A study of the biodegradation of organic pollutants in a dilute aqueous system

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1969

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The biochemical oxygen demand test (BOD) and the chemical oxygen demand test (COD) have often been designated as tests to monitor bio degradation of organic pollutants in dilute aqueous systems. Specific limitations to oxygen demand measurements for these purposes have been found to be due to nonspecific identification of reaction mechanisms, metabolic by-products, and interfering components. Gas chromatography together with carbon analyses and dissolved oxygen measurements have proved to be effective analytical methods for defining the mechanisms, related metabolic by-products, and rates of biodegradation of organic pollutants in dilute aqueous systems. Gas chromatographic analysis of the biodegradation of secondary- butanol and tertiary butanol in the single dilution system made possible the detection of two intermediate metabolic by-products produced during biodegradation. One of the by-products was identified as 2-butanone; the other product, suspected to be acetoacetic acid, was not positively identified. During the growth phase of the heterogeneous mixed culture, 2 mg/1 of 2-butanone was produced for each mg/1 oxygen utilized and 0.6 mg/1 of biomass was produced. When the microbial population reached a maximum, biodegradation continued without further increase in biomass. The rate of oxygen utilization, during this stage of the reaction, was dependent upon the rate of metabolic by-product production. The formation of by-products ceased when the heterogeneous mixed culture entered the die-off phase of growth. At this point in the reaction, endogenous respiration determined the oxygen demand of the system.

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