Sustained anaerobic degradation of 4-chloro-2-methylphenoxyacetic acid by acclimated sludge in a continuous-flow reactor

Comprehensive study of flusulfinam in paddy water-sediment microcosms: Enantioselective fate, degradation pathways, and toxicity assessment

Flusulfinam, a novel chiral herbicide, demonstrates effective weed control in paddy fields. Nevertheless, a comprehensive investigation into its environmental fate in paddy systems, particularly at the enantiomeric level, remains deficient. Herein, paddy water-sediment microcosms were constructed across four sites to explore the enantiomeric behavior of flusulfinam. Enantioselective environmental behavior results show S-flusulfinam was found to preferentially accumulate in sediment, while R-flusulfinam showed preferential degradation in water and the overall system. Following this, the metabolic pathway of flusulfinam in the microcosms was also proposed. Eight metabolites were identified for the first time, and the synthesis and quantification of main metabolites M299 and M100 further substantiated the proposed flusulfinam metabolic pathways. In addition, enantioselective of R-M299 was also found in the Anhui microcosms. As predicted by Toxicity Estimation Software Tool, acute toxicity assessments revealed that M299 and M100 exhibit lower toxicity toward Danio rerio larvae and Selenastrum capricornutumwere compared to flusulfinam. Then, Illumina sequencing revealed that the degradation of flusulfanam had a significant impact on the abundance of key microbial genera, including Anaeromyxobacter, Nitrospira, Reyranella, and Sphingomonas. Overall, this study offers novel insights into the enantioselective fate of flusulfinam in paddy water-sediment ecosystems, provides a valuable reference for the assessment of environmental and ecological risks associated with flusulfinam. Finally, the R-flusulfinam is considered the safer enantiomer, as evidenced by its preferential degradation in microcosms systems and our prior research highlighting the high efficacy and low toxicity characteristic of R-flusulfinam.

Acclimation Time Enhances Adaptation of Heterotrophic Nitrifying-Aerobic Denitrifying Microflora to Linear Anionic Surfactant Stress

Linear anionic surfactants (LAS) pose significant stress to microbial denitrification in wastewater treatment. This study investigated the performance and adaptation mechanisms of heterotrophic nitrification-aerobic denitrification (HN-AD) microbial consortia under LAS exposure after short-term (SCM, 2 months) and long-term (LCM, 6 months) acclimation. Results showed a dose-dependent inhibition of total nitrogen (TN) removal, with LCM achieving 97.40% TN removal under 300 mg/L LAS, which was 16.89% higher than SCM. Biochemical assays indicated that LCM exhibited lower reactive oxygen species (ROS) levels, a higher ATP content, and reduced LDH release, suggesting enhanced oxidative stress resistance and membrane stability. EPS secretion also increased in LCM, contributing to environmental tolerance. Metagenomic analysis revealed that long-term acclimation enriched key genera including Pseudomonas, Aeromonas, and Stutzerimonas, which maintained higher expression of denitrification (e.g., nosZ, nirS) and ammonium assimilation genes (glnA, gltB). Although high LAS concentrations reduced overall community diversity and led to convergence between SCM and LCM structures, LCM retained greater functional capacity and stress resistance. These findings underscore the importance of acclimation in sustaining denitrification performance under surfactant pressure and offer valuable insights for engineering robust microbial consortia in complex wastewater environments.

Efficiently intensified nitrogen transformation in electrolysis-integrated constructed wetlands: Comparative performance and mechanism

This study developed constructed wetlands (CWs) with direct current (DC) electrolysis and iron-carbon (IC) microelectrolysis. Ammonium removal was more significantly enhanced with IC by 12.7-27.3 %, while the promotion of DC only existed with lower voltage. DC electrolysis continuously promoted nitrate conversion by 5.7-13.3 % compared to the control. Total nitrogen removal was 75.0-92.7 % and 85.4-93.4 % with DC and IC electrolysis, respectively limited by ammonium and nitrite accumulation. Bioelectrolysis enriched nitrifying bacteria such as Ellin6067, Nitrospira, and Nitrosomonas. Moreover, IC stimulated hydrogenotrophic denitrifying bacteria (Paracoccus, Pseudomonas, and Dechloromonas) and up-regulated gene narG, narH, and narI, aligned with higher nitrate reductase activity. In contrast, DC caused higher abundance involved in electroautotrophic denitrifying bacteria (Thiobacillus) and genes of assimilatory nitrate and nitrite reduction (narB and nirA). Additionally, both electrolysis stimulated electron production and energy metabolism for nitrogen cycling. This work provided comparative methods to intensify nitrogen transformation in CW systems.

Invisible threats from typical endocrine disrupting compounds in estuarine environments caused by continuing seawater incursion: In-situ evidence of bio-geochemical processes captured by diffusive gradients in thin films

Continued seawater incursion significantly affects the fate of pollutants in coastal estuaries, yet understanding of the in-situ behavior of endocrine-disrupting compounds (EDCs) in these areas remains limited. The distribution, transport and microbial response of two model EDCs, bisphenol A (BPA) and nonylphenol (NP), in three estuarine zones of slight (SZ), moderate (MZ) and complete (CZ) seawater incursion were investigated in-situ. Results showed seawater incursion reshaped the environmental gradients of the coastal estuaries on a spatial scale. Varying salinity gradient and tidal hydrodynamic conditions altered the dependence of EDCs on organic carbon, and promoted the release of accumulated EDCs from estuarine sediments resulting in the lowest residues of BPA (2.74 ± 0.76 μg/kg) and NP (10.25 ± 5.86 μg/kg) in the MZ. The resupply potential of BPA (R = 0.171 ± 0.058) and NP (R = 0.107 ± 0.015) from sediment to porewater was significantly higher in the SZ than in other zones (p < 0.001), due to both higher contaminant accumulation in this zone and inhibited resupply in MZ and CZ caused by seawater incursion. Furthermore, seawater incursion significantly reduced the microbial community diversity in the CZ (p < 0.001), being dominated by Vibrio (67.00 ± 1.13 %), and accordingly weakened the ability to transform organic matter in this region. Based on predicted sea level rise and the transport characteristics of EDCs under increased seawater incursion, it is estimated that the cumulative additional release of BPA and NP in the estuary will reach 1.8 and 1.5 tons by 2100, respectively. In order to mitigate the risk of additional estuarine EDCs release due to seawater incursion, increasing vegetation cover, strict monitoring, and climate policy interventions may be effective strategies.

Study on the mechanism by which anaerobic organisms remove nitrogen and sulfur from low-C/N rare earth tail water simultaneously

The low-C/N limits the simultaneous removal of the high sulfate and high ammonia nitrogen content in the rare earth tail water. How bacteria cycle sulfur and nitrogen in this environment is still unknown. As a result, there is a pressing need to treat such complicated tail water. This study built an anaerobic reactor to treat the rare earth tail water and employed anaerobic microorganisms. Following 104 days of operation, the rates of nitrogen removal for nitrate and nitrite are above 90%, and the removal rates of ammonia nitrogen and sulfate could reach 14.36 mg/(L·day) and 21.31 mg/(L·day), respectively. To identify the nitrogen and sulfur cycle in the reactor, the bacterial population and gene abundance were characterized using 16S rRNA sequencing and functional gene prediction. The results demonstrated that nitrogen from ammonia was primarily eliminated via assimilation, while nitrogen from nitrate was primarily eliminated by denitrification, which was strongly associated with Comamonas. The principal mechanism for eliminating the sulfate is assimilation, which is linked to the bacterium SBR1031. In conclusion, the nitrogen and sulfur cycle theoretically supports the simultaneous removal of sulfate and ammonia nitrogen from rare earth tail water under low-C/N circumstances.

Green manure plants enhance atrazine degradation in agriculture soil through modulating rhizosphere microbial communities

The widespread use of atrazine in agriculture threatens soil health and the safety of agricultural products. In this study, the removal and mechanism of green manure plants (GMPs) hairy vetch (Vicia villosa Roth, VV) and ryegrass (Lolium perenne L., LP) to atrazine were investigated. The results showed that VV and LP show a certain tolerance to 5-25 mg/kg atrazine contamination compared to VV and LP without atrazine (VV0 and LP0), with LP exhibiting higher tolerance. Moreover, compared to CK, VV and LP significantly promoted the removal of atrazine by 13.49%∼26.41% and 13.98%∼23.42%, respectively. VV was more effective at lower concentrations (5-10 mg/kg), while LP showed better results at 25 mg/kg. Soil enzyme activities (catalase and urease), as well as bacterial abundance and diversity, were significantly increased by VV and LP treatments. LP had a stronger effect. The function analysis revealed that VV enhances the Cell growth and death pathway in the rhizosphere soil, while LP primarily boosts the Replication and repair pathway to cope with atrazine stress. This difference likely results from the distinct root structures of the two plants, which create varying rhizosphere environments. Additionally, VV and LP upregulate the Atrazine degradation pathway by enriching atrazine-degrading bacteria, thereby promoting atrazine removal. VV growth was affected under 25 mg/kg atrazine treatment, which may lead to lower Atrazine degradation pathway abundance in the rhizosphere compared to LP. This study provides a theoretical basis for selecting plant species for the remediation of atrazine-contaminated soils.

Enhanced Dechlorination of the Herbicide Acetochlor by an Anaerobic Consortium via Sulfate Acclimation

Acetochlor residues can contaminate anoxic habitats where anaerobic microbial transformation dominates. Herein, a highly efficient anaerobic acetochlor-degrading consortium ACT6 was enriched using sulfate and acetochlor as selection pressures. The acclimated consortium ACT6 showed an 8.7-fold increase in its ability to degrade acetochlor compared with the initial consortium ACT1. Two degradation pathways of acetochlor were found: reductive dechlorination and thiol-substitution dechlorination in the chloroacetyl group, in which the latter dominated. Acclimation enhanced the abundances of Desulfovibrio, Proteiniclasticum, and Lacrimispora from 0.7 to 28.0% (40-fold), 4.7 to 18.1% (4-fold), and 2.3 to 12.3% (5-fold), respectively, which were positively correlated with sulfate concentrations and acetochlor degradation ability. Three acetochlor-degrading anaerobes were isolated from the acclimated consortium ACT6, namely Cupidesulfovibrio sp. SRB-5, Proteiniclasticum sp. BAD-10, and Lacrimispora sp. BAD-7. This study provides new insights into the anaerobic catabolism of acetochlor and the anaerobic treatment of acetochlor in wastewater.

A novel simultaneous short-course nitrification, denitrification and fermentation process: bio-enhanced phenol degradation and denitrification in a single reactor

The feasibility of a simultaneous nitrification, denitrification and fermentation process (SNDF) under electric stirrer agitation conditions was verified in a single reactor. Enhanced activated sludge for phenol degradation and denitrification in pharmaceutical phenol-containing wastewater under low dissolved oxygen conditions, additional inoculation with Comamonas sp. BGH and optimisation of co-metabolites were investigated. At a hydraulic residence time (HRT) of 28 h, 15 mg/L of substrate as strain BGH co-metabolised substrate degraded 650 ± 50 mg/L phenol almost completely and was accompanied by an incremental increase in the quantity of strain BGH. Strain BGH showed enhanced phenol degradation. Under trisodium citrate co-metabolism, strain BGH combined with activated sludge treated phenol wastewater and degraded NO2--N from 50 ± 5 to 0 mg/L in only 7 h. The removal efficiency of this group for phenol, chemical oxygen demand (COD) and TN was 99.67%, 90.25% and 98.71%, respectively, at an HRT of 32 h. The bioaugmentation effect not only promotes the degradation of pollutants, but also increases the abundance of dominant bacteria in activated sludge. Illumina MiSeq sequencing research showed that strain BGH promoted the growth of dominant genera (Acidaminobacter, Raineyella, Pseudarcobacter) and increased their relative abundance in the activated sludge system. These genera are resistant to toxicity and organic matter degradation. This paper provides some reference for the activated sludge to degrade high phenol pharmaceutical wastewater under the action of biological enhancement.

Anaerobic Degradation of Dicamba via a Novel Catabolic Pathway by a Consortium Enriched from Deep Paddy Soil

Dicamba is widely used in the paddy field to control broadleaf weeds. Dicamba easily migrates to deep soil, which is anoxic; however, the anaerobic catabolism of dicamba in paddy soil is still unknown. In this study, an anaerobic dicamba-degrading consortium was enriched from deep paddy soil. The consortium completely degraded 0.83 mM dicamba within 7 days. Five metabolites were identified, one of which is a new metabolite, 2,5-dichlorophenol, and a novel anaerobic dicamba degradation pathway was proposed. 2.5 mM dicamba, 1.5-2.0% NaCl, and 20 mM electron acceptors Na2SO4, NaNO3, and FeCl3, and 0.5 mM or more of metabolites 3-CP and 2,5-DCP strongly inhibited the degradation efficiency. During enrichment, the microbial community of the consortium was significantly changed with OTU numbers, and diversity decreased. The study is valuable to elucidate the catabolism and ecotoxicology studies of dicamba in paddy soil and to facilitate the engineering application of anaerobic technology to treat dicamba-manufacturing wastewater.