Ferricyanide mediated biochemical oxygen demand - development of a rapid biochemical oxygen demand assay

The use of an artificial electron acceptor in microbial respiration was inv estigated with a view to developing a rapid assay for biochemical oxygen de mand (BOD). The use of ferricyanide resulted in a significant increase in t he rate of the biochemical reaction and allowed for biodegradative conversi on efficiencies similar to the 5-day BOD assay to be achieved in 1 h. The extent and rate of the ferricyanide mediated microbial reaction was det ermined by monitoring the concentration of the microbially produced ferrocy anide during or after incubation of microorganisms in the presence of ferri cyanide, and organic substrate. Spectrophotometry, potentiometry and ampero metry using microelectrodes were evaluated as detection methods, with the l atter providing the most convenient, stable and reproducible results. Exper imental parameters investigated included incubation time, incubation temper ature, microbial concentration, ferricyanide concentration and substrate co ncentration. In all cases, the results obtained were analogous to that expe cted in conventional aerobic microbial oxidation of organic material, with the major difference being the considerable increase in rate. The microorganisms used in this study were Escherichia coli and Pseudomonas putida. Results showed that while E. coli could successfully catabolise a standard BOD solution containing glucose and glutamic acid, its use for oth er substrates was limited. Preliminary investigations into the use of P. pu tida, however, showed significantly improved performance and demonstrated t he promise of this approach for rapid BOD determinations. (C) 2001 Elsevier Science B.V. All rights reserved.