A Kinetic Study on the Microbial Remediation of Soil Contaminated with the Herbicide 2,4-dichlorophenoxy acetic acid

In this paper the bioremediation of soil contaminated with the herbicide, 2,4-dichlorophenoxy acetic acid has been studied applying Ralstonia eutropha. The effects of temperature, pH and moisture on the rate of degradation of the latter poison has been investigated.Taguchi experimental design method were applied to determine the relative impacts of pertinent system's variables. According to such an approach, four series of experiments were performed under various operating conditions. In all four series of experiments the poison was degraded efficiently, however, the highest rate was observed at the temperature of 35°C, pH 6 and 80% moisture content. A kinetic model for the biodegradation of the herbicide was developed for this particular condition. To present the model, a general stoichiometric equation was assumed for the degrading process.The growth rate of bacteria was assumed to follow a Monod type equation. In addition, based on the present observation, the biodegradation of the herbicide was considered to be an autocatalytic type reaction. The kinetic parameters were obtained from the experimental results, applying the non linear least square technique. The final relation takes the following form:where, XP is the extent of degradation of the herbicide and t, is time.A close correlation has been observed between the experimental data and those predicted from the model. The degree of agreement was within 85-90%