Biochemical oxidation of organic matter in the media with different C/N ratios.

Abstract

This study is undertaken to identify how the constant rate of biochemical oxidation varies with the C/N ratio in glucosae solution supplemented with inorganic nitrogen. The biochemical oxidation of organic matter has been defined by a stoichiometric model, and the commonly-accepted reaction of this model consists of three chemical reactions. In this paper, the progress BOD is mathematically expressed by using composite three first order kinetics. The influence of the C/N ratio on the progress BOD is evaluated by estimating the parameters of the kinetic equation. Kinetics parameters are determined by modifying Lee's graphical method. In the glucose solution with C/N ratios ranging from 4 to 20, the rate constant of endogenous respiration has a tendency to increase with increasing ratios of C/N. And the rate constants in the first and second steps of microbial growth phase decrease from 3.5 to 2.0/day and from 1.2 to 0.4/day with increasing ratios of C/N, respectively. On the other hand, total ultimate oxygen demand is a similar value at C/N ratios between 4 and 20. The value is equivalent to 67.5 per cent of the theoretical oxygen demand of glucose. These results mean that the amount of nitrogen needed is not directly related to the organic matter undergoing degradation but rather to the amount of new cells synthesizing in the degradation process.