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(T/MF164) Risk assessment and treatability evaluation of industrial wastewaters. Zgajnar Gotvajn, A.1, Zagorc-Koncan, J.1, 1 ABSTRACT- Risk assessment of wastewasters should include an evaluation of biodegradability and toxicity. Both are also crucial for determination of biological treatability. Databases on environmental behaviour of chemicals are comprehensive, but there is still a lack of risk information on the wastewaters, due to the mixing effects and non-harmonized test methods. The aim of our study was to implement whole effluent approach to determine hazardous impact and biological treatability of two industrial wastewaters: from the pig farm and metals industry. We determined aerobic biodegradability (ISO 9804, 1991) in a closed respirometer measuring O2 consumption and CO2 production as net values (mg/l) and as degradation rates (mg/l day). Toxicity was determined with three bacterial tests. The inhibition of bioluminiscence of Vibrio fischeri (DIN 38412 (L34, L341), 1991/1993) was evaluated and two methods with mixed culture of microorganisms (activated sludge) were conducted. Results of the Test of inhibition of O2 consumption by activated sludge (ISO 8192, 1986) were upgraded with the Test for the determination of the inhibition of water constituents on the growth (ISO 15522, 1998), to obtain data on chronic toxicity. Wastewater from the pig farm inhibited oxygen consumption (30minEC50 = 25.6 vol.%) less than growth (2hEC50 = 3.1 vol.%). Adaptation of microorganisms to pig farm wastewater was confirmed measuring growth rates. EC50 increased from 3.1 vol.% to 46.9 vol.% in 2 hours. Wastewater from the metals industry was less biodegradable and less toxic. 30minEC20 was 27.0 vol.% according to O2 measurements, while in the growth inhibition test increase of EC10 from 39.6 vol.% (2 hours of exposure) to 74.6 vol.% (4 hours) indicated adaptation. Wastewater from the pig farm was estimated as suitable for biological treatment. Key words: Activated sludge, biodegradation, toxicity, wastewaters |
