Abstract
A rapid and simple method for estimating BOD in waters was investigated by using a DO (Dissolved Oxygen) electrode and activated sludge acclimated to substrates. When the substrate was not added to the ML (Mixed Liquor) saturated with DO, a negative straight line for the DO decrease was obtained against the time signifying endogenous respiration of the activated sludge. On the other hand, when sodium sulfite or organic compounds was added as the substrate to the ML after a few minutes, the negative straight line with the similar slope to that obtained initially was obtained again, after a steep decrease in DO cocentration due to the biological oxidation of the substrate with the DO. The difference in DO concentration between two negative straight lines obtained before and after the addition of the substrate is directly proportional to the concentration of added substrate. This DO consumption is applied to determin the rapid BOD (BODr). The time required to measure the BODr is about 10 min. The present method was applied to the estimation of the BODr for some typical organic substrates such as ethanol, phenol, and glucose-glutamic acid with satisfactory results.
