Bio-stimulation with low-intensity ultrasonication
Loh, Aron Shu Tien
Date of Issue2017-11-17
School of Civil and Environmental Engineering
Nanyang Environment and Water Research Institute
This report represents the findings of an experimental study on the enhanced bio-stimulation effect on anaerobic digestion by using low-intensity ultrasonication. The bio-stimulation effect can be determined based on the overall amount of biogas generated and biogas flow rate over time by using the Automatic Methane Potential Test System (AMPTS) to monitor the biogas generation hourly. The power intensity of 0.0062 W/mL at 30 seconds sonication exposure time can achieve 126% more biogas in 1 hour compared to control samples, respectively. Furthermore, the overall biogas generated after 6 hours was 10% more than control samples, respectively. The enhanced bio-stimulation effect had lasted 2 hours. The effect of sonication power intensity and exposure time on cell lysis were also determined. The increase in the concentration of phosphate, ammonium, and potassium were the indications of cell lysis occurring at a known sonication power intensity and exposure time. Thus, cell lysis can be avoided before commencing the AMPTS experiment. However, there were signs of microbes experienced ‘shock’ or ‘stress’, due to sonication despite no cell lysis occurred. As a result, the overall biogas (%) generated at the first hour was lower than the control for 0.01 ~ 0.05 w/ml under 50 seconds sonication exposure time. Over time, the microbes overcome the ‘shock’ and return its original state. This study also shows that anaerobic microbes experienced different phases, like cell lysis, ‘shocked’ and the enhanced bio-stimulation effect depending on the sonication intensity and exposure time. The results of this study show that low-intensity ultrasonication can be a promising solution to enhance the process efficiency by increasing the biogas production during anaerobic digestion of organic wastes i.e. wastewater, sludge etc.
Final Year Project (FYP)
Nanyang Technological University