Evaluating the low-rank coal biodegradation efficiency bioaugmented with activated sludge 

Abstract

Microbiological treatment of coal is considered an effective and environmentally friendly method. In this work, the effect of microbiological impact on low-rank coal after enrichment with activated sludge was studied. Today, the search for new strategies for separating high-value products from low-quality coal represents a huge niche to explore. In connection with this need, efforts have been made to develop methods for coal solubilization through microbial activities. The microcosm was built with the addition of activated sludge and long-term cultivation. Bacterial communities of coal samples consist predominantly of the phyla Actinobacteria, and Proteobacteria, while Firmicutes and Bacteroidetes were the most abundant phyla for activated sludge. The low-quality coal and biodegradation products were characterized using infrared spectroscopy (FT-IR), and excitation-emission matrix spectrofluorimetry. Using the EEM model, the detected fluorophores were observed at specific wavelength positions at peak E, peak O, peak K, peak E1, peak O1, and peak K1. Peak O, Peak E, and Peak K of the six fluorophores showed the existence of naturally occurring organic materials with humic properties. Based on the FTIR results, it was found that in the bioaugmented microcosm, the transformation of coals was faster than that in the control variant. After incubation, the amount of carboxyl groups in the coals increased, most likely as a result of aerobic oxidation of peripheral non-aromatic structural components of brown coal. The results of CLPP showed that samples of activated sludge have a high metabolic activity of the microbial community when compared to coal. This study shows that the addition of exogenous microflora in the form of activated sludge stimulates the transformation of brown coal.