A new mediator method for BOD measurement under non-deaerated condition

Monitoring biochemical oxygen demand (BOD) by mediator method (BODMed) has been developed for recent years and deaerated condition was generally adopted to avoid the effect of oxygen, but the deaerated condition was unfavorable in practical applications. Herein, we first proposed another way to explore non-deaerated BODMed (called NDA-BODMed) method utilizing ferricyanide, which was reduced by Escherichia coli upon catalyzing organic substrate to produce ferrocyanide. We attempted to explain the feasibility of NDA-BODMed by the two aspects. Firstly, the obtained biodegradation efficiencies of the bacteria under the deaerated and non-deaerated conditions were similar, and the concentration of O2 (0.25 mM at 8 mg/L O2) is 1–2 order of magnitude lower than that of mediator commonly used (55 mM ferricyanide), so the effect of O2 to measurements could be neglected. Secondly, the relationship between the artificial and the natural electron acceptor was investigated, and it was found that the oxygen consumption in the NDA-BODMed measurement was mainly contributed to endogenous values. Furthermore, the performance of present NDA-BODMed was reported, and this method was optimized for measuring the low-concentration samples, synthetic wastewater and real polluted wastewater. The NDA-BODMed provides a simple and efficient way in rapid BOD determinations, especially advantageous for in situ monitoring of water system.