Microbial community response and SDS-PAGE reveal possible mechanism of waste activated sludge acidification enhanced by microaeration coupled thermophilic pretreatment

Abstract

Aiming to strengthen the performance of waste activated sludge digestion, pretreatment is a prerequisite for keeping operations within an industrially acceptable time-frame. In this study, the performance of microaeration coupled with thermophilic (MT) pretreatment on waste activated sludge solubilization and acidification was investigated. The results showed that the maximum soluble organics concentrations, including soluble proteins and carbohydrates, reached 2290 mg COD/L in 24 h when the ventilation rate and temperature were 0.05 vvm and 70 °C. SDS-polyacrylamide gel electrophoresis (SDS-PAGE) test on pure-culture (E.coli) and scanning electron microscopy analysis indicated that MT pretreatment effectively destroyed microbial cell wall and resulted in an increase in soluble proteins. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis revealed that MT pretreatment reduced the diversity of the bacterial community during pretreatment. Along with the dissolution of a large quantity of organic matter, microbial species such as Lactococcus and Methyloversatilisbloomed at the end of acidification period, which contributed to SCFAs production. This study revealed that MT pretreatment facilitated the WAS hydrolysis efficiency and enhanced SCFAs (3149 mg COD/L with fermentation for 96 h) production, especially for acetic acid (50%) accumulation, which provides a new perspective for the application and recovery of sludge resources.

Microaerobic conditions in anaerobic sludge promote changes in bacterial composition favouring biodegradation of polymeric siloxanes

“…The correlation between oxygen consumption and methane production demonstrates that aerobic/facultative bacteria reduce dissolved oxygen concentrations (and thus oxygen partial pressures), protecting strictly anaerobic methaneproducing organisms. This particular mutualistic relationship, studied previously using non-siloxane substrates, 42,82,95 supports the hypothesis that the presence of oxygen leads to a change in the bacterial community structure. This change could favour the production of new enzymes and the possibility of harvesting more energy from substrates, which may explain why PDMS is more biodegradable under microaerated conditions.…”

“…57 On the other hand, controlled oxygen additions appear as a more suitable option, due to its easy management, low concentration required, and more regulated redox potential. Furthermore, the anaerobic digestion (AD) microbiome has a lower diversity of microorganisms than its microaerobic counterpart, 40,42,43 impacting both the production and variety of hydrolytic enzymes. This is why hydrolysis usually becomes the rate-limiting step for the anaerobic digestion of inuent streams composed of particulate and/or recalcitrant compounds.…”

“…Alternatively, the controlled addition of small amounts of oxygen to the anaerobic environment (i.e., microaeration) can promote the required microbial changes and full the thermodynamic requirements to allow for the catabolism of more recalcitrant compounds in general. [39][40][41] A microaerobic environment may help overcome the low energy production, low microbial diversity, and weak biolm formation issues of strictly anaerobic environments, [41][42][43] while increasing hydrolysis rates and produce more diverse enzymes. 38,44 Consequently, microaeration arises as a useful strategy to extract the positive aspects of both aerobic and anaerobic conditions without their drawbacks.…”

How Do Biocides That Occur in Waste Activated Sludge Affect the Resource Recovery for Short-Chain Fatty Acids Production

“…Acidaminobacter , which was reported to be involved in the sludge biological hydrolysis and organics fermentation for acetic and propionic acids production, , was found to be respectively 8.87% and 22.05% in the CHD and HTAB reactors, while it was only 0.08% in the control. Saccharibacteria and Proteiniclasticum , which were generally linked to the proteins metabolism with acetate as the major product, , were also highly enriched in the biocide reactors. Particularly, the Saccharibacteria was 23.85% and 19.85% in the CHD and HTAB reactors, respectively, and became one of the predominant groups in WAS anaerobic reactors.…”