The dissolved oxygen in natural water in winter is usually super-saturated.The five-day biochemical oxygen demand(BOD5)was determined by shaking out supersaturated dissolved oxygen before culture,the escape of super-saturated dissolved oxygen in samples was studied by artificial oscillation,ultrasonic oscillation,static vacuuming and vacuum oscillation.The results show that the vacuum oscillation mode can make the super-saturated dissolved oxygen in the sample escape quickly,and the escape rate is proportional to the initial dissolved oxygen concentration and the sample volume.When the sample volume is 600 mL and the concentration of dissolved oxygen is 9-10 mg/L,the super-saturated dissolved oxygen can be escaped by vacuum oscillation for 10 s;when the concentration of dissolved oxygen is 10-12 mg/L,the super-saturated dissolved oxygen can be escaped by vacuum oscillation for 20-30 s;when the concentration of dissolved oxygen is＞12 mg/L,the super-saturated dissolved oxygen can be escaped by vacuum oscillation for 50-70 s.The vacuum oscillation mode can quickly escape the super-saturated dissolved oxygen in the sample in 10-70 s,and the results of BOD5 determination were accurate and the relative deviation was small.The time and difficulty of escape of supersaturated dissolved oxygen were reduced by vacuum oscillation method,which provided reference and basis for BOD5 determination in laboratory.
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