Ferricyanide mediated microbial reactions were employed for the rapid determination of the biochemical oxygen demand (BOD) of a range of synthetic and industrial wastewater samples. By replacing oxygen with a highly soluble artificial electron acceptor, such as ferricyanide, the rates of microbial catabolism were greatly enhanced, providing the basis of a rapid BOD assay. The microbial species used in this study were Klebsiella oxytoca, Serratia liquefaciens, Pseudomonas aeruginosa, Saccharomyces cerevisiae and Enterobacter cloace. A synthetically prepared consortium of the five species was evaluated on its ability to rapidly degrade real industrial samples in the presence of ferricyanide. A linear range of 200-300 mg.BOD5.L-1 was observed for industrial samples, which is significantly greater than the linear range of the BOD5 assay and many other rapid BOD assays reported. The ferricyanide mediated BOD responses obtained for industrial samples (n=16) using the mixed microbial consortium were found to correlate very well to the BOD5 assay (r = 0.973, m=1.05) – this occurred at a greatly reduced incubation time (typically 2-3 hours).