Composition of bacterial communities in municipal wastewater treatment plant

Microbial community structure and functional characteristics in a membrane bioreactor used for real rural wastewater treatment

Membrane bioreactors (MBRs) have been widely used in the field of wastewater treatment because of their small footprint and high treatment efficiency. In this research, 10 rural wastewater treatment sites in China that employ the MBR process were systematically studied. Specifically, treatment of actual domestic wastewater using MBRs was examined by high-throughput 16S rRNA gene sequencing to explore the microbial community composition and perform function prediction. The data of water quality parameters revealed high removal rates of chemical oxygen demand and NH4+-N in all the sites. Proteobacteria were absolutely dominant in all the sites. Thauera, Nitrospira, Ferribacterium, and Dechloromonas were the main functional genera responsible for nitrogen and phosphorus removal at the tested sites. Nitrospira includes conventional nitrite-oxidizing bacteria and complete ammonia-oxidizing bacteria. Among them, 26 genes related to nitrogen metabolism were retrieved according to gene prediction, which verified the good NH4+-N removal efficiency at the tested sites. This study focuses on the analysis of microbial community structure and functional characteristics of MBR-based treatment systems for rural wastewater treatment, thereby providing a microbial basis for improving rural wastewater treatment processes.

The Gut-Brain Axis and Neuroinflammation in Traumatic Brain Injury

Traumatic brain injury (TBI) is a major global disability and mortality cause, with the gut-brain axis playing a crucial role in its pathophysiology. Neuroinflammation, triggered by microglia and astrocytes, contributes to neuronal damage and cognitive impairment. This paper aims to explore the relationship between the gut-brain axis and neuroinflammation in TBI and its potential implications for therapeutic interventions. A comprehensive review of the literature was conducted using PubMed, MEDLINE, and Google Scholar databases. Studies investigating the gut-brain axis, neuroinflammation, and TBI were included. Evidence suggests that TBI disrupts the gut-brain axis, leading to alterations in gut microbiota composition, intestinal permeability, and immune responses. These gut-related changes promote the activation of microglia and astrocytes in the central nervous system, contributing to neuroinflammation and neuronal damage. Conversely, interventions that modulate gut microbiota or reduce intestinal permeability have been shown to attenuate neuroinflammation and improve cognitive outcomes in TBI models. The gut-brain axis plays a significant role in the pathogenesis of neuroinflammation following TBI. Targeting the gut-brain axis through interventions that restore gut homeostasis and reduce intestinal permeability holds promise as a novel therapeutic strategy for mitigating neuroinflammation and improving cognitive function in TBI patients. Further research is needed to elucidate the specific mechanisms involved and to develop effective therapies based on this understanding.

Are adding carbon sources and activated sludge helpful to the full-scale packing-reinforced multistage biological contact oxidation process?

The performance of wastewater treatment plants (WWTPs) is closely related to the structure and function of microbial communities which are frequently regulated by inoculating carbon source or new microbes. However, the status of microbial communities may be determined by the homeostasis of the bioreactors or properties of the influent especially in full-scale wastewater treatment plants. In this study, a full-scale packing-reinforced multistage biological contact oxidation process (PMBCOP) was used for investigating the durative impacts of carbon source addition and new sludge inoculation on the structure, stability and metabolic pathways of microbial communities. The results showed that inoculation of carbon sources or new sludge significantly increased the diversity (Chao1 and Shannon index) and reciprocal cooperations among microorganisms which further improved the stability of microbial communities and the COD (by 15%) and NH3-N (by 3%) removal efficiencies. Proteobacteria and Bacteroidota were two dominant phyla in the system and were responsible for the main metabolic pathway, i.e. amino acid metabolism. Nevertheless, the modifications of key genera, stability, up-regulated metabolites and enriched metabolic pathways as well as the improved removal efficiencies were not able to persist. The resistant ability of microbial community declined after stopping adding carbon source and new sludge which resulted in the instability and low removal efficiencies of the PMBCOP and aroused the requirements on exploring deep homeostatic mechanism of microbial communities and new promoting strategies. This study provided new insights on the durative effects on the succession and metabolism of microbial communities combing with the performances of the full-scale wastewater treatment plant which is helpful for the management of full-scale WWTPs.

Treatment of cold pressed Zanthoxylum schinifolium oil wastewater: Process, sludge characteristics, and microbial diversity analysis using biochemical methods

Cold-pressed Zanthoxylum schinifolium oil wastewater (ZOW), rich in organic pollutants, poses serious environmental challenges. This study examined ZOW treatment using a biochemical process, analyzing changes in activated sludge (AS) characteristics and microbial diversity to clarify pollutant removal pathways. Optimal parameters were established for biological treatment: a temperature of 30 °C, mixed liquor suspended solids (MLSS) of 4000 mg/L, initial pH of 7.5, rotational speed of 200 rpm, and a hydraulic retention time (HRT) of 48 h. For flocculation, 400 mg/L of polymeric aluminum sulfate and 60 mg/L of amphoteric polyacrylamide at pH 8 were identified as ideal. The biochemical process significantly reduced chemical oxygen demand (94.03 ± 0.31%), total phosphorus (93.33 ± 0.25%), total nitrogen (97.03 ± 0.26%), and turbidity (98.97 ± 0.02%). AS characterization showed enhanced sedimentation, larger particle size, increased extracellular polymer production indicating greater adsorption capacity, and higher biomass. 16S rRNA sequencing revealed Proteobacteria and Bacteroidota as dominant taxa (>50%), with aerobic denitrifiers such as Chryseobacterium and Pseudomonas showing strong adaptation to ZOW. Functional annotation confirmed the AS community's efficacy in pollutant removal.

Sludge water: a potential pathway for the spread of antibiotic resistance and pathogenic bacteria from hospitals to the environment

Hospitals play an important role in the spread of antibiotic resistance genes (ARGs) and antimicrobial resistance (AMR). The ARGs present in hospital wastewater tend to accumulate in activated sludge, with different ARGs exhibiting varying migration rates. As a result, sludge water produced during the activated sludge treatment process may be a significant source of ARGs entering the environment. Despite this, research into the behavior of ARGs during sludge concentration and dewatering remains limited. This study hypothesizes that ARGs might exhibit new behaviors in sludge water during sludge concentration. Using metagenomic analysis, we explored the distribution and migration risks of ARGs and human pathogenic bacteria (HPB) in sludge water, comparing them with those in hospital wastewater. The findings reveal a strong correlation between ARGs in sludge water and hospital wastewater, with subtypes such as arlR, efpA, and tetR showing higher abundance in sludge water. Although the horizontal gene transfer potential of ARGs is greater in hospital wastewater than in sludge water, the resistance mechanisms and migration pathways are similar even when their HPB host associations differ. ARGs in both environments are primarily transmitted through coexisting mobile genetic elements (MGEs). This suggests that sludge water serves as a critical route for the release of hospital-derived ARGs into the environment, posing potential threats to public health and ecological safety.

Gene abundance and microbial syntrophy as key drivers of anaerobic digestion revealed through 16S rRNA gene and metagenomic analysis

Genes in microorganisms influence the biological processes in anaerobic digestion (AD). However, key genes involved in the four metabolic steps (hydrolysis, acidogenesis, acetogenesis, and methanogenesis) remain largely unexplored. This study investigated the abundance and distribution of key functional genes in full-scale anaerobic digesters processing food waste (FWDs) and municipal wastewater (MWDs) through 16S rRNA gene and shotgun metagenomic analysis. Our results revealed that FWDs exhibited a higher abundance of key genes in the metabolic steps, despite having significantly lower microbial diversity compared to MWDs. Pathways and genes associated with syntrophic oxidation of acetate (SAO) and butyrate (SBO) were more present in FWDs. SAO potentially used both the conventional reversed Wood-Ljungdahl pathway and its integration with the glycine cleavage system in FWDs, which complements pathways for acetate oxidation under ammonia stress conditions. Similarly, genes associated with SBO (atoB and croR) were notably more prevalent in FWDs compared to MWDs with an 8.4-fold and 108-fold increase, respectively, indicating the adaptation of SBO bacteria to convert butyrate into acetate. The higher abundance of key genes in FWDs was driven by microbes adapting to the feedstock compositions with higher levels of substrate content, volatile fatty acids, and ammonia. This study quantified the genes central to AD metabolism and uncovered the contributions of microbial diversity, gene abundance, syntrophy, and feedstock characteristics to the functionality of AD processes. These findings enhance understanding of the microbial ecology in AD and provide a foundation for developing innovative strategies to enhance biogas production and waste management.

Read-Across of Biotransformation Potential between Activated Sludge and the Terrestrial Environment: Toward Making It Practical and Plausible

Recent emphasis on the development of safe-and-sustainable-by-design chemicals highlights the need for methods facilitating the early assessment of persistence. Activated sludge experiments have been proposed as a time- and resource-efficient way to predict half-lives in simulation studies. Here, this persistence "read-across" approach was developed to be more broadly and robustly applicable. We evaluated 21 previously used reference plant protection products (PPPs) for their broader applicability in calibrating regression and classification models for predicting half-lives in soil (DT50OECD307) and water-sediment systems (DT50OECD308) based on their half-life in sludge and the organic carbon-water partition coefficient KOC as predictors. The calibrated regression models showed satisfactory predictions of DT50OECD307 for another 22 test PPPs. Performance was less satisfying for the prediction of DT50OECD308 for 46 active pharmaceutical ingredients (APIs), suggesting a need for expanding the set of calibration substances and more experimental KOC values. The classification models mostly correctly classified persistent and non-persistent test compounds for both PPPs and APIs, which is relevant for early-stage screening of persistence. Transformation products of the reference compounds in activated sludge samples were consistent with the reported degradation pathways in soil, particularly with respect to major aerobic, enzyme-catalyzed transformation reactions. Overall, "reading across" biotransformation in environmental compartments such as soils or sediments from experiments with activated sludge outperformed three widely used in silico approaches for estimating half-lives and hence has immediate potential to support early assessment of biodegradability when aiming to develop chemicals that are safe and sustainable by design.

Impact of fall ammonia fluctuations on winter nitrification in moving bed biofilm reactors

This pilot-scale study investigated nitrifying moving bed biofilm reactors (MBBRs) in a post-lagoon treatment setup over two years to evaluate the impact of seasonal ammonia fluctuations on winter nitrification. In Year 2, reactors without fall ammonia starvation achieved significantly higher winter ammonia removal (97.2 ± 1.5 %) and surface area ammonia removal rates (SARR) (0.69 ± 0.06 g N/m2·d) compared to Year 1 (63.7 ± 2.5 % ammonia removal, SARR of 0.35 ± 0.04 g N/m2·d), demonstrating the critical role of fall ammonia availability for winter nitrification. Biofilms in Year 2 were thinner and denser, with higher biomass concentrations, potentially supporting more active biomass and improved substrate uptake. Seasonal shifts and diversity loss were observed within the biofilm microbial community, and nitrifiers were identified as Nitrosomonadaceae and Nitrospiraceae. Moreover, linear relationships were explored between winter ammonia removals and two ratios: (1) days with influent ammonia levels ≤ 5 mg N/L to days with temperatures above 5 °C, and (2) average ammonia concentration during fall to peak winter ammonia concentration. The modeling results indicated that winter ammonia removal performance could be enhanced by minimizing low-ammonia periods in the fall and maximizing pre-winter ammonia concentration. Overall, this study not only provided a deeper understanding of the year-round nitrifying MBBR process but also highlighted the importance of maintaining adequate substrate levels during fall to ensure sufficient biomass accumulation and activity for robust winter nitrification performance. These findings are essential for enhancing wastewater treatment performance in cold climates and offer practical guidance for optimizing biofilm-based nitrification systems.

Relationship assessment of microbial community and cometabolic consumption of 2-chlorophenol

The relationship of microbial community and cometabolic consumption of 2-chlorophenol (2-CP) in a nitrifying sequencing batch reactor (SBR) was studied. The assessment of the population dynamics of the nitrifying sludge during the cometabolic 2-CP consumption with increasing ammonium (NH4+) concentrations in the SBR showed the presence of 39 different species of which 10 were always present in all cycles. Fifty-five percent of the species found were grouped as Proteobacteria (45% as β-proteobacteria and 10% as γ-proteobacteria class), 30% as Acidobacteria, and 15% as Deinococcus-Thermus phyla. NH4+ and cometabolic 2-CP consumption could be related to the presence and permanence of ammonium-oxidizing bacteria (AOB) species and heterotrophic bacteria, while the complete nitrification to the presence of nitrite-oxidizing bacteria (NOB) species. A correlation analysis showed that the complete and stable nitrifying performance (NH4+ consumption efficiencies (ENH4+-N) > 99% and nitrate production yields (YNO3--N) between 0.93 and 0.99), as well as the increase in specific rates (ammonium (qNH4+-N) and 2-CP (q2-CP-C) consumption and nitrate production (qNO3--N)), was associated with the homogeneity of the bacterial community (J index = 0.99). The increase in the proportion of individuals of AOB species such as Nitrosomonas oligotropha and Nitrosomonas marina was associated with the increase in qNH4+-N (r ≥ 0.69) and q2-CP-C (r ≥ 0.64) and, therefore, with the 2-CP cometabolic consumption in the SBR. Finally, the increase in the proportion of individuals of heterotrophic species such as Dokdonella ginsengisoli, Deinococcus peraridilitoris, Truepera radiovictrix, and Stenotrophobacter terrae was associated with the increase in q2-CP-C (r ≥ 0.59). KEY POINTS: • Thirty-nine bacterial species were identified in the nitrifying sludge population of the SBR. • β-Proteobacteria and Acidobacteria were the prevalent (85%) bacterial groups. • AOB and heterotrophic bacteria participate in NH4+ and cometabolic 2-CP consumption.

Enhanced Nitrogen Removal from a Recirculating Aquaculture System Using a Calcined FeS x -Packed Denitrification Bioreactor

In this study, a recirculating aquaculture system (RAS) was constructed, and a denitrification bioreactor was installed to enhance nitrogen removal. In addition, the nitrogen removal performance of the system was investigated. FeS x was prepared by calcining iron (Fe) and S0 powder, which was used as an electron donor for denitrification. In the phase using simulating aquaculture wastewater, the concentrations of NO2 --N and NH4 +-N in the RAS were lower than 0.20 and 0.50 mg/L, respectively, and NO3 --N gradually accumulated without the operation of the FeS x -packed denitrification bioreactor. After introducing cultured fish and operating the denitrification bioreactor, NO2 --N and NH4 +-N in the fish tank were lower than 0.01 mg/L and lower detection limit, respectively, and the NO3 --N removal efficiency was 79.04%. After 24 days of operation, the SO4 2- concentration was lower than 200 mg/L, and the pH was stable at around 7. The survival rate of fish was 95%, and they grew 6 to 7 cm at the end of the experiment. The average weight gain of fish was 5.31 g, and the culture density increased from the initial 10 to 26.54 kg/m3. Microbial community structure analysis showed that the diversity in the denitrification bioreactor operated in the RAS (RAS_Sludge) was higher than that in the reactor operated using synthetic wastewater (Synthetic_Sludge) due to the introduction of organic matter. Thermomonas, Longilina, Arenimonas, and Thiobacillus were dominant in RAS_Sludge, while unclassified genera were dominant in Synthetic_Sludge. Functional genes in RAS_Sludge and Synthetic_Sludge were predicted based on Functional Annotation of Prokaryotic Taxa, revealing differences in genes related to denitrification as well as sulfur and iron oxidation. This study provides a theoretical basis for the application of FeS x -based autotrophic denitrification technology in RASs, promoting it from theoretical research to engineering practice.

Assessment of Bacterial Community Structure, Associated Functional Role, and Water Health in Full-Scale Municipal Wastewater Treatment Plants

The present study collected wastewater samples from fourteen (14) full-scale wastewater treatment plants (WWTPs) at different treatment stages, namely, primary, secondary, and tertiary, to understand the impact of WWTP processes on the bacterial community structure, their role, and their correlation with environmental variables (water quality parameters). The findings showed that the bacterial communities in the primary, secondary, and tertiary treatment stages are more or less similar. They are made up of 42 phyla, 84 classes, 154 orders, 212 families, and 268 genera. Proteobacteria, Bacteroidetes, Cloacimonetes, Firmicutes, Euryarchaeota, Verrucomicrobia, Cyanobacteria, Desulfomicrobium, Thauera, Zavarzinia, and Nitrospirae, among others, dominated the bacterial community structure in all treatment stages. The biochemical oxygen demand was 7-12 times, chemical oxygen demand (COD) was 6 times, and total suspended solids (TSS) was 3.5 times higher in the wastewater than what the Central Pollution Control Board (CPCB) in New Delhi, India, allows as standard discharge. The correlation analysis using the Pearson r matrix and canonical correspondence analysis (CCA) also confirmed the fact that these water quality parameters (especially BOD and COD) play a pivotal role in deciphering the community structure in WWTPs.

New insight to the enriched microorganisms driven by pollutant concentrations and types for industrial and domestic wastewater via distinguishing the municipal wastewater treatment plants

Enriched microbial communities and their metabolic function were investigated from the three wastewater treatment plants (WWTPs), which were CWWTP (coking wastewater), MWWTP1 (domestic wastewater), and MWWTP2 (mixed wastewater with domestic wastewater and effluent from various industrial WWTPs that contained the mentioned CWWTP). Pollutant types and concentrations differed among the three WWTPs and the reaction units in each WWTP. CWWTP had a higher TCN and phenol concentrations than the MWWTPs, however, in MWWTP2 no phenol was discovered but 0.72 mg/L TCN was found in its anaerobic unit. RDA results revealed that COD, TN, TP, TCN, NO3--N, and phenol were the main factors influencing the microbial communities (P < 0.05). CPCoA confirmed the microbial community difference driven by pollutant types and concentrations (65.1% of variance, P = 0.006). They provided diverse growth environments and ecological niches for microorganisms, shaping unique bacterial community in each WWTP, as: Thiobacillus, Tepidiphilus, Soehngenia, Diaphorobacter in CWWTP; Saccharibacteria, Acidovorax, Flavobacterium, Gp4 in MWWTP1; and Mesorhizobium, Terrimicrobium, Shinella, Oscillochloris in MWWTP2. Group comparative was analyzed and indicated that these unique bacteria exhibited statistically significant difference (P < 0.01) among the WWTPs, and they were the biomarkers in each WWTP respectively. Co-occurrence and coexclusion patterns of bacteria revealed that the most of dominant bacteria in each WWTP were assigned to different modules respectively, and these microorganisms had a closer positive relationship in each module. Consistent with the functional profile prediction, xenobiotics biodegradation and metabolism were higher in CWWTP (3.86%) than other WWTPs. The distinct functional bacteria metabolized particular xenobiotics via oxidoreductases, isomerases, lyases, transferases, decarboxylase, hydroxylase, and hydrolase in each unit or WWTP. These results provided the evidences to support the idea that the pollutant types and concentration put selection stress on microorganisms in the activated sludge, shaping the distinct microbial community structure and function.

Simultaneous nitrification and denitrification framework for decentralized systems: Long-term study utilizing rope-type biofilm media under field conditions

This research introduces a novel approach to achieve simultaneous nitrification-denitrification (SND) under dynamic load conditions using a cost-effective rope-type biofilm technology. The approach represents a significant advancement in wastewater treatment, particularly beneficial for remote and decentralized communities. The biofilm-based SND process was developed using a pilot-scale flow-through reactor by implementing upstream carbon management with constant-timer-based aeration control versus dynamic-sensor-based aeration control strategies. The findings indicate that adding an upstream anaerobic pretreatment process to handle excess carbon plays a substantial role in achieving a sustainable SND process under a dynamic load environment using simple aeration on-off control. The most optimal nitrification performance of 0.32 g NH3-N/m2/d (89 % removal) was achieved under a 1-hour ON/30-minute OFF aeration. The process sustained an average bulk liquid DO of 5.16 mg/L and 3.80 mg/L during the aeration ON and OFF periods, respectively, facilitating a 0.13 g N/m2/d (41 %) total inorganic nitrogen (TIN) removal, notably, implementing advanced aeration strategies driven by DO, NH3, and NO3 sensors enhanced TIN removal efficiency to 72 %. The nitrification performance remained comparable (89 % removal), resulting in 3 and 10 mg N/L effluent ammonia and TIN concentration, respectively. Additionally, utilizing two multivariate approaches accounting for 82 % and 64 % of the variance, this study discerned patterns in monitored variables and performance. Additionally, the analysis underscored the difference of bulk liquid DO levels in the biofilm versus suspended systems inhibiting the SND process. Distinct bacterial communities were established in biofilms under aerobic, anaerobic, and SND conditions, with the SND reactor showing a hierarchy of functional group and enzymes, enriched sequentially from heterotrophs to denitrifiers, nitrifiers, and anammox bacteria. These innovations underline the potential of tailored control strategies to enhance a passive biofilm-based SND process efficiency under dynamic conditions, providing scalable solutions for diverse target water quality demands in remote communities and decentralized systems.

Refractory wastewater shapes bacterial assembly and key taxa during long-term acclimatization

Bacterial assembly and key taxa during long-term acclimatization in refractory wastewater treatment systems is of paramount importance for optimizing system performance and improving management strategies. Therefore, this study employed high-throughput sequencing, coupled with machine learning models and statistical analysis approaches, to comprehensively elucidate key features of bacterial communities and assembly processes in pesticide wastewater treatment systems. A nine-month monitoring showed substantial variation in diversity and composition of bacterial community between two interconnected biological treatment units (designated as BA and PA). Dynamics of bacterial communities in both units were similar. Moreover, water quality played crucial roles in regulating the bacterial community structure of activated sludge, which were primarily driven by deterministic patterns. Homogeneous selection contributed to 62.85 % and 64.43 % of the variations in BA and PA samples, respectively. Additionally, network analysis revealed significant modularity in bacterial compositions in both groups. Linear regression analysis identified major bacterial modules associated with metabolism and degradation functions. Notably, Module 2 in PA samples has significant positive correlations with functions related to metabolism of nucleotide, amino acid, and xenobiotics, as well as benzoate degradation. Furthermore, key taxa in ecological modules identified by Random Forest model, such as Pseudomonas, Sphingobium, and PHOS-HE28, were dominant populations with metabolism and degradation functions. Particularly, Sphingobium, appeared to be a potential multifunctional degrading bacterium, related to amino acid and xenobiotics metabolism, as well as fatty acid, valine, leucine, isoleucine, fluorobenzoate, and aminobenzoate degradation. These findings are important for developing operating strategies to maintain stable system performance during refractory wastewater treatment.

Assessing the effectiveness of performic acid disinfection on effluents: focusing on bacterial abundance and diversity

Poorly-treated wastewater harbors harmful microorganisms, posing risks to both the environment and public health. To mitigate this, it is essential to implement robust disinfection techniques in wastewater treatment plants. The use of performic acid (PFA) oxidation has emerged as a promising alternative, due to its powerful disinfection properties and minimal environmental footprint. While PFA has been used to inactivate certain microbial indicators, its potential to tackle the entire microbial community in effluents, particularly resistant bacterial strains, remains largely unexplored. The present study evaluates the efficacy of PFA disinfection on the microbial communities of a WWTP effluent, through microbial resistance mechanisms due to their membrane structure. The effluent microbiome was quantified and identified. The results showed that the number of damaged cells increases with CT, reaching a maximum for CT = 240 mg/L•min and plateauing around 60 mg/L•min, highlighting the optimal conditions for PFA-disinfection against microbial viability. A low PFA level with a 10-min contact time significantly affected the microbial composition. It is worth noting the sensitivity of several bacterial genera such as Flavobacterium, Pedobacter, Massilia, Exiguobacterium, and Sphingorhabdus to PFA, while others, Acinetobacter, Leucobacter, Thiothrix, Paracoccus, and Cloacibacterium, showed resistance. The results detail the resistance and sensitivity of bacterial groups to PFA, correlated with their Gram-positive or Gram-negative membrane structure. These results underline PFA effectiveness in reducing microbial levels and remodeling bacterial composition, even with minimal concentrations and short contact times, demonstrating its suitability for widespread application in WWTPs.

Comparative analysis of microbial community under acclimation of linear alkylbenzene sulfonate (LAS) surfactants and degradation mechanisms of functional strains

Linear alkylbenzene sulfonate (LAS) is one of the most widely used anionic surfactants and a common toxic pollutant in wastewater. This study employed high throughput sequencing to explore the microbial community structure within activated sludge exposed to a high concentration of LAS. Genera such as Pseudomonas, Aeromonas, Thauera and Klebsiella exhibited a significant positive correlation with LAS concentrations. Furthermore, Comamonas and Klebsiella were significantly enriched under the stress of LAS. Moreover, bacterial strains with LAS-degrading capability were isolated and characterized to elucidate the degradation pathways. The Klebsiella pneumoniae isolate L1 could effectively transform more than 60 % of 25 mg/L of LAS within 72 h. Chemical analyses revealed that L1 utilized the LAS sulfonyl group as a sulfur source to support its growth. Genomic and transcriptomic analyses suggested that strain L1 may uptake LAS through the sulfate ABC transport system and remove sulfonate with sulfate and sulfite reductases.

Response and recovery of nitrifying moving bed biofilm reactor systems exposed to 1°C with varying levels of ammonia starvation

This study investigated the impact of varying total ammonia nitrogen (TAN) feed levels along with water temperature decreases on the performance of nitrifying moving bed biofilm reactor (MBBR) at 1 °C and its recovery at 3 °C. Five MBBR reactors were operated with different TAN concentrations as water temperature decreased from 20 to 3 °C: reactor R1 at 30 mg N/L, reactor R2 at 20 mg N/L, reactor R3 at 15 mg N/L, reactor R4 at 10 mg N/L and reactor R5 at 0 mg N/L. The corresponding biofilm characteristics were also analyzed to understand further nitrifying MBBR under different TAN feeding scenarios. The findings revealed that the higher TAN levels were before reaching 1 °C, the better nitrification performance and the more biomass grew. However, the highest TAN concentration (30 mg N/L) might negatively affect the nitrification performance, the activity of nitrifiers, and the growth of biofilms at 1 °C because of the toxic effects of un-ionized or free ammonia (FA). It was observed that the activities of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) were affected by FA concentrations ranging from 0.2 to 0.7 mg N/L at 1 °C, but they could gradually be adapted to such inhibitory environment, with NOB recovering more quickly and robustly than AOB. The study identified 20 mg N/L (67 % of maximum influent TAN at 1 °C in R2 as the optimal TAN feeding concentration, achieving over 90 % TAN removal and a surface area removal rate (SARR) of 0.78 ± 0.02 g N/m2·d at 1 °C. Meanwhile, R2 also exhibited the highest biofilm mass, with total solids at 13.3 mg/carrier and volatile solids at 11.3 mg/carrier. As TAN was removed, nitrite accumulation was observed at 1 °C, and higher influent TAN concentrations prior to 1 °C appeared to delay the accumulation. When water temperature increased from 1 °C to 3 °C, nitrification performance improved significantly in all reactors without nitrite accumulation, and the higher TAN feeding in the previous stage led to faster recovery. Compared with 20 °C, biofilm became thinner and denser at 1 °C and 3 °C. Furthermore, this study revealed significant shifts in microbial community composition and nitrifier abundances in response to changes in water temperature and influent TAN levels. The dominant nitrifiers were identified as Nitrosomonadaceae (AOB) and Nitrospiraceae (NOB). At 1 °C, the nitrifier abundances were significantly correlated with SARRs, FA, and biofilm density. R2, which exhibited the best nitrification performance, maintained higher nitrifier abundances at 1 °C.

Distinct microbial communities enriched in water-saturated and unsaturated reactors influence performance of integrated hydroponics-microbial electrochemical technology

This study aimed to understand the wastewater treatment and electricity generation performance besides the microbial communities of the integrated Hydroponics-Microbial Electrochemical Technology (iHydroMET) systems operated with water-saturated and water-unsaturated reactors. The organics removal was slightly higher in the water-unsaturated system (93 ± 4 %) than in the water-saturated system (87 ± 2 %). The total nitrogen removal and electric voltage were considerably higher in the water-saturated system (42 ± 5 %; 111 ± 8 V per reactor) than in the water-unsaturated system (18 ± 3 %; 95 ± 9 V per reactor). The enhanced organics and nitrogen removal and high voltage output in respective conditions were due to the dominance of polysaccharide-degrading aerobes (e.g., Pirellula), anammox bacteria (e.g., Anammoximicrobium), denitrifiers (e.g., Thauera and Rheinheimera), and electroactive microorganisms (e.g., Geobacter). The differential performance governed by distinct microbial communities under the tested conditions indicates that an appropriate balancing of water saturation and unsaturation in reactors is crucial to achieving optimum iHydroMET performance.

Temperature-Driven Activated Sludge Bacterial Community Assembly and Carbon Transformation Potential: A Case Study of Industrial Plants in the Yangtze River Delta

Temperature plays a critical role in the efficiency and stability of industrial wastewater treatment plants (WWTPs). This study focuses on the effects of temperature on activated sludge (AS) communities within the A2O process of 19 industrial WWTPs in the Yangtze River Delta, a key industrial region in China. The investigation aims to understand how temperature influences AS community composition, functional assembly, and carbon transformation processes, including CO2 emission potential. Our findings reveal that increased operating temperatures lead to a decrease in alpha diversity, simplifying community structure and increasing modularity. Dominant species become more prevalent, with significant decreases in the relative abundance of Chloroflexi and Actinobacteria, and increases in Bacteroidetes and Firmicutes. Moreover, higher temperatures enhance the overall carbon conversion potential of AS, particularly boosting CO2 absorption in anaerobic conditions as the potential for CO2 emission during glycolysis and TCA cycles grows and diminishes, respectively. The study highlights that temperature is a major factor affecting microbial community characteristics and CO2 fluxes, with more pronounced effects observed in anaerobic sludge. This study provides valuable insights for maintaining stable A2O system operations, understanding carbon footprints, and improving COD removal efficiency in industrial WWTPs.

Bacterial networks and enzyme genes in bacterial floccules from hydrolysis and aeration reactors in a dairy wastewater treatment system

The dairy industry generates substantial wastewater, which is commonly treated using integrated anaerobic hydrolysis and aerated biofilm reactors. However, the bacterial composition and functional differences within the generated floccules remain unclear. In this study, we employed 16S rRNA and metagenomic sequencing to compare bacterial communities and enzyme gene profiles between suspended floccules from the hydrolysis ponds and the aeration ponds. Results revealed that the bacterial phyla Firmicutes, Proteobacteria, and Bacteroidetes dominated the wastewater treatment system and the relative abundance of these bacterial phyla varied in each pond. Additionally, the aeration ponds exhibited higher bacterial operational taxonomic units and enzyme gene abundance. Network analysis demonstrated a more complex bacterial network structure in the hydrolysis ponds compared to the aeration ponds. Furthermore, enzyme gene abundance revealed higher metabolic enzyme genes in the hydrolysis ponds, while signal transduction enzyme genes were more abundant in the aeration ponds. Notably, the top 10 bacterial genera, primarily Hydromonas in the hydrolysis ponds and Ferruginibacter in the aeration ponds, exhibited distinct contributions to signal transduction enzyme genes. Hydromonas dominated the metabolic enzyme genes in both ponds. These findings provide crucial insights for optimizing dairy wastewater treatment technologies.

Regulatory of salinity on assembly of activated sludge microbial communities and nitrogen transformation potential in industrial plants of the lower Yangtze River basin

This study aims to thoroughly investigate the impact mode of salinity carried by industrial wastewater on the anaerobic-anoxic-oxic (A2O) sludge in wastewater treatment plants (WWTPs). Through comprehensive investigation of the A2O stage activated sludge (AS) from 19 industrial WWTPs in the downstream area of the Yangtze River, China, A total of 38 samples of anaerobic sludge and oxic sludge were collected and analyzed. We found that salinity stress significantly inhibits the growth of the AS community, particularly evident in the anaerobic sludge community. Furthermore, the high-saline environment induces changes in the structure and functional patterns of the AS community, leading to intensive interactions and resource exchanges among microorganisms. Halophilic microorganisms may play a crucial role in this process, significantly impacting the overall community structure, especially in the oxic sludge community. Additionally, salinity stress not only suppresses the nitrogen transformation potential of the AS but also leads to the accumulation of nitrite, thereby increasing the emission potential of both NO and N2O, exacerbating the greenhouse effect of the A2O process in industrial WWTPs. The findings of this study provide necessary theoretical support for maintaining the long-term stable operation of the A2O sludge system in industrial WWTPs, reducing carbon footprint, and improving nitrogen removal efficiency.

Unbalanced predatory communities and a lack of microbial degraders characterize the microbiota of a highly sewage-polluted Eastern-Mediterranean stream

Wastewater pollution of water resources takes a heavy toll on humans and on the environment. In highly polluted water bodies, self-purification is impaired, as the capacity of the riverine microbes to regenerate the ecosystem is overwhelmed. To date, information on the composition, dynamics and functions of the microbial communities in highly sewage-impacted rivers is limited, in particular in arid and semi-arid environments. In this year-long study of the highly sewage-impacted Al-Nar/Kidron stream in the Barr al-Khalil/Judean Desert east of Jerusalem, we show, using 16S and 18S rRNA gene-based community analysis and targeted qPCR, that both the bacterial and micro-eukaryotic communities, while abundant, exhibited low stability and diversity. Hydrolyzers of organics compounds, as well as nitrogen and phosphorus recyclers were lacking, pointing at reduced potential for regeneration. Furthermore, facultative bacterial predators were almost absent, and the obligate predators Bdellovibrio and like organisms were found at very low abundance. Finally, the micro-eukaryotic predatory community differed from those of other freshwater environments. The lack of essential biochemical functions may explain the stream's inability to self-purify, while the very low levels of bacterial predators and the disturbed assemblages of micro-eukaryote predators present in Al-Nar/Kidron may contribute to community instability and disfunction.

Enhancing wastewater treatment efficiency: A hybrid technology perspective with energy-saving strategies

The study aimed to investigate how hybrid technology, combined with various intermittent aeration (IA) strategies, contributes to reducing the energy costs of wastewater treatment while simultaneously ensuring a high treatment efficiency. Even with IA subphases lasting half as long as those without aeration, and oxygen levels reduced from 3.5 to 1.5 mg O2/L, pollutants removal efficiency remains robust, allowing for a 1.41-fold reduction in energy consumption (EO). Hybrid technology led to a 1.34-fold decrease in EO, along with improved denitrification efficiency from 74.05 ± 4.71 to 81.87 ± 2.43 % and enhanced biological phosphorus removal from 35.03 ± 4.25 to 87.32 ± 3.64 %. The high nitrification efficiency may have been attributed to the abundance of Pseudomonas, Acinetobacter, and Rhodococcus, which outcompeted the genera of autotrophic nitrifying bacteria, suggesting that the hybrid system is favorable for the growth of heterotrophic nitrifiers.

Unveiling the power of COD/N on constructed wetlands in a short-term experiment: Exploring microbiota co-occurrence patterns and assembly dynamics

Constructed wetlands (CWs) are a cost-effective and environmentally friendly wastewater treatment technology. The influent chemical oxygen demand (COD)/nitrogen (N) ratio (CNR) plays a crucial role in microbial activity and purification performance. However, the effects of CNR changes on microbial diversity, interactions, and assembly processes in CWs are not well understood. In this study, we conducted comprehensive mechanistic experiments to investigate the response of CWs to changes in influent CNR, focusing on the effluent, rhizosphere, and substrate microbiota. Our goal is to provide new insights into CW management by integrating microbial ecology and environmental engineering perspectives. We constructed two groups of horizontal subsurface flow constructed wetlands (HFCWs) and set up three influent CNRs to analyse the microbial responses and nutrient removal. The results indicated that increasing influent CNR led to a decrease in microbial α-diversity and niche width. Genera involved in nitrogen removal and denitrification, such as Rhodobacter, Desulfovibrio, and Zoogloea, were enriched under medium/high CNR conditions, resulting in higher nitrate (NO3--N) removal (up to 99 %) than that under lower CNR conditions (<60 %). Environmental factors, including water temperature (WT), pH, and phosphorus (P), along with CNR-induced COD and NO3--N play important roles in microbial succession in HFCWs. The genus Nitrospira, which is involved in nitrification, exhibited a significant negative correlation (p < 0.05) with WT, COD, and P. Co-occurrence network analysis revealed that increasing influent CNR reduced the complexity of the network structure and increased microbial competition. Analysis using null models demonstrated that the microbial community assembly in HFCWs was primarily driven by stochastic processes under increasing influent CNR conditions. Furthermore, HFCWs with more stochastic microbial communities exhibited better denitrification performance (NO3--N removal). Overall, this study enhances our understanding of nutrient removal, microbial co-occurrence, and assembly mechanisms in CWs under varying influent CNRs.

Mechanisms of total phosphorus removal and reduction of β-lactam antibiotic resistance genes by exogenous fungal combination activated sludge

This study utilized Trichoderma and activated sludge to construct combined activated sludge (TAS). The metagenomic approach was employed to examine the shifts in microbial community structure and function of TAS under amoxicillin stress and investigate the mechanism underlying the reduction of β-lactam antibiotic resistance genes (β-ARGs). The findings demonstrated that the elevated aundance of glpa, glpd, ugpq, glpq, and glpb were primarily responsible for the reduction in total phosphorus (TP) removal by TAS. The increased abundance of Proteobacteria and Verrucomicrobia led to enhanced expression of ugpb, phnd, and phne, thereby improving the TP removal of TAS. Furthermore, antibiotic inactivation has gradually become the primary antibiotic resistance mechanism in TAS. Specifically, an increase in the abundance of OXA-309 in TAS will decrease the probability of amoxicillin accumulation in TAS. A decrease in β-ARGs diversity confirmed this. This study presents a novel approach to reducing antibiotic and ARG accumulation in sludge.

Metagenomic analysis reveals the distribution, function, and bacterial hosts of degradation genes in activated sludge from industrial wastewater treatment plants

For comprehensive insights into the bacterial community and its functions during industrial wastewater treatment, with a particular emphasis on its pivotal role in the bioremediation of organic pollutants, this study utilized municipal samples as a control group for metagenomic analysis. This approach allowed us to investigate the distribution, function, and bacterial hosts of biodegradation genes (BDGs) and organic degradation genes (ODGs), as well as the dynamics of bacterial communities during the industrial wastewater bioprocess. The results revealed that BDGs and ODGs associated with the degradation of benzoates, biphenyls, triazines, nitrotoluenes, and chlorinated aromatics were notably more abundant in the industrial samples. Specially, genes like clcD, linC, catE, pcaD, hbaB, hcrC, and badK, involved in the peripheral pathways for the catabolism of aromatic compounds, benzoate transport, and central aromatic intermediates, showed a significantly higher abundance of industrial activated sludge (AS) than municipal AS. Additionally, the BDG/ODG co-occurrence contigs in industrial samples exhibited a higher diversity in terms of degradation gene carrying capacity. Functional analysis of Clusters of Orthologous Groups (COGs) indicated that the primary function of bacterial communities in industrial AS was associated with the category of "metabolism". Furthermore, the presence of organic pollutants in industrial wastewater induced alterations in the bacterial community, particularly impacting the abundance of key hosts harboring BDGs and ODGs (e.g. Bradyrhizobium, Hydrogenophaga, and Mesorhizobium). The specific hosts of BDG/ODG could explain the distribution characteristics of degradation genes. For example, the prevalence of the Adh1 gene, primarily associated with Mesorhizobium, was notably more prevalent in the industrial AS. Overall, this study provides valuable insights into the development of more effective strategies for the industrial wastewater treatment and the mitigation of organic pollutant contamination.

Microbial community and gene dynamics response to high concentrations of gadolinium and sulfamethoxazole in biological nitrogen removal system

The impact of high antibiotic and heavy metal pollution levels on biological nitrogen removal in wastewater treatment plants (WWTPs) remains poorly understood, posing a global concern regarding the issue spread of antibiotic resistance induced by these contaminants. Herein, we investigated the effects of gadolinium (Gd) and sulfamethoxazole (SMX), commonly found in medical wastewater, on biological nitrogen removal systems and microbial characteristics, and the fate of antibiotic resistance genes (ARGs), metal resistance genes (MRGs), and mobile genetic elements (MGEs). Our findings indicated that high SMX and Gd(III) concentrations adversely affected nitrification and denitrification, with Gd(III) exerting a strong inhibitory effect on microbial activity. Metagenomic analysis revealed that high SMX and Gd(III) concentrations could reduce microbial diversity, with Thauera and Pseudomonas emerging as dominant genera across all samples. While the relative abundance of most ARGs decreased under single Gd(III) stress, MRGs increased, and nitrification functional genes were inhibited. Conversely, combined SMX and Gd(III) pollution increased the relative abundance of intl1. Correlation analysis revealed that most genera could host ARGs and MRGs, indicating co-selection and competition between these resistance genes. However, most denitrifying functional genes exhibited a positive correlation with MRGs. Overall, our study provides novel insights into the impact of high concentrations of antibiotics and heavy metal pollution in WWTPs, and laying the groundwork for the spread and proliferation of resistance genes under combined SMX and Gd pollution.

Linking the shifts in the metabolically active microbiota in a UASB and hybrid anaerobic-aerobic bioreactor for swine wastewater treatment

Due to the high concentration of pollutants, swine wastewater needs to be treated prior to disposal. The combination of anaerobic and aerobic technologies in one hybrid system allows to obtain higher removal efficiencies compared to those achieved via conventional biological treatment, and the performance of a hybrid system depends on the microbial community in the bioreactor. Here, we evaluated the community assembly of an anaerobic-aerobic hybrid reactor for swine wastewater treatment. Sequencing of partial 16S rRNA coding genes was performed using Illumina from DNA and retrotranscribed RNA templates (cDNA) extracted from samples from both sections of the hybrid system and from a UASB bioreactor fed with the same swine wastewater influent. Proteobacteria and Firmicutes were the dominant phyla and play a key role in anaerobic fermentation, followed by Methanosaeta and Methanobacterium. Several differences were found in the relative abundances of some genera between the DNA and cDNA samples, indicating an increase in the diversity of the metabolically active community, highlighting Chlorobaculum, Cladimonas, Turicibacter and Clostridium senso stricto. Nitrifying bacteria were more abundant in the hybrid bioreactor. Beta diversity analysis revealed that the microbial community structure significantly differed among the samples (p < 0.05) and between both anaerobic treatments. The main predicted metabolic pathways were the biosynthesis of amino acids and the formation of antibiotics. Also, the metabolism of C5-branched dibasic acid, Vit B5 and CoA, exhibited an important relationship with the main nitrogen-removing microorganisms. The anaerobic-aerobic hybrid bioreactor showed a higher ammonia removal rate compared to the conventional UASB system. However, further research and adjustments are needed to completely remove nitrogen from wastewater.

Up-flow anaerobic sludge blanket treatment of swine wastewater: Effect of heterologous and homologous inocula on anaerobic digestion performance and the microbial community

The effects of heterogenous (anaerobic sludge from treating distillery sewage, ASDS) and homologous (anaerobic sludge from treating swine wastewater, ASSW) inocula on anaerobic digestion and the microbial community in an up-flow anaerobic sludge blanket treating swine wastewater were compared. The highest chemical oxygen demand removal efficiencies with ASDS (84.8%) and ASSW (83.1%) were obtained with an organic loading rate of 15 kg COD/m3/d. For ASSW compared with ASDS, methane production efficiency was 15.3% higher and excess sludge production was 73.0% lower. The abundance of the cellulose hydrolyzing bacterium Clostridium sensu stricto_1 with ASDS (36.1%) was 1.5 times that with ASSW, while that of Methanosarcina with ASSW (22.9%) was > 100 times that with ASDS. ASDS reduced the content of pathogenic bacteria by 88.0%, while ASSW maintained a low level of pathogenic bacteria. ASSW greatly improved the methane production efficiency of wastewater and is more suitable for treating swine wastewater.

Synergistic analysis of performance, microbial community, and metabolism in aerobic granular sludge under polyacrylonitrile microplastics stress

Aerobic granular sludge (AGS) has proved to be a promising biotechnology for microplastics wastewater treatment. However, polyacrylonitrile microplastics (PAN MPs), the most widely used plastic in textile materials, have not been investigated. Therefore, the effect of the neglected PAN MPs on AGS at different concentrations (1, 10, and 100 mg/L) was evaluated. The results indicated that PAN MPs with 1 and 10 mg/L concentrations had no obvious effect on granular stability and nutrient removal performance, but greatly promoted the secretion of EPS. Remarkably, the granule structure was severely damaged under 100 mg/L PAN MPs. Moreover, microbial community analysis showed that phylum Proteobacteria played a dominant role in resistance to PAN MPs. Metabolic analysis further revealed that genes related to denitrification pathway (nasA, nirK, nirS and norB) and membrane transport were significantly inhibited under PAN MPs stress. This study may provide additional information on the treatment of microplastics wastewater using AGS.

Exposure of the static magnetic fields on the microbial growth rate and the sludge properties in the complete-mix activated sludge process (a Lab-scale study)

BACKGROUND

In this study, the effect of static magnetic fields (SMFs) on improving the performance of activated sludge process to enhance the higher rate of microbial growth biomass and improve sludge settling characteristics in real operation conditions of wastewater treatment plants has been investigated. The effect of SMFs (15 mT), hydraulic retention time, SRT, aeration time on mixed liquor suspended solids (MLSS) concentrations, mixed liquor volatile suspended solids (MLVSS) concentrations, α-factor, and pH in the complete-mix activated sludge (CMAS) process during 30 days of the operation, were evaluated.

RESULTS

There were not any differences between the concentration of MLSS in the case (2148.8 ± 235.6 mg/L) and control (2260.1 ± 296.0 mg/L) samples, however, the mean concentration of MLVSS in the case (1463.4 ± 419.2 mg/L) was more than the control samples (1244.1 ± 295.5 mg/L). Changes of the concentration of MLVSS over time, follow the first and second-order reaction with and without exposure of SMFs respectively. Moreover, the slope of the line and, the mean of α-factor in the case samples were 6.255 and, - 0.001 higher than the control samples, respectively. Changes in pH in both groups of the reactors were not observed. The size of the sluge flocs (1.28 µm) and, the spectra of amid I' (1440 cm-1) and II' (1650 cm-1) areas related to hydrogenase bond in the case samples were higher than the control samples.

CONCLUSIONS

SMFs have a potential to being considered as an alternative method to stimulate the microbial growth rate in the aeration reactors and produce bioflocs with the higher density in the second clarifiers.

Microbial denitrification characteristics of typical decentralized wastewater treatment processes based on 16S rRNA sequencing

Despite the widespread application of decentralized wastewater treatment (WWT) facilities in China, relatively few research has used the multi-media biological filter (MMBF) facilities to investigate the microorganism characteristics. This study utilizes 16S rRNA high-throughput sequencing (HTS) technology to examine the microbial biodiversity of a representative wastewater treatment (WWT) system in an expressway service area. The pathways of nitrogen removal along the treatment route were analyzed in conjunction with water quality monitoring. The distribution and composition of microbial flora in the samples were examined, and the dominant flora were identified using LEfSe analysis. The FAPROTAX methodology was employed to investigate the relative abundance of genes associated with the nitrogen cycle and to discern the presence of functional genes involved in nitrogen metabolism. On average, the method has a high level of efficiency in removing COD, TN, NH3-N, and TP from the effluent. The analysis of the microbial community identified a total of 40 phyla, 111 classes, 143 orders, 263 families, and 419 genera. The phyla that were predominantly observed include Proteobacteria, Acidobacteria, Chloroflexi, Actinobacteria, Nitrospirae, Bacteroidetes. The results show that the system has achieved high performance in nitrogen removal, the abundance of nitrification genes is significantly higher than that of other nitrogen cycle genes such as denitrification, and there are six nitrogen metabolism pathways, primarily nitrification, among which Nitrospirae and Nitrospira are the core differentiated flora that can adapt to low temperature conditions and participate in nitrification, and are the dominant nitrogen removal flora in cold regions. This work aims to comprehensively investigate the diversity and functional properties of the bacterial community in decentralized WWT processes.

Stress response and signalling of a low-temperature bioaugmentation system in decentralized wastewater treatment: Degradation characteristics, community structure, and bioaugmented mechanisms

Low temperatures present challenges for stable wastewater treatment operations in cold regions. Low-temperature effective microorganisms (LTEM) were added as a bioaugmentation strategy at a decentralized treatment facility to improve performance. The effects of a low-temperature bioaugmentation system (LTBS) with LTEM at low temperatures (4 °C) on organic pollutant performance, microbial community changes, and the metabolic pathways of functional genes and functional enzymes were studied. To explore the bioaugmentation mechanism of LTBS based on stress response and signalling. The results showed that the start-up time of the LTBS (S2) with LTEM was shorter (8 days) and that it removed COD and NH₄⁺-N at higher rates (87 % and 72 %, respectively) at 4 °C. LTEM effectively degraded complex macromolecular organics into small molecular organics, and decomposing sludge flocs and the changing the extracellular polymeric substances (EPS) structure removed more organics and nitrogen. LTEM and local microbial communities (nitrifying and denitrifying bacteria) improved the ability of organic matter degradation and denitrification of the LTBS and formed a core microbial community dominated by LTEM (Bacillus and Pseudomonas). Finally, based on the functional enzymes and metabolic pathways of the LTBS, a low-temperature strengthening mechanism consisting of 6 cold stress responses and signal pathways under low temperatures was formed. This study demonstrated that the LTEM-dominated LTBS could provide an engineering alternative for future decentralized wastewater treatment in cold regions.

Model-based fractionation of biomass in a biological nutrient removal system and its effect on the removal efficiencies

Fractionation of active biomass in a five-stage Bardenpho process was accomplished using an MS Excel wastewater treatment plant modeling tool based on Activated Sludge Model No. 3 extended with a bio-P module. The biomass fractions within the treatment system were predicted as autotrophs, ordinary heterotrophs, and phosphorus accumulating organisms (PAOs). Several simulations were performed in a Bardenpho process using various C/N/P ratios in primary effluent. Biomass fractionation was obtained from steady-state simulation results. The results suggest that the mass percentage of autotrophs, heterotrophs, and PAOs in active biomass range from 1.7 to 7.8%, 5.7-69.0%, and 23.2-92.6%, respectively, depending on characteristics of primary effluent. Results of principal component analysis showed that TKN/COD ratio in primary effluent determines the population of autotrophs and ordinary heterotrophs whereas PAO population is mainly a function of TP/COD ratio.

Research on microbial community structure and treatment of dye wastewater with the enhancement of activated sludge by magnetic field at low temperature

This study characterized the effect of different magnetic field (MF) intensities (10-40 mT) on the degradation of dye wastewater by activated sludge and the diversity of the microbial community at a low temperature (5 °C). The examined MF range promoted the degradation of dye wastewater by the microorganisms in the activated sludge at a low temperature. It was found that the optimal degradation performance was achieved at 30 mT. Additionally, the maximum degradation efficiency of COD and chromaticity (66.30% and 60.87%, respectively) were also achieved at 30 mT and the peak TTC-dehydrogenase activity (TTC-DHA) was 9.44 mg TF g^-1 SS. Furthermore, it was revealed that MF enhancement increased the richness and diversity of activated sludge microorganisms, thus promoting the growth and reproduction of activated sludge microorganisms at low temperatures. Bacterial taxa known to effectively participate in the degradation of pollutants by activated sludge were enriched at 30 mT. The dominant bacteria under 30 mT were Flavobacterium, Hydrogenophaga, Gemmatimonadaceae, Zoogloea, Saprospiraceae, Pseudomonas, and Geothrix.

Improvement of cadmium immobilization in contaminated paddy soil by using ureolytic bacteria and rice straw

Cadmium (Cd) in paddy soil can be immobilized via microbially induced carbonate precipitation (MICP), but it poses a risk to the properties and eco-function of the soil. In this study, rice straw coupled with Sporosarcina pasteurii (S. pasteurii) was used to treat Cd-contaminated paddy soil with minimizing the detrimental effects of MICP. Results showed that the application of rice straw coupled with S. pasteurii reduced Cd bioavailability. The X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) confirmed that Cd immobilization efficiency was increased in the rice straw coupled with S. pasteurii treatment via co-precipitating with CaCO₃. Moreover, rice straw coupled with S. pasteurii enhanced soil fertility and ecological functions as reflected by the high amount of alkaline hydrolysis nitrogen (AN) (14.9 %), available phosphorus (AP) (13.6 %), available potassium (AK) (60.0 %), catalase (9.95 %), dehydrogenase (736 %), and phosphatase (214 %). Further, the relative abundance of dominant phyla such as Proteobacteria and Firmicutes significantly increased when applying both rice straw coupled with S. pasteurii. The most significant environmental factors that affected the composition of the bacterial community were AP (41.2 %), phosphatase (34.2 %), and AK (8.60 %). In conclusion, using rice straw mixed with S. pasteurii is a promising application to treat Cd-contaminated paddy soil due to its positive effects on treating soil Cd as well as its ability to reduce the detrimental effects of the MICP process.

Microplastic biofilm, associated pathogen and antimicrobial resistance dynamics through a wastewater treatment process incorporating a constructed wetland

Microplastics in wastewater are colonized by biofilms containing pathogens and antimicrobial resistance (AMR) genes that can be exported into receiving water bodies. This study investigated establishment and changes in microplastic-associated biofilm and AMR during a conventional full-scale 2100 population equivalent wastewater treatment process combined with a free water surface polishing constructed wetland. Sequential microplastic colonization experiments were conducted at different stages of the wastewater treatment process, including in raw sewage, treated effluent and the constructed wetland. Two scenarios were tested in which the constructed wetland served as either (i) a polishing step or (ii) as primary recipient of sewage inoculated microplastics. Bacterial 16S rRNA gene sequencing was carried out for qualitative bacterial community analysis. qPCR was applied for quantitative analysis of AMR genes (sul1, ermB, tetW, intiI1), bacterial biomass (16S rRNA) and a human fecal marker (HF183). Microbial diversity on microplastics increased with incubation time. The initial sewage-derived biofilm composition changed more significantly in the wastewater effluent compared to the constructed wetland. Pathogen and AMR load decreased by up to two orders of magnitude after coupled conventional and constructed wetland treatment, while less impact was observed when sewage-inoculated microplastic material was directly transferred into the constructed wetland. Aeromonas, Klebsiella, and Streptococcus were key pathogenic genera correlated with AMR in microplastic-associated biofilms. Despite decreasing trends on human pathogens and AMR load along the treatment process, microplastic-associated biofilms were a considerable potential hotspot for AMR (intI1 gene) and accommodated Cyanobacteria and fish pathogens.

Analysis on the properties of hydrolyzed amino acids in typical municipal sludge

In this study, amino acids, proteins, and microbial communities in sludge from different wastewater treatment plants (WWTPs) were analyzed. The results showed that the bacterial communities of different sludge samples were similar at the phylum level, and the dominant bacterial species in sludge samples with the same treatment process were the consistent. The main amino acids in EPS of different layers were different, and the amino acid results of different sludge samples were quite different, but the content of hydrophilic amino acids in all samples was higher than that of hydrophobic amino acids. And the total content of glycine, serine, and threonine related to sludge dewatering was positively correlated with protein content in sludge. In addition, the content of nitrifying bacteria and denitrifying bacteria in sludge was also positively correlated with the content of hydrophilic amino acids. In this study, the correlations between proteins, amino acids, and microbial communities in sludge were analyzed respectively, and the internal relationship was found. And it provided ideas for further study of sludge dewatering characteristics in the future.

Impacts of dibutyl phthalate on bacterial community composition and carbon and nitrogen metabolic pathways in a municipal wastewater treatment system

Dibutyl phthalate (DBP) is a typical toxic and hazardous pollutant in pharmaceutical wastewater, affecting the metabolism of microbial flora, leading to decreased treatment efficiency, and deteriorated effluent quality in municipal wastewater treatment plants (WWTPs). This study conducted a long-term experiment with 6 operational stages in a pilot-scale A²O-MBR system, analyzing the effect of DBP on the bacterial community and their carbon and nitrogen metabolic pathways. 16S rRNA gene amplicon sequencing analysis and principal components analysis (PCA) showed that DBP at 8 mg/L significantly influenced the structure of bacterial community (P < 0.05), resulting in reduced bacterial community diversity. Metagenomic analysis was used to explore the embedded carbon and nitrogen metabolic pathways. At the presence of DBP, the metabolism of saccharides, lipids, and aromatic compounds were blocked owing to the vanishment of key enzyme (such as acetylaminohexosyltransferase (EC 2.4.1.92) and UDP-sugar pyro phosphorylase (EC 2.7.7.64)) encoding genes, resulting in weakened carbon metabolism, and thus reduced COD removal performance. The resultant deficiency of the genes such as those encoding hydroxyproline dehydrogenase (EC 1.5.5.3) gave rise to interrupted metabolic pathways of amino acid (arginine, proline, tyrosine, and tryptophan), resulting in declined function of nitrogen metabolism and thus reduced TN removal efficiency. The uncovery of the mechanisms by which DBP affects wastewater treatment system efficiency and microbial metabolism is of theoretical importance for the efficient operation of municipal and pharmaceutical wastewater treatment systems.

Seasonal monitoring of microbial activity using conventional approaches in a full-scale urban biological wastewater treatment plant

Activated sludge processes contain various groups of microorganisms with different metabolic properties, which are responsible for contaminants removal. Therefore, it is important to elucidate the general structure and functional properties of biomass in activated sludge processes. For this purpose, a full-scale domestic biological wastewater treatment plant in Tunceli (Turkey), Tunceli WWTP (wastewater treatment plant), was monitored to observe seasonal variations in process performance and biomass properties for a year. It was observed that nitrifying bacteria developed abundantly in the rainy and cool spring season as they were suppressed in summer because their large losses took place due to an environment containing high alkalinity values. In September, aerobic heterotrophic, nitrify, denitrify, and anaerobic activities increased. It can be said that the biomass contained young and mature microorganism in this environment in which the sludge volume index (SVI) value increased to 196 mL/g. As a result of the improvement in the structural and functional properties of biomass, the nitrogen removal efficiency reached 99%. Throughout the whole study, the structural improvement observed in biomass was reflected in its removal activity. The amount of biomass and removal activity decreased with the abundance of organic matter in the influent at the period in which biomass was closer to being categorized in the aged sludge class. The results showed that as the lowest mixed liquid suspended solids (MLSS) and mixed liquid volatile suspended solids (MLVSS) values of the year were 530 and 400 mg/L, respectively, in November 2017, MLSS and MLVSS values reached the highest amount (1700 and 1400 mg/L, respectively) in December 2017 when aerobic heterotrophic activity accelerated with a decrease in organic matter level.

Revealing the role of microalgae-bacteria niche for boosting wastewater treatment and energy reclamation in response to temperature

Conventional biological treatment usually cannot achieve the same high water quality as advanced treatment when conducted under varied temperatures. Here, satisfactory wastewater treatment efficiency was observed in a microalgae-bacteria consortia (MBC) over a wide temperature range because of the predominance of microalgae. Microalgae contributed more toward wastewater treatment at low temperature because of the unsatisfactory performance of the accompanying bacteria, which experienced cold stress (e.g., bacterial abundance below 3000 sequences) and executed defensive strategies (e.g., enrichment of cold-shock proteins). A low abundance of amoA-C and hao indicated that conventional nitrogen removal was replaced through the involvement of microalgae. Diverse heterotrophic bacteria for nitrogen removal were identified at medium and high temperatures, implying this microbial niche treatment contained diverse flexible consortia with temperature variation. Additionally, pathogenic bacteria were eliminated through microalgal photosynthesis. After fitting the neutral community model and calculating the ecological niche, microalgae achieved a maximum niche breadth of 5.21 and the lowest niche overlap of 0.38, while the accompanying bacterial community in the consortia were shaped through deterministic processes. Finally, the maximum energy yield of 87.4 kJ L^-1 and lipid production of 1.9 g L^-1 were achieved at medium temperature. Altogether, this study demonstrates that advanced treatment and energy reclamation can be achieved through microalgae-bacteria niche strategies.

High-throughput sequencing as a tool for monitoring prokaryote communities in a wastewater treatment plant

In this study, the DNA metabarcoding technique was used to explore the prokaryote diversity and community structure in wastewater collected in spring and winter 2020-2021 as well as the efficiency of the treatment in a wastewater treatment plant (WWTP) in Ría de Vigo (NW Spain). The samplings included raw wastewater from the inlet stream (M1), the discharge water after the disinfection treatment (M3) and mussels used as bioindicators of possible contamination of the marine environment. Significant differences were discovered in the microbiome of each type of sample (M1, M3 and mussels), with 92 %, 45 % and 44 % of exclusive OTUs found in mussel, M3 and M1 samples respectively. Seasonal differences were also detected in wastewater samples, with which abiotic parameters (temperature, pH) could be strongly involved. Bacteria present in raw wastewater (M1) were associated with the human gut microbiome, and therefore, potential pathogens that could be circulating in the population in specific periods were detected (e.g., Arcobacter sp. and Clostridium sp.). A considerable decrease in putative pathogenic organisms from the M1 to M3 wastewater fractions and the scarce presence in mussels (<0.5 % total reads) confirmed the effectiveness of pathogen removal in the wastewater treatment plant. Our results showed the potential of the DNA metabarcoding technique for monitoring studies and confirmed its application in wastewater-based epidemiology (WBE) and environmental contamination studies. Although this technique cannot determine if the infective pathogens are present, it can characterize the microbial communities and the putative pathogens that are circulating through the population (microbiome of M1) and also confirm the efficacy of depuration treatment, which can directly affect the aquaculture sector and even human and veterinary health.

Variations in antibiotic resistance genes and microbial community in sludges passing through biological nutrient removal and anaerobic digestion processes in municipal wastewater treatment plants

Antimicrobial resistance (AMR) represents a relentless, silent pandemic. Contributing to this are wastewater treatment plants (WWTPs), a potential source of antibiotic resistance genes' (ARGs) transmission to the environment, threatening public health. The presence of ARGs in pathogenic bacteria and their release into the environment by WWTPs threatens the public health. The current study investigated changes in ARGs' abundance in biological nutrient removal (BNR) processes and anaerobic digestion (AD) reactors of two WWTPs. Also, microbial community structure, which is known to shape the distribution and abundance of ARGs, was also analyzed. The relative abundance of eight ARGs (tetX, tetA, tetM, TEM, sul1, sul2, ermB and qnrD) was quantified as ARGs' copies/16 S rRNA gene copies using quantitative polymerase chain reaction (qPCR). Microbial community composition was assessed by 16 S rRNA microbiome sequencing analysis. TetX was prevalent among the eight ARGs, followed by TEM and sul1. However, its abundance was decreased in the AD sludges compared to BNR sludges. Proteobacteria was the major bacterial phylum found in all the sludge samples, while Arcobacter, 12up and Acidovorax were the predominant genera. Acinetobacter and Flavobacterium were significantly more abundant in the BNR sludges, while 12up and Aeromonas were predominant in AD sludges. Principal component analysis (PCA) revealed a clear difference in dominant ARGs and bacteria between the sludges in the processes of BNR and AD of the two WWTPs. Clinically relevant bacterial genera, Klebsiella and Enterococcus, found in both the BNR and AD sludges, were significantly correlated with the tetX gene. Throughout this study, the relationship between microbial communities and specific ARGs was revealed, illustrating that the composition of the microbial community could play a vital role in the abundance of ARGs. These results will better inform future studies aimed at controlling the spread of ARGs and their potential hosts from WWTPs.

Co-existence effect of copper oxide nanoparticles and ciprofloxacin on simultaneous nitrification, endogenous denitrification, and phosphorus removal by aerobic granular sludge

Nanoparticles and antibiotics are toxic to humans and ecosystems, and they inevitably coexist in the wastewater treatment plants. Hence, the co-existence effects and stress mechanism of copper (II) oxide nanoparticles (CuO NPs) and ciprofloxacin (CIP) on simultaneous nitrification, endogenous denitrification and phosphorus removal (SNEDPR) by aerobic granular sludge (AGS) were investigated here. The co-existence stress of 5 mg/L CuO NPs and 5 mg/L CIP resulted in the synergistic inhibitory effect on nutrient removal. Transformation inhibition mechanisms of carbon (C), nitrogen (N) and phosphorus (P) with CuO NPs and CIP addition were time-dependent. Furthermore, the long-term stress mainly inhibited PO₄^3--P removal by inhibiting phosphorus release process, while short-term stress mainly inhibited phosphorus uptake process. The synergistic inhibitory effect of CuO NPs and CIP may be due to the changes of physicochemical characteristics under the co-existence of CuO NPs and CIP. This further altered the sludge characteristics, microbial community structure and functional metabolic pathways under the long-term stress. Resistance genes analysis exhibited that the co-existence stress of CuO NPs and CIP induced the amplification of qnrA (2.38 folds), qnrB (4.70 folds) and intI1 (3.41 folds) compared with the control group.

Changes in the composition of bacterial communities and pathogen levels during wastewater treatment

Wastewater treatment plants have been described as a potential source of spreading pathogens to the receiving water. However, few studies are reporting the presence and concentration changes of pathogens in these matrices. High-throughput sequencing provides new insights into understanding the changes of bacterial communities throughout wastewater treatment plants (WWTPs). In this study, the changes in microbial community composition and the levels of representative pathogens of effluents during the wastewater treatment process in two municipal WWTPs (A and B) were analyzed using Illumina NovaSeq sequencing and qPCR. Proteobacteria was the most abundant phylum in all samples, accounting for 45.0-75.2% of the bacterial community, followed by Firmicutes, Bacteroidetes, Actinobacteria, and Nitrospirae. A slight difference was observed between the bacterial community compositions of WWTPs A and B. However, a significant difference in the community compositions of effluent samples at different treatment stages was observed. Nutrients had a more substantial impact on bacterial community composition than physicochemical factors. Most human-associated Bacteroides and Mycobacterium were eliminated during the wastewater treatment process in both WWTPs. The bacterial community richness in WWTP A was significantly higher than that in WWTP B. The results of this study will provide insights into the potential problems that exist in WWTPs. In turn, these insights can enable the efficient and stable operation of WWTPs and help prevent the spread of pathogens.

Impacts of dibutyl phthalate on biological municipal wastewater treatment in a pilot-scale A2/O-MBR system

Dibutyl phthalate (DBP) is a typical contaminant in pharmaceutical wastewater with strong bio-depressive properties which potentially affects the operation of municipal wastewater treatment systems. Based on a year-round monitoring of the quality of influent and effluent of a full-scale pharmaceutical wastewater treatment plant in Northeast China, the DBP was found to be the representative pollutant and its concentration in the effluent ranged 4.28 ± 0.93 mg/L. In this study, the negative effects of DBP on a pilot-scale A²/O-MBR system was investigated. When the influent DBP concentration reached 8.0 mg/L, the removals of chemical oxygen demand (COD) and total nitrogen (TN) were significantly inhabited (P < 0.01), with the effluent concentration of 54.7 ± 2.6 mg/L and 22.8 ± 3.7 mg/L, respectively. The analysis of pollutant removal characteristics of each process unit showed that DBP had the most significant effects on the removals of COD and TN in the anoxic tank. The α- and β-diversity in the system decreased significantly when the influent DBP concentration reached 8.0 mg/L. The impacts of DBP on known nitrifying bacteria, such as Nitrospira, and phosphorus accumulating organisms (PAOs), such as Cadidatus Accumulibacter, were not remarkable. Whereas, DBP negatively affected the proliferation of key denitrifying bacteria, represented by Simplicispira, Dechloromonas and Acinetobacter. This study systematically revealed the impacts of DBP on the pollutants removal performance and the bacterial community structure of the biological municipal wastewater treatment process, which would provide insights for understanding the potential impacts of residues in treated pharmaceutical wastewater on biological municipal wastewater treatment.

A novel aquatic worm (Limnodrilus hoffmeisteri) conditioning method for enhancing sludge dewaterability by decreasing filamentous bacteria

In this study, a novel aquatic worm conditioning method was proposed to enhance sludge dewaterability by reducing filamentous bacteria. The optimal treatment time was 4 days and the optimal sludge concentration was 5000 mg/L. Under these conditions, the sludge dewaterability was improved with CST of 16.69 s, reduction in sludge SRF of 48.95 %, and reduction in LfA of 58.23 %. After bio-conditioning, sludge flocs broke up by the aquatic worm predation. The absolute zeta potential decreased to -8.27 mV, and the particle size increased from 36.64 μm to 48.05 μm. Proteins, polysaccharides and other organic substances in sludge EPS and microbial cells were released, with the viscosity reduced to 1.16 mPa·s and the bound water converted into free water. Besides, the number and abundance of representative filamentous Chloroflexi decreased, resulting in the enhancement of sludge dewatering performance. Overall, the aquatic worm conditioning process can be divided into two steps: Sludge destruction by the aquatic worm predation and sludge re-coagulation by filamentous bacteria as a skeleton.

Microbial mechanisms of refractory organics degradation in old landfill leachate by a combined process of UASB-A/O-USSB

A combined process of anaerobic digestion (UASB), shortcut nitrification-denitrification (A/O), and semi-anoxic co-metabolism (operated by an up-flow semi-anoxic sludge bed; USSB) was constructed for the treatment of old landfill leachate (>10 years). The performance and mechanism of refractory organics degradation by the combined process (UASB-A/O-USSB) were investigated. The results showed that the semi-anoxic co-metabolism contributes 57 % of the totally degraded refractory organics. Specific microorganisms and their corresponding metabolic functions drive the degradation of refractory organics in each unit of the UASB-A/O-USSB process. In detail, organics with simple molecular structures were preferentially degraded by anaerobic digestion and shortcut denitrification, whereas those with complex structures were subsequently degraded in the oxic tanks and USSB reactor by shortcut nitrification and semi-anoxic co-metabolism. The structural equation model showed that the combined process of shortcut nitrification and semi-anoxic co-metabolism had a better effect on the degradation of recalcitrant organics than the single process. These findings provide information on how refractory organics are metabolically degraded in a combined process.

Airborne bacterial communities in the poultry farm and their relevance with environmental factors and antibiotic resistance genes

The accelerating occurrence and environmental dissemination of bacteria, gas pollutants and antibiotic resistance genes (ARGs) in aerosols of poultry farms have become emerging environmental issues due to their potential threat to animals, workers, and the communities located near such farms. Here, aerosol samples were gathered from inside and outside of the chicken house in winter with a transportable high-flow bioaerosol sampler. Then, 16S rRNA gene amplicon sequencing was used to categorize the bacteria in air samples, and the abundance of 12 ARG subtypes was researched via the real-time quantitative polymerase chain reaction (qPCR). Results indicated that the bacterial richness and diversity and total absolute abundance of ARGs were similar in the bioaerosols from indoor and downwind site of the poultry farm. The zoonotic pathogens, Staphylococcus and Corynebacterium, were detected both inside and outside of the chicken house, and the four most abundant target genes were bla_TEM, tetQ, ermB and sul1 in aerosols. Moreover, the correlation between the bacterial communities and environmental factors, such as NH₃ and H₂S concentrations, wind speed, temperature and relative humidity, was analyzed. The result revealed that the indoor bacteria community was positively associated with temperature and concentrations of air pollutants (NH₃ and H₂S), and could spread from confinement buildings to the ambient atmosphere through wind. In addition, the network analysis result showed that the airborne bacteria might significantly contribute in shaping the ARGs' profiles in bioaerosol from inside and outside of the poultry house. Overall, our results revealed the airborne bacterial communities and their associated influencing factors in the micro-environment (inside of the chicken house and nearby the boundary of the farm), and brought a new perspective for studying the gas pollutants and bioaerosol from poultry farms in winter.

Polyaniline-Derived Nitrogen-Containing Carbon Nanostructures with Different Morphologies as Anode Modifier in Microbial Fuel Cells

Anode modification with carbon nanomaterials is an important strategy for the improvement of microbial fuel cell (MFC) performance. The presence of nitrogen in the carbon network, introduced as active nitrogen functional groups, is considered beneficial for anode modification. In this aim, nitrogen-containing carbon nanostructures (NCNs) with different morphologies were obtained via carbonization of polyaniline and were further investigated as anode modifiers in MFCs. The present study investigates the influence of NCN morphology on the changes in the anodic microbial community and MFC performance. Results show that the nanofibrillar morphology of NCNs is beneficial for the improvement of MFC performance, with a maximum power density of 40.4 mW/m2, 1.25 times higher than the anode modified with carbonized polyaniline with granular morphology and 2.15 times higher than MFC using the carbon cloth-anode. The nanofibrillar morphology, due to the well-defined individual nanofibers separated by microgaps and micropores and a better organization of the carbon network, leads to a larger specific surface area and higher conductivity, which can allow more efficient substrate transport and better bacterial colonization with greater relative abundances of Geobacter and Thermoanaerobacter, justifying the improvement of MFC performance.