Bacterial diversity and population shifts driven by spotlight wastewater micropollutants in low-temperature highly nitrifying activated sludge

Static Magnetic Field Increases Polyhydroxyalkanoates Biosynthesis in Haloferax mediterranei: Parameter Optimization and Mechanistic Insights from Metabolomics

Polyhydroxyalkanoates (PHAs), as biosynthetic and biodegradable polymers, serve as alternatives to petroleum-based plastics, yet face critical cost barriers in large-scale production. While magnetic field (MF) stimulation enhances microbial activity, the optimal MF parameters and metabolic mechanisms for PHA biosynthesis remain unexplored. This study optimized magnetic field parameters to increase PHA biosynthesis in Haloferax mediterranei. A custom-engineered electromagnetic system identified 110 mT of static magnetic field (SMF) as the optimal level for biosynthesis, reaching 77.97 mg/(L·h) PHA volumetric productivity. A pulsed magnetic field caused oxidative stress and impaired substrate uptake despite increasing PHA synthesis. Prolonged SMF exposure (72 h) maximized PHA productivity, while 48 h of exposure attained 90% efficiency. Metabolomics revealed that SMF-driven carbon flux redirection via regulated butanoate metabolism led to a 2.10-fold increase in (R)-3-hydroxybutanoyl-CoA), while downregulating acetoacetate (0.51-fold) and suppressing PHA degradation (0.15-fold). This study pioneers the first application of metabolomics in archaea to decode SMF-induced metabolic rewiring in Haloferax mediterranei. Our findings establish SMF as a scalable bioenhancement tool, offering sustainable solutions for the circular bioeconomy.

Soil microbial community composition and nitrogen enrichment responses to the operation of electric power substation

The surge in global energy demand mandates a significant expansion of electric power substations. Nevertheless, the ecological consequences of electric power substation operation, particularly concerning the electromagnetic field, on soil microbial communities and nitrogen enrichment remain unexplored. In this study, we collected soil samples from six distinct sites at varying distances from an electric power substation in Xintang village, southeastern China, and investigated the impacts of electromagnetic field on the microbial diversity and community structures employing metagenomic sequencing technique. Our results showed discernible dissimilarities in the fungal community across the six distinct sites, each characterized by unique magnetic and electric intensities, whereas comparable variations were not evident within bacterial communities. Correlation analysis revealed a diminished nitrogen fixation capacity at the site nearest to the substation, characterized by low moisture content, elevated pH, and robust magnetic induction intensity and electric field intensity. Conversely, heightened nitrification processes were observed at this location compared to others. These findings were substantiated by the relative abundance of key genes associated with ammonium nitrogen and nitrate nitrogen production. This study provides insights into the relationships between soil microbial communities and the enduring operation of electric power substations, thereby contributing fundamental information essential for the rigorous environmental impact assessments of these facilities.

Riverine mycobiome dynamics: From South African tributaries to laboratory bioreactors

Riverine fungi have the capacity for both pathogenicity, pertinent for countries with elevated immunosuppressed individuals, and bioremediation potential. The purpose was (i) to screen for the presence of clinically relevant riverine fungi and associations with anthropogenic influence, and (ii) the acclimatisation of environmental communities toward potential bioremediation application. Communities were harvested from polluted rivers in Stellenbosch, South Africa, and mycobiomes characterised by high-throughput amplicon sequencing. The remainder of the biomass was inoculated into continuous bioreactors with filtered river water or sterile minimal medium. Seven weeks later, the mycobiomes were re-sequenced. At least nine clinically relevant species were detected, including agents of mycoses belonging to the genus Candida. The occurrence of genera that harbour opportunisticstrains was significantly higher (P = 0.04) at more polluted sites. Moreover, positive correlations occured between some genera and pollution indices, demonstrating the potential of fungi for addition to water quality indicators. Despite biomass increase, almost all pathogens were undetectable after seven weeks, demonstrating less resilience in conditions mimicking rivers. Thus, when screening riverine biomes for bioremediation potential, ambient reactors select against human pathogens. This indicates a transient introduction of allochthonous opportunistic species into rivers due to insufficient sanitation, and the potential of bioremediation strategies that selects for environmental rather than pathogenic traits.

The dangerous transporters: A study of microplastic-associated bacteria passing through municipal wastewater treatment

Microplastics (MPs) provide a stable and protective habitat for diverse wastewater bacteria, including pathogenic and antibiotic-resistant species. Therefore, MPs may potentially transport these bacteria through wastewater treatment steps to the environment and far distances. This study investigated bacterial communities of MP-associated bacteria from different stages of municipal wastewater treatment processes to evaluate the potential negative effect of these biofilms on the environment. The results showed a high diversity of bacteria that were strongly attached to MPs. After all treatment steps, the core bacterial groups remained attached to MPs and escaped from the wastewater treatment plant with effluent water. Several pathogenic bacteria were identified in MP samples from all treatment steps, and most of them were found in effluent water. These data provide new insights into the possible impacts of wastewater-derived MPs on the environment. MP-associated biofilms were proved to be important sources of pathogens and antibiotic-resistant genes in natural waters.

Acceleration of start-up of moving bed biofilm reactor at low temperature by adding specialized quorum sensing bacteria

This study aims to accelerate biofilm formation and operational performance of moving bed biofilm reactor (MBBR) at 5 ℃ by adding specialized Quorum Sensing bacteria (sphingomonas rubra BH3^T). Results showed that bio augmented MBBR (R_S) achieved a higher chemical oxygen demand and NH₄⁺-N removal rate (93% and 75%), which in accordance with its increased biofilm thickness, higher biofilm activity, and nitrifying bacteria abundance (Nitrospira). The increased biofilm thickness (60.23 %) during the whole operating time, accompanied by more potent adhesion force (61.59 %), was related to increased polysaccharides and proteins in the biofilm. Pyrosequencing analysis indicated that BH3^T contributed to higher species richness and triggered the rapid growth of precursor microorganisms (Nakamurella, Micropruina, and Zoogloea) and the enrichment of multifunctional microorganisms (Pseudomonas, Aeromonas, Arcobacter, Dechloromonas, and Flavobacterium) at low temperatures. This study provides an economical and practical new insight into accelerating start-up of MBBR system at low temperature.

Coupling Magnetic Field and Salinity Upshock To Improve Polyhydroxyalkanoate Productivity by Haloferax mediterranei Feeding on Molasses Wastewater

Low polyhydroxyalkanoate (PHA) volumetric productivity from wastewater limits low-cost PHA production. To resolve this problem, an external magnetic field (MF) coupled with upshock salinity was applied to PHA production by Haloferax mediterranei (family Halobacteriaceae). Elevating the fermentation salinity over the optimal growth salinity (200 g/L) increased the PHA cell content while inhibiting cell proliferation, decreasing volumetric productivity. When a MF of 50 mT in 300 g/L salinity was applied, H. mediterranei proliferation and PHA cell content were promoted, leading to a 7.95% increase in PHA volumetric productivity in synthetic molasses wastewater and a 13.82% increase in glucose feeding compared with those in 200 g/L salinity. Under the MF, osmotic pressure regulation was activated by accumulating K⁺ and increasing betaine synthesis. The maximum betaine content increased by 74.33% in 300 g/L salinity with a 50-mT MF compared with that in 200 g/L salinity. When a 50-mT MF in 300 g/L salinity was applied, the malondialdehyde (MDA) content decreased by 32.66% and the activity of superoxide dismutase (SOD) increased by 46.89%, which reduced the oxidative damage. This study provides a new solution to enhance PHA volumetric productivity by MF and an insight into the magnetic effects of H. mediterranei. IMPORTANCE The obstacle to replacing petroplastics with PHA is its high production cost. To increase the fermentation economy, a novel strategy of coupling a MF with salinity upshock was applied, which enhanced the PHA volumetric productivity of H. mediterranei in fermenting molasses wastewater. The magnetic effect of H. mediterranei was found at a MF of 50 mT, which improved the salt tolerance of H. mediterranei and reduced the oxidative damage induced by the elevated salinity, thereby promoting proliferation and PHA cell content. This is the first time a technical method for enhancing PHA volumetric productivity by means of a MF has been proposed. Such a strategy can advance the utilization of H. mediterranei for the industrial production of PHA using organic wastewater.

Comparison of pharmaceutical removal in two membrane bioreactors with/without powdered activated carbon addition

The present study investigates the removal of six selected pharmaceuticals from municipal wastewater in two membrane bioreactors (MBRs) with and without powdered activated carbon (PAC) addition. Two approaches were carried out for obtaining different carbon dosages related to the influent: (1) with a fixed solids retention time (SRT) and varying PAC concentrations; (2) with varying SRTs and a fixed PAC concentration. The results reveal that a PAC dosage related to influent of 21 mg L⁻¹ and SRT of 20 d are optimal. The first approach achieved a better removal performance than the second. The removal of amidotrizoic acid (up to 46%), bezafibrate (>92%) and iopromide (around 85%) were mainly caused by biological process, but were also enhanced by PAC addition. Efficient removal (>95%) of sulfamethoxazole, carbamazepine and diclofenac were highly dependent on the PAC dosage. However, carbamazepine shows re-metabolization properties during biological processing. Decreasing the SRT as done in the second approach, not only increased the PAC amount, but also decreased the mass of activated sludge and reduced the capability to degrade complex organic matter. Consequently, biodegradability and adsorbability played decisive roles in the removal of each compound.

The present study investigates the removal of six selected pharmaceuticals from municipal wastewater in two membrane bioreactors (MBRs) with and without powdered activated carbon (PAC) addition.

Removal of nickel(II) from wastewater using a zeolite-packed anaerobic bioreactor: Bacterial diversity and community structure shifts

In recent years, overexploited industrialization and urbanization activities have led to significant amounts of heavy metals released into the environment. Metal ion contamination of water, especially with toxic metals such as nickel(II) [Ni(II)], which is extensively applied in the electroplating industry, has been a serious problem. The aim of the present study was to evaluate the Ni(II) removal from real industrial wastewater using a 2 L, lab-scale, up-flow, anaerobic, zeolite-packed bioreactor inoculated with a heterotrophic consortium as the bioadsorbent. High-throughput sequencing of 16S rRNA genes revealed significant shifts in their bacterial diversity and structural composition along the bioreactor treatment location, where the bacterial genus was dominated by Kosmotogae followed by Firmicutes as Ruminococcus and Clostridium. However, Fervidobacterium and the Geobacter genus were absent at the end of the bioreactor treatment, suggesting that they play a key role in the beginning of Ni(II) removal anaerobic treatment. The physico-chemical results revealed that the Ni(II) removal rate was 99% for 250-500 ppm metal tested, with an efficient alkalinity rate and high production of biogas, which confirmed that anaerobic digestion of microorganisms was successfully performed through the process. Finally, this anaerobic bioreactor configuration offers an accessible and ecofriendly high-rate metal removal strategy from mining and electroplating effluents.

Effescts of acute diclofenac exposure on intestinal histology, antioxidant defense, and microbiota in freshwater crayfish (Procambarus clarkii)

In the present study, we exposed Procambarus clarkii to different doses (0, 1, and 10 mg/L) of diclofenac (DCF). Meanwhile, we investigated the effects of exposure to DCF on intestinal histology, antioxidant defense, and microbial communities in P. clarkii. The results showed DCF caused histological changes in the intestines. Additionally, DCF induced significant changes in the expression of antioxidant genes including Mn-sod, cat, gst, and gpx. High-throughput sequencing of 16 S rRNA gene revealed DCF changed the diversity, richness, and composition of intestinal microbial communities. The relative abundances of the predominant phyla Proteobacteria, Firmicutes, Bacteroidetes, and Actinobacteria showed significant changes at the phylum level after treatment with DCF. At the genus level, the most predominant genera with marked differences in abundance were Lucibacterium, Shewanella, Bacteroides, Anaerorhabdus, Aeromonas, Acinetobacter, Clostridium XlVb, Arcobacter, Bosea, and so on. To conclude, treatment with DCF could cause intestinal histological damage, induce significant changes of the expression of intestinal antioxidant genes, and impact the composition of intestinal microbiota in P. clarkii. This research will provide novel insights into the toxic effects of DCF on aquatic crustaceans.

Comparative evaluation on the utilization of applied electrical potential in a conductive granule packed biotrickling filter for continuous abatement of xylene: Performance, limitation, and microbial community

This study investigates the use of electrically conductive granules as packing material in biotrickling filter (BTF) systems as to provide insights on the specific microbial abundance and functions during the treatment of xylene-containing waste gas. In addition, the effect of applied potential on attached biofilm on conductive granules during xylene degradation was briefly investigated. During stable operation period, the conductive granules packed BTF achieved reactor performance of no less than 80% with a maximum EC of 137.7 g/m³ h. Under applied potential of 1V, the BTF system showed deterioration of xylene removal by ranging from 21 to 76%, which also affected the distribution and relative abundance of the major microorganisms such as Xanthobacter, Acidovorax, Rhodococcus, Hydrogenophaga, Arthrobacter, Brevundimonas, Pseudoxanthomonas, Devosia, Shinella, Sphingobium, Dokdonella, Pseudomonas and Bosea. The acclimation of applied potential led to the enrichment of autotrophic bacteria and strains, which are correlated to improved nitrogen cycling. In general, applying electrical potential is feasible to shape the microbiological structure of biofilms to selectively adjust their biochemical functions.

Low-Temperature Adapted Nitrifying Microbial Communities of Finnish Wastewater Treatment Systems

In this study, the microbial community of nitrifying activated sludge adapted to Finnish climate conditions was studied to clarify the microbial populations involved in low-temperature nitrification. Microbial community analysis of five full-scale wastewater treatment plants (WWTPs) showed several differences compared to WWTPs from other countries with a similar climate. In particular, very low abundance of ammonium oxidizing bacteria (AOBs) (altogether ˂ 0.25% of total community) as well as typical NOBs (˂0.35%) and a high abundance of orders Cytophagales and Micrococcales was observed in all Finnish WWTPs. To shed light on the importance of autotrophic and heterotrophic nitrifying processes, laboratory studies of activated sludge were carried out with a presence of and a lack of organic carbon in wastewater at 10 ± 1 °C. Two different sludge retention times (SRTs) were compared to determine the effect of this operational parameter on low-temperature nitrogen removal. The important role of previously reported Candidatus Nitrotogaarctica for nitrite oxidizing in cold climate conditions was confirmed in both full-scale and laboratory scale results. Additionally, potential participation of Dokdonella sp. and Flexibacter sp. in nitrogen removal at low-temperatures is proposed. Operation at SRT of 100 days demonstrated more stable and efficient nitrogen removal after a sharp temperature decrease compared to 14 days SRT.

Mercury/silver resistance genes and their association with antibiotic resistance genes and microbial community in a municipal wastewater treatment plant

Municipal wastewater treatment plants (WWTPs) are an important reservoir for heavy metal (e.g., Hg and Ag) resistance genes and antibiotic resistance genes (ARGs). However, current knowledge on Hg/Ag resistance genes and their association with ARGs in WWTPs remains largely unknown. In this study, the fates of five Hg/Ag resistance genes (merB, merD, merR, silE, and silR), five ARGs (sulI, sulII, tetO, tetQ, tetW), and class 1 integrase (intI1) in a WWTP were investigated. Results show that the absolute abundances of all target genes were greatly reduced through the treatment systems. The dynamics of merB, merD and silE were significantly correlated with tetW and sulII. Based on network analysis, Hg/Ag resistance genes might share the same microbial hosts with tetQ and tetW, implying the potential importance of Hg/Ag in ARGs evolution and spread. These findings advanced our understanding of the occurrence of Hg/Ag resistance genes and ARGs in WWTPs.

Applications of membrane bioreactors for water reclamation: Micropollutant removal, mechanisms and perspectives

Membrane bioreactors (MBRs) have attracted attention in water reclamation as a result of the recent technical advances and cost reduction in membranes. However, the increasing occurrence of micropollutants in wastewaters has posed new challenges. Therefore, we reviewed the current state of research to identify the outstanding needs in this field. In general, the fate of micropollutants in MBRs relates to sorption, biodegradation and membrane separation processes. Hydrophobic, nonionized micropollutants are favorable in sorption, and the biological degradation shows higher efficiency at relatively long SRTs (30-40 days) and HRTs (20-30 h), as a result of co-metabolism, metabolism and/or ion trapping. Although the membrane rejection rates for micropollutants are generally minor, final water quality can be improved via combination with other technologies. This review highlights the challenges and perspectives that should be addressed to facilitate the extended use of MBRs for the removal of micropollutants in water reclamation.

Effect of sulfadiazine and trimethoprim on activated sludge performance and microbial community dynamics in laboratory-scale membrane bioreactors and sequencing batch reactors at 8°C

The effect of antibiotics sulfadiazine and trimethoprim on activated sludge operated at 8°C was investigated. Performance and microbial communities of sequencing batch reactors (SBRs) and Membrane Bioreactors (MBRs) were compared before and after the exposure of antibiotics to the synthetic wastewater. The results revealed irreversible negative effect of these antibiotics in environmentally relevant concentrations on nitrifying microbial community of SBR activated sludge. In opposite, MBR sludge demonstrated fast adaptation and more stable performance during the antibiotics exposure. Dynamics of microbial community was greatly affected by presence of antibiotics. Bacteria from classes Betaproteobacteria and Bacteroidetes demonstrated the potential to develop antibiotic resistance in both wastewater treatment systems while Actinobacteria disappeared from all of the reactors after 60 days of antibiotics exposure. Altogether, results showed that operational parameters such as sludge retention time (SRT) and reactor configuration had great effect on microbial community composition of activated sludge and its vulnerability to antibiotics. Operation at long SRT allowed archaea, including ammonium oxidizing species (AOA) such as Nitrososphaera viennensis to grow in MBRs. AOA could have an important role in stable nitrification performance of MBR-activated sludge as a result of tolerance of archaea to antibiotics. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 35: e2708, 2019.

Use of aged sludge bioaugmentation in two-stage activated sludge system to enhance the biodegradation of toxic organic compounds in high strength wastewater

This research investigates the toxic organic compounds biodegradation efficiency of two-stage activated sludge systems with (bioaugmented) and without aged sludge bioaugmentation (non-bioaugmented). The influent was a mixture of leachate and agriculture wastewater (1:1, v/v), used as the representative high strength wastewater. The bioaugmented and non-bioaugmented systems were operated in parallel, with three levels (low, moderate, and high) of concentrations of organics, nitrogen, and toxic organic compounds in the influent (conditions 1, 2, and 3). The results showed that both systems could efficiently degrade the organic compounds. Nevertheless, the toxic organic compounds biodegradation efficiency of the bioaugmented system was higher than that of the non-bioaugmented one. The bioaugmentation enhanced the overall removal efficiency under conditions 1 and 2. However, the bioaugmented system became less effective under condition 3. Further analysis indicated that the bacterial groups essential to the toxic organic compounds biodegradation were abundant in the aged sludge, including heterotrophic bacteria, heterotrophic nitrifying bacteria, and nitrifying bacteria. The abundance of the effective bacteria improved the biodegradation and wastewater treatment performance of the bioaugmented system. In essence, the aged sludge bioaugmentation is a viable and eco-friendly solution to improving the treatment efficiency of the biological activated sludge system, despite limited biodegradation efficiency in an elevated compounds-concentration environment.

Nitrogen loading effects on nitrification and denitrification with functional gene quantity/transcription analysis in biochar packed reactors at 5 °C

This study investigated the nitrogen transformation rates of different nitrogen-loading (20, 30, and 50 mg TN/L) biochar packed reactors (C:N:P = 100:5:1) within 125 days at 5 °C. The results showed that high nitrogen loading resulted in an NH4+ (TN) removal efficiency decline from 98% (57%) to 83% (29%), with biochar yielding a higher NH4+, TN and DON removal rate than conventional activated sludge. Moreover, all biochar packed reactors realized a quick start-up by dropping in temperature stage by stage, and the effluent dissolved organic nitrogen (DON) concentrations of R20, R30, and R50 were 0.44 ± 0.18, 0.85 ± 0.35, and 0.66 ± 0.26 mg/L, respectively. The nirS/amoA, nxrA/amoA, and amoA/(narG + napA) were deemed to be the markers of ammonium oxidation rate (SAOR), specific nitrite oxidation rate (SNOR), and specific nitrate reduction rate (SNRR), respectively. Compared with functional gene quantity data, transcription data (mRNA) introduced into stepwise regression analyses agreed well with nitrogen transformation rates. High nitrogen loading also resulted in the cell viability decreased in R50. Nitrogen loadings and operation time both led to a significant variation in cell membrane composition, and unsaturated fatty acids (UFAs) significantly increased in R30 (46.49%) and R50 (36.34%). High-throughput sequencing revealed that nitrogen loadings increased the abundance of nitrifying bacteria (e.g., Nitrospira) and reduced the abundance of denitrifying bacteria (e.g., Nakamurella, Thermomonas, and Zoogloea) through linear discriminant analysis (LDA).

Performance and bacterial diversity of biotrickling filters filled with conductive packing material for the treatment of toluene

Toluene has high toxicity and mutagenicity, thus, the removal of toluene from air is necessary. In this study, two biotrickling filters (BTFs) were constructed and packed with conductive packing material to treat toluene waste gas. BTF-O exhibited good toluene removal performance even under high toluene inlet concentration, and over 80% of removal efficiency was observed. The elimination capacity reached 120.1 g/m³ h corresponding to an inlet concentration of 2.259 g/m³ under 61.5 s of empty bed retention time. During toluene biodegradation, the output voltage was observed in BTF-O and BTF-E, moreover BTF-E also showed slight power storage capacity. The applied voltage inhibited toluene removal and affected the bacterial community. The predominant bacterial genera in BTF-O were Acidovorax, Rhodococcus, Hydrogenophaga, Brevundimonas, Arthrobacter, Pseudoxanthomonas, Devosia, Gemmobacter, Rhizobium, Dokdonella and Pseudomonas. Genera Xanthobacter and Pelomonas accounted for the main bacterial community in BTF-E.