The use of a mixed microbial consortium in a rapid ferricyanide mediated biochemical oxygen demand assay

Abstract

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. Each species, as well as a synthetically prepared consortium of the five species, were compared in their ability to rapidly degrade organic samples in the presence of ferricyanide. The microbial consortium demonstrated a greater extent and rate of biodegradation compared to the individual microbial seeds. An improved correlation to the BOD sub(5) method was also demonstrated for the microbial mixture compared to the single species for synthetically prepared samples. A linear range of 200-300 mg. BOD sub(5).L super(-1) was observed for industrial samples, which is significantly greater than the linear range of the BOD sub(5) assay and many other rapid BOD assays reported. The ferricyanide mediated BOD responses obtained for industrial samples (n=15) using the mixed microbial consortium were found to correlate very well to the BOD sub(5) assay (r = 0.973, m=1.05) - this occurred at a greatly reduced incubation time (typically 2-3 hours).