Experience with a bacterial inoculum for use in respirometric tests for oxygen demand

Abstract

Attempts have been made to develop a rapid, general test for waste waters, based on the oxygen uptake during a few hours in the presence of a specially prepared inoculum. The inoculum was obtained freshly as required by the aeration of settled sewage with organic additives, and was developed with the requirements of reproducibility, high activity, and low endogenous demand in mind. Preparation of the inoculum and its application were carried out at 30°C in the presence of inorganic nutrients and 0·04 M phosphate buffer, pH 7. The concentration of inoculum applied was usually in the range 100–400 mg 1 −1. The inoculum degraded a wide range of pure compounds in a few hours with good reproducibility. In the case of substances of relatively low biodegradability, some degree of adaptation was obtained by growing the inoculum in the presence of the substance in question. The oxygen uptake with settled sewage in 6 h was usually about 60–70 per cent of the BOD and 30–40 per cent of the COD. Promising results were obtained in tests carried out with industrial waste waters, but more work would be needed before the method could be recommended as a general one.