In recent years, an increasing interest in sandmixes containing inorganic binders has been observed. These binders, including water-glass, are harmless for the environment, neutral for humans, and relatively cheap. In spite of numerous advantages, their wide application is restricted by poor knock-out properties and problems related to rebonding. Therefore, numerous researches aimed at eliminating the disadvantages of water-glass binders are directed, among others, to modifying the structure of hydrated sodium silicate or to applying new hardening techniques. An innovative method of rapid hardening by microwave heating, permitting the restriction of the quantity of binder used and thus improving knock-out properties, meets the expectations of present-day foundries. In this paper, available information is compiled on microwave hardening of water-glass containing sandmixes; furthermore, the costs of practical application of this technology are evaluated on the grounds of the authors' own research.
Heavy metal pollution of soil is a significant environmental problem and has a negative impact on human health and agriculture. Phytoremediation can be an alternative environmental treatment technology, using the natural ability of plants to take up and accumulate pollutants or transform them. Proper development of plants in contaminated areas (e.g. heavy metals) requires them to generate the appropriate protective mechanisms against the toxic effects of these pollutants. This paper presents an overview of the physiological mechanisms of stress avoidance and tolerance by plants used in phytoremediation of heavy metals.
The aim of this work was to determine the effect of various cadmium and copper concentrations on the activated sludge dehydrogenase activity. The investigations were carried out in six aerated chambers with activated sludge, volume of 1L each, by the continuous culture method (one control chamber, not contaminated with heavy metals and five with 0.5; 1; 2; 4; 8 mg L-1 Cu+2 and 0.1; 0.3; 0.9; 2.7; 8.1 mg L-1 Cd2+). Cadmium sulfate and copper sulfate as a source of heavy metals were used. The concentrations of these metal ions, causing 50% dehydrogenase activity inhibition were determined. The particular attention was paid to the toxic effect of metal ions, as well as the variations of the microbial respiration activity proceeded during toxins exposition. The investigation showed that even the lowest concentration of the investigated metal ions caused significant changes of the activated sludge dehydrogenases activity. Copper ions showed to be more toxic than cadmium ions.
The aim of the work was to estimate the influence of plants mycorrhizas on the number of hydrocarbons degrading bacteria, saprophytic bacteria and molds fungi during the remediation of the soil samples contaminated with used engine oil. The investigation were carried out in laboratory conditions. Nine modifications of the soil substrate were prepared and divided into three groups: the first one - without used engine oil; the second one - with 10% (w/w) of used engine oil; the third one - with 25% (w/w) of used oil. In each group one sample was sown with ribwort, one was inoculated with living spores of mycorrhizal fungi and sown with ribwort, and the third one was left without plants and mycorrhizal fungi. The sample of the uncontaminated soil was the control. The investigation showed a significant effect of used engine oil, the presence of ribwort and mycorrhizal fungi on the number of soil microorganisms. The increase of the number of hydrocarbons degrading bacteria, in respect to the control sample was observed in the used engine oil contaminated samples. The seeding of soil samples with plants and additional inoculation with spores of mycorrhizal fungi stimulated the increase of the number of microorganisms in the all studied groups.