BOD Test Variables

It has been reported that the oxidation rate in a stream is higher than the corresponding rate obtained from the laboratory BOD test. This study was undertaken to observe the effect of such stream conditions as turbulence, light and turbidity, separately and in combinations, on the BOD test, using raw domestic sewage. Mixing was found to increase the BOD₅ by an average of 15%, while light only increased the BOD₅ by 4.0%. Turbidity demonstrated an average reduction of about 24% on BOD₅ values. Mixing and turbidity, in combination, reduced the BOD₅ by 28%, turbidity and light by less than 6%, light and turbidity and mixing by 26%, while mixing and light increased the BOD₅ by about 15%. This study has shown that without further research, extrapolation from laboratory to field conditions, from the existing standard BOD test, yields questionable results. Inclusion in the BOD test, of the physical characteristics of the stream, is a possible solution to obtaining more meaningful results.