Using bubble respirometer to monitor microbial activity in passive bioventing system

Abstract

Aim : The study aimed to investigate the relationship between the diesel degradation efficiency in soil and microbial activity during the wind-driven bioventing remediation. The study also aimed to compare the indicators of cumulative oxygen uptake and 24-hr oxygen uptake rate with the analysis results of diesel concentration. Methodology: A self-made wind-driven bioventing equipment was used as passive bioventing device.In the wind-driven bioventing pilot study for highly diesel contaminated soil (approximately 20,000 mg kg-1). the bubble respirometer collocated with the bioslurry method was used to monitor the microbial activity in soil. The diesel concentration was analyzed by GC/FID. Results: The result of respiration assays showed that the microbial activities of Bacillus subtilis and Pseudomonas putida, which are capable of degrading diesel, could be consecutively bioaugmented for two weeks, and that of Achromobacter xylosoxidans could be consecutively bioaugmented for three weeks after adding individual microorganism. While appropriate amount of nutrients were added in the pilot, the cumulative oxygen uptake in the Pseudomonas putida set elevated from 219 mg-02 to 328 mg-02 in one week that inferred the microbial activity of Pseudomonas putida and which could be elevated rapidly in a highly diesel contaminated environment. However, the 24-hour oxygen uptake rate in the Achromobacter xylosoxidans set could be maintained in the first three weeks between 4.8 mg-02 hr-1 and 5.0 mg-02 hr-1 that illustrated the microbial activity of Achromobacter xylosoxidans, which was the highest among three microorganisms in the highly diesel contaminatedenvironment. Interpreration: The research results demonstrated a positive correlation between the diesel degradation efficiency and 24-hour average oxygen uptake rate of microorganisms during the experiment, suggesting that the 24-hour average oxygen uptake rate could be used as an indicator of microbial activity.