Biosensor for the Determination of Biochemical Oxygen Demand in Rivers

Population growth and industrialization have caused serious environmental pollution. Environmental pollution has become global issues beyond a region or a country, and is the introduction of contaminants, which are synthetic chemicals, pesticides, and heavy metals etc, into environmental system. Biopersistent organic chemicals of them particularly cause instability, disorder, harm or discomfort to ecosystem. Biopersistent organic chemicals are present as pollutants in wastewater effluents from industrial manufacturers or normal households. Environmental problems with such organic pollutants are becoming progressively worse all over the world. They are increasingly found in groundwater wells, rivers, lakes, and seas. Our drinking water sources, in particular, have also become polluted. A rapid and online monitoring of organic pollutants in water systems is a process that is essential for not only health of human but also environmental protection and ecosystem. Environmental pollutants in water systems have been evaluated as indicators including biochemical oxygen demand (BOD), chemical oxygen demand (COD), and total organic carbon (TOC) etc. Unlike chemical analyses such as COD and TOC, BOD is a method evaluated by the microbial ecosystem by the American Public Health Association (APHA) (APHA, 1986) because the indicator is based on the metabolic activity of aerobic microorganisms. Therefore, BOD analysis directly represents some influences of organic pollutants on natural ecosystems. In 1884, the modern concept of biochemical oxidation aroses, when it was showed that the decrease in the dissolved oxygen (DO) content of incubated samples was caused by metabolic activity of the microorganisms present (Leblanc, 1974). The 5-day BOD (BOD5) test method, however, requires an incubation period of 5 days under specified standard conditions described by the American Public Health Association Standard Methods Committee. This method is not desirable not only for process control and environmental monitoring, but also for remediation it produces a quick feedback. Thus, a fast and simple estimation of BOD is required as an alternative method to circumvent the disadvantages of the conventional test (BOD5). A rapid and reliable method for BOD estimation was first developed by Karube et al. (Karube et al., 1977b). Since then many kinds of microbial sensors instead of BOD5 analysis have been reported (Kulys & Kadziauskiene, 1980; Lin et al., 2006; Riedel et al., 1990; Sakaguchi et al., 2003; Stand & Carlson, 1984; Tanaka et al., 1994; Yang et al., 1997; Yoshida et al., 2000). They generally consist of microorganisms