Current situation and development of Biochemical Oxygen Demand (BOD) detection standard

Abstract: Water quality monitoring is an essential step in the management of freshwater resources for better ecological civilization. Biochemical oxygen demand (BOD) refers to the consumed amount of dissolved oxygen during the biochemical reaction when the microorganisms decompose into the biodegradable organic matters in water. The higher BOD indicated that the more dissolved oxygen is consumed in water, leading to the accelerated reproduction of anaerobic bacteria, the corruption of organic substances, and the deterioration of water quality. The BOD can also be an important index to reflect the content of organic pollutants in water for the monitoring work of cities, towns, industries, agriculture, and rural areas. However, the actual detection of BOD is still lacking in generality and accuracy. The current standard system of BOD detection cannot fully meet the high efficiency of water environmental protection and intelligent integrated system at present. In this study, a systematic analysis was made on the standards and technologies of BOD detection in the world, including the "first-generation" dilution and seeding, the "second-generation" microbial electrode, and the "third generation" so far. Specifically, fluorescence labeling is the process of binding fluorescent dyes (tryptophan) to functional groups contained in biomolecules. The fluorescence intensity closely related to microbial activities can be converted into the corresponding BOD value. The near-infrared spectroscopy can be used to determine the BOD value, particularly depending on the absorption intensity of substances. A microbial fuel cell depends on the current intensity generated by the cell and transferred the coulomb charge directly related to the anode organic matter concentration. Furthermore, a comparison was made on the formulation of emission limits. The structure and framework of the current BOD standard system were summarized from three aspects, including the national, local, and industry standards. It is highly urgent to define the types of water pollutant discharge standards in the local community. Therefore, it is of great significance for accurate, scientific, and legal pollution control. Moreover, the influencing factors were determined for the establishment of local mandatory standards under the guidance of national regulations and local policies, as well as the promotion relationship between the supervision of law enforcement departments and the supervision of the community. As such, a mandatory standard system can also be established to support suitable management. Three aspects were evaluated, including the standard distribution, strength of formulation, and iteration of testing. Some recommendations were made on the key development direction and revision suggestions of the standard system, including the construction of local BOD standard system, the water quality testing, the domestic BOD emission, the accurate and precise testing, updating and revising the technical content of the standard in time, as well as the testing station under scientific surveys. The finding can provide strong support to promote environment protection and resources utilization for better ecological protection and high-quality development of water systems.