Analysis of a simple biodegradation process for the removal of volatile organic chemicals from wastewater based on a gas stripping principle

A simple biodegradation system consisting of an air stripping tank and a bioreactor was proposed for the treatment of volatile organic chemicals in wastewater. Toluene was used as a model of volatile organic chemicals. An aqueous solution of toluene and a basic mineral medium were placed in the air stripping tank and bioreactor, respectively. Toluene was stripped by supplying compressed air into the stripping tank through a sparger, and the stripped toluene was degraded by Pseudomonas putida mt-2 (ATCC 33015) in the bioreactor under aerobic conditions. The effect of the air stripping rate on bacterial growth was examined. A quantitative relationship was found between the air flow rate in the air stripping tank ( Q a) and the stripping rate constant. During cultivation, the bacterial cells grew by utilizing toluene as the sole carbon source, and reached their maximum cell concentration ( X m) at the stationary phase. X m showed a gradual decrease with increase in Q a from 1.8 to 7.2 l/h, indicating a decrease in the rate of toluene degradation with increasing Q a. The X m at Q a=1.8 l/h was the highest among the experiments under different values of Q a, which was almost twice that at Q a=7.2 l/h. Mathematical analysis taking the growth kinetics and mass transfer of toluene into consideration satisfactorily explained the system performance.