Mechanism of dielectric barrier discharge plasma technology to improve the quantity of short-chain fatty acids in anaerobic fermentation of waste active sludge

Abstract

The mechanism of improving the anaerobic fermentation performance of waste active sludge by using dielectric barrier discharge (DBD) plasma pretreatment technology was investigated. The maximum accumulation of short-chain fatty acids (SCFAs) was observed on the 7th day of anaerobic fermentation when the DBD power was 76.50 W, which was 1726.70 mg COD/L, 1.50 times of the control group. The ratio of acetic acid in DBD group was 9.30% higher than that in the control. Further mechanism research indicated that DBD pretreatment can destroy the structure of extracellular polymer substances and release organic substances such as protein and polysaccharide. The dissolved organic matter analysis indicated that the DBD technique could increase the release of biodegradable organics (eg., tyrosine proteins, soluble microbial by-products), thus accelerate the biotransformation of organic substance. Bacterial community structure analysis showed that the increase in the abundance of Firmicutes and Bacteroidetes and the decrease in the abundance of Proteobacteria in DBD group were beneficial to the accumulation of SCFAs. Besides, further archaeal analysis indicated that the decrease of Methanosaeta sp. and Methanosarcina sp. abundance in the DBD group facilitate acetic acid accumulation. This study demonstrated that the DBD technique can be used as an effective and potential pretreatment method to improve sludge anaerobic fermentation performance.

Plasma‐Assisted CO2 Reduction into Nanocarbon in Water Using Sonochemically Dispersed Liquid Gallium

“…CO 2 conversion was reported in a bubble flow reactor at 200 °C which resulted in a 9.6% increase in carbon content. [1h] Likewise, an autoclave reactor can achieve 89.78% column efficiency at 600 °C, [48] while microwave plasma reactors show 80% CO 2 conversion to carbon at 300 °C. [49] Although thermal and combustion processes can achieve high CO 2 conversion at high temperature, they require high energy input.…”

“…In this work we do not envisage separating the carbon from the GaOOH particles as this will be time intensive to ensure high purity carbon without any traces of Ga. Therefore, we propose that the resulting GaOOH‐C composite from this process could be used in various applications such as adsorption, supercapacitors [ 46,47 ] or Li‐ion batteries. [ 48 ] This opens the opportunity for future investigation to optimize the process parameters, reactor design or catalyst morphology to adjust the extent of CO 2 conversion and the final carbon content depending on the required application.…”