Biodegradation of Emerging Pharmaceuticals from Domestic Wastewater by Membrane Bioreactor: The Effect of Solid Retention Time

Adaptation towards catabolic biodegradation of trace organic contaminants in activated sludge

Trace organic contaminants (TrOCs) are omnipresent in wastewater treatment plants (WWTPs), yet, their removal during wastewater treatment is oftentimes incomplete and underlying biotransformation mechanisms are not fully understood. In this study, we elucidate how different factors, including pre-exposure levels and duration, influence microbial adaptation towards catabolic TrOC biodegradation and its potential role in biological wastewater treatment. Four sequencing batch reactors (SBRs) were operated in parallel in three succeeding phases, adding and removing a selection of 26 TrOCs at different concentration levels. After each phase of SBR operation, a series of batch experiments was conducted to monitor biotransformation kinetics of those same TrOCs across various spike concentrations. For half of our test TrOCs, we detected increased biotransformation in sludge pre-exposed to TrOC concentrations ≥5 µg L-1 over a 30-day period, with most significant differences observed for the insect repellent DEET and the artificial sweetener saccharin. Accordingly, 16S rRNA amplicon sequencing revealed enrichment of taxa that have previously been linked to catabolic biodegradation of several test TrOCs, e.g., Bosea sp. and Shinella sp. for acesulfame degradation, and Pseudomonas sp. for caffeine, cyclamate, DEET, metformin, paracetamol, and isoproturon degradation. We further conducted shotgun metagenomics to query for gene products previously reported to be involved in the TrOCs' biodegradation pathways. In the future, directed microbial adaptation may be a solution to improve bioremediation of TrOCs in contaminated environments or in WWTPs.

Favipiravir biotransformation by a side-stream partial nitritation sludge: Transformation mechanisms, pathways and toxicity evaluation

Information on biotransformation of antivirals in the side-stream partial nitritation (PN) process was limited. In this study, a side-stream PN sludge was adopted to investigate favipiravir biotransformation under controlled ammonium and pH levels. Results showed that free nitrous acid (FNA) was an important factor that inhibited ammonia oxidation and the cometabolic biodegradation of favipiravir induced by ammonia oxidizing bacteria (AOB). The removal efficiency of favipiravir reached 12.6% and 35.0% within 6 days at the average FNA concentrations of 0.07 and 0.02 mg-N L-1, respectively. AOB-induced cometabolism was the sole contributing mechanism to favipiravir removal, excluding AOB-induced metabolism and heterotrophic bacteria-induced biodegradation. The growth of Escherichia coli was inhibited by favipiravir, while the AOB-induced cometabolism facilitated the alleviation of the antimicrobial activities with the formed transformation products. The biotransformation pathways were proposed based on the roughly identified structures of transformation products, which mainly involved hydroxylation, nitration, dehydrogenation and covalent bond breaking under enzymatic conditions. The findings would provide insights on enriching AOB abundance and enhancing AOB-induced cometabolism under FNA stress when targeting higher removal of antivirals during the side-stream wastewater treatment processes.

Phenotypic and metabolic adaptations of Rhodococcus cerastii strain IEGM 1243 to separate and combined effects of diclofenac and ibuprofen

Introduction

The increasing use of non-steroidal anti-inflammatory drugs (NSAIDs) has raised concerns regarding their environmental impact. To address this, understanding the effects of NSAIDs on bacteria is crucial for bioremediation efforts in pharmaceutical-contaminated environments. The primary challenge in breaking down persistent compounds lies not in the biochemical pathways but in capacity of bacteria to surmount stressors.

Methods

In this study, we examined the biodegradative activity, morphological and physiological changes, and ultrastructural adaptations of Rhodococcus cerastii strain IEGM 1243 when exposed to ibuprofen, diclofenac, and their mixture.

Results and Discussion

Our findings revealed that R. cerastii IEGM 1243 exhibited moderate biodegradative activity towards the tested NSAIDs. Cellular respiration assay showed higher metabolic activity in the presence of NSAIDs, indicating their influence on bacterial metabolism. Furthermore, catalase activity in R. cerastii IEGM 1243 exposed to NSAIDs showed an initial decrease followed by fluctuations, with the most significant changes observed in the presence of DCF and the NSAID mixture, likely influenced by bacterial growth phases, active NSAID degradation, and the formation of multicellular aggregates, suggesting potential intercellular synergy and task distribution within the bacterial community. Morphometric analysis demonstrated alterations in size, shape, and surface roughness of cells exposed to NSAIDs, with a decrease in surface area and volume, and an increase in surface area-to-volume ratio (SA/V). Moreover, for the first time, transmission electron microscopy confirmed the presence of lipid inclusions, polyphosphates, and intracellular membrane-like structures in the ibuprofen-treated cells.

Conclusion

These results provide valuable insights into the adaptive responses of R. cerastii IEGM 1243 to NSAIDs, shedding light on the possible interaction between bacteria and pharmaceutical compounds in the environment.

Characterization and biodegradation of paracetamol by biomass of Bacillus licheniformis strain PPY-2 isolated from wastewater

Industrialization leads to the entry of diverse xenobiotic compounds into the environment. One such compound is paracetamol (APAP), which is emerging as a pharmaceutical and personal care pollutant (PPCP). In this study, the APAP degrading bacterium was isolated by enrichment culture method from the sewage sample. The microscopy, biochemical, and 16S rRNA gene sequence analyzed the isolate PPY-2, which belongs to Bacillus licheniformis, and GenBank assigned accession number MN744328. Physiological and batch culture degradation studies have indicated that the strain involved in the degradation of APAP. The optimum pH for degradation of the PPY-2 was 7.7, whereas the temperature was 25 °C, agitation speed was 142 rpm, and concentration of APAP was 621 mg/L reported, and the optimum temperatures were 42 °C and 32 °C, respectively. Biomass kinetic was studied at optimal physical conditions, which suggested that the specific growth rate (μ) was 721 mg/L. The GC-MS chromatogram peaks have detected metabolites, viz., oxalic acid, 2-isopropyl-5-methyl cyclohexanone, and phenothiazine. The study confirmed that Bacillus licheniformis strain PPY-2 exhibits metabolic potential to biodegradation APAP and can be further deployed in bioremediation.

Efficiency of Diclofenac Removal Using Activated Sludge in a Dynamic System (SBR Reactor) with Variable Parameters of pH, Concentration, and Sludge Oxygenation

Recently, traditional wastewater treatment systems have not been adapted to remove micropollutants, including pharmaceutical substances, which, even at low concentrations, cause adverse changes in aquatic and terrestrial living organisms. The problem of drug residues in the environment has been noticed; however, no universal legal regulations have been established for concentrations of these compounds in treated wastewater. Hence, the aim of the article was to determine the possibility of increasing the efficiency of diclofenac removal from activated sludge using the designed SBR reactor. This study included six cycles, working continuously, where each of them was characterized by changing conditions of pH, oxygenation, and composition of the synthetic medium. In each cycle, three concentrations of diclofenac were analyzed: 1 mg/L, 5 mg/L, 10 mg/L for the hydraulic retention time (HRT) of 4 d and the sludge retention time (SRT) of 12 d. The highest removal efficiency was achieved in the first test cycle for pH of natural sediment at the level of 6.7-7.0 (>97%), and in the third test cycle at pH stabilized at 6.5 (>87%). The reduced content of easily assimilable carbon from synthetic medium indicated a removal of >50%, which suggests that carbon in the structure of diclofenac restrained microorganisms to the rapid assimilation of this element. Under half-aerobic conditions, the drug removal effect for a concentration of 10 mg/L was slightly above 60%.

Anaerobic membrane bioreactors for pharmaceutical-laden wastewater treatment: A critical review

Pharmaceuticalsare a diverse group of chemical compounds widely used for prevention and treatment of infectious diseases in both humans and animals. Pharmaceuticals, either in their original or metabolite form, find way into the wastewater treatment plants (WWTPs) from different sources. Recently, anaerobic membrane bioreactors (AnMBR) has received significant research attention for the treatment of pharmaceuticals in various wastewater streams. This review critically examines the behaviour and removal of a wide array of pharmaceuticals in AnMBR with primary focus on their removal efficiencies and mechanisms, critical influencing factors, and the microbial community structures. Subsequently, the inhibitory effects of pharmaceuticals on the performance of AnMBR and membrane fouling are critically discussed. Furthermore, the imperative role of membrane biofouling layer and its components in pharmaceuticals removal is highlighted. Finally, recent advancements in AnMBR configurations for membrane fouling control and enhanced pharmaceuticals removal are systemically discussed.

Comparing the efficiency of N-doped TiO2 and commercial TiO2 as photo catalysts for amoxicillin and ciprofloxacin photo-degradation under solar irradiation

Advanced oxidation processes (AOPs) have gained traction as alternative solutions for eliminating pollutants from pharmaceutical wastewater for reuse. In this research, the performance of two photo-catalysts (Commercial TiO₂ and synthesis N-doped TiO₂) were compared in terms of the degradation of amoxicillin and ciprofloxacin from an aqueous solution using a photo-catalytic batch system under solar irradiation. The influence of five operating factors is: pH (5-11), H₂O₂ concentrations (200-600) mg/L, catalyst concentrations (25-100 mg/L), Antibiotic concentration (25-100) mg/L and reaction time (30-120 min), on the oxidation of the listed above pollutants were investigated using the central composite design (CCD) of response surface methodology (RSM). The catalyst of N-doping TiO₂ was synthesized by sol-gel method, using the urea (CH₄N₂O) as a nitrogen source. The resulting material was analyzed using Scanning Electron Microscopy (SEM), X-Ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Additionally, it can be observed from the analysis of the characteristics of N-doped TiO₂ the homogenous dispersion of nitrogen molecules, small particle sizes, and energy-gap reduction, prompting a 6% increase in antibiotic degradation compared with Com. TiO₂. In the RSM analysis, the ideal conditions were found to be a pH of 5, H₂O₂ conc. of 400 mg/L, catalyst conc. of 50 mg, and antibiotics conc. of 25 mg/L for an antibiotics reduction rate of 89.31% (AMOX/Com. TiO₂/Solar), 90.2 (CFX/Com. TiO₂/Solar), 95.8% (AMOX/N-TiO₂/Solar) and 97.3% (CFX/N-TiO₂/Solar). Experimental results were in good agreement with predictions because the predicted R² matched well with the adjusted R².

State-of-the-Art Review on the Application of Membrane Bioreactors for Molecular Micro-Contaminant Removal from Aquatic Environment

In recent years, the emergence of disparate micro-contaminants in aquatic environments such as water/wastewater sources has eventuated in serious concerns about humans’ health all over the world. Membrane bioreactor (MBR) is considered a noteworthy membrane-based technology, and has been recently of great interest for the removal micro-contaminants. The prominent objective of this review paper is to provide a state-of-the-art review on the potential utilization of MBRs in the field of wastewater treatment and micro-contaminant removal from aquatic/non-aquatic environments. Moreover, the operational advantages of MBRs compared to other traditional technologies in removing disparate sorts of micro-contaminants are discussed to study the ways to increase the sustainability of a clean water supplement. Additionally, common types of micro-contaminants in water/wastewater sources are introduced and their potential detriments on humans’ well-being are presented to inform expert readers about the necessity of micro-contaminant removal. Eventually, operational challenges towards the industrial application of MBRs are presented and the authors discuss feasible future perspectives and suitable solutions to overcome these challenges.