Responses of microbial communities and their interactions to ibuprofen in a bio-electrochemical system

Optimization of operating parameters and microbiological mechanism of a low C/N wastewater treatment system dominated by iron-dependent autotrophic denitrification

Ferrous iron (Fe2+) reduces the amount of external carbon source used for the denitrification of low-C/N wastewater. The effects of key operating parameters on the efficiency of ferrous-dependent autotrophic denitrification (FDAD) and the functioning mechanism of the microbiome can provide a regulatory strategy for improving the denitrification efficiency of low C/N wastewater. In this study, the response surface method (RSM) was used to explore the influence of four important parameters-the molar ratio of Fe2+ to NO3--N (Fe/N), total organic carbon (TOC), the molar ratio of inorganic carbon to NO3--N (IC/N) and sludge volume (SV, %)-on the FDAD efficiency. Functional prediction and molecular ecological networks based on high-throughputs sequencing techniques were used to explore changes in the structure, function, and biomarkers of the sludge microbial community. The results showed that Fe/N and TOC were the main parameters affecting FDAD efficiency. Higher concentrations of TOC and high Fe/N ratios provided more electron donors and improved denitrification efficiency, but weakened the importance of biomarkers (Rhodanobacter, Thermomonas, Comamonas, Thauera, Geothrix and unclassified genus of family Gallionellaceae) in the sludge ecological network. When Fe/N > 4, the denitrification efficiency fluctuated significantly. Functional prediction results indicated that genes that dominated N2O and NO reduction and the genes that dominated Fe2+ transport showed a slight decrease in abundance at high Fe/N levels. In light of these findings, we recommend the following optimization ranges of parameters: Fe/N (3.5-4); TOC/N (0.36-0.42); IC/N (3.5-4); and SV (approximately 35%).

Response of sulfide autotrophic denitrification process and microbial community to oxytetracycline stress

The coexistence of antibiotics with sulfide and nitrate is common in sewage. Thus, this study explored the removal performance of nitrate and sulfide, and the response of extracellular polymer substances (EPS) and the microbial community to the sulfide autotrophic denitrification (SAD) process under oxytetracycline (OTC) stress. In Phase Ⅰ, the SAD system showed favouranle performance (nitrate removal rate ＞ 92.57%, sulfide removal rate ＞ 97.75%). However, in Phase Ⅳ, at OTC concentrations of 10, 15, and 20 mg/L, the NRE decreased to 76.13%, 40.71%, 11.37%, respectively, and the SRE decreased to 97.58%, 97.09%, 92.84%, respectively. At OTC concentrations of 0, 10, 15, and 20 mg/L, the EPS content were 1.62, 1.75, 2.03, and 1.42 mg/gVSS, respectively. The results showed that SAD performance gradually deteriorated under OTC stress. In particular, when the OTC concentration was 20 mg/L, the EPS content was lower than that of the control test, which could be attributed to the occurrence of microbial death. Finally, high-throughput sequencing results showed that OTC exposure led to gradual domination by heterotrophic denitrifying bacteria.

Enhanced nitrate removal efficiency and microbial response of immobilized mixed aerobic denitrifying bacteria through biochar coupled with inorganic electron donors in oligotrophic water

The nitrogen removal characteristics and microbial response of biochar-immobilized mixed aerobic denitrifying bacteria (BIADB) were investigated at 25 °C and 10 °C. BIADB removed 53.51 ± 1.72 % (25 °C) and 39.90 ± 4.28 % (10 °C) nitrate in synthetic oligotrophic water. Even with practical oligotrophic water, BIADB still effectively removed 47.66-53.21 % (25 °C), and 39.26-45.63 % (10 °C) nitrate. The addition of inorganic electron donors increased nitrate removal by approximately 20 % for synthetic and practical water. Bacterial and functional communities exhibited significant temperature and stage differences (P < 0.05), with temperature and total dissolved nitrogen being the main environmental factors. The dominant genera and keystone taxa exhibited significant differences at the two temperatures. Structural equation model analysis showed that dissolved organic matter had the highest direct and indirect effects on diversity and function, respectively. This study provides an innovative pathway for utilizing biochar and inorganic electron donors for nitrate removal from oligotrophic waters.

Effect of ibuprofen (IBU) on the sulfur-based and calcined pyrite-based autotrophic denitrification (SCPAD) systems with two filling modes: Performance and toxic response mechanism

To investigate the effect of ibuprofen (IBU) on the sulfur-based and calcined pyrite-based autotrophic denitrification (SCPAD) systems, two individual reactors with the layered filling (L-SCPAD) and mixed filling (M-SCPAD) systems were established via sulfur and calcined pyrite. Effluent NO3--N concentration of the L-SCPAD and M-SCPAD systems was first increased to 6.44, 0.93 mg/L under 0.5 mg/L IBU exposure and gradually decreased to 1.66 mg/L, 0 mg/L under 4.0 mg/L IBU exposure, indicating that NO3--N removal performance of the M-SCPAD system was better than that of the L-SCPAD system. The variation of extracellular polymeric substances (EPS) characteristics demonstrated that more EPS was secreted in the M-SCPAD system compared to the L-SCPAD system, which contributed to forming a more stable biofilm structure and protecting microorganisms against the toxicity of IBU in the M-SCPAD system. Moreover, the increased electron transfer impedance and decreased cytochrome c implied that IBU inhibited the electron transfer efficiency of the L-SCPAD and M-SCPAD systems. The decreased adenosine triphosphate (ATP) and electron transfer system activity (ETSA) content showed that IBU inhibited metabolic activity, but the M-SCPAD system exhibited higher metabolic activity compared to the L-SCPAD system. In addition, the analysis of the bacterial community indicated a more stable abundance of nitrogen removal function bacteria (Bacillus) in the M-SCPAD system compared to the L-SCPAD system, which was conducive to maintaining a stable denitrification performance. The toxic response mechanism based on the biogeobattery effect was proposed in the SCPAD systems under IBU exposure. This study provided an important reference for the long-term toxic effect of IBU on the SCPAD systems.

Effect of ibuprofen on the sulfur autotrophic denitrification process and microbial toxic response mechanism

The effect of ibuprofen (IBU) on the sulfur autotrophic denitrification (SAD) process and microbial toxic response mechanism were investigated. Nitrate removal performance was inhibited by high IBU concentrations (10 and 50 mg/L), and the effect of low IBU concentrations (1 mg/L) on nitrate removal performance was negligible. The low IBU concentration induced basal oxidative stress for microbial self-protection, while the high IBU concentration induced high-intensity oxidative stress to damage the microbial cell membrane structure. Electrochemical characterization showed that the low IBU concentration stimulated the electron transfer efficiency, which was inhibited at the high IBU concentration. Moreover, the variation content of nicotinamide adenine dinucleotide (NADH) and nitrate reductase showed that metabolic activity increased at low IBU concentrations and decreased at high IBU concentrations during the sulfur autotrophic nitrate reduction process. This study proposed the hormesis toxic response mechanism of the SAD process to IBU exposure.

Role of bio-electrochemical technology for enzyme activity stimulation in high-consumption pharmaceuticals biodegradation

Active pharmaceutical ingredients (APIs) and their intermediate residues have recently been considered a serious concern. Among technologies, bio-electrochemical technologies (BETs) have stimulated the production of bio-electrical energy. This review aims to examine the benefit and mechanism of BETs on the degradation of high-consumption pharmaceutical compounds, including antibiotic, anti-inflammatory, and analgesic drugs, and the stimulation of enzymes induced in a bioreactor. Moreover, intermediates and the proposed pathways of pharmaceutical compound biodegradation in BETs are to be explained in this review. According to studies performed exclusively, the benefit of BETs is using bio-electroactive microbes to mineralize recalcitrant pharmaceutical contaminants by promoting enzyme activity and energy. Since BETs use the electron transfer chain between bio-anode/-cathode and pharmaceuticals, the enzyme activity is essential in the oxidation and reduction of phenolic rings of drugs and the ineffective detoxification of effluent from the treatment plant. This study is suggested a vital and influential role of BETs in mineralizing and enzyme induction in bioreactors. Eventually, a content of future developments or outlooks of BETs are propounded to improve the pharmaceutical industries' wastewater problems.

Insight into pharmaceutical and personal care products removal using constructed wetlands: A comprehensive review

Pharmaceutical and personal care products (PPCPs) were regarded as emerging environmental pollutants due to their ubiquitous appearance and high environmental risks. The wastewater treatment plants (WWTPs) became the hub of PPCPs receiving major sources of PPCPs used by humans. Increasing concern has been focused on promoting cost-effective ways to eliminate PPCPs within WWTPs for blocking their route into the environment through effluent discharging. Among all advanced technologies, constructed wetlands (CWs) with a combination of plants, substrates, and microbes attracted attention due to their cost-effectiveness and easier maintenance during long-term operation. This study offers baseline data for risk control and future treatment by discussing the extent and dispersion of PPCPs in surface waters over the past ten years and identifying the mechanisms of PPCPs removal in CWs based on the up-to-present research, with a special focus on the contribution of sediments, vegetation, and the interactions of microorganisms. The significant role of wetland plants in the removal of PPCPs was detailed discussed in identifying the contribution of direct uptake, adsorption, phytovolatilization, and biodegradation. Meanwhile, the correlation between the physical-chemical characteristics of PPCPs, the configuration operation of wetlands, as well as the environmental conditions with PPCP removal were also further estimated. Finally, the critical issues and knowledge gaps before the real application were addressed followed by promoted future works, which are expected to provide a comprehensive foundation for study on PPCPs elimination utilizing CWs and drive to achieve large-scale applications to treat PPCPs-contaminated surface waters.

Long-term exposure to nanoplastics reshapes the microbial interaction network of activated sludge

Wastewater treatment plants have been identified as an important gathering spot for nanoplastics, possibly having unintended impacts on important biological nutrient removal processes. The underlying effects of long-term exposure of activated sludge to nanoplastics on nutrient removal and the mechanisms involved remain unclear. This study investigated the effect of polystyrene nanoplastics (Nano-PS) on the treatment performance and microbial community structure, and network in activated sludge. The results indicate that 1000 μg/L Nano-PS had chronic negative effects on the treatment performance in a continuous test over 140 days. Nano-PS had no significant impact in the earlier stages (0-50 days). However, as exposure time increased, the removal efficiencies of chemical oxygen demand, total phosphorous, and total nitrogen (TN) decreased by 2.7, 33.2, and 23.5%, respectively, in the later stages (87-132 days). These adverse impacts further manifested as a change in the topological characteristics, forming a smaller scale, lower complexity, and weaker transfer efficiency of the microbial network. Moreover, the scale and complexity of subnetwork-nitrogen removal bacteria and subnetwork-nitrifier were inhibited, leading to an increase in the effluent TN and NH₄⁺-N. The decreased modules and connectors (keystone taxa) likely caused the deterioration of treatment performance and functional diversity, which was consistent with the change in PICRUSt results. Less competition, denser nodes, and more complex module structures were induced as a strategy to mediate the long-term stress of nano-PS. To our knowledge, this is the first attempt to explore the long-term effects of nano-PS on the microbial interaction network of activated sludge, laying an experimental foundation for reducing the risks associated with nanoplastics.

Impact of Voltage Application on Degradation of Biorefractory Pharmaceuticals in an Anaerobic-Aerobic Coupled Upflow Bioelectrochemical Reactor

Diclofenac, ibuprofen, and carbamazepine are frequently detected in the environment, where they pose a threat to organisms and ecosystems. We developed anaerobic-aerobic coupled upflow bioelectrochemical reactors (AO-UBERs) with different voltages, hydraulic retention times (HRTs), and types of electrode conversion, and evaluated the ability of the AO-UBERs to remove the three pharmaceuticals. This study showed that when a voltage of 0.6 V was applied, the removal rate of ibuprofen was slightly higher in the system with aerobic cathodic and anaerobic anodic chambers (60.2 ± 11.0%) with HRT of 48 h than in the control systems, and the removal efficiency reached stability faster. Diclofenac removal was 100% in the 1.2 V system with aerobic anodic and anaerobic cathodic chambers, which was greater than in the control system (65.5 ± 2.0%). The contribution of the aerobic cathodic-anodic chambers to the removal of ibuprofen and diclofenac was higher than that of the anaerobic cathodic-anodic chambers. Electrical stimulation barely facilitated the attenuation of carbamazepine. Furthermore, biodegradation-related species (Methyloversatilis, SM1A02, Sporomusa, and Terrimicrobium) were enriched in the AO-UBERs, enhancing pharmaceutical removal. The current study sheds fresh light on the interactions of bacterial populations with the removal of pharmaceuticals in a coupled system.

Weak electrostimulation enhanced the microbial transformation of ibuprofen and naproxen

Ibuprofen (IBU) and naproxen (NPX) are commonly used non-steroidal anti-inflammatory drugs (NSAIDs) with high-risk quotients and are frequently detected in various aquatic environments. A weak electrostimulated biofilm not only had improved removal efficiencies to IBU and NPX, but also transformed different enantiomers with comparable efficiency and without configuration inversion. IBU was transformed mainly by oxidation (hydroxyl-IBU, carboxy-IBU), while NPX was mainly detoxified. The microbial analysis of IBU and NPX biofilm showed that the shared core consortia (> 1%) contained typical electro-active bacteria (Geobacter, Desulfovibrio), fermenters (Petrimonas, Acetobacterium) and potential degraders (Pandoraea, Nocardiaceae), which exhibited synergistic interactions by exchanging the additional electrons, H⁺, coenzyme NAD(H) or NAD(P) (H) and energy. The fungal community has a significant correlation to those core bacteria and they may also play transformation roles with their diverse enzymes. Plenty of nonspecific oxidoreductase, decarboxylase, hydrolase, cytochrome P450, and other enzymes relating to xenobiotic degradation were high-abundance encoded by the core consortia and could potentially participate in IBU and NPX biotransformation. This study offers new insights into the functional microbes and enzymes working on complex NSAIDs biotransformation and provided a feasible strategy for the enhanced removal of NSAIDs (especially IBU and NPX).

Biochar-based microbial agent reduces U and Cd accumulation in vegetables and improves rhizosphere microecology

Microbial remediation of heavy metals in soil has been widely studied. However, bioremediation efficiency is limited in practical applications because of nutritional deficiency, low efficiency, and competition with indigenous microorganisms. Herein, we prepared a biochar-based microbial agent (BMA) by immobilizing the microbial agent (MA, containing Bacillus subtilis, Bacillus cereus, and Citrobacter sp.) on biochar for the remediation of U and Cd in soil. The results showed that BMA increased soil organic matter, cation exchange capacity, and fluorescein diacetate hydrolysis activity and dehydrogenase activity by 58.7%, 38.2%, 42.9%, and 51.1%. The availability of U and Cd were significantly decreased by 67.4% and 54.2% in BMA amended soil, thereby reducing their accumulation in vegetables. BMA greatly promoted vegetable growth. Additionally, BMA significantly altered the structure and function of rhizosphere soil microbial communities. Coincidently, more abundant ecologically beneficial bacteria like Nitrospira, Nitrosomonas, Lysobacter, and Bacillus were observed, whereas plant pathogenic fungi like Fusarium and Alternaria reduced in BMA amended soil. The network analysis revealed that BMA amendment increased the tightness and complexity of microbial communities. Importantly, the compatibility of niches and microbial species within co-occurrence network was enhanced after BMA addition. These findings provide a promising strategy for suppressing heavy metal accumulation in vegetables and promoting their growth.

Novel highly-active Ag/Bi dual nanoparticles-decorated BiOBr photocatalyst for efficient degradation of ibuprofen

The surface plasmon resonance (SPR) effect of noble nanometals can be utilized to effectively improve the catalytic performance of semiconductor photocatalysts. In this work, a novel composite photocatalyst of BiOBr microspheres simultaneously decorated by Ag and Bi dual nanoparticles (NPs) has been successfully synthesized by the hydrothermal method plus one-step reduction method. And the morphology, structure, chemical composition and photoelectrical properties of this composite photocatalyst (Ag/Bi-BiOBr) were further characterized. Due to the SPR effect of Ag and Bi dual NPs, Ag/Bi-BiOBr showed the high light absorption with narrow band gap, as well as fast charge separation via metal-semiconductor heterojunction so as to realize an efficient degradation of ibuprofen (IBP) under simulated solar irradiation. Through the further optimization of the loading amounts of Ag and Bi dual NPs, the excellent photocatalytic activity in the Ag/Bi-BiOBr has been achieved that 92.3% of IBP was removed within 60 min, which is among the best results reported so far for IBP degradation via photocatalysis.

Degradation of Ibuprofen by the Electro/Fe3+/Peroxydisulfate Process: Reactive Kinetics, Degradation Products and Mechanism

Ibuprofen (IBU), a nonsteroidal anti-inflammatory drug, is one of the most widely used and frequently detected pharmaceuticals and personal care products in water bodies. This study examined the IBU degradation in aquatic solutions via ferric ion activated peroxydisulfate (PDS) coupled with electro-oxidation (EC/Fe3+/PDS). The degradation mechanisms involved three synergistic reactions in the EC/Fe3+/PDS system, including: (1) the electro-oxidation; (2) SO4•− generated from the activation of PDS by ferrous ions formed via cathodic reduction; (3) SO4•− generated from the electron transfer reaction. The radical scavenging experiments indicated that SO4•− and •OH dominated the oxidation process. The effects of the applied current density, PDS concentration, Fe3+ dosage, initial IBU concentration and initial pH as well as inorganic anions and humic acid on the degradation efficiency, were studied, and the degradation process of IBU followed the pseudo-first-order kinetic model. About 99.37% of IBU was removed in 60 min ((Fe3+ concentration) = 2.0 mM, (PDS concentration) = 12 mM, (initial IBU concentration) = 30 mg/L, current density = 15 mA/cm2, initial pH = 3). Finally, seven intermediate compounds were identified and probable IBU degradation pathways in the EC/Fe3+/PDS system were speculated.

Biodegradation of pharmaceuticals in photobioreactors - a systematic literature review

This work is a systematic review that reports state-of-the-art in removal of pharmaceuticals from water and wastewater by photosynthetic organisms in photobioreactors. The PRISMA protocol-based review of the most recent literature data from the last 10 years (2011–2021) was reported. Articles were searched by the combination of the following keywords: photobioreactor, pharmaceuticals, drugs, hormones, antibiotics, biodegradation, removal, wastewater treatment. The review focuses on original research papers (not reviews), collected in 3 scientific databases: Scopus, Web of Knowledge, PubMed. The review considered the following factors: type of microorganisms, type of micropollutants removed, degradation efficiency and associated products, types of photosynthetic organisms and photobioreactor types. The conclusion from the systematic review is that the main factors that limit widespread pharmaceuticals removal in photobioreactors are high costs and the problem of low efficiency related with low concentrations of pharmaceuticals. The review indicated a need for further research in this area due to increasing amounts of metabolites in the food chain, such as p-aminophenol and estrone, which can cause harm to people and ichthyofauna. Pharmaceuticals removal can be improved by adapting the type of microorganism used to the type of contamination and implementing photoperiods, which increase the removal efficiency of e.g. sulfamethazine by up to 28%. In the future, it is necessary to search for new solutions in terms of the construction of photobioreactors, as well as for more effective species in terms of pharmaceuticals biodegradation that can survive the competition with other strains during water and wastewater treatment.

Comprehensive evaluation of the long-term effect of Cu2+ on denitrifying granular sludge and feasibility of in situ recovery by phosphate

With increased industrial development, vast heavy metals are inevitably discharged into wastewater. Cu²⁺ is one of the most hazardous heavy metals in biotreatment. However, the potential effect of Cu²⁺ on denitrifying granular sludge is still unknown. This work assesses the response of denitrifying granular sludge to Cu²⁺ stress from multiple aspects. The denitrifying granular sludge could tolerate 5 mg L^-1 Cu²⁺, while the nitrogen removal efficiency decreased to 48.5% under 10 mg L^-1 Cu²⁺. Enzyme activity and carbohydrate metabolism were inhibited, and the denitrifying bacteria were washed out under Cu²⁺ stress. The resulting deteriorated state was reversed by phosphate. The nitrogen removal efficiency recovered to 99% after 10 days, and the enzyme activity also recovered to the original level. Membrane transport, transcription and cellular processes were promoted. Overall, the results of this work provide a feasible strategy to rapidly restore the metabolic activity of denitrifying granular sludge under Cu²⁺ stress.