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The use of activated sludge (AS) to assess the environmental impact of chemicals and wastewaters suffers from several drawbacks related to the heterogeneity, absence of standardization and health risk associated with such a mixed sewage population. To search for reliable testing inoculum alternatives, the potential of a standardized soil inoculum and a pure culture (Pseudomonas sp.), as reference material in a 5-day BOD test, was evaluated using the dilution and manometric methods and testing the standard glucose-glutamic acid solution. The results obtained for the BOD5 of the standard solution fall in the range referred for the AS in the standards of the cited methods, demonstrating the potential of these inocula as an alternative to AS in the BOD5 test. Moreover, testing on real wastewater samples showed highly significant correlations (P < 0.001) between the BOD5 values obtained with these two inocula and with the standard inoculum. Analysis of metabolic patterns also pointed to a similar catabolic profile between soil inoculum and AS and to the potential of a mixed Pseudomonas-soil inoculum as an AS surrogate culture. [ABSTRACT FROM AUTHOR]