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Inhibitory effects of compounds with guaiacyl and syringyl structure, representing the structure of native lignin, were studied on model cultures of bacteria, yeasts, yeast-like microorganisms and moulds. Isoeugenol exhibited the most pronounced inhibitory effect on growth of the studied microorganisms.

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Sludges produced in huge amounts by wastewater treatment plants (WWTP) display high fertility properties; however, the presence of heavy metals restricts their use for agricultural purposes. Sorption capacity of sludge is generally much higher and it can also be considered as a cheap sorbent of heavy metals. The paper describes cobalt sorption by dried activated sludge (DAS) obtained from the aerobic phase of a WWTP. DAS was characterized by FT-IR spectroscopy, cation exchange capacity (CEC), and atomic absorption spectrometry (AAS) analysis. Sorption capacity of DAS (Q eq) increased with the initial concentration (C 0) of Co2+ (CoCl2) within the range from 100 μmol g−1 to 4000 μmol g−1, reaching 15 μmol g−1 and 200 μmol g−1, respectively. The maximum uptake capacity (Q max) at pH 6.0 calculated from the Langmuir isotherm model was (256 ± 9) μmol g−1 for Co2+ ions. Obtained Q values were dependent on pH within the range from 3.0 to 7.0. Competitive effect of other bivalent cations such as Ni2+ in Co2+ sorption equilibrium was confirmed; which is in agreement with the hypothesis of the decisive role of ion-exchange mechanism in metal sorption. The obtained data are discussed from the point of view of potential utilization of sludges as sorbents, i.e. in non-agricultural application.

Cobalt is one of the possible contaminants originating from radioactive wastes or from metal mines and refineries. This paper describes sorption of cobalt by the foliose lichen Hypogymnia physodes from CoCl2 solutions spiked with 60 Co 2+in laboratory experiments. Maximum uptake was reached within 1 hour; the biosorption after 24 hours is not pH-dependent within the range of pH 4-7, negligible at pH 2 and is not dependent on metabolic activity. The process can be described by the Freundlich adsorption isotherm with ln k = 2.77, 1/n = 0.22 and R 2 = 0.94. Bivalent metal ions showed a concentrationdependent competitive effect on cobalt biosorption, decreasing in the order: Cu > Ni > Ca > Mg. Monovalent ions, such as K + and Na + , showed only very weak competitive effect. Up to 98% of Co taken up by lichen can be removed by washing with 0.1 M NiCl2 at 20• C. This means that only a small fraction of the cobalt is localized intracellularly. These results can be used for elucidating the behaviour of lichens as bioindicators of cobalt pollution in water systems, including the risk of cobalt leakage from lichen probes under the influence of rain, snow and atmospheric humidity.

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