Biochemical Oxygen Demand (BOD)

Biochemical oxygen demand (BOD) is a widely used parameter to assess the organic pollution in water systems. This parameter can be detected by the amount of oxygen consumed via microorganisms in aerobic metabolism of organic matter present in the water. The authorized test to analyze biodegradable organic compounds is given by the American Public Health Association Standard Method Committee that is called a 5-day biochemical oxygen demand (BOD5) test. In this conventional BOD procedure, the analyte is kept in the dark and in properly sealed biological reactors after inoculating with a microbial culture (seed), nutrients, and plenty of oxygen. Afterwards, the amount of oxygen is measured which is consumed by the microorganisms during biological oxidation of organic solutes over a time period of 5 days. Such prolonged analysis makes BOD5 expensive and requires experienced personnel for reproducible results. This procedure produces good results; however, it cannot be used for rapid analysis such as environmental monitoring and/or process control. The first rapid BOD sensor was proposed by Karube et al. in 1997. In this approach, microbes were immobilized on a collagen membrane and an oxygen electrode was used as an indicator device. The results were obtained by this method in a short period of time (1 h) and were closely related to BOD estimates (obtained in 5 days).