Biological and electrochemical treatment of used metalworking fluids: a toxicity-reduction evaluation.

The aim of this study was to evaluate and compare the toxicity of spent metalworking fluids (MWFs) and two different effluents obtained by biologic and electrochemical treatment of spent MWFs toward aquatic organisms of different trophic levels. The obtained toxicity data was used to calculate safe concentrations of both effluents. The spent MWFs without treatment showed the highest toxicity among the tested samples and should be classified as "extremely toxic" (toward invertebrates) or "very toxic" (toward other test organisms). Both methods applied for MWFs treatment resulted in a significant decrease in toxicity of the treated MWFs, but the obtained effluents had still to be regarded as "toxic". The ranges of the values of acute toxic units for both effluents were significantly narrower than for the untreated spent MWFs. The values of the safe concentrations of the spent MWFs, the biologic effluent, and the water phase resulting from electrochemical emulsion breaking were equal to 0.013%, l.8%, and 1.3%, respectively, corresponding to chemical oxygen demand concentrations of 1.8%, 32, and 34 mg O(2)*L(-1). These values are far lower than the discharging limit of 125 mg O(2)*L(-1) for industrial effluents, according to the relevant Polish regulations. It is therefore recommended to include toxicity bioassay parameters into guidelines for wastewater discharges to surface waters because the existing chemical and physical parameters are not sufficient to describe the environmental impact of industrial wastewater. Toxicity bioassays can be a promising tool for evaluating the efficacy of unit operations in industrial wastewater treatment (toxicity reduction evaluation) as well as identification of toxic substances in effluents (toxicity identification evaluation).

Isolation and identification of bacteria from petroleum derivatives contaminated soil.

One of the aspects of bioremediation of petroleum derivatives contaminated soil using autochtonic microorganisms is isolation and identification of bacterial strains from polluted soil in order to choose the most active ones and to eliminate pathogens. In this research work some strains mainly from genus Pseudomonas, Acinetobacter, Micrococcus, Chryseomonas, Agrobacterium and Aeromonas were isolated from samples of soil contaminated with various petroleum derivatives. The population of bacteria capable to utilize hydrocarbons as the only source of carbon appeared as a tiny fraction (0.01-1.09%) of the total number of bacteria in the soil.