Effect of Seasonal Temperature on the Performance and on the Microbial Community of a Novel AWFR for Decentralized Domestic Wastewater Pretreatment

Antibiotic Residues and Resistance in Three Wastewater Treatment Plants in Romania

This study evaluates antibiotic residues and bacterial loads in influent and effluent samples from three wastewater treatment plants (WWTPs) in Romania, across four seasons from 2021 to 2022. Analytical methods included solid-phase extraction and high-performance liquid chromatography (HPLC) to quantify antibiotic concentrations, while microbiological assays estimated bacterial loads and assessed antibiotic resistance patterns. Statistical analyses explored the impact of environmental factors such as temperature and rainfall on antibiotic levels. The results showed significant seasonal variations, with higher antibiotic concentrations in warmer seasons. Antibiotic removal efficiency varied among WWTPs, with some antibiotics being effectively removed and others persisting in the effluent, posing high environmental risks and potential for antibiotic resistance development. Bacterial loads were higher in spring and summer, correlating with increased temperatures. Eight bacterial strains were isolated, with higher resistance during warmer seasons, particularly to amoxicillin and clarithromycin.

Microbial characteristics in anaerobic membrane bioreactor treating domestic sewage: Effects of HRT and process performance

Two anaerobic membrane bioreactors (AnMBRs) equipped with different membrane pore size (0.4 or 0.05 µm) were operated at 25˚C and fed with domestic wastewater. The hydraulic retention time (HRT) of the reactors was shortened. The microbial communities of the two AnMBRs were investigated by 16S rRNA gene amplicon sequencing to see the effects of HRT. The predominant Archaea was an aceticlastic methanogen Methanosaeta. The composition of hydrogenotrophic methanogens changed with the HRTs: the population of Methanobacterium was higher for longer HRTs, whereas the population of unclassified Methanoregulaceae was higher for shorter HRTs. The Anaerolineae, Bacteroidia and Clostridia bacteria were dominant in both of the reactors, with a combined relative abundance of over 55%. The relative abundance of Anaerolineae was proportional to the biogas production performance. The change in the population of hydrogenotrophic methanogens or Anaerolineae can be used as an indicator for process monitoring. The sum of the relative abundance of Anaerolineae and Clostridia fluctuated slightly with changes in the HRT in both AnMBRs when the reactor was stably operated. The co-occurrence analysis revealed the relative abundance of the operational taxonomic units belonging to Anaerolineae and Clostridia was functionally equivalent during the treatment of real domestic sewage. A principal coordination analysis revealed that the changes in the microbial community in each reactor were consistent with the change of HRT. In addition, both the HRT and the stability of the process are important factors for maintaining microbial community structures.

Important effects of temperature on treating real municipal wastewater by a submerged anaerobic membrane bioreactor: Removal efficiency, biogas, and microbial community

A submerged anaerobic membrane bioreactor (SAnMBR) was used in the treatment of real municipal wastewater at operation temperatures ranging from 15 °C to 25 °C and hydraulic retention time (HRT) of 6 h. The treatment process was evaluated in terms of organic removal efficiency, biogas production, sludge growth and membrane filtration. During long-term operation, the SAnMBR achieved chemical oxygen demand removal efficiencies of about 90% with a low sludge yield (0.12-0.19 g-VSS/g-COD_rem) at 20-25 °C. Approximately 1.82-2.27 kWh/d of electric energy was generated during the wastewater treatment process at 20-25 °C, 0.67 kWh/d was generated at 15 °C. The microbial community analysis results showed that microbial community was dominated by aceticlastic methanogens, coupled by hydrogenotrophic methanogens and a very small quantity of methylotrophic methanogens. It was also shown that the stabilization of the microbial community could be attributed to the carbohydrate-protein degrading bacteria and the carbohydrate degrading bacteria.

The effect of temperature fluctuation on the microbial diversity and community structure of rural household biogas digesters at Qinghai Plateau

Seasonal temperature-fluctuation has been regarded as a key environmental factor affecting rural biogas fermentation yields. The present study investigated the impact of seasonal temperature-fluctuation on operating-temperatures and biogas production in rural household digesters at Qinghai Plateau and revealed the related changes in microbial diversity and community structure by 16S rRNA gene high-throughput sequencing (HTS) analysis. Our results showed closely positive correlation between operating-temperatures and biogas production. HTS analysis indicated the highest diversity for bacteria community in autumn (at highest operating-temperatures) and late winter (at lowest operating-temperatures) and for archaea community only in autumn. HTS analysis classified bacteria into 21 phyla and 346 genera with the most predominant phyla Firmicutes, Bacteroidetes and Proteobacteria (> 72.4% in total) and the most predominant genera Proteiniphilum, Clostridium sensustricto 1, Petrimonas, Pseudomonas and Fastidiosipila (37.09-38.61% in total). HTS analysis also revealed two main archaea orders (Methanomicrobiales and Methanobacteriales) and one predominant genus Methanogenium to support plateau biogas fermentation. Especially, a remarkable impact of temperature on the community abundances of bacteria phyla Synergistetes and archaea genera Methanogenium and Thermogymnomonas was observed, and such microbial community structure changes were positively consistent with the biogas production. The present work provided the first set of evidences to link temperature-controlled modulation of microbial community structure with rural household biogas production at Qinghai Plateau.