A simple simulation method for river self-purification studies

A simple simulation system is described for the study of river self-purification processes. A linear relationship between the organic load and the critical deficit on the sag curve was obtained for each temperature, corresponding to 36–52 per cent assimilation. The rate is not constant, and the monomolecular theory is not suitable to describe the results. Two distinct phases are observed. Nitrification appears as a second and distinct sag in the oxygen curve. It is limited by oxygen transfer and equilibrates at an O₂ tension of 0·6–1·05 mg 1⁻¹.