Modeling of Pharmaceutical Biotransformation by Enriched Nitrifying Culture under Different Metabolic Conditions

Unassuming Lichens: Nature's Hidden Antimicrobial Warriors

In a hidden corner of the Earth, an ongoing war is being waged: a battle between lichens and microorganisms. Lichens, ancient and unique symbiotic organisms, with their unique survival wisdom, are bursting with vitality in extreme environments. Over 80% of secondary metabolites in lichens are not found in other organisms, making lichen-derived compounds a promising resource for the development of new drugs, particularly against drug-resistant microorganisms, due to their distinctive chemical structures and biological activities. This article aims to explore in depth the lichen species exhibiting antimicrobial activity and their antimicrobial metabolites and focus on unique compounds such as divaricatic acid, usnic acid, vulpinic acid, salazinic acid, and rhizocarpic acid, which demonstrate significant antimicrobial effects against various resistant microorganisms, including methicillin-resistant Staphylococcus aureus, drug-resistant Mycobacterium tuberculosis, and Candida albicans and other drug-resistant microorganisms. Meanwhile, this paper discusses the potential applications and challenges associated with the use of lichens in medicine, agriculture, and food industry, aiming to elucidate these mysterious organisms for lichen researchers and enthusiasts while promoting further research and applications in the field of antimicrobials.

Acyclovir contamination in environment: Occurrence, transformation, toxicity, risk, and evaluation as a pharmaceutical indicator

Acyclovir (ACV), a widely used antiviral medication effective against herpes simplex viruses (HSV), is raising concern due to its pervasive presence in global water and the associated potential risks. ACV can undergo transformation under varying conditions, leading to the generation of diverse transformation products that may exhibit heightened toxicity. This review aims to present a comprehensive overview of the environmental impact of ACV. We compile data on ACV concentrations in different water sources worldwide to shed light on its global prevalence. The levels of ACV detected in both wastewater and natural water sources generally remain at low concentrations, typically in the range of ng L-1 level. ACV poses minimal threats to aquatic organisms and humans in comparison to its transformation products, and conventional wastewater treatment methods utilizing biological processes can reduce ACV concentrations, yet only achieve transformation rather than complete elimination of risks, as the intermediates often demonstrate elevated toxicity levels and increased persistence. Additionally, perspectives are proposed to inspire future research on risk assessment of ACV, its intermediates and other pharmaceuticals. Given the challenges in keeping pace with the proliferation of chemical varieties, prioritizing and optimizing risk assessment methodologies is imperative. To this end, the suitability of ACV indicators is evaluated by summarizing data across diverse water bodies.

Modeling Free Nitrous Acid Inhibition on the Removal of Nitrogen and Atenolol during Sidestream Partial Nitritation Processes

Sidestream serves as an important reservoir collecting pharmaceuticals from sludge. However, the knowledge on sidestream pharmaceutical removal is still insufficient. In this work, atenolol biodegradation during sidestream partial nitritation (PN) processes characterized by high free nitrous acid (FNA) accumulation was modeled. To describe the FNA inhibition on ammonia oxidation and atenolol removal, Vadivelu-type and Hellinga-type inhibition kinetics were introduced into the model framework. Four inhibitory parameters along with four biodegradation kinetic parameters were calibrated and validated separately with eight sets of batch experimental data and 60 days' PN reactor operational data. The developed model could accurately reproduce the dynamics of nitrogen and atenolol. The model prediction further revealed that atenolol biodegradation efficiencies by ammonia-oxidizing bacteria (AOB)-induced cometabolism, AOB-induced metabolism, and heterotrophic bacteria-induced biodegradation were 0, ∼ 60, and ∼35% in the absence of ammonium and FNA; ∼ 14, ∼ 29, and ∼28% at 0.03 mg-N L-1 FNA; and 7, 15, and 5% at 0.19 mg-N L-1 FNA. Model simulation showed that the nitritation efficiency of ∼99% and atenolol removal efficiency of 57.5% in the PN process could be achieved simultaneously by controlling pH at 8.5, while 89.2% total nitrogen and 57.1% atenolol were removed to the maximum at pH of 7.0 in PN coupling with the anammox process. The pH-based operational strategy to regulate FNA levels was mathematically demonstrated to be effective for achieving the simultaneous removal of nitrogen and atenolol in PN-based sidestream processes.

What Approaches Should be Used to Prioritize Pharmaceuticals and Personal Care Products for Research on Environmental and Human Health Exposure and Effects?

Pharmaceuticals and personal care products (PPCPs) are released from multiple anthropogenic sources and thus have a ubiquitous presence in the environment. The environmental exposure and potential effects of PPCPs on biota and humans has aroused concern within the scientific community and the public. Risk assessments are commonly conducted to evaluate the likelihood of chemicals including PPCPs that pose health threats to organisms inhabiting various environmental compartments and humans. Because thousands of PPCPs are currently used, it is impractical to assess the environmental risk of all of them due to data limitations; in addition, new PPCPs are continually being produced. Prioritization approaches, based either on exposure, hazard, or risk, provide a possible means by which those PPCPs that are likely to pose the greatest risk to the environment are identified, thereby enabling more effective allocation of resources in environmental monitoring programs in specific geographical locations and ecotoxicological investigations. In the present review, the importance and current knowledge concerning PPCP occurrence and risk are discussed and priorities for future research are proposed, in terms of PPCP exposure (e.g., optimization of exposure modeling in freshwater ecosystems and more monitoring of PPCPs in the marine environment) or hazard (e.g., differential risk of PPCPs to lower vs. higher trophic level species and risks to human health). Recommended research questions for the next 10 years are also provided, which can be answered by future studies on prioritization of PPCPs. Environ Toxicol Chem 2024;43:488-501. © 2022 SETAC.

Optimizing ciprofloxacin removal through regulations of trophic modes and FNA levels in a moving bed biofilm reactor performing sidestream partial nitritation

The performance of partial nitritation (PN)-moving bed biofilm reactor (MBBR) in removal of antibiotics in the sidestream wastewater has not been investigated so far. In this work, the removal of ciprofloxacin was assessed under varying free nitrous acid (FNA) levels and different trophic modes. For the first time, a positive correlation was observed between ciprofloxacin removal and FNA levels, either in the autotrophic PN-MBBR or in the mixotrophic PN-MBBR, mainly ascribed to the FNA-stimulating effect on heterotrophic bacteria (HB)-induced biodegradation. The maximum ciprofloxacin removal efficiency (∼98 %) and removal rate constant (0.021 L g-1 SS h-1) were obtained in the mixotrophic PN-MBBR at an average FNA level of 0.056 mg-N L-1, which were 5.8 and 51.2 times higher than the corresponding values in the autotrophic PN-MBBR at 0 mg FNA-N L-1. Increasing FNA from 0.006 to 0.056 mg-N L-1 would inhibit ammonia oxidizing bacteria (AOB)-induced cometabolism and metabolism from 10.2 % and 6.9 % to 6.2 % and 6.4 %, respectively, while HB-induced cometabolism and metabolism increased from 31.2 % and 22.7 % to 41.9 % and 34.5 %, respectively. HB-induced cometabolism became the predominant biodegradation pathway (75.9 %-85.8 %) in the mixotrophic mode. Less antimicrobial biotransformation products without the piperazine or fluorine were newly identified to propose potential degradation pathways, corresponding to microbial-induced metabolic types and FNA levels. This work shed light on enhancing antibiotic removal via regulating both FNA accumulation and organic carbon addition in the PN-MBBR process treating sidestream wastewater.

The biosynthesis of amidated bacterial cellulose derivatives via in-situ strategy

Bacterial cellulose, as a kind of natural biopolymer produced by bacterial fermentation, has attracted wide attention owing its unique physical and chemical properties. Nevertheless, the single functional group on the surface of BC greatly hinders its wider application. The functionalization of BC is of great significance to broaden the application of BC. In this work, N-acetylated bacterial cellulose (ABC) was successfully prepared using K. nataicola RZS01-based direct synthetic method. FT-IR, NMR and XPS confirmed the in-situ modification of BC by acetylation. The SEM and XRD results demonstrated that ABC has a lower crystallinity and higher fiber width compare with pristine 88 BCE % cell viability on NIH-3 T3 cell and near zero hemolysis ratio indicate its good biocompatibility. In addition, the as-prepared acetyl amine modified BC was further treated by nitrifying bacteria to enrich its functionalized diversity. This study provides a mild in-situ pathway to construct BC derivatives in an environmentally friendly way during its metabolism.

Prediction of pharmaceuticals removal in activated sludge system under different operational parameters using an extended ASM-PhACs model

Removal of pharmaceuticals is essential in wastewater treatment systems due to their release and accumulation in the environment, which are raising issues for the environment and human health. A mathematical model could be used to predict pharmaceuticals removal under various operational parameters and assess the contributions of different removal pathways to pharmaceuticals removal. Here an ASM-PhACs model was established to describe pharmaceuticals removal including diclofenac (DCF), erythromycin (ERY), gemfibrozil (GEM) and carbamazepine (CBZ) removal in activated sludge system. The pharmaceuticals removal processes linked to co-metabolic biodegradation through the growth of ammonia oxidizing bacteria (AOB), metabolic biodegradation through AOB, metabolic biodegradation through heterotrophic bacteria (HB) and sludge adsorption were incorporated into activated sludge model (ASM1) framework. The kinetic equations were established for each pharmaceuticals removal process. To provide the experimental data for model calibration and validation, two sets of batch tests were designed and conducted in the laboratory scale using SBR technology. According to the batch test data and results of sensitivity analysis, the newly added parameters and some original default parameters affecting pharmaceuticals removal processes were screened and calibrated. The model could accurately simulate all the dynamics of chemical oxygen demand, nitrogen and pharmaceuticals under various conditions. To explore the effect of operational parameters on pharmaceuticals removal efficiency, the wide range of operational parameters was analyzed during model simulation. According to the simulation results, both influent NH₄⁺-N concentration and DO were found to be the significant parameters that impact the removal of DCF, ERY and GEM. AOB biodegradation played an important role in DCF, ERY and GEM removal. The developed model framework helps to investigate the removal mechanisms and key influencing factors of pharmaceuticals removal, thus providing guidelines for reactor design, operation and optimization aiming at pharmaceuticals removal.

Unravelling ciprofloxacin removal in a nitrifying moving bed biofilm reactor: Biodegradation mechanisms and pathways

Although moving bed biofilm reactors (MBBRs) have shown excellent antibiotic removal potentials, the information on underlying mechanisms is yet limited. This work assessed the removal of ciprofloxacin in an enriched nitrifying MBBR by clarifying the contribution of adsorption and microbial-induced biodegradation. Results demonstrated the considerable biomass adsorption (55%) in first 30 min. Limiting nitrite oxidizing bacteria growth or inhibiting nitrification would lead to lower adsorption capacities. The highest ciprofloxacin biodegradation rate constant was 0.082 L g SS^-1 h^-1 in the presence of ammonium, owing to ammonia oxidizing bacteria (AOB)-induced cometabolism, while heterotrophs played an insignificant role (∼9%) in ciprofloxacin biodegradation. The developed model also suggested the importance of AOB-induced cometabolism and metabolism over heterotrophs-induced biodegradation by analyzing the respective biodegradation coefficients. Cometabolic biodegradation pathways of ciprofloxacin mainly involved the piperazine ring cleavage, probably alleviating antimicrobial activities. It implies the feasibility of nitrifying biofilm systems towards efficient antibiotic removal from wastewater.

Free Nitrous Acid Inhibits Atenolol Removal during the Sidestream Partial Nitritation Process through Regulating Microbial-Induced Metabolic Types

Limited studies have attempted to evaluate pharmaceutical removal during the sidestream partial nitritation (PN) process. In this work, atenolol biodegradation by PN cultures was investigated by maintaining ammonium and pH at different levels. For the first time, free nitrous acid (FNA), other than ammonium, pH, and free ammonia, was demonstrated to inhibit atenolol removal, with biodegradation efficiencies of ∼98, ∼67, and ∼28% within 6 days at average FNA levels of 0, 0.03, and 0.19 mg-N L^-1, respectively. Ammonia-oxidizing bacteria (AOB)-induced metabolism was predominant despite varying FNA concentrations. In the absence of ammonium/FNA, atenolol was mostly biodegraded via AOB-induced metabolism (65%) and heterotroph-induced metabolism (33%). AOB-induced metabolism was largely inhibited (down to 29%) at 0.03 mg-N L^-1 FNA, while ∼27 and ∼11% were degraded via heterotroph-induced metabolism and AOB-induced cometabolism, respectively. Higher FNA (0.19 mg-N L^-1) substantially reduced atenolol biodegradation via heterotroph-induced metabolism (4%), AOB-induced metabolism (16%), and AOB-induced cometabolism (8%). Newly identified products and pathways were related to metabolic types and FNA levels: (i) deamination and decarbonylation (AOB-induced cometabolism, 0.03 mg-N L^-1 FNA); (ii) deamination from atenolol acid (heterotrophic biodegradation); and (iii) nitro-substitution (reaction with nitrite). This suggests limiting FNA to realize simultaneous nitrogen and pharmaceutical removal during the sidestream process.

Ammonium-assimilating microbiome: A halophilic biosystem rationally optimized by carbon to nitrogen ratios with stable nitrogen conversion and microbial structure

The contradiction between theoretical metabolism of ammonium assimilation and experiential understanding of conventional biosystems makes the rational optimization of the ammonium-assimilating microbiome through carbon to nitrogen (C/N) ratios perplexing. The effect of different C/N ratios on ammonium-assimilating biosystems was investigated in saline wastewater treatment. C/N ratios significantly hindered the nutrient removal efficiency, but ammonium-assimilating biosystems maintained functional stability in nitrogen conversions and microbial communities. With sufficient biomass, higher than 86% ammonium and 73% phosphorus were removed when C/N ratios were higher than 25. Ammonium assimilation dominated the nitrogen metabolism in all biosystems even under relatively low C/N ratios, evidenced by the extremely low abundances of nitrification functional genes. Different C/N ratios did not significantly change the bacterial community structure of ammonium-assimilating biosystems. It is anticipated that the ammonium-assimilating biosystem with advantages of clear metabolic pathway and easy optimization can be applied to nutrient removal and recovery in saline environments.

Nitrogen recovery by a halophilic ammonium-assimilating microbiome: A new strategy for saline wastewater treatment

Wastewater with high salinity is one of the major challenges for conventional wastewater treatment. Although nitrogen management is vital for wastewater treatment, efficient strategies for nitrogen recovery and removal from saline wastewater remain challenging. Here we propose microbial ammonium assimilation to achieve efficient nitrogen removal and recovery into biomass from saline wastewater without gaseous nitrogen release opposite to the conventional wastewater treatment, . We find one marine bacterium Psychrobacter aquimaris A4N01 with the ability to form sedimentary granular biofilms that can be engineered to construct an efficient ammonium-assimilating microbiome followed the bottom-up design. We demonstrate that the microbiome removes ammonium through assimilation without reactive nitrogen intermediates and gaseous nitrogen emission, according to the functional gene abundance and nitrogen balance. More than 80% of ammonium, total nitrogen and total phosphorus are removed and recovered into biomass, with more than 98% of COD removed from saline wastewater. As one prototypic microbe to form ammonium-assimilating biofilms, Psychrobacter aquimaris A4N01 plays key role in nutrient metabolism and microbiome construction. We stress that ammonium assimilation with a clear and short pathway is a promising method in future saline wastewater treatment and sustainable nitrogen management.

Cometabolic biotransformation of benzotriazole in nitrifying batch cultures

Benzotriazole (BT) is a corrosion inhibitor widely distributed in aquatic environments. Little is known about the cometabolic capacity of stabilized nitrifying sludge to biotransform BT. The contribution of the nitrification process in the simultaneous oxidation of ammonium and biotransformation of BT (5 mg/L) was evaluated in 49 d batch cultures inoculated with a sludge produced in steady-state nitrification. The nitrifying sludge could consume BT in the obligate presence of ammonium. A higher cometabolic biotransformation capacity was obtained by increasing the initial ammonium concentration (100-300 mg N/L), reaching 2.3- and 5.8-fold increases for efficiency and specific rate of BT removal. At 300 mg NH₄⁺-N/L, the sludge biotransform 40.8% of BT and 77.6% of ammonium which was completely oxidized into nitrate. In assays with allylthiourea added as specific inhibitor of ammonium monooxygenase (AMO), it was shown that the totality of BT cometabolic biotransformation was associated with the AMO activity. The addition of acetate did not favor heterotrophic biotransformation of BT. BT provoked inhibitory effects on nitrification. This is the first study showing the role of ammonium oxidizing bacteria in the cometabolic biotransformation of BT and their potential use for cometabolism application in treatment of wastewater contaminated with ammonium and BT.

A review of partial nitrification in biological nitrogen removal processes: from development to application

To further reduce the energy consumption in the wastewater biological nitrogen removal process, partial nitrification and its integrated processes have attracted increasing attentions owing to their economy and efficiency. Shortening the steps of ammonia oxidation to nitrate saves a large amount of aeration, and the accumulated nitrite could be reduced by denitritation or anammox, which requires less electron donors compared with denitrification. Therefore, the strategies through mainstream suppression and sidestream inhibition for the achievement of partial nitrification in recent years are reviewed. Specifically, the enrichment strategies of functional microorganisms are obtained on the basis of their growth and metabolic characteristics under different selective pressures. Furthermore, the promising developments, current application bottlenecks and possible future trends of some biological nitrogen removal processes integrating partial nitrification are discussed. The obtained knowledge would provide a new idea for the fast realization of economic, efficient and long-term stable partial nitrification and biological nitrogen removal process.

Removal of pharmaceutical and personal care products (PPCPs) from wastewater using microalgae: A review

Pharmaceuticals and personal care products (PPCPs) are a group of emerging micro-pollutants causing detrimental effects on living organisms even at low doses. Previous investigations have confirmed the presence of PPCPs in the environment at hazardous levels, mainly due to the inefficiency of conventional wastewater treatment plants (CWWTPs). Their stable structure induces longer persistence in the environment. Microalgae are currently used to bioremediate numerous pollutants of different characteristics and properties released from the domestic, industrial, agricultural, and farm sectors. CO₂ mitigation during culture and the use of biomass as feedstock for biodiesel or biofuel production are, briefly, other benefits of microalgae-mediated treatment over CWWTPs. This review provides a comprehensive summary of recent literature, an overview of approaches and treatment systems, and breakthrough in the field of algal-mediated removal of PPCPs in wastewater treatment processes. The mechanisms involved in phycoremediation, along with their experimental approaches, have been discussed in detail. Factors influencing the removal of PPCPs from aqueous media are comprehensively described and assessed. A comparative study on microalgal strains is analyzed for a more efficient implementation of future processes. The role of microalgae to mitigate the most severe environmental impacts of PPCPs and the generation of antibiotic-resistant bacteria is discussed. Also, a detailed assessment of recent research on potential toxic effects of PPCPs on microalgae was conducted. The current review highlights microalgae as a promising and sustainable approach to efficiently bio-transform or bio-adsorb PPCPs.

Removal of pharmaceuticals by ammonia oxidizers during nitrification

The adverse effect of pharmaceuticals on ecosystem and human health raises great interest for the removal of pharmaceuticals in wastewater treatment plants (WWTPs). Enhanced removal of pharmaceuticals by ammonia oxidizers (AOs) has been observed during nitrification. This review provides a comprehensive summary on the removal of pharmaceuticals by AOs-ammonia oxidizing bacteria (AOB), ammonia oxidizing archaea (AOA), and complete ammonia oxidizer (comammox) during nitrification in pure ammonia oxidizing culture and mixed microbes systems. The superior removal of pharmaceuticals by AOs in conditions with nitrifying activity compared with the conditions without nitrifying activity was proposed. The contribution of AOs on pharmaceuticals removal in pure and mixed microbe systems was discussed and activated sludge modeling was suggested as the proper measure on assessing the contribution of AOs on the removal of pharmaceuticals in mixed microbe culture. Three transformation processes and the involved reaction types of pharmaceuticals transformation during nitrification were reviewed. The present paper provides a systematical summary on pharmaceuticals removal by different AOs across pure and mixed microbes culture during nitrification, which opens up the opportunity to optimize the wastewater biological treatment systems for enhanced removal of pharmaceuticals. KEY POINTS: • The superior removal of pharmaceuticals by ammonia oxidizers (AOs) was summarized. • The removal contribution of pharmaceuticals attributed by AOs was elucidated. • The transformation processes and reaction types of pharmaceuticals were discussed.

β-blockers in the environment: Distribution, transformation, and ecotoxicity

β-blockers are a class of medications widely used to treat cardiovascular disorders, including abnormal heart rhythms, high blood pressure, and angina pectoris. The prevalence of β-blockers has generated a widespread concern on their potential chronic toxicity on aquatic organisms, highlighting the necessity of comprehensive studies on their environmental distribution, fate, and toxicity. This review summarizes the up-to-date knowledge on the source, global distribution, analytical methods, transformation, and toxicity of β-blockers. Twelve β-blockers have been detected in various environmental matrices, displaying significant temporal and spatial variations. β-blockers can be reduced by 0-99% at wastewater treatment plants, where secondary processes contribute to the majority of removal. Advanced oxidation processes, e.g., photocatalysis and combined UV/persulfate can transform β-blockers more rapidly and completely than conventional wastewater treatment processes, but the transformation products could be more toxic than the parent compounds. Propranolol, especially its (S)-enantiomer, exhibits the highest toxicity among all β-blockers. Future research towards improved detection methods, more efficient and cost-effective removal techniques, and more accurate toxicity assessment is needed to prioritize β-blockers for environmental monitoring and control worldwide.

Biotransformation of ibuprofen in biological sludge systems: Investigation of performance and mechanisms

Ibuprofen (IBU), a common non-steroidal anti-inflammatory drug (NSAID), is widely used by humans for controlling fever and pain, and is frequently detected in the influent of wastewater treatment plants and different aquatic environments. In this study, the biotransformation of IBU in activated sludge (AS), anaerobic methanogenic sludge (AnMS) and sulfate-reducing bacteria (SRB)-enriched sludge systems was investigated at three different concentrations of 100, 500 and 1000 μg/L via a series of batch and continuous studies. IBU at concentration of 100 μg/L was effectively biodegraded by AS whereas AnMS and SRB-enriched sludge were less effective in IBU biodegradation at all concentrations tested. However, at higher IBU concentrations of 500 and 1000 μg/L, AS showed poor IBU biodegradation and chemical oxygen demand (COD) removal due to inhibition of aerobic heterotrophic bacteria (i.e., Candidatus Competibacter) by IBU and/or IBU biotransformation products. The microbial analyses showed that IBU addition shifted the microbial community structure in AS, AnMS and SRB-enriched sludge systems, however, the removals of COD, nitrogen and sulfur in both anaerobic sludge systems were not affected significantly (p > 0.05). The findings of this study provided a new insight into biotransformation of IBU in three important biological sludge systems.

Interaction between 17β-estradiol degradation and nitrification in mariculture wastewater by Nitrosomonas europaea and MBBR

This study investigated the relation between 17β-estradiol (E2) degradation and nitrification in synthetic mariculture wastewater by ammonia oxidizing bacterium Nitrosomonas europaea and moving bed biofilm reactor (MBBR). Batch experiments showed that E2 degradation by N. europaea in wastewater followed zero-order reaction kinetics (r² = 0.944, 4.07 μg/ L h^-1) when ammonia presented. Nitrite yield in N. europaea inoculation decreased by 77.8% exposed to 1 mg/L E2. The inhibitory impact on ammonia oxidation was enhanced with increasing E2 dosage from 50 ng/L to 1 mg/L. Notably, E2 as low as 50 ng/L still had significant interference with nitrite production, bacterial density and ammonia monooxygenase (AMO) activity of N. europaea. Still, the following continuous 68-day degradation test revealed that 84.5%-98.7% E2 could be removed by a bench-scale MBBR. Whereas, ammonia removal remarkably decreased from 94.7% ± 2.1% to 85.6% ± 2.1% (p < .05) along with the enhanced E2 removal (from 84.5% ± 2.0% to 98.7% ± 0.4%, p < .05) when inlet E2 increased from 10 μg/L to 1 mg/L, indicating the great role of heterotrophs in E2 degradation. In contrast, nitrite oxidation was not affected upon E2 exposure irrespective of E2 concentrations. In summary, nitrification was effective in removing E2, while E2 interfered with ammoxidation process, but this interference was negligible at the reactor level given the low level of E2 in practical field conditions.

Roles of ammonia-oxidizing bacteria in improving metabolism and cometabolism of trace organic chemicals in biological wastewater treatment processes: A review

While there has been a significant recent improvement in the removal of pollutants in natural and engineered systems, trace organic chemicals (TrOCs) are posing a major threat to aquatic environments and human health. There is a critical need for developing potential strategies that aim at enhancing metabolism and/or cometabolism of these compounds. Recently, knowledge regarding biodegradation of TrOCs by ammonia-oxidizing bacteria (AOB) has been widely developed. This review aims to delineate an up-to-date version of the ecophysiology of AOB and outline current knowledge related to biodegradation efficiencies of the frequently reported TrOCs by AOB. The paper also provides an insight into biodegradation pathways by AOB and transformation products of these compounds and makes recommendations for future research of AOB. In brief, nitrifying WWTFs (wastewater treatment facilities) were superior in degrading most TrOCs than non-nitrifying WWTFs due to cometabolic biodegradation by the AOB. To fully understand and/or enhance the cometabolic biodegradation of TrOCs by AOB, recent molecular research has focused on numerous crucial factors including availability of the compounds to AOB, presence of growth substrate (NH₄-N), redox potentials, microorganism diversity (AOB and heterotrophs), physicochemical properties and operational parameters of the WWTFs, molecular structure of target TrOCs and membrane-based technologies, may all significantly impact the cometabolic biodegradation of TrOCs. Still, further exploration is required to elucidate the mechanisms involved in biodegradation of TrOCs by AOB and the toxicity levels of formed products.