Search Results (9)

The bacterial communities of activated sludge are correlative with influent characteristics, geographical discrepancies, and environmental variables, which are essential for wastewater treatment plants (WWTPs). However, the comprehensive deciphering of bacterial community diversity in high-altitude WWTPs is scarce in Tibet, China. This study collected activated sludge samples from four A²O WWTPs (2980–3650 m above sea level) in Tibet. Illumina NovaSeq high-throughput sequencing revealed that Proteobacteria was the most abundant phylum (46.2–62.9%), followed by Bacteroidetes (14.8–21.8%) and Actinobacteria (3.5–10.9%). Candidatus Accumulibacter (7.2–15.1%) was the dominant denitrifying polyphosphate-accumulating organisms (DPAOs). Moreover, a principal coordinate analysis (PCA) revealed strong correlations between environmental factors and dominant phyla, while Candidatus Accumulibacter as a dominant genus was unaffected by environmental factors. Additionally, the reaction mechanisms were analyzed based on the functional gene abundance of carbon, nitrogen, and phosphorus metabolic pathways in high-altitude WWTPs. The carbon metabolism pathway, especially carbohydrate metabolism (14.52%), has more abundant functional genes in Nyingchi (LZ). Nitrogen metabolism mainly consists of assimilatory nitrate reduction, dissimilatory nitrate reduction, and denitrification; the high abundance of functional genes in phosphorus metabolism ensures efficient phosphorus removal. The obtained microbial information in the WWTPs could provide essential guidance for the sustainable management of wastewater treatment systems in high-altitude environments. Future research should focus on monitoring the seasonal dynamics of bacterial communities in high-altitude WWTPs and responses to environmental disturbances, to optimize treatment efficiency and ensure long-term sustainability. Full article

This study demonstrated the feasibility of enhanced biological phosphorus removal coupled with in-situ fermentation (EBPR-F) to improve phosphorus removal from real digested swine wastewater. We used fermentable substrates (casein hydrolysate and glucose) as the external carbon sources to promote in-situ fermentation and enhance biological phosphorus removal. Compared with conventional EBPR dominated by Candidatus Accumulibacter, EBPR-F had significantly better phosphorus removal with enriched polyphosphate-accumulating organisms (PAOs). Under supplementation with 100 mg/L glucose, total phosphorus (TP) removal was over 95% in EBPR-F, with an average TP concentration in the effluent below 1.0 mg/L, satisfying the discharge standard (8 mg P/L) in China. The PAO activity and relative abundance of Candidatus Accumulibacter (44.7% ± 3.1%) and Tetrasphaera (18.1% ± 6.6%) in EBPR-F were much higher than those in EBPR. The improvement in phosphorus removal of EBPR-F was due to the enrichment of Tetrasphaera through the enhanced in-situ fermentation, as Tetrasphaera can efficiently ferment complex organic matter and provide bioavailable organics for phosphorus removal. Full article

Candidatus Accumulibacter belongs to phosphate-accumulating organisms (PAOs) which exhibit a cyclic metabolism and are capable of intracellular polyphosphate accumulation and their hydrolysis under feast-famine anaerobic-aerobic cycling. In consortia of activated sludge microorganisms, these bacteria are responsible for enhanced biological phosphorus removal (EBPR). The spectrum of the substrates used by Ca. Accumulibacter remains insufficiently studied. It was investigated by measuring the oxygen uptake rates (OUR) of Ca. Accumulibacter-enriched culture supplemented with 17 different organic substrates. The highest oxygen uptake rate values were observed in the presence of tryptone, volatile fatty acids (acetate, propionate, and butyrate), succinate, pyruvate, and amino acids (aspartate and glutamate). Phosphate dynamics in the medium under shifts from anaerobic to aerobic cultivation in batch experiments were studied for these compounds (except for tryptone). All tested substrates were shown to cause phosphate cycling (release in the anaerobic phase and uptake in the aerobic one), with OURs for the substrates correlating with the number of phosphates consumed during the aerobic phase. It was concluded that OUR may be used as an indicator of the monosubstrates used by Ca. Accumulibacter in the anaerobic/aerobic cycle. The possible pathways for substrate transport and metabolism by Ca. Accumulibacter are discussed using stoichiometric data and the results of metagenomic analysis. Full article

The application of enhanced biological phosphorus removal (EBPR) in wastewater treatment plants (WWTPs) has commonly been utilized worldwide. However, the optimum efficiency has not been realized over the past decades, prompting many studies and publications. The limitations, especially comprehension of the abundance and actual potential of polyphosphate-accumulating organisms (PAOs), are not fully understood. Recently identified putative PAOs, Tetrasphaera, present a vast metabolic versatility compared to Candidatus Accumulibacter. The characterisation of Tetrasphaera unique abilities to utilize various carbon substrates, volatile fatty acids production and consistent high abundance, presents potential boosts towards the process efficiency improvement. This paper provides the existing knowledge on the physiology, morphology and genetic description of PAOs with a special attention to the current state of research on Tetrasphaera and its potential. In addition, process conditions and their influence on the microbial activities in EBPR systems are discussed. Full article

Bacterial diversity and community composition are of great importance in wastewater treatment; however, little is known about the diversity and community structure of bacteria in tropical municipal wastewater treatment plants (WWTPs). Therefore, in this study, activated sludge samples were collected from the return sludge, anaerobic sludge, anoxic sludge, and aerobic sludge of an A²O WWTP in Haikou, China. Illumina MiSeq high-throughput sequencing was used to examine the 16S ribosomal RNA (rRNA) of bacteria in the samples. The microbial community diversity in this tropical WWTP was higher than in temperate, subtropical, and plateau WWTPs. Proteobacteria, Bacteroidota, Patescibacteria, and Chloroflexi were the dominant phyla. Nitrification bacteria Nitrosomonas, and Nitrospira were also detected. Tetrasphaera, instead of Candidatus Accumulibacter, were the dominant polyphosphate accumulating organisms (PAOs), while, glycogen accumulating organisms (GAOs), such as Candidatus Competibacter and Defluviicoccus were also detected. The bacterial community functions predicted by PICRUSt2 were related to metabolism, genetic information processing, and environmental information processing. This study provides a reference for the optimization of tropical municipal WWTPs. Full article

In this study, the microbiomes linked with the operational parameters in seven mesophilic full-scale AD plants mainly treating food waste (four plants) and sewage sludge (three plants) were analyzed. The results obtained indicated lower diversity and evenness of the microbial population in sludge digestion (SD) plants compared to food digestion (FD) plants. Candidatus Accumulibacter dominated (up to 42.1%) in SD plants due to microbial immigration from fed secondary sludge (up to 89%). Its potential activity in SD plants was correlated to H₂ production, which was related to the dominance of hydrogenotrophic methanogens (Methanococcus). In FD plants, a balance between the hydrogenotrophic and methylotrophic pathways was found, while Flavobacterium and Levilinea played an important role during acidogenesis. Levilinea also expressed sensitivity to ammonia in FD plants. The substantial differences in hydraulic retention time (HRT), organic loading rate (OLR), and total ammonium nitrogen (TAN) among the studied FD plants did not influence the archaeal methane production pathway. In addition, the bacterial genera responsible for acetate production through syntrophy and homoacetogenesis (Smithella, Treponema) were present in all the plants studied. Full article

The evaluation of effluent wastewater quality mainly relies on the assessment of conventional bacterial indicators, such as fecal coliforms and enterococci; however, little is known about opportunistic pathogens, which can resist chlorination and may be transmitted in aquatic environments. In contrast to conventional microbiological methods, high-throughput molecular techniques can provide an accurate evaluation of effluent quality, although a limited number of studies have been performed in this direction. In this work, high-throughput amplicon sequencing was employed to assess the effectiveness of chlorination as a disinfection method for secondary effluents. Common inhabitants of the intestinal tract, such as Bacteroides, Arcobacter and Clostridium, and activated sludge denitrifiers capable of forming biofilms, such as Acidovorax, Pseudomonas and Thauera, were identified in the chlorinated effluent. Chloroflexi with dechlorination capability and the bacteria involved in enhanced biological phosphorus removal, i.e., Candidatus Accumulibacter and Candidatus Competibacter, were also found to resist chlorination. No detection of Escherichia indicates the lack of fecal coliform contamination. Mycobacterium spp. were absent in the chlorinated effluent, whereas toxin-producing cyanobacteria of the genera Anabaena and Microcystis were identified in low abundances. Chlorination significantly affected the filamentous bacteria Nocardioides and Gordonia, whereas Zoogloea proliferated in the disinfected effluent. Moreover, perchlorate/chlorate- and organochlorine-reducing bacteria resisted chlorination. Full article

The removal of antibiotics and widespread of antibiotic resistance genes (ARGs) have received continuous attention due to the possible threats to environment. However, little information is available on the evolution of antibiotic resistance and the relationship between ARGs and microbial communities under long-term exposure to sub-inhibitory concentrations of antibiotics. In our study, two laboratory-scale anoxic-aerobic wastewater treatment systems were established and operated for 420 days to investigate the evolution of antibiotic resistance under exposure of 5 mg·L⁻¹ tetracycline (TC) or 5 mg·L⁻¹ TC and 1 mg·L⁻¹ sulfamethoxazole (SMX). The average removal rates of TC and SMX were about 59% and 72%, respectively. The abundance of the main ARGs responsible for resistance to TC and SMX increased obviously after antibiotics addition, especially when TC and SMX in combination (increased 3.20-fold). The tetC and sul1 genes were the predominant genes in the development of TC and SMX resistance, in which gene sul1 had the highest abundance among all the detected ARGs. Network analysis revealed that under antibiotic pressure, the core bacterial groups carrying multiple ARGs formed and concentrated in about 20 genera such as Dechloromonas, Candidatus Accumulibacter, Aeromonas, Rubrivivax, in which intI1 played important roles in transferring various ARGs except sul3. Full article

Using sludge obtained from municipal sewage treatment plants, the response of viable bacterial populations during the sludge ozonation process was investigated by a combination of adenosine triphosphate (ATP) assay and propidium monoazide (PMA)-Miseq sequencing. The ATP assay was first optimized for application on sludge samples by adjusting the sludge solid contents and reaction time. PMA-modified polymerase chain reaction (PCR) was also optimized by choosing the suitable final PMA concentration. The quantity and composition of viable bacterial populations during sludge ozonation were further elucidated using the optimized ATP and PMA-modified PCR methods. The results indicated that after the sludge was exposed to ozone (O₃) at 135 mg·O₃/g total suspended solids (TSS), the viable biomass displayed a substantial decrease, with a reduction rate reaching 70.89%. The composition of viable bacterial communities showed a faster succession, showing that an ozone dosage of 114 mg·O₃/g TSS is enough to significantly change the viable bacterial population structure. Floc-forming genera, such as Zoogloea, Ferruginibacter, Thauera and Turneriella, are sensitive to ozonation, while the relative abundances of some functional bacterial genera, including SM1A02, Nitrospira and Candidatus Accumulibacter, remained constant or increased in the viable bacterial population during sludge ozonation, indicating that they are more resistant to ozonation. Full article