Predicting the Toxicity of Oil-shale Industry Wastewater by its Phenolic Composition

Anne Kahru, Lee Põllumaa, Rain Reiman and Annely Rätsep

The chemical composition and toxicity of five phenolic wastewater samples collected from the Kohtla-Järve (Estonia) oil-shale industry region were analysed. The total phenolic contents (HPLC data) of these samples ranged from 0.7mg/l to 195mg/l. A total of 11 phenolic compounds were found in the wastewater samples, the most abundant being phenol (up to 84mg/l) and p-cresol (up to 74mg/l). Artificial phenolic mixtures were also composed, to mimic the content of phenolic compounds in the wastewater samples. The theoretical toxicities of these artificial mixtures were calculated by using the toxicities of the individual phenolic constituents to photobacteria (the BioToxTM test) and were assumed to have an additive mode of action. From the BioTox data, the additive toxic effects of phenolic compounds in the artificial mixtures were confirmed to be highly probable. The toxicities of the wastewater samples and their artificial phenolic analogues (mixtures) were studied by using a battery of Toxkit microbiotests (Daphtoxkit FTM magna, Thamnotoxkit FTM, Protoxkit FTM and Rotoxkit FTM) and three photobacterial tests (MicrotoxTM, BioToxTM and Vibrio fischeri 1500). The wastewaters were classified as toxic (two samples), very toxic (two samples) and extremely toxic (one sample). Comparison of the test battery responses showed that the industrial wastewaters were 2–28-fold more toxic than the respective artificial phenolic mixtures. The photobacterial tests proved to be the most appropriate for screening purposes. This was the first attempt to use a test battery approach in the toxicity testing of Estonian wastewaters. The study showed that the toxicity of oil-shale industry wastewaters could not be predicted solely on the basis of their phenolic composition, since only 7–50% of their toxicity was shown to be due to phenolic compounds. It is true, to a certain extent, that the majority of environmental samples are usually very complex and contain various types of pollutants. As even a full chemical analysis (which is very expensive) can easily miss the constituent(s) with the greatest toxic effect(s), the use of toxicity tests in parallel to chemical analysis should be encouraged.
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Toxicological Investigation of Soils with the Solid-phase Flash Assay: Comparison with Other Ecotoxicological Tests

Lee Põllumaa, Anne Kahru, Adolf Eisenträger, Rain Reiman, Alla
Maloveryan and Annely Rätsep

A new direct-contact toxicity test, the solid-phase flash assay, which utilises photobacteria in direct contact with soil particles during the exposure, was evaluated on four soil samples. Samples HTNT1 and HTNT2 originated from former military sites in Germany, and were highly contaminated with nitroaromatics (approximately 20g/kg), lead and polycyclic aromatic hydrocarbons. Samples LMKW1 and LMKW2, from bioremediation stacks in Germany, were mainly contaminated with mineral oils. The solid-phase flash assay was applied to soilwater slurries, and the results were compared with the toxicity data for soil-water extracts obtained by using various conventional ecotoxicological tests, in which photobacteria, crustaceans, protozoa and algae were used as test organisms. The LMKW1 and LMKW2 samples were not toxic (EC20 > 12.5%) according to all the tests applied, except for the Photobacterium phosphoreum conventional luminescence-inhibition test for LMKW1 (15-minute EC20 = 5.4%). The HTNT1 and HTNT2 samples were toxic according to all the tests applied, with the majority of EC20 values being lower than 1%. The solid-phase flash assay (1 minute of extraction and 30 seconds of exposure time) gave comparable results to the conventional tests. Therefore, this flash assay could be applied as a fast screening test in parallel with conventional toxicity tests that use soil 24-hour extracts. The flash assay results will be ready by the start of the conventional assays, and could serve as range-finders for these slower and more expensive tests.
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Study of the Environmental Hazard Caused by the Oil Shale Industry Solid Waste

Lee Põllumaa, Alla Maloveryan, Marina Trapido, Helgi Sillak and Anne Kahru

The environmental hazard was studied of eight soil and solid waste samples originating from a region of Estonia heavily polluted by the oil shale industry. The samples were contaminated mainly with oil products (up to 7231mg/kg) and polycyclic aromatic hydrocarbons (PAHs; up to 434mg/kg). Concentrations of heavy metals and water-extractable phenols were low. The toxicities of the aqueous extracts of solid-phase samples were evaluated by using a battery of Toxkit tests (involving crustaceans, protozoa, rotifers and algae). Waste rock and fresh semi-coke were classified as of “high acute toxic hazard”, whereas aged semi-coke and most of the polluted soils were classified as of “acute toxic hazard”. Analysis of the soil slurries by using the photobacterial solid-phase flash assay showed the presence of particle-bound toxicity in most samples. In the case of four samples out of the eight, chemical and toxicological evaluations both showed that the levels of PAHs, oil products or both exceeded their respective permitted limit values for the living zone (20mg PAHs/kg and 500mg oil products/kg); the toxicity tests showed a toxic hazard. However, in the case of three samples, the chemical and toxicological hazard predictions differed markedly: polluted soil from the Erra River bank contained 2334mg oil/kg, but did not show any water-extractable toxicity. In contrast, spent rock and aged semi-coke that contained none of the pollutants in hazardous concentrations, showed adverse effects in toxicity tests. The environmental hazard of solid waste deposits from the oil shale industry needs further assessment.
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