In this study we compared three methods for the treatment of electroplating sludge highly loaded with zinc and iron: (1) calcium oxide-based solidifi cation/stabilisation; (2) conversion into inert material by adsorption of organic and inorganic pollutants onto activated carbon; and (3) conversion of mobile waste components into insoluble phosphates. All three methods proved highly effi cient in the conversion of hazardous waste into inert material. Under optimum treatment conditions zinc concentration in the leachate of solidifi ed waste was reduced by 99.7 % compared to untreated sludge. Zinc retention effi ciency in the waste treated with activated carbon and phosphoric acid was 99.9 % and 98.7 %, respectively. The advantages of electroplating sludge treatment with activated carbon over the other two methods are high sorption capacity, insignifi cant pH and volume changes of the sludge, and simple use.
Višnja Oreščanin, Ivanka Lovrenčić Mikelić, Robert Kollar, Nenad Mikulić and Gordana Medunić
Gordana Medunić, Iva Juranović Cindrić, Ivanka Lovrenčić Mikelić, Nenad Tomašić, Dražen Balen, Višnja Oreščanin, Štefica Kampić and Ivana Ivković
The aim of this study was to establish the fractionation of copper and zinc in a small apple orchard using the revised (four-step) Bureau Communautaire de Reference (BCR) sequential extraction procedure and assess their potential mobility in soil. Soil samples were collected at the depth of 10 cm to 25 cm, sixteen from the orchard and five control samples from a meadow located some 200 m away from the orchard. As the distribution of trace-element concentrations in the control samples was normal, they were used for comparison as background levels. We also determined soil mineralogical composition, carbonate content, soil pH, cation exchange capacity, and soil organic matter. The extraction yields of Cu and Zn from the control soil were lower than from the orchard soil (25 % vs. 34 % and 47 % vs. 52 %, respectively), which pointed to natural processes behind metal bonding in the control soil and greater influence of man-made activities in the orchard soil. Compared to control, the orchard soil had significantly higher concentrations of total Cu (P=0.0009), possibly due to the application of Cu-based fungicides. This assumption was further supported by greater speciation variability of Cu than of zinc, which points to different origins of the two, Cu from pesticides and Zn from the parent bedrock. Copper levels significantly better (P=0.01) correlated with the oxidisable fraction of the orchard soil than of control soil. Residual and organically bound copper and zinc constituted the most important fractions in the studied soils. However, the use of Cu-based fungicides in the apple orchard did not impose environmental and health risk from Cu exposure.