ni, Pb and As) leached at 15, 30, 60 and 120 cm depths after six months application of raw and composted RPMS.The cumulative amount of Cu, Mn, Zn, Ni, Pb and As leached after sixmonths application of raw and composted RPMS ranged from 7.9 to 72 mu g, 8.6 to 212 jug, 17.9 to 462 mu g, 1.2 to 18.4 mu g, 0.4 to 3.5 fig and 0.05 to 2.4 mu g, respectively. After 6 months of application of raw and composted RPMS, the trend of heavy metals leached seemed to increase with increasing depth (15, 30, 60 and 120 cm) for every treatment. The general trend was that only very small fractions (below 1%) of Cu, Mn, Zn, Ni, Pb and As leached relative to the total amount added with the raw and composted RPMS after six months of experiment. The percentage and cumulative amounts of heavy metals leached were very low; possibly maybe the sludge was not fully mineralized within the duration of this experiment.