An attempt to stimulate aniline degrading bioreactor by exogenous auto-inducer: Decontamination performance, sludge characteristics, and microbial community structure response

Impacts of disinfectant and antipyretic on aged ethylene-vinyl acetate copolymer microplastics in hospital wastewater: Resistance genes, microbial community and carbon source metabolism

Global transmission of resistance genes (RGs) by non-antibiotic substances and microplastics (MPs) pollution deserves in-depth research and discussion. The impacts of the existence of benzethonium chloride (BZC) and acetaminophen (APAP) on pristine and aged ethylene-vinyl acetate copolymer (EVA) MPs in hospital wastewater had not been studied. In this study, RGs, microbial community composition and carbon source metabolism activity were explored on EVA plastisphere in hospital wastewater containing BZC and APAP. After aging treatment, EVA MPs showed an increase in particle size, cracks on the surface and changes in functional groups. Moreover, aged EVA MPs became an excellent carrier and transmitter of RGs and accelerated microbial colonization after soaking in wastewater containing BZC and APAP. The abundances of RGs in wastewater containing pollutants were 6.19-665.49 times higher than those in wastewater without pollutants. These results indicated that the coexistence of BZC and APAP had higher environmental risk compared with single existence. Furthermore, quaternary ammonium compounds RGs were enriched in wastewater and on plastisphere with the presence of BZC. Network analysis demonstrated that Nitrosomonas (5.76-25.25 %) and pathogen Legionella (0.01-40.75 %) had high abundances in wastewater and on plastisphere and the potential to transfer multiple RGs. This study will fill the knowledge gap on the changes in microbial community structure, RGs transmission and carbon source metabolism of pristine and aged EVA MPs in wastewater containing BZC and APAP.

Salinity stress and recovery of the algal-bacterial granular sludge (ABGS) system under the influence of different N-acyl-homoserine lactones (AHLs)

The algal-bacterial granular sludge (ABGS) system was established to explore the effect of 1% salinity condition, determine the recovery process following salinity disturbance, and probe the impacts of two N-acyl-homoserine lactones (AHLs) on the system. Exposure to 1% salinity led to the reduction of filaments and an increase in TB-EPS contents within the ABGS system. The phosphorus removal performance of the ABGS system severely decreased at 1% salinity and did not restore fully during the subsequent recovery stage, demonstrating that salinity stress induced long-term inhibition. Oligotrophic bacteria were found to be enriched at 1% salinity, indicating the self-adaptation of the ABGS system against salinity stress. The addition of AHLs helped mitigate the inhibitory effect of salinity stress. Specifically, C6-HSL slowed down the decline in microbial diversity, while 3-oxo-C12-HSL weakened the inhibition on microalgae growth. This study provided novel insights into the effects of salinity stress and AHLs on ABGS systems.

Redundancy and resilience of microbial community under aniline stress during wastewater treatment

Aniline is one of the most toxic and widespread organic pollutants. Although biological treatment is cost-effective and generates minimal secondary pollution, microbial communities are significantly affected by high aniline concentrations, which result in low degradation efficiency. However, a comprehensive understanding of the microbial community response to aniline stress is lacking. Here, we performed a cyclic experiment with aniline concentrations (200, 600, 1200, 600, and 200 mg/L) to investigate the ability of microbial communities to recover their performance after exposure to high aniline concentrations. At aniline concentrations up to 600 mg/L, the bioreactor exhibited high aniline removal efficiency (almost 100 %). Comamonas, Zoogloea, and Delftia played crucial roles in removing aniline and microbial beta diversity changed. Additionally, alpha diversity and network complexity decreased with increasing aniline concentration, but these metrics recovered to their original levels when the aniline concentration was returned to 200 mg/L. Homogeneous and heterogeneous selection dominated microbial community assembly. Therefore, according to the observed variations in community structure and the recovery of keystones after aniline stress, microbial community redundancy and resilience are pivotal for ensuring system stability. Overall, this study provides valuable insights into the redundancy and resilience of microbial communities under aniline stress and establishes a scientific basis for managing and evaluating wastewater treatment plants.

Unraveling the mechanisms and responses of aniline-degrading biosystem to salinity stress in high temperature condition: Pollutants removal performance and microbial community

To explore the intrinsic influence of different salinity content on aniline biodegradation system in high temperature condition of 35 ± 1 °C, six groups at various salinity concentration (0.0%-5.0%) were applied. The results showed that the salinity exerted insignificant impact on aniline removal performance. The low-level salinity (0.5%-1.5%) stimulated the nitrogen metabolism performance. The G5-2.5% had excellent adaptability to salinity while the nitrogen removal capacity of G6-5.0% was almost lost. Moreover, high throughput sequencing analysis revealed that the g__norank_f__NS9_marine_group, g__Thauera and g__unclassified_f__Rhodobacteraceae proliferated wildly and established positive correlation each other in low salinity systems. The g__SM1A02 occupying the dominant position in G5 ensured the nitrification performance. In contrast, the Rhodococcus possessing great survival advantage in tremendous osmotic pressure competed with most functional genus, triggering the collapse of nitrogen metabolism capacity in G6. This work provided valuable guidance for the aniline wastewater treatment under salinity stress in high temperature condition.

The potential effects of N-Acyl homoserine lactones on aerobic sludge granulation during phenolic wastewater treatment

The formation of aerobic granular sludge (AGS) is relatively difficult during the treatment of refractory wastewater, which generally shows small granular sizes and poor stability. The formation of AGS is regulated by N-Acyl homoserine lactones (AHLs)-mediated quorum sensing (QS). However, the potential role of AHLs in AGS formation under the toxic stress of refractory pollutants and the heterogeneity in the distribution and function of AHLs across different aggregates are not well understood. This study investigated the potential effects of AHLs on the formation of AGS during phenolic wastewater treatment. The distribution and succession of AHLs across varying granular sizes and development stages of AGS were investigated. Results showed that AGS was successfully formed in 13 days with an average granular size of 335 ± 39 μm and phenol removal efficiency of >99%. The levels of AHLs initially increased and then decreased. C4-HSL and 3-oxo-C10-HSL were enriched in large granules, suggesting they may play a pivotal role in regulating the concentration and composition of extracellular polymeric substances (EPS). The content of EPS constantly increased to 149.4 mg/gVSS, and protein (PN) was enriched in small and large granules. Luteococcus was the dominant genus constituting up to 62% after the granulation process, and exhibited a strong association with C4-HSL. AHLs might also regulate the bacterial community responsible for EPS production, and pollutant removal, and facilitate the proliferation of slow-growing microorganisms, thereby enhancing the formation of AGS. The synthesis and dynamics of AHLs were mainly governed by AHLs-producing bacterial strains of Rhodobacter and Pseudomonas, and AHLs-quenching strains of Flavobacterium and Comamonas. C4-HSL and 3-oxo-C10-HSL might be the major contributors to promoting sludge granulation under phenol stress and play critical roles in large granules. These findings enhance our understanding of the roles that AHLs play in sludge granulation under toxic conditions.

Integrated control strategy for dual sludge ages in the high-concentration powder carrier bio-fluidized bed (HPB) technology: Enhancing municipal wastewater treatment efficiency

The high-concentration powder carrier bio-fluidized bed (HPB) technology is an emerging approach that enables on-site upgrading of wastewater treatment plants (WWTPs). HPB technology promotes the formation of biofilm sludge with micron-scale composite powder carriers as the core and suspended sludge mainly composed of flocs surrounding the biofilm sludge. This study proposed a novel integrated strategy for assessing and controlling the sludge ages in suspended/bio-film activated sludge supported by micron-scale composite powder carrier. Utilizing the cyclone unit and the corresponding theoretical model, the proposed strategy effectively addresses the sludge ages contradiction between denitrifying bacteria and polyphosphate-accumulating organisms (PAOs), thereby enhancing the efficiency of municipal wastewater treatment. The sludge age of the suspended (25 d) and bio-film (99 d) sludge, calculated using the model, contribute to the simultaneous removal of nitrogen and phosphorus. Meanwhile, the model further estimates distinct contributions of suspended and bio-film sludge to chemical oxygen demand (COD) and total nitrogen (TN), which are 55% and 42% for COD, 20% and 57% for TN of suspended sludge and bio-film sludge, respectively. This suggests that the contribution of suspended sludge and bio-film sludge to COD and TN removal efficiency can be determined and controlled by the operational conditions of the cyclone unit. Additionally, the simulation values for COD, ammonia nitrogen (NH4+-N), TN and total phosphorus (TP) closely align with the actual values of WWTPs over 70 days (p < 0.001) with the correlation coefficients (R2) of 0.9809, 0.9932, 0.9825, and 0.837, respectively. These results support the theoretical foundation of HPB technology for simultaneous nitrogen and phosphorus removal in sewage treatment plants. Therefore, this model serves as a valuable tool to guide the operation, design, and carrier addition in HPB technology implementation.

Strengthen high-loading operation of wastewater treatment plants by composite micron powder carrier: Microscale control of carbon, nitrogen, and sulfur metabolic pathways

The concentration of activated sludge is a crucial factor influencing the capacity and efficiency of sewage wastewater treatment plants (WWTPs). However, high sludge concentrations can lead to sludge loss in the secondary sedimentation tank, resulting in reduced processing capacity, particularly during low-temperature stages and sludge bulking. This study investigated the impact of adding composite micron powder carriers (CMPC) in high-concentration powder carrier biofluidized bed (HPB) technology to the biochemical units of WWTPs on sludge concentration and settling performance. For the traditional activated sludge method (ASM), its hydraulic retention time (HRT) was 8 h, with an average effluent total nitrogen (TN) of 15.14 mg/L. Sludge bulking was prone to occur in low-temperature environments, resulting in a high average sludge volume index (SVI) of 560 mL/g. Conversely, with a CMPC dosage of 4 g/L, the HRT of HPB technology was 4.8 h, and the average effluent TN was 11.40 mg/L, with a removal efficiency of 67.43 %. During operation of HPB technology under high sludge concentration conditions (8 g/L), the average SVI remained at 85 mL/g, indicating excellent settling characteristics. Moreover, in the sequencing batch reactor (SBR), the SVI value of bulking sludge decreased from the original 695 to 111 mL/g by the 9th day of operation with the CMPC dosage of 2 g/L. At the same time, the filamentous bacteria almost disappeared, suggesting that CMPC inhibit the growth of filamentous bacteria. Metagenomic analysis demonstrated that CPMC enhance the utilization of small molecular fatty acids in activated sludge and promote electron transfer between nitrate and nitrite, thereby improving wastewater treatment capacity. Additionally, CMPC enhanced the relative abundance of Saprospiraceae in sludge, which accelerate the degradation of polysaccharides in extracellular polymeric substances, weaken sludge's hydrophilic properties, and improve sludge's settling performance. Overall, these findings suggested that CMPC effectively strengthen the high-loading operation of WWTPs by improving sludge concentration and sedimentation performance.

Evolution of aniline degradation and nitrogen removal performance in electro-enhanced sequence batch reactor under salinity stress: Sludge characteristics and microbial diversity

To explore the influence mechanism of different concentrations of salinity on the electro-enhanced aniline biodegradation system, a control group and experimental groups (0%-NaCl, 0.5%-NaCl, 1.5%-NaCl, 2.5%-NaCl, 3.5%-NaCl) were established. The experimental results showed that the electric field strengthened the denitrification performance, while salinity had little effect on the degradation efficiency of aniline and chemical oxygen demand (COD). The removal rate of TN reached 79.6% and 74.9% in 0.5%-NaCl and 1.5%-NaCl, respectively, which were superior than 0%-NaCl. As salinity increased, the nitrogen removal effect was negatively affected. Microbial diversity analysis indicated that the microbial community structure was uniform in the control group, 0%-NaCl, and 0.5%-NaCl, with the dominant genus OLB8 ensuring the nitrogen removal performance. In contrast, in the 2.5%-NaCl and 3.5%-NaCl experimental groups, the organic degrading bacteria were still active, while nitrifiers and denitrifiers were severely damaged. In conclusion, this study suggested that low concentrations of salinity can improve the decontamination performance of the electro-enhanced aniline biodegradation system, while high concentrations of salinity could lead to the collapse of the decontamination mechanism.

Impact of zero-valent iron on nitrifying granular sludge for 17α-ethinylestradiol removal and its mechanism

Aerobic granulation of nitrifying activated sludge could enhance the removal of 17α-ethinylestradiol (EE2) via abiotic nitration induced by reactive nitrogen species, cometabolism by ammonia-oxidizing bacteria and biodegradation by heterotrophic bacteria. Zero-valent iron (ZVI), a promising and low-cost material, has previously been applied to effectively enhance biological wastewater treatment. The impact and the effect mechanism of ZVI on nitrifying granular sludge (NGS) for EE2 removal was investigated in this study. The results showed that the addition of ZVI achieved better EE2 removal, though ZVI was not conducive to the accumulation of nitrite in NGS which reduced the abiotic transformation of EE2. Moreover, ZVI enriched heterotrophic denitrifying bacteria such as Arenimonas, thus changing the EE2 removal pathway and improving the degradation and mineralization of EE2. In addition, ZVI reduced the emission risk of the greenhouse gas N₂O and strengthened the stability of the granules. Metagenomic analysis further revealed that the functional genes related to EE2 mineralization, nitrite oxidation, N₂O reduction and quorum sensing in NGS were enriched with ZVI addition. This study provides meaningful guidance for ZVI application in the NGS process to achieve efficient and simultaneous removal of ammonia and emerging contaminants.

Understanding the impacts of intermittent electro field on the bioelectrochemical aniline degradation system: Performance, microbial community and functional enzyme

On account of the lack of a sustainable electron donor source and the inhibitory effect of aniline on denitrogenation make it tough to achieve simultaneous removal of aniline and nitrogen. Herein, the strategy of adjusting electric field mode was applied to the electro-enhanced sequential batch reactors (E-SBRs: R1 (continuous ON), R2 (2 h-ON/2 h-OFF), R3 (12 h-ON/12 h-OFF), R4 (in the aerobic phase ON), R5 (in the anoxic phase ON)) to treat aniline wastewater. Aniline removal rate reached approximately 99% in the five systems. Decreasing electrical stimulation interval from 12 to 2 h significantly improved the electron utilization efficiency for aniline degradation and nitrogen metabolism. The total nitrogen removal was achieved from 70.31% to 75.63%. Meanwhile, the hydrogenotrophic denitrifiers of Hydrogenophaga, Thauera, and Rhodospirillales, enriched in reactors of minor electrical stimulation interval. Accordingly, the expression of functional enzyme related to electron transport was incremental with the proper electrical stimulation frequency.

Micro-aeration assisted with electrogenic respiration enhanced the microbial catabolism and ammonification of aromatic amines in industrial wastewater

Improvement of refractory nitrogen-containing organics biodegradation is crucial to meet discharged nitrogen standards and guarantee aquatic ecology safety. Although electrostimulation accelerates organic nitrogen pollutants amination, it remains uncertain how to strengthen ammonification of the amination products. This study demonstrated that ammonification was remarkably facilitated under micro-aerobic conditions through the degradation of aniline, an amination product of nitrobenzene, using an electrogenic respiration system. The microbial catabolism and ammonification were significantly enhanced by exposing the bioanode to air. Based on 16S rRNA gene sequencing and GeoChip analysis, our results indicated that aerobic aniline degraders and electroactive bacteria were enriched in suspension and inner electrode biofilm, respectively. The suspension community had a significantly higher relative abundance of catechol dioxygenase genes contributing to aerobic aniline biodegradation and reactive oxygen species (ROS) scavenger genes to protect from oxygen toxicity. The inner biofilm community contained obviously higher cytochrome c genes responsible for extracellular electron transfer. Additionally, network analysis indicated the aniline degraders were positively associated with electroactive bacteria and could be the potential hosts for genes encoding for dioxygenase and cytochrome, respectively. This study provides a feasible strategy to enhance nitrogen-containing organics ammonification and offers new insights into the microbial interaction mechanisms of micro-aeration assisted with electrogenic respiration.

Retrospect and prospect of aerobic biodegradation of aniline: Overcome existing bottlenecks and follow future trends

Aniline is a highly bio-toxic industrial product, even at low concentrations, whose related wastewater has been flowing out worldwide on a large scale along with human production. As a green technology, aerobic biological treatment has been widely applied in industrial wastewater and exhibited various characteristics in the field of aniline wastewater. Meanwhile, this technology has shown its potential of synchronous nitrogen removal, but it still consumes energy badly. In the face of resource scarcity, this review comprehensively discusses the existing research in aerobic biodegradation of aniline wastewater to find out the developmental dawn of aerobic biological treatment. Primarily, it put forward the evolution history details of aniline biodegradation from pure culture to mixed culture and then to simultaneous nitrogen removal. On this basis, it presented the existing challenges to further expand the application of aerobic biotechnology, including the confusions of aniline metabolic mechanism, the development of co-degradation of multiple pollutants and the lack of practical experience of bioreactor operation for aniline and nitrogen removal. Additionally, the prospects of the technological shift to meet the needs of an energy-conserving society was described according to existing experiences and feasibility. Including but not limiting to the development of multifunctional bacteria, the reduction of greenhouse gases and the combination of green technologies.