Microbial dynamics and bioreactor performance are interlinked with organic matter removal from wastewater treatment plant effluent

Divergences of granules and flocs microbial communities and contributions to nitrogen removal under varied carbon to nitrogen ratios

Aerobic granular sludge (AGS) reactors are promising for treating high ammonia wastewaters, yet the roles of granules and flocs in nitrogen removal under varying carbon to nitrogen (COD/N) ratios remain unclear. This study investigated microbial communities and their contributions to N removal as the COD/N ratio shifted from 6 to 4, and to 2. Results showed granules contributed 53-64 % nitrification capacity at higher COD/N ratios (6 and 4), but flocs contributed more (50-63 %) at a ratio of 2. Granules consistently exhibited higher denitrification capacity (>50 %). Heterotrophic bacteria dominated in both granules and flocs across all ratios. As the COD/N ratio reduced, the relative abundance of anaerobic ammonia oxidation microorganisms (Candidatus Anammoximicrobium) and filamentous bacteria increased in granules, while ammonia oxidizing bacteria (Nitrosomonas) and complex organic degraders increased in flocs. These findings highlight the importance of selectively retaining granules or flocs under varying COD/N ratios to optimize nitrogen removal efficiency.

The potential role of viruses in antibiotic resistance gene dissemination in activated sludge viromes

The dissemination of antibiotic resistance genes (ARGs) in activated sludge (AS) systems poses significant environmental and public health challenges. The role of viruses, primarily bacteriophages, in storing and spreading ARGs in AS systems remains largely unexplored. This study characterized the viral community, virus-associated ARGs (vir_ARGs), and mobile genetic elements (MGEs) of aerobic AS viromes from eight wastewater treatment plants (WWTPs) in eastern China. 78,604 viral operational taxonomic units (vOTUs) were identified, including 1685 temperate vOTUs (T-vOTUs). Five ARG types were detected in 37 vOTUs, indicating a low proportion of ARG-carrying viruses. The co-occurrence rate between vir_ARGs and MGEs was 37.83 %, and six ARG-carrying vOTUs contained multiple MGEs, indicating a transfer potential of vir_ARGs. Additionally, ARG and MGE profiles of AS metagenomes were analyzed to evaluate the transfer potential of phage activity on ARGs. The results showed that phage-associated MGEs showed a significant coupling with both the abundance and composition of ARGs, suggesting a potential role of phages in ARG propagation. These findings offer preliminary insights into understanding the viral resistome and its transfer potential in AS systems. Future research necessitates rigorous pure culture and molecular biology experiments to elucidate the precise mechanisms through which viruses contribute to the dissemination and persistence of ARGs.

Differentiated cognition of the effects of human activities on typical persistent organic pollutants and bacterioplankton community in drinking water source

Accelerated urbanization in developing countries led to a typical gradient of human activities (low, moderate and high human activities), which affected the pollution characteristics and ecological functions of aquatic environment. However, the occurrence characteristics of typical persistent organic pollutants, including organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons (PAHs), and bacterioplankton associated with the gradient of human activities in drinking water sources is still lacking. Our study focused on a representative case - the upper reaches of the Dongjiang River (Pearl River Basin, China), a drinking water source characterized by a gradient of human activities. A comprehensive analysis of PAHs, OCPs and bacterioplankton in the water phase was performed using gas chromatography-mass spectrometry (GC-MS) and the Illumina platform. Moderate human activity could increase the pollution of OCPs and PAHs due to local agricultural activities. The gradient of human activities obviously influenced the bacterioplankton community composition and interaction dynamics, and low human activity resulted in low bacterioplankton diversity. Co-occurrence network analysis indicated that moderate human activity could promote a more modular organization of the bacterioplankton community. Structural equation models showed that nutrients could exert a negative influence on the composition of bacterioplankton, and this phenomenon did not change with the gradient of human activities. OCPs played a negative role in shaping bacterioplankton composition under the low and high human activities, but had a positive effect under the moderate human activity. In contrast, PAHs showed a strong positive effect on bacterioplankton composition under low and high human activities and a weak negative effect under moderate human activity. Overall, these results shed light on the occurrence characteristics of OCPs, PAHs and their ecological effects on bacterioplankton in drinking water sources along the gradient of human activities.

Biobased short chain fatty acid production - Exploring microbial community dynamics and metabolic networks through kinetic and microbial modeling approaches

In recent years, there has been growing interest in harnessing anaerobic digestion technology for resource recovery from waste streams. This approach has evolved beyond its traditional role in energy generation to encompass the production of valuable carboxylic acids, especially volatile fatty acids (VFAs) like acetic acid, propionic acid, and butyric acid. VFAs hold great potential for various industries and biobased applications due to their versatile properties. Despite increasing global demand, over 90% of VFAs are currently produced synthetically from petrochemicals. Realizing the potential of large-scale biobased VFA production from waste streams offers significant eco-friendly opportunities but comes with several key challenges. These include low VFA production yields, unstable acid compositions, complex and expensive purification methods, and post-processing needs. Among these, production yield and acid composition stand out as the most critical obstacles impacting economic viability and competitiveness. This paper seeks to offer a comprehensive view of combining complementary modeling approaches, including kinetic and microbial modeling, to understand the workings of microbial communities and metabolic pathways in VFA production, enhance production efficiency, and regulate acid profiles through the integration of omics and bioreactor data.