To decontaminate spent offset-printing developer Polychrome 4003, several microorganisms were separated from the soil that has been used for developer dumping for 3 years. Two organism cultures were isolated and identified to genus Geomyces pannorum and Bacteria spp. These organisms, as well as commercial Septic Gobbler (SG) bacteria, were used to decontaminate the developer. Reduction of both the chemical oxygen demand (COD) and the amount of total identified organic compounds reached 30% after 40 day treatment of waste suspension by G. pannorum and Bacteria spp. A substantially higher degree of COD reduction by similar to80% and the total amount of identified organic compounds by similar to90% was achieved when SG bacteria have been applied for the same period. According to a rapid electrophysiological test with macrophytic algae Nitellopsis obtusa, the toxicity of spent offset-printing developer Polychrome 4003 was classified as extremely toxic (>100 toxic units, T.U.), and it remained at the same level after treatment with G. pannorum and Bacteria spp. More effective biodegradation with SG bacteria din-finished toxicity substantially. (C) 2004 Elsevier B.V. All rights reserved.