Development of a novel method of biochemical oxygen demand colorimetric detection and its application in actual water

In this study, a novel and efficient colorimetric biosensor was constructed for biochemical oxygen demand (BOD) detection based on visual analysis and Qualcomm measurement with enzyme-labeling instrument. Microorganisms cultured in situ with actual water and Prussian blue were used as model bacteria and indicator of colorimetric biosensor, respectively. To accurately detect BOD content in water, the reaction conditions such as cell concentration, K₃[Fe(CN)₆] concentration, reaction temperature, and reaction time were optimized. The optimal conditions were OD₆₀₀ = 7, 10 mM, 37 °C and 40 min, respectively. The dominant bacteria in the color reaction process were Acinetobacter, Bacillus and Exiguobacterium. The detection range of the biosensor was 5-80 mg L^-1, and the detection limit was 3.32 mg L^-1. The relative error of BOD content in actual water was 15.49 %. In summary, the high-efficiency colorimetric biosensor can detect BOD content quickly and sensitively, which implied its potential application prospects in the field of BOD detection.