Abstract
A previous study indicated that the oxidative assimilation capacity of a heterogeneous microbial population for acetic acid did not return to the initial value after a period of endogenous respiration in the presence of ammonium sulfate. In view of this finding it was not possible to recommend fully the use of a continuous oxidative assimilation process for the treatment of nitrogen-deficient waste waters of noncarbohydrate nature. To put the process to a severe test, a laboratory-scale pilot plant study was done. Acetate (1,000 mg/liter) was fed continuously to a completely mixed, aerated reactor vessel, from which the mixed liquor was channeled to a settling basin. The settling basin supernatant fluid was continuously discharged, and a portion of the settled biological sludge was subjected to endogenous respiration in the presence of ammonium sulfate and was recycled to the aeration vessel. Experiments were conducted at three levels of ammonia nitrogen in the endogenous phase. Approximately 90% removal of the carbon source (expressed as chemical oxygen demand, COD) was attained with a low level of supplemental nitrogen (COD/N = 70:1) and a fairly low reactor detention time (4 hr). Based upon these and previous results, it has been concluded that the process shows promise for application to the treatment of a wide variety of nitrogen-deficient industrial wastes.