Biodegradation of naproxen by freshwater algae Cymbella sp. and Scenedesmus quadricauda and the comparative toxicity

Visible-Light-Induced Photocatalytic Degradation of Naproxen Using 5% Cu/TiO2, Transformation Products, and Mechanistic Studies

The presence of drugs in wastewater effluent is of concern due to their effects on the aquatic fauna and flora and there are growing efforts for their removal from the environment. In this paper, we study the photocatalytic visible-light degradation of naproxen, an over-the-counter anti-inflammatory drug, using 5% copper-doped TiO2. The photocatalyst was characterized by XRD and BET surface area measurements. The optimal conditions for the degradation of 1 × 10-3 M of naproxen were found to be 3 h, with a catalyst loading of 50 mg/100 mL of the drug solution, and an acidic pH of 4.55. The degradation followed pseudo-first order kinetics and achieved a photodegradation efficiency of 44.8%. HPLC was used to separate the degradation products and their structures were determined using MS/MS data. A pathway for the degradation of naproxen is proposed along with degradation mechanisms. The major degradation events involve the formation of hydroxyl radicals, hydroxylation, keto-enol tautomerism, and decarboxylation.

A sensitive and reliable method for the quantitative determination of hydrogen peroxide produced by microalgae cells

One of the reactive forms of oxygen is hydrogen peroxide (H2O2), which has been investigated as a key component of growth processes and stress responses. Different methods for the determination of H2O2 production by animal and bacterial cells exist; however, its detection in algal cell cultures is more complicated due to the presence of photosynthetic pigments in the cells and the complex structure of cell walls. Considering these issues, a reliable, quick, and simple method for H2O2 detection is needed in phycological research. The aim of this methodological study was to optimize an Amplex UltraRed method for the fluorometric detection of H2O2 produced by microalgae cells, using a wild-type strain of Chlamydomonas reinhardtii as a model. The results showed that (i) potassium phosphate is the most suitable reaction buffer for this method, (ii) a 560 nm wavelength variant is the most appropriate as the excitation wavelength for fluorescence spectra measurement, (iii) a 50:50 ratio for the reaction mixture to sample was the most suitable, (iv) the fluorescence signal was significantly influenced by the density of the microalgae biomass, and (v) sample fortification with H2O2 allowed for an increase of the method's reliability and repeatability. The proposed protocol of the Amplex UltraRed method for the fluorometric detection of H2O2 produced by microalgae cells can yield a sensitive and accurate determination of the content of the test compound, minimizing measurement errors, eliminating chlorophyll autofluorescence problem, and compensating for the matrix effect. This method can be applied to the study of other microalgae species.

Theoretical analysis of naproxen reaction with sulfate and hydroxyl radicals in the aqueous phase: Investigating reactive sites and reaction kinetics

In this study, we have utilized theoretical calculations to predict the reaction active sites of naproxen when reacting with radicals and to further study the thermodynamics and kinetics of the reactions with ·OH and SO4-·. The evidence, derived from the average local ionization energy and electrostatic potential, points to the naphthalene ring as the preferred site of attack, especially for the C2, C6, C9, and C10 sites. The changes in Gibbs free energy and enthalpy of the reactions initiated by ·OH and SO4-· ranged between -19.6 kcal/mol - 26.3 kcal/mol and -22.3 kcal/mol -18.5 kcal/mol, respectively. More in-depth investigation revealed that RA2 pathway for ·OH exhibited the lowest free energy of activation, suggesting this reaction is more inclined to proceed. The second-order rate constant results indicate the ·OH attacking reaction is faster than reactions initiated by SO4·-, yet controlled by diffusion. The consistency between theoretical findings and experimental data underscores the validity of this computational method for our study.

Ecotoxicological impact of naproxen on Eisenia fetida: Unraveling soil contamination risks and the modulating role of microplastics

Soils represent crucial sinks for pharmaceuticals and microplastics, making them hotspots for pharmaceuticals and plastic pollution. Despite extensive research on the toxicity of pharmaceuticals and microplastics individually, there is limited understanding of their combined effects on soil biota. This study focused on the earthworm Eisenia fetida as test organism to evaluate the biotoxicity and bioaccumulation of the typical pharmaceutical naproxen and microplastics in earthworms. Results demonstrated that high concentrations of naproxen (100 mg kg-1) significantly increased the malondialdehyde (MDA) content, inducing lipid peroxidation. Even though the low exposure of naproxen exhibits no significant influence to Eisenia fetida, the lipid peroxidation caused by higher concentration than environmental relevant concentrations necessitate attention due to temporal and spatial concentration variability found in the soil environment. Meanwhile, microplastics caused oxidative damage to antioxidant enzymes by reducing the superoxide dismutase (SOD) activity and MDA content in earthworms. Metabolome analysis revealed increased lipid metabolism in naproxen-treated group and reduced lipid metabolism in the microplastic-treated group. The co-exposure of naproxen and microplastics exhibited a similar changing trend to the microplastics-treated group, emphasizing the significant influence of microplastics. The detection of numerous including lipids like 17-Hydroxyandrostane-3-glucuronide, lubiprostone, morroniside, and phosphorylcholine, serves to identify potential biomarkers for naproxen and microplastics exposure. Additionally, microplastics increased the concentration of naproxen in earthworms at sub-organ and subcellular level. This study contributes valuable insights into the biotoxicity and distribution of naproxen and microplastics in earthworms, enhancing our understanding of their combined ecological risk to soil biota.

Pharmaceutical removal from wastewater by introducing cytochrome P450s into microalgae

Pharmaceuticals are of increasing environmental concern as they emerge and accumulate in surface- and groundwater systems around the world, endangering the overall health of aquatic ecosystems. Municipal wastewater discharge is a significant vector for pharmaceuticals and their metabolites to enter surface waters as humans incompletely absorb prescription drugs and excrete up to 50% into wastewater, which are subsequently incompletely removed during wastewater treatment. Microalgae present a promising target for improving wastewater treatment due to their ability to remove some pollutants efficiently. However, their inherent metabolic pathways limit their capacity to degrade more recalcitrant organic compounds such as pharmaceuticals. The human liver employs enzymes to break down and absorb drugs, and these enzymes are extensively researched during drug development, meaning the cytochrome P450 enzymes responsible for metabolizing each approved drug are well studied. Thus, unlocking or increasing cytochrome P450 expression in endogenous wastewater microalgae could be a cost-effective strategy to reduce pharmaceutical loads in effluents. Here, we discuss the challenges and opportunities associated with introducing cytochrome P450 enzymes into microalgae. We anticipate that cytochrome P450-engineered microalgae can serve as a new drug removal method and a sustainable solution that can upgrade wastewater treatment facilities to function as "mega livers".

Biotransformation activities of fungal strain apiotrichum sp. IB-1 to ibuprofen and naproxen

Ibuprofen (IBU) and naproxen (NPX), as widely prescribed non-steroidal anti-inflammatory drugs (NSAIDs), are largely produced and consumed globally, leading to frequent and ubiquitous detection in various aqueous environments. Previously, the microbial transformation of them has been given a little attention, especially with the isolated fungus. A yeast-like Apiotrichum sp. IB-1 has been isolated and identified, which could simultaneously transform IBU (5 mg/L) and NPX (2.5 mg/L) with maximum efficiencies of 95.77% and 88.31%, respectively. For mono-substrate, the transformation efficiency of IB-1 was comparable to that of co-removal conditions, higher than most of isolates so far. IBU was oxidized mainly through hydroxylation (m/z of 221, 253) and NPX was detoxified mainly via demethylation (m/z of 215) as shown by UPLC-MS/MS results. Based on transcriptome analysis, the addition of IBU stimulated the basic metabolism like TCA cycle. The transporters and respiration related genes were also up-regulated accompanied with higher expression of several dehydrogenase, carboxylesterase, dioxygenase and oxidoreductase encoding genes, which may be involved in the transformation of IBU. The main functional genes responsible for IBU and NPX transformation for IB-1 should be similar in view of previous studies, which needs further confirmation. This fungus would be useful for potential bioremediation of NSAIDs pollution and accelerate the discovery of functional oxidative genes and enzymes different from those of bacteria.

Nabumetone and flufenamic acid pose a serious risk to aquatic plants: A study with Chlamydomonas reinhardtii as a model organism

The aquatic environment is constantly under threat due to the release of numerous pollutants. Among them, pharmaceuticals constitute a huge and diverse group. Non-steroidal anti-inflammatory drugs (NSAIDs) are increasingly found in water bodies, but knowledge about their potential toxicity is still low. In particular, there is a lack of information about their influences on aquatic plants and algae. We estimated the susceptibility of the microalgae Chlamydomonas reinhardtii to nabumetone (NBT) and flufenamic acid (FFA), focusing on photosynthesis. Due to the differences in the structures of these compounds, it was assumed that these drugs would have different toxicities to the tested green algae. The hypothesis was confirmed by determining the effective concentration values, the intensity of photosynthesis, the intensity of dark respiration, the contents of photosynthetic pigments, the fluorescence of chlorophyll a in vivo (OJIP test), and cell ultrastructure analysis. Assessment of the toxicity of the NSAIDs was extended by the calculation of an integrated biomarker response index (IBR), which is a valuable tool in ecotoxicological studies. The obtained results indicate an over six times higher toxicity of NBT compared to FFA. After analysis of the chlorophyll a fluorescence in vivo, it was found that NBT inhibited electron transport beyond the PS II. FFA, unlike NBT, lowered the intensity of photosynthesis, probably transforming some reaction centers into "silent centers", which dissipate energy as heat. The IBR estimated based on photosynthetic parameters suggests that the toxic effect of FFA results mainly from photosynthesis disruption, whereas NBT significantly affects other cellular processes. No significant alteration in the ultrastructure of treated cells could be seen, except for changes in starch grain number and autophagic vacuoles that appeared in FFA-treated cells. To the best of our knowledge, this is the first work reporting the toxic effects of NBT and FFA on unicellular green algae.

Non-steroidal anti-inflammatory drugs (NSAIDs) in the environment: Recent updates on the occurrence, fate, hazards and removal technologies

Non-steroidal Anti-inflammatory Drugs (NSAIDs) are extensively utilized pharmaceuticals worldwide. However, owing to the improper discharge and disposal practices, they have emerged as significant contaminants that are widely distributed in water, soils, and sewage sediments. This ubiquity poses a substantial threat to the ecosystem and human health. Consequently, it is imperative to develop rapid, cost-effective, efficient and reliable approaches for containing these substance in order to mitigate the deleterious impact of NSAIDs. This research provides a comprehensive review of the occurrence, fate, and hazards associated with NSAIDs in the general environment. Additionally, various removal technologies, including advanced oxidation processes, biodegradation, and adsorption, were systematically summarized. The study also presents a comparative analysis of the benefits and drawbacks of different removal technologies while interpreting challenges related to NSAIDs' removal and proposing strategies for future development.

Pharmaceutically active compounds in aqueous environment: recent developments in their fate, occurrence and elimination for efficient water purification

The existence of pharmaceutically active compounds (PhACs) in the water is a major concern for environmentalists due to their deleterious effects on living organisms even at minuscule concentrations. This review focuses on PhACs such as analgesics and anti-inflammatory compounds, which are massively excreted in urine and account for the majority of pharmaceutical pollution. Furthermore, other PhACs such as anti-epileptics, beta-blockers and antibiotics are discussed because they also contribute significantly to pharmaceutical pollution in the aquatic environment. This review is divided into two parts. In the first part, different classes of PhACs and their fate in the wastewater environment are presented. In the second part, recent advances in the removal of PhACs by conventional wastewater treatment plants, including membrane bioreactors (MBRs), activated carbon adsorption and bench-scale studies concerning a broad range of advanced oxidation processes (AOPs) that render practical and appropriate strategies for the complete mineralization and degradation of pharmaceutical drugs, are reviewed. This review indicates that drugs like diclofenac, naproxen, paracetamol and aspirin are removed efficiently by conventional systems. Activated carbon adsorption is suitable for the removal of diclofenac and carbamazepine, whereas AOPs are leading water treatment strategies for the effective removal of reviewed PhACs.

Degradation characteristics of refractory organic matter in naproxen pharmaceutical secondary effluent using vacuum ultraviolet-ozone treatment

Vacuum ultraviolet-ozone (VUV-O3) treatment was found to be superior to ultraviolet-ozone (UV-O3) treatment in terms of ozone utilization and hydroxyl radicals (·OH) generation when used to treat the secondary effluent (SE) from a naproxen pharmaceutical plant. VUV-O3 treatment was beneficial in terms of decolorization (100%), chemical oxygen demand removal (43.29%), and total organic carbon removal (54.81%). The VUV-O3 process was applicable over a wide pH range, and the presence of various anions had no significant influence on the oxidation efficiency. After treatment, the genotoxicity, unsaturation degree, and polarity of the SE decreased. In addition, the oxidation sensitivities of the fluorescent organic compounds were ranked as follows: humic acid-like > tyrosine-like > fulvic acid-like > tryptophan-like Moreover, the VUV-O3 process effectively converted refractory organic matter (molecular weights, MW > 2000 Da) into short-chain molecules with low MWs. The removal efficiency of dissolved organic matter (DOM) was 63.27%, and 77.27% of the DOM was found to be reactive to VUV-O3 oxidation. The unsaturation, polarity, and compositional complexity of the DOM decreased after VUV-O3 treatment. Finally, it was deduced that the direct O3 oxidation,·OH, O2·- and 1O2 played a role in the VUV-O3 oxidation process.

Evaluation of the toxicity of clozapine on the freshwater diatom Navicula sp. using the FTIR spectroscopy

Clozapine is an often prescribed neuroactive pharmaceutical and frequently detected in the aquatic environments. However, its toxicity on low trophic level species (i.e., diatoms) and associated mechanisms are seldom reported. In this study, the toxicity of clozapine on a widely distributed freshwater diatom Navicula sp. was evaluated using the FTIR spectroscopy along with biochemical analyses. The diatoms were exposed to various concentrations of clozapine (0, 0.01, 0.05, 0.10, 0.50, 1.00, 2.00, 5.00 mg/L) for 96 h. The results revealed that clozapine reached up to 392.8 μg/g in the cell wall and 550.4 μg/g within the cells at 5.00 mg/L, suggesting that clozapine could be adsorbed extracellularly and accumulated intracellularly in diatoms. In addition, hormetic effects were displayed on the growth and photosynthetic pigments (chlorophyll a and carotenoid) of Navicula sp., with a promotive effect at concentrations less than 1.00 mg/L while an inhibited effect at concentrations over 2 mg/L. Clozapine induced oxidative stress in Navicula sp., accompanied by decreased levels of total antioxidant capacity (T-AOC) (>0.05 mg/L), in which, the activity of superoxide dismutase (SOD) (at 5.00 mg/L) was increased whereas the activity of catalase (CAT) (>0.05 mg/L) was decreased. Furthermore, FTIR spectroscopic analysis showed that exposure to clozapine resulted in accumulation of lipid peroxidation products, increased sparse β-sheet structures, and altered DNA structures in Navicula sp. This study can facilitate the ecological risk assessment of clozapine in the aquatic ecosystems.

Polyaniline-modified halloysite nanotubes as high-efficiency adsorbents for removing of naproxen in the presence of different heavy metals

In this work, novel adsorbent polyaniline-modified halloysite nanotubes (HNT@PA-2) were synthesized successfully by in situ polymerization to increase active adsorption sites. With the increase of the amount of aniline, the adsorption capacity of naproxen becomes higher. The optimal ratio of halloysite nanotubes to aniline was 1 : 2. The effects of adsorption conditions such as pH, mass of HNT@PA-2, time and initial concentration of naproxen were systematically researched. The optimum adsorption for naproxen was pH 9, mass 10 mg and contact time 4 h. The adsorption of naproxen conformed to the pseudo-first-order kinetic model, and the maximum adsorption capacity was 242.58 mg g-1 at 318 K. In addition, the effects of ionic strength and different heavy metals also were studied. Higher ionic strength of the system could influence the adsorption of naproxen. The effects of Al3+, Pb2+, Zn2+ and Co2+ ions on the adsorption of naproxen could be ignored, while Cu2+ and Fe3+ ions inhibited the process. The mechanisms for naproxen adsorbed by the HNT@PA-2 were π-π interaction, hydrogen bonding and hydrophobic reaction. Therefore, the HNT@PA-2 could be used for the treatment of medical wastewater for removing naproxen.

Plants, animals, and fisheries waste-mediated bioremediation of contaminants of environmental and emerging concern (CEECs)-a circular bioresource utilization approach

The release of contaminants of environmental concern including heavy metals and metalloids, and contaminants of emerging concern including organic micropollutants from processing industries, pharmaceuticals, personal care, and anthropogenic sources, is a growing threat worldwide. Mitigating inorganic and organic contaminants, which can be coined as contaminants of environmental and emerging concern (CEECs), is a big challenge as traditional physicochemical processes are not economically viable for managing mixed contaminants of low concentrations. As a result, low-cost materials must be designed to provide high CEEC removal efficiency. One of the environmentally viable and energy-efficient approaches is biosorption, which involves using biomass or biopolymers isolated from plants or animals to decontaminate heavy metals in contaminated environments using inherent biological mechanisms. Among chemical constituents in plant biomass, cellulose, lignin, hemicellulose, proteins, polysaccharides, phenolic compounds, and animal biomass include polysaccharides and other compounds to bind heavy metals covalently and non-covalently. These functional groups include carboxyl, hydroxyl, carbonyl, amide, amine, and sulfhydryl. Cation-exchange capacities of these bioadsorbents can be improved by applying chemical modifications. The relevance of chemical constituents and bioactives in biosorbents derived from agricultural production such as food and fodder crops, bioenergy and cash crops, fruit and vegetable crops, medicinal and aromatic plants, plantation trees, aquatic and terrestrial weeds, and animal production such as dairy, goatery, poultry, duckery, and fisheries is highlighted in this comprehensive review for sequestering and bioremediation of CEECs, including as many as ten different heavy metals and metalloids co-contaminated with other organic micropollutants in circular bioresource utilization and one-health concepts.

Emerging challenges of the impacts of pharmaceuticals on aquatic ecosystems: A diatom perspective

Pharmaceuticals are a ubiquitous group of emerging pollutants of considerable importance due to their biological potency and potential to elicit effects in wildlife and humans. Pharmaceuticals have been quantified in terrestrial, marine, fresh, and transitional waters, as well as the fauna and macro-flora that inhabit them. Pharmaceuticals can enter water ways through different human and veterinary pathways with traditional wastewater treatment, unable to completely remove pharmaceuticals, discharging often unknown quantities to aquatic ecosystems. However, there is a paucity of available information regarding the effects of pharmaceuticals on species at the base of aquatic food webs, especially on phytoplankton, with research typically focussing on fish and aquatic invertebrates. Diatoms are one of the main classes of phytoplankton and are some of the most abundant and important organisms in aquatic systems. As primary producers, diatoms generate ∼40 % of the world's oxygen and are a vital food source for primary consumers. Diatoms can also be used for bioremediation of polluted water bodies but perhaps are best known as bio-indicators for water quality studies. However, this keystone, non-target group is often ignored during ecotoxicological studies to assess the effects of pollutants of concern. Observed effects of pharmaceuticals on diatoms have the potential to be used as an indicator of pharmaceutical-induced impacts on higher trophic level organisms and wider ecosystem effects. The aim of this review is to present a synthesis of research on pharmaceutical exposure to diatoms, considering ecotoxicity, bioremediation and the role of diatoms as bio-indicators. We highlight significant omissions and knowledge gaps which need addressing to realise the potential role of diatoms in future risk assessment approaches and help evaluate the impacts of pharmaceuticals in the aquatic environment at local and global scales.

Ambiguous changes in photosynthetic parameters of Lemna minor L. after short-term exposure to naproxen and paracetamol: Can the risk be ignored?

Non-steroidal anti-inflammatory drugs (NSAID) are recently monitored in the aquatic environment. Naproxen (NPX), paracetamol (PCT) and their transformation products can influence the biochemical and physiological processes at the sub-cellular and cellular levels taking part in the growth and development of plants. This study aimed to compare the effects of NPX and PCT, drugs with different physico-chemical properties, on the growth and photosynthetic processes in Lemna minor during a short-term (7 days) exposure. Although duckweed took up more than five times higher amount of PCT as compared to NPX (275.88 µg/g dry weight to 43.22 µg/g when treated with 10 mg/L), only NPX limited the number of new plants by 9% and 26% under 1 and 10 mg/L, respectively, and increased their dry weight (by 18% under 10 mg/L) and leaf area per plant. A considerable (by 30%) drop in the content of photosynthetic pigments under 10 mg/L treatment by both drugs did not significantly affect the efficiency of the primary processes of photosynthesis. Values of induced chlorophyll fluorescence parameters (F₀, F_V/F_M, Φ_II, and NPQ) showed just a mild stimulation by PCT and a negative effect by NPX (by up to 10%), especially on the function of photosystem II and electron transport in both intact duckweed plants and isolated chloroplasts. Lowered efficiency of Hill reaction activity (by more than 10% under 0.1 - 10 mg/L treatments) in isolated chloroplasts suspension proved the only inhibition effect of PCT to primary photosynthetic processes. In intact plants, higher treatments (0.5 - 10 mg/L) by both NPX and PCT induced an increase in RuBisCO content. The results prove that the potential effect of various drugs on plants is hard to generalise.

Metabolomic response of microalgae towards diclofenac sodium during its removal from water and concomitant recovery of pigments and lipids

The aim of this work was to assess the efficiency of freshwater green microalga, Chlorella sorokiniana for diclofenac sodium (DFS) removal, and metabolic response of alga to comprehend the metabolic pathways involved/affected during DFS decontamination. Results showed 91.51 % removal of DFS could be achieved within 9 days of algal treatment along with recovery of enhanced value-added bioresources i.e. chlorophyll, carotenoids, and lipids from the spent biomass. DFS also had an effect on enzyme activity including superoxide dismutase (SOD), catalase (CAT), and lipid peroxidation (MDA). Furthermore, metabolomics profiling provided an in-depth insight into changes in the metabolic response of C. sorokiniana wherein DFS induced 32 metabolites in microalgae compared to unexposed-control. This study offers microalgae as a green option for DFS removal, and the metabolomics study complemented with DFS could be an approach to understand the stress-induced strategies of C. sorokiniana for concomitant value-added products recovery in presence of DFS.

A review on microalgae-mediated biotechnology for removing pharmaceutical contaminants in aqueous environments: Occurrence, fate, and removal mechanism

Pharmaceutical compounds in aquatic environments have been considered as emerging contaminants due to their potential risks to living organisms. Microalgae-based technology showed the feasibility of removing pharmaceutical contaminants. This review summarizes the occurrence, classification, possible emission sources, and environmental risk of frequently detected pharmaceutical compounds in aqueous environments. The efficiency, mechanisms, and influencing factors for the removal of pharmaceutical compounds through microalgae-based technology are further discussed. Pharmaceutical compounds frequently detected in aqueous environments include antibiotics, hormones, analgesic and non-steroidal anti-inflammatory drugs (NSAIDs), cardiovascular agents, central nervous system drugs (CNS), antipsychotics, and antidepressants, with a concentration ranging from ng/L to μg/L. Microalgae-based technology majorly remove the pharmaceutical compounds through bioadsorption, bioaccumulation, biodegradation, photodegradation, and co-metabolism. This review identifies the opportunities and challenges for microalgae-based technology and proposed suggestions for future studies to tackle challenges. The findings of this review advance our understanding of the occurrence and fate of pharmaceutical contaminants in aqueous environments, highlighting the potential of microalgae-based technology for pharmaceutical contaminants removal.

Using δFIP as a potential biomarker for risk assessment of environmental pollutants in aquatic ecosystem: A case study of marine cyanobacterium Synechococcus sp. PCC7002

Increased hazardous substances application causes more environmental pollution and risks for human health. Microalgae are the important biological groups in marine ecosystem, and considered to be sensitive to environmental pollutants. Therefore, toxicity test on marine microalgae could provide the most efficient method for aquatic toxicity assessment, and could also be used as the early warning signals in aquatic ecosystem. In view of this, our study aimed at investigating the toxicity potential of two typical organic compounds, and screening out novel photosynthetic indicators for the risk assessment of environmental pollutants. In this study, benzyl alcohol and 2-phenylethanol were chosen as the target organic compounds, and preliminary toxicity mechanism of these organic compounds on marine cyanobacterium Synechococcus sp. PCC7002 was investigated with chlorophyll fluorescence technology. Results showed that PCC7002 could be affected by benzyl alcohol or 2-phenylethanol stress, and the toxicity effect was concentration-dependent. And external benzyl alcohol and 2-phenylethanol stress damaged the oxygen evolving complex, and suppressed electron transport at the donor and receptor sides of photosystem II (PSII), influencing the absorption, transfer, and application of light energy. Furthermore, potential biomarkers were screened by half maximal inhibitory concentration (IC₅₀) on the basis of pearson correlation coefficient analysis, and fluorescence intensity difference between the I-step and P-step of OJIP curve (δF_IP) seems to be the most sensitive indicator for external stress. This study would be of significant interest to the biomarker community, and pave the way for the practical resource for marine pollution monitoring and assessment.

Production and use of Scenedesmus acuminatus biomass in synthetic municipal wastewater for integrated biorefineries

Bioethanol production from algal biomass is a promising alternative for sustainable biofuel production. Algae possess a high photosynthetic capacity and an adaptive ability to thrive under harsh environmental conditions. The potential properties of Scenedesmus acuminatus CCALA 436 were assessed in this research for its bioethanol efficiency, and the effects of growing the algae in wastewater and at different concentrations of mepiquat chloride were studied. Also, pre-treatment efficiencies of different concentrations of calcium oxide were carried out on microalgae biomass. Superoxide dismutase, catalase activity, glutathione, and malondialdehyde contents of microalgae were examined, and the changes in chlorophyll, photoprotective carotenoid contents, and protein concentrations were determined. The results revealed that the maximum sugar and ethanol contents of Scenedesmus acuminatus CCALA 436 were 44.7 ± 1.5% and 20.32 g/L, respectively, for 50% wastewater and mepiquat chloride (2.5 mg/L) after pre-treatment with calcium oxide (0.08%). Additionally, the levels of oxidative enzymes varied depending on the wastewater concentrations. These findings indicate Scenedesmus acuminatus CCALA 436 grown in wastewater and mepiquat chloride can be used for the treatment of wastewater and the production of ethanol and high-value products such as carotenoid.

Advancement in algal bioremediation for organic, inorganic, and emerging pollutants

Rapidly changing bioremediation prospects are key drive to develop sustainable options that can offer extra benefits rather than only environmental remediation. Algal remediating is gaining utmost attention due to its mesmerising sustainable features, removing odour and toxicity, co-remediating numerous common and emerging inorganic and organic pollutants from gaseous and aqueous environments, and yielding biomass for a range of valuable products refining. Moreover, it also improves carbon footprint via carbon-capturing offers a better option than any other non-algal process for several high CO₂-emitting industries. Bio-uptake, bioadsorption, photodegradation, and biodegradation are the main mechanisms to remediate a range of common and emerging pollutants by various algae species. Bioadsorption was a dominant remediation mechanism among others implicating surface properties of pollutants and algal cell walls. Photodegradable pollutants were photodegraded by microalgae by adsorbing photons on the surface and intracellularly via stepwise photodissociation and breakdown. Biodegradation involves the transportation of selective pollutants intracellularly, and enzymes help to convert them into simpler non-toxic forms. Robust models are from the green microalgae group and are dominated by Chlorella species. This article compiles the advancements in microalgae-assisted pollutants remediation and value-addition under sustainable biorefinery prospects. Moreover, filling the knowledge gaps, and recommendations for developing an effective platform for emerging pollutants remediation and realization of commercial-scale algal bioremediation.

Assessing the potential for nevirapine removal and its ecotoxicological effects on Coelastrella tenuitheca and Tetradesmus obliquus in aqueous environment

Remediation of the antiretroviral (ARV) drug, nevirapine (NVP) has attracted considerable scientific attention in recent years due to its frequent detection and persistence in aquatic environments and potential hazards to living organisms. Algae-based technologies have been emerging as an environmentally friendly option for the removal of pharmaceutical compounds, but their ARV drug removal potential has not been fully explored yet. This study aimed to explore the ecotoxicity and removal potential of NVP by two microalgal species, Coelastrella tenuitheca and Tetradesmus obliquus. Lower environmental concentrations (up to 200 ng L^-1) of NVP enhanced the microalgal growth, and the highest dry cell weight of 941.27 mg L^-1 was obtained in T. obliquus at 50 ng L^-1 NVP concentration. Both microalgae showed varying removal efficiencies (19.53-74.56%) when exposed to NVP concentration levels of up to 4000 ng L^-1. At the late log phase (day 8), T. obliquus removed the highest percentage of NVP (74.56%), while C. tenuitheca removed 48% at an initial NVP concentration of 50 ng L^-1. Photosynthetic efficiency (Fv/Fm and rETR) of the two microalgal species, however, was not affected by environmental concentrations of NVP (up to 4000 ng L^-1) at the mid log phase of growth. SEM analysis demonstrated that both algal species produced distinct ridges on their cell surfaces after NVP uptake. In the ecotoxicity study, the calculated IC₅₀ values of NVP (0-100 mg L^-1) after 96 h of exposure were 23.45 mg L^-1 (C. tenuitheca) and 18.20 mg L^-1 (T. obliquus). The findings of the present study may contribute to a better understanding of the environmental hazards associated with NVP and the efficacy of microalgae in removing this pharmaceutical from aquatic environments.

Phycoremediation for carbon neutrality and circular economy: Potential, trends, and challenges

Phycoremediation is gaining attention not only as a pollutant mitigation approach but also as one of the most cost-effective paths to achieve carbon neutrality. When compared to conventional treatment methods, phycoremediation is highly effective in removing noxious substances from wastewater and is inexpensive, eco-friendly, abundantly available, and has many other advantages. The process results in valuable bioproducts and bioenergy sources combined with pollutants capture, sequestration, and utilization. In this review, microalgae-based phycoremediation of various wastewaters for carbon neutrality and circular economy is analyzed scientometrically. Different mechanisms for pollutants removal and resource recovery from wastewaters are explained. Further, critical parameters that influence the engineering design and phycoremediation performance are described. A comprehensive knowledge map highlighting the microalgae potential to treat a variety of industrial effluents is also presented. Finally, challenges and future prospects for industrial implementation of phycoremediation towards carbon neutrality coupled with circular economy are discussed.

The growth, biochemical composition, and antioxidant response of Microcystis and Chlorella are influenced by Ibuprofen

Non-steroidal anti-inflammatory drugs like ibuprofen (IBU) are extensively used, causing substantial amounts to end up in aquatic ecosystems. Unfortunately, little research has been done on how these medications influence the physiology of phytoplankton. This study aimed to investigate the toxicological and physiological effects of IBU on the cyanobacteria Microcystis aeruginosa LE3 and Microcystis aeruginosa EAWAG 198, and the chlorophyte Chlorella sorokiniana. Exponential growth phase cultures were exposed to IBU at 10 to 10,000 μg/L for 96 h. The medium effect concentrations revealed varied sensitivity to IBU in the order Chlorella sorokiniana > Microcystis aeruginosa LE3 > Microcystis aeruginosa EAWAG 198. The drug caused a significant difference from control in cell density and chlorophyll-a of the three strains, except for chlorophyll-a in M. aeruginosa EAWAG 198 cultures where a significant difference occurred at 100 μg/L. The cell density of M. aeruginosa LE3 cultures exposed to 10 μg/L IBU increased 24 h post-exposure. Increasing concentrations of IBU induced higher total microcystins content of the Microcystis aeruginosa. Intracellular hydrogen peroxide content, peroxidase, and glutathione S-transferase activities, and lipid peroxidation increased as a function of IBU exposure. Total lipid, carbohydrate, and protein content of Chlorella sorokiniana were stimulated following IBU exposure. We conclude that the increasing presence of IBU in aquatic ecosystems could significantly alter the population dynamics of the investigated and other phytoplankton species.

Microalgae, a current option for the bioremediation of pharmaceuticals: a review

In this review, research on the use of microalgae as an option for bioremediation purposes of pharmaceutical compounds is reported and discussed thoroughly. Pharmaceuticals have been detected in water bodies around the world, attracting attention towards the increasing potential risks to humans and aquatic biota. Unfortunately, pharmaceuticals have no regulatory standards for safe disposal in many countries. Despite the advances in new analytical techniques, the current wastewater treatment facilities in many countries are ineffective to remove the whole presence of pharmaceutical compounds and their metabolites. Though new methods are substantially effective, removal rates of drugs from wastewater make the cost-effectiveness ratio a not viable option. Therefore, the necessity for investigating and developing more adequate removal treatments with a higher efficiency rate and at a lower cost is mandatory. The present review highlights the algae-based removal strategies for bioremediation purposes, considering their pathway as well as the removal rate and efficiency of the microalgae species used in assays. We have critically reviewed both application of living and non-living microalgae biomass for bioremediation purposes considering the most commonly used microalgae species. In addition, the use of modified and immobilized microalgae biomass for the removal of pharmaceutical compounds from water was discussed. Furthermore, research considering various microalgal species and their potential use to detoxify organic and inorganic toxic compounds were well evaluated in the review. Further research is required to exploit the potential use of microalgae species as an option for the bioremediation of pharmaceuticals in water.

Mechanisms and application of microalgae on removing emerging contaminants from wastewater: A review

This study reviews the development of the ability of microalgae to remove emerging contaminants (ECs) from wastewater. Contaminant removal by microalgae-based systems (MBSs) includes biosorption, bioaccumulation, biodegradation, photolysis, hydrolysis, and volatilization. Usually, the existence of ECs can inhibit microalgae growth and reduce their removal ability. Therefore, three methods (acclimation, co-metabolism, and algal-bacterial consortia) are proposed in this paper to improve the removal performance of ECs by microalgae. Finally, due to the high removal performance of contaminants from wastewater by algal-bacterial consortia systems, three kinds of algal-bacterial consortia applications (algal-bacterial activatedsludge, algal-bacterial biofilm reactor, and algal-bacterial constructed wetland system) are recommended in this paper. These applications are promising for ECs removal. But most of them are still in their infancy, and limited research has been conducted on operational mechanisms and removal processes. Extra research is needed to clarify the applicability and cost-effectiveness of hybrid processes.

Removal of naproxen and diclofenac using magnetic nanoparticles/nanocomposites

Magnetic iron oxide and iron/copper nanoparticles were synthesized using Lathyrus brachypterus extract, and then magnetic Fe₃O₄–CS, Fe₃O₄–AT, Fe/Cu–CS and Fe/Cu–AT nanocomposite beads were synthesized using chitosan and alginate natural polymers. They were used for both adsorption and heterogeneous catalysts for the catalytic wet peroxidation (CWPO) of naproxen (NPX), diclofenac (DCF) and NPX + DCF drugs which are important micro-organic pollutants, separately and together (NPX + DCF) from aqueous media. In adsorption studies, the drugs were adsorbed very quickly in the first minutes and then, desorbed in between 8 and 10 min. In competitive adsorption, the adsorbents showed selective properties for DCF and NPX. In CWPO technique, drug removal was achieved in 9 min with a conversion capacity of 92% for DCF with Fe/Cu–CS and 84% for NPX with Fe/Cu–AT optimum experimental conditions, such as pH 5, 30% of H₂O₂, 100 mg catalyst and 298 K. Based on reusability of the catalysts, it was seen that there was a slight decrease in the removal efficiencies in the third cycle and the stable and active structure of the catalyst was preserved to the desired extent. Furthermore, the oxidation reaction was in good agreement with the pseudo-first-order kinetic model.

Ecotoxicological effects of the antidepressant fluoxetine and its removal by the typical freshwater microalgae Chlorella pyrenoidosa

The antidepressant fluoxetine (FLX) has gained increasing attention due to its frequent detection in aquatic environments and negative effects on non-target organisms. However, knowledge on the ecotoxicological effects of FLX and its removal by microalgae is still limited. In this study, the ecotoxicological effects of FLX (10 -1000 μg/L) were assessed using batch cultures of the freshwater microalgae Chlorella pyrenoidosa for 10 days based on changes in growth, antioxidant response, and photosynthetic process. The removal efficiency, removal mechanism, and degradation pathway of FLX by C. pyrenoidosa were also investigated. The results showed that the growth of C. pyrenoidosa was inhibited by FLX with a 4 d EC₅₀ of 0.464 mg/L. Additionally, FLX significantly inhibited photosynthesis and caused oxidative stress on day 4. However, C. pyrenoidosa can produce resistance and acclimatize to FLX, as reflected by the declining growth inhibition rate, recovered photosynthetic efficiency, and disappearance of oxidative stress on day 10. Despite the toxicity of FLX, C. pyrenoidosa showed 41.2%- 100% removal of FLX after 10 days of exposure. Biodegradation was the primary removal mechanism, accounting for 88.2%- 92.8% of the total removal of FLX. A total of five metabolites were found in the degradation processes of FLX, which showed less toxicity than FLX. The main degradation pathways were proposed as demethylation, O-dealkylation, hydroxylation, and N-acylation. Our results not only highlight the potential application of microalgae in FLX purification, but also provide insight into the fate and ecological risk of FLX in aquatic environments.

Recent Strategies for Bioremediation of Emerging Pollutants: A Review for a Green and Sustainable Environment

Environmental pollution brought on by xenobiotics and other related recalcitrant compounds have recently been identified as a major risk to both human health and the natural environment. Due to their toxicity and non-biodegradability, a wide range of pollutants, such as heavy metals, polychlorinated biphenyls, plastics, and various agrochemicals are present in the environment. Bioremediation is an effective cleaning technique for removing toxic waste from polluted environments that is gaining popularity. Various microorganisms, including aerobes and anaerobes, are used in bioremediation to treat contaminated sites. Microorganisms play a major role in bioremediation, given that it is a process in which hazardous wastes and pollutants are eliminated, degraded, detoxified, and immobilized. Pollutants are degraded and converted to less toxic forms, which is a primary goal of bioremediation. Ex situ or in situ bioremediation can be used, depending on a variety of factors, such as cost, pollutant types, and concentration. As a result, a suitable bioremediation method has been chosen. This review focuses on the most recent developments in bioremediation techniques, how microorganisms break down different pollutants, and what the future holds for bioremediation in order to reduce the amount of pollution in the world.

Pharmaceuticals in the Aquatic Environment: A Review on Eco-Toxicology and the Remediation Potential of Algae

The pollution of the aquatic environment has become a worldwide problem. The widespread use of pesticides, heavy metals and pharmaceuticals through anthropogenic activities has increased the emission of such contaminants into wastewater. Pharmaceuticals constitute a significant class of aquatic contaminants and can seriously threaten the health of non-target organisms. No strict legal regulations on the consumption and release of pharmaceuticals into water bodies have been implemented on a global scale. Different conventional wastewater treatments are not well-designed to remove emerging contaminants from wastewater with high efficiency. Therefore, particular attention has been paid to the phycoremediation technique, which seems to be a promising choice as a low-cost and environment-friendly wastewater treatment. This technique uses macro- or micro-algae for the removal or biotransformation of pollutants and is constantly being developed to cope with the issue of wastewater contamination. The aims of this review are: (i) to examine the occurrence of pharmaceuticals in water, and their toxicity on non-target organisms and to describe the inefficient conventional wastewater treatments; (ii) present cost-efficient algal-based techniques of contamination removal; (iii) to characterize types of algae cultivation systems; and (iv) to describe the challenges and advantages of phycoremediation.

Progress in microalgal mediated bioremediation systems for the removal of antibiotics and pharmaceuticals from wastewater

Worldwide demand for antibiotics and pharmaceutical products is continuously increasing for the control of disease and improvement of human health. Poor management and partial metabolism of these compounds result in the pollution of aquatic systems, leading to hazardous effects on flora, fauna, and ecosystems. In the past decade, the importance of microalgae in micropollutant removal has been widely reported. Microalgal systems are advantageous as their cultivation does not require additional nutrients: they can recover resources from wastewater and degrade antibiotics and pharmaceutical pollutants simultaneously. Bioadsorption, degradation, and accumulation are the main mechanisms involved in pollutant removal by microalgae. Integration of microalgae-mediated pollutant removal with other technologies, such as biodiesel, biochemical, and bioelectricity production, can make this technology more economical and efficient. This article summarizes the current scenario of antibiotic and pharmaceutical removal from wastewater using microalgae-mediated technologies.

Bioremediation of sulfonamides by a microalgae-bacteria consortium - Analysis of pollutants removal efficiency, cellular composition, and bacterial community

Antibiotics in wastewaters (e.g., sulfonamides (SAs)) are not effectively removed by the conventional bacterial processes. In this study, a microalgae (Scenedesmus obliquus)-based process was evaluated for the removal of SAs. The maximum removal efficiency of sulfadiazine (SDZ) and sulfamethoxazole (SMX) by the consortium was 5.85% and 40.84%, respectively. The lower SDZ biodegradation efficiency could be due to the difference in the lipophilic degree related to cell binding. The presence of SAs did not significantly inhibit the biomass production of the consortium (1311-1952 mg/L biomass) but led to a 36-51% decrease in total polysaccharide content and an increase in microalgae's protein content, which caused granule formation. The presence of SMX and SDZ resulted in an increase in lipid peroxidation activity with a 6.2 and 23.5-fold increase in malondialdehyde content, respectively. Rhodobacter and Phreatobacter were abundant in the consortium with SAs' presence, while alinarimonas, Catalinimonas and Cecembia were seen in their absence.

Transcriptomic and Physiological Responses of Chlorella pyrenoidosa during Exposure to 17α-Ethinylestradiol

17α-ethinylestradiol (17α-EE₂) is frequently detected in water bodies due to its use being widespread in the treatment of prostate and breast cancer and in the control of alopecia, posing a threat to humans and aquatic organisms. However, studies on its toxicity to Chlorella pyrenoidosa have been limited to date. This study investigated the effects of 17α-EE₂ on the growth, photosynthetic activity, and antioxidant system of C. pyrenoidosa and revealed related molecular changes using transcriptomic analysis. The cell density of algae was inhibited in the presence of 17α-EE₂, and cell morphology was also altered. Photosynthetics were damaged, while reactive oxygen species (ROS), superoxide dismutase (SOD), and malondialdehyde (MDA) content increased. Further transcriptomic analysis revealed that the pathways of photosynthesis and DNA replication were affected at three concentrations of 17α-EE₂, but several specific pathways exhibited various behaviors at different concentrations. Significant changes in differentially expressed genes and their enrichment pathways showed that the low-concentration group was predominantly impaired in photosynthesis, while the higher-concentration groups were biased towards oxidative and DNA damage. This study provides a better understanding of the cellular and molecular variations of microalgae under 17α-EE₂ exposure, contributing to the environmental risk assessment of such hazardous pollutants on aquatic organisms.

Pharmaceuticals as emerging pollutants: Case naproxen an overview

Nonsteroidal anti-inflammatory drugs (NSAIDs), including naproxen (NP), diclofenac, ibuprofen, etc., are widely used for fever and pain relief. NP is one of the most widely consumed drugs in the world, because it is available over the counter in many countries. Many studies have proven that NP is not eliminated in conventional water treatment processes and its biodegradation in the environment is also difficult compared to other drugs. Along these lines, we are aware that both the original compound and its metabolites can be found in different destinations in the environment. To assess the environmental exposure and the risks associated with NP, it is important to understand better the environment where they finally reach, the behavior of its original compounds, its metabolites, and its transformation products. In this sense, the purpose of this review is to summarize the current state of knowledge about the introduction and behavior of NP in the environments they reach and highlight research needs and gaps. Likewise, we present the sources, environmental destinations, toxicology, environmental effects, and quantification methodologies.

Current perspective of innovative strategies for bioremediation of organic pollutants from wastewater

Organic contaminants in water are a growing environmental threat to sustainable development, with detrimental effects on the biosphere. In recent years, researchers have increasingly focused their attention on the area of bioremediation as an important tool to eliminate harmful pollutants from the environment. This review examines the application of bioremediation technologies to the removal of organic pollutants, with an emphasis on hydrocarbons and textile dyes. It applies a descriptive bibliometric analysis to study statistical practicality-vs-applicability of bioremediation of emerging organic pollutants. The paper identifies efficient pathways for bioremediation of different types of organic pollutants and outlines the potential for an eco-friendly and economical approach for the biological remediation of micropollutants by microalgae. Facts and figures on various hazardous pollutants, constraints in their current removal from water at an industrial level, and promising future solutions are carefully presented here.

Modification of cyclodextrin and use in environmental applications

Water pollution, which has become a global problem in parallel with environmental pollution, is a problem that needs to be solved urgently, considering the gradual depletion of water resources. The inadequacy of the water treatment methods and the materials used somehow directed the researchers to look for dual character structures such as biocompatible and biodegradable β-cyclodextrin (β-CD). β-CD, which is normally insoluble in water, is used in demanding wastewater applications by being modified with the help of different agents to be water soluble or transformed into polymeric adsorbents as a result of co-polymerization via cross-linkers. In this way, in addition to the host-guest interactions offered by β-CD, secondary forces arising from these interactions provide advantages in terms of regeneration and reusability. However, the adsorption efficiency and synthesis steps need to be improved. Based on the current studies presented in this review, in which cross-linkers and modification methods are also mentioned, suggestions for novel synthesis methods of new-generation β-CD-based materials, criticisms, and recent methods of removal of micropollutants such as heavy metals, industrial dyes, harmful biomolecules, and pharmaceutics wastes are mentioned.

Algae bioprocess to deal with cosmetic chemical pollutants in natural ecosystems: A comprehensive review

Elevated demand and extensive exploitation of cosmetics in day-to-day life have hiked up its industrial productions worldwide. Organic and inorganic chemicals like parabens, phthalates, sulfates, and so forth are being applied as constituents towards the formulations, which tend to be the mainspring ecological complication due to their enduring nature and accumulation properties in various sections of the ecosystem. These cosmetic chemicals get accrued into the terrestrial and aquatic systems on account of various anthropogenic activities involving agricultural runoff, industrial discharge, and domestic effluents. Recently, the use of microbes for remediating persistent cosmetic chemicals has gained immense interest. Among different forms of the microbial community being applied as an environmental beneficiary, algae play a vital role in both terrestrial and aquatic ecosystems by their biologically beneficial metabolites and molecules, resulting in the biobenign and efficacious consequences. The use of various bacterial, fungal, and higher plant species has been studied intensely for their bioremediation elements. The bioremediating property of the algal cells through biosorption, bioassimilation, biotransformation, and biodegradation has made it favorable for the removal of persistent and toxic pollutants from the environment. However, the research investigation concerned with the bioremediation potential of the algal kingdom is limited. This review summarizes and provides updated and comprehensive insights into the potential remediation capabilities of algal species against ecologically hazardous pollutants concerning cosmetic chemicals.

A review on environmental occurrence, toxicity and microbial degradation of Non-Steroidal Anti-Inflammatory Drugs (NSAIDs)

In recent years, Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) have surfaced as a novel class of pollutants due to their incomplete degradation in wastewater treatment plants and their inherent ability to promote physiological predicaments in humans even at low doses. The occurrence of the most common NSAIDs (diclofenac, ibuprofen, naproxen, and ketoprofen) in river water, groundwater, finished water samples, WWTPs, and hospital wastewater effluents along with their toxicity effects were reviewed. The typical concentrations of NSAIDs in natural waters were mostly below 1 μg/L, the rivers receiving untreated wastewater discharge have often showed higher concentrations, highlighting the importance of effective wastewater treatment. The critical analysis of potential, pathways and mechanisms of microbial degradation of NSAIDs were also done. Although studies on algal and fungal strains were limited, several bacterial strains were known to degrade NSAIDs. This microbial ability is attributed to hydroxylation by cytochrome P450 because of the decrease in drug concentrations in fungal cultures of Phanerochaete sordida YK-624 on incubation with 1-aminobenzotriazole. Moreover, processes like decarboxylation, dehydrogenation, dechlorination, subsequent oxidation, demethylation, etc. also constitute the degradation pathways. A wide array of enzymes like dehydrogenase, oxidoreductase, dioxygenase, monooxygenase, decarboxylase, and many more are upregulated during the degradation process, which indicates the possibility of their involvement in microbial degradation. Specific hindrances in upscaling the process along with analytical research needs were also identified, and novel investigative approaches for future monitoring studies are proposed.

Antibiotic fate in an artificial-constructed urban river planted with the algae Microcystis aeruginosa and emergent hydrophyte

The behavior and removal of six antibiotics, that is, azithromycin, clarithromycin, sulfathiazole, sulfamethoxazole, ciprofloxacin, and tetracycline, in an artificial-controllable urban river (ACUR) were investigated. The ACUR was constructed to form five artificial eco-systems by planting three emergent hydrophytes and Microcystis aeruginosa: (1) Control; (2) MA: M. aeruginosa only; (3) MA-J-C: M. aeruginosa combined with Juncus effusus and Cyperus alternifolius; (4) MA-C-A: M. aeruginosa combined with C. alternifolius and Acorus calamus L.; (5) MA-A-J: M. aeruginosa combined with A. calamus L. and J. effusus. The MA-C-A system achieved the best removal of azithromycin and clarithromycin after 15-day test with the final concentrations 0.92 and 0.83 μg/L. The contents of ciprofloxacin and tetracycline in sediment were highest, up to 1453 and 1745 ng/g. The antibiotic plant bioaccumulation was higher in roots rather than the shoots (stem and leaves). No target antibiotics were detected in algae cells. The combination of hybrid hydrophytes had a certain effect on the removal of antibiotics, and thus selecting appropriate hydrophytes in urban rivers could greatly improve water quality. The overall removal of six antibiotics was greatly improved by the ACUR containing the hybrid hydrophytes and the algae, indicating a synergistic effect on antibiotic removal. PRACTITIONER POINTS: Controllable-mobile artificial eco-systems were developed with emergent hydrophytes and M. aeruginosa. The M. aeruginosa + Cyperus alternifolius + Acorus calamus L. system removed azithromycin and clarithromycin most at the end of tests. Emergent hydrophytes and M. aeruginosa have a synergistic effect on the removal of antibiotics. The combination of emergent hydrophytes did play an important role in the removal of antibiotics. The artificial eco-systems containing the hybrid hydrophytes and the algae could greatly improve the overall removal of antibiotics.

Phycoremediation of wastewater for pollutant removal: A green approach to environmental protection and long-term remediation

Surface and water bodies in many parts of the world are affected due to eutrophication, contamination and depletion. The approach of wastewater treatment using algae for eliminating nutrients and other pollutants from domestic wastewater is growing interest among the researchers. However, sustainable treatment of the wastewater is considered to be important in establishing more effective nutrient and pollutant reduction using algal systems. In comparison to the conventional method of remediation, there are opportunities to commercially viable businesses interest with phycoremediation, thus by achieving cost reductions and renewable bioenergy options. Phycoremediation is an intriguing stage for treating wastewater since it provides tertiary bio-treatment while producing potentially valuable biomass that may be used for a variety of applications. Furthermore, the phycoremediation provides the ability to remove heavy metals as well as harmful organic substances, without producing secondary contamination. In this review, the role of microalgae in treating different wastewaters and the process parameters affecting the treatment and future scope of research have been discussed. Though several algae are employed for wastewater treatment, species of the genera Chlamydomonas, Chlorella, and Scenedesmus are extensively utilized. Interestingly, there is a vast scope for employing algal species with high flocculation capacity and adsorption mechanisms for the elimination of microplastics. In addition, the algal biomass generated during phycoremediation has been found to possess high protein and lipid contents, promising their exploitation in biofuel, food and animal feed industries.

Toxicities of three metal oxide nanoparticles to a marine microalga: Impacts on the motility and potential affecting mechanisms

With the fast growth of the production and application of engineered nanomaterials (ENMs), nanoparticles (NPs) that escape into the environment have drawn increasing attention due to their ecotoxicological impacts. Motile microalgae are a type of primary producer in most ecosystems; however, the impacts of NPs on the motility of microalgae have not been studied yet. So the toxic impacts of three common metal oxide NPs (nTiO₂, nZnO, and nFe₂O₃) on swimming speed and locomotion mode of a marine microalgae, Platymonas subcordiformis, were investigated in this study. Our results demonstrated that both the velocity and linearity (LIN) of swimming were significantly decreased after the exposure of P. subcordiformis to the tested NPs. In addition, the obtained data indicate that NPs may suppress the motility of P. subcordiformis by constraining the energy available for swimming, as indicated by the significantly lower amounts of intracellular ATP and photosynthetic pigments and the lower activities of enzymes catalyzing glycolysis. Incubation of P. subcordiformis with the tested NPs generally resulted in the overproduction of reactive oxygen species (ROS), aggravation of lipid peroxidation, and induction of antioxidant enzyme activities, suggesting that imposing oxidative stress, which may impair the structural basis for swimming (i.e. the membrane of flagella), could be another reason for the observed motility suppression. Moreover, NP exposure led to significant reductions in the cell viability of P. subcordiformis, which may be due to the disruption of the energy supply (i.e., photosynthesis) and ROS-induced cellular damage. Our results indicate that waterborne NPs may pose a great threat to motile microalgae and subsequently to the health and stability of the marine ecosystem.

Toxicity evaluation of butyl acrylate on the photosynthetic pigments, chlorophyll fluorescence parameters, and oxygen evolution activity of Phaeodactylum tricornutum and Platymonas subcordiformis

Butyl acrylate is a hazardous and noxious substance (HNS) listed in the top 50 chemicals that is most likely to be involved in HNS spilling incident. At present, information about toxicity effect of butyl acrylate on marine organisms was insufficient, especially on marine microalgae. Phaeodactylum tricornutum (P. tricornutum) and Platymonas subcordiformis (P. subcordiformis) were used as test organism to evaluate the toxic effect of butyl acrylate on their photosynthetic system. Results showed that chlorophyll a (Chl-a) content, the net photosynthetic oxygen evolution rate (NOR), and chlorophyll fluorescence parameters including maximal photochemical efficiency (Fv/Fm), electron transfer rate (ETR), photochemical quenching (qP), and non-photochemical quenching (NPQ) were all stimulated in the toxic dose of 5,10, and 25 mg/L while those were significantly inhibited in the highest concentration of 25 mg/L groups after 96 h. Meanwhile, it was also found that Fv/Fm would be a suitable indicator for evaluating the toxicity of butyl acrylate on the photosynthetic system of two marine microalgae according to the analysis of Pearson correlation coefficient and integrated biomarker response (IBR). Once butyl acrylate enters the marine ecosystem, the toxicity data obtained in this study could be used as a reference for evaluating the effect of butyl acrylate on the photosynthetic capacity of marine microalgae.

Metabolism of non-steroidal anti-inflammatory drugs by non-target wild-living organisms

The presence of the non-steroidal anti-inflammatory drugs (NSAIDs) in the environment is a fact, and aquatic and soil organisms are chronically exposed to trace levels of these emerging pollutants. This review presents the current state of knowledge on the metabolic pathways of NSAIDs in organisms at various levels of biological organisation. More than 150 publications dealing with target or non-target analysis of selected NSAIDs (mainly diclofenac, ibuprofen, and naproxen) were collected. The metabolites of phase I and phase II are presented. The similarity of NSAIDs metabolism to that in mammals was observed in bacteria, microalgae, fungi, higher plants, invertebrates, and vertebrates. The differences, such as newly detected metabolites, the extracellular metabolism observed in bacteria and fungi, or phase III metabolism in plants, are highlighted. Metabolites detected in plants (conjugates with sugars and amino acids) but not found in any other organisms are described. Selected, in-depth studies with isolated bacterial strains showed the possibility of transforming NSAIDs into assimilable carbon sources. It has been found that some of the metabolites show higher toxicity than their parent forms. The presence of metabolites of NSAIDs in the environment is the cumulative effect of their introduction with wastewaters, their formation in wastewater treatment plants, and their transformation by non-target wild-living organisms.

Ecotoxicological effects, environmental fate and risks of pharmaceutical and personal care products in the water environment: A review

Due to the extensive use and incomplete removal, pharmaceutical and personal care products (PPCPs) are introduced into the water continuously. It has been proved that the unique properties of PPCPs are influential to organisms and the environment, and gradually affect human health. In this paper, the toxicological effects of typical PPCPs, and the environmental behavior of PPCPs in aquatic are reviewed. The risk assessments of PPCPs in the water are summarized. The research directions of environmental toxicology research of PPCPs in the future are proposed. Many PPCPs were found to be toxic or even highly toxic toward aquatic organisms, and have the potential for bioaccumulation. It is essential to study the acute and long-term toxicity of PPCPs and their metabolites, evaluate the environmental behaviors and make a reasonable assessment of ecotoxicology and human health risks of PPCPs.

Current progress in electrochemical anodic-oxidation of pharmaceuticals: Mechanisms, influencing factors, and new technique

Various pharmaceuticals have been detected in natural water and wastewater bodies, causing threats to water ecosystem and human health. Although electrochemical anodic-oxidation (EAO) has been shown to be efficient for pharmaceuticals degradation from aqueous solution, it still has a distinct need to apply EAO technology for pharmaceuticals removal rationally. This review provides the most recent progress on the mechanisms, influencing factors, and new technique of EAO for pharmaceuticals degradation. The mechanism and superiority of EAO were analyzed. Major influencing factors (e.g., electrode materials, electrochemical reactor, applied current density, anode-cathode distance, electrolyte type and concentration, initial solution pH value, and initial pharmaceuticals concentration) were discussed on the removal of pharmaceuticals. The latest development of reactive electrochemical membranes (REM) was regarded as an emerging EAO technique, and it was also highlighted. This work revealed that the EAO of pharmaceuticals has extraordinary application prospects in the field of water and wastewater treatment.

Acute toxic effect of typical chemicals and ecological risk assessment based on two marine microalgae, Phaeodactylum tricornutum and Platymonas subcordiformis

With the increasing demand for typical hazardous and noxious substances (HNS) in chemical industry, there is an increased leakage risk of these HNS during transportation by vessel and storage nearby seashore. In this study, the acute toxicity of nonylphenol, butyl acrylate and 1, 2-dichloroethane to Phaeodactylum tricornutum (P. tricornutum) and Platymonas subcordiformis (P. subcordiformis), was investigated to assess their ecological risk. The results showed that the three kinds of HNS showed significant time- and dose-dependent patterns on the growth inhibition of two marine microalgae. The 96 h-EC₅₀ of nonylphenol, butyl acrylate and 1, 2-dichloroethane on P. tricornutum was 1.088, 45.908 and 396 mg L^-1, respectively, and the 96 h-EC₅₀ of that on P. subcordiformis was 0.851, 52.621 and 389 mg L^-1, respectively. It was a common method to evaluate the harm of pollutants to organisms by calculating HC₅ value (the minimum pollutant concentration value harmful to 95 % of the studied species, which was no-effect concentration) with Species Sensitivity Distribution (SSD). On the basis of EC₅₀, the ecological risk assessment was further carried out, and HC₅ value of nonylphenol and 1, 2-dichloroethane to aquatic organism was 0.079 and 44 mg L^-1, respectively.

Comparative study on the toxicity and removal of bisphenol S in two typical freshwater algae

Bisphenol S (BPS), one of the most widely used bisphenol A substitutes, has recently received more attention because of its high detection in water and potential toxicity. In the present study, the toxicity and removal of BPS in typical freshwater algae Navicula sp. were investigated under laboratory conditions and the comparative study with Chlorella vulgaris was also explored. BPS was more toxic to Navicula sp. than C. vulgaris with their 120-h EC₅₀ values of 3.89 and 25.19 mg/L, respectively. It may be mainly ascribed to the high tolerance of C. vulgaris to BPS. For instance, the superoxide dismutase (SOD) and catalase (CAT) activities of C. vulgaris were increased under the exposure of 20 mg BPS/L, whereas they were increased in Navicula sp. at 1 mg BPS/L. It is implied that the detoxification mechanism of C. vulgaris was activated until BPS concentration reach to 20 mg L^-1. Moreover, the results had demonstrated that both algae had promoted the removal of BPS at 0.5 mg/L, but the removal could be inhibited as BPS concentration increased. Navicula sp. presented a better removal of BPS because of their higher accumulation, implying that they may be good materials for the removal of BPS. In addition, the sharp increase of BCF value at 72 h in Navicula sp. under the exposure of environmental-related BPS concentration (0.5 mg/L) may indicate a high risk of BPS to aquatic ecosystem. These findings will provide a reference for the risk assessment of BPS in natural waters.

Toxicity reduction of persistent pollutants through the photo-fenton process and radiation/H2O2 using different sources of radiation and neutral pH

The presence of toxic compounds in aquatic bodies is of great concern, and the Fenton, photo-Fenton and radiation/H₂O₂ processes can be applied in the remediation of these compounds due to their efficiency and advantages. However, these processes need to be investigated to make them more viable and environmentally friendly. Thus, the reduction of toxicity was evaluated, through ecotoxicological tests with Artemia salina and Lactuca sativa, of the compounds 2,4-D, diazepam, nicotine and paracetamol (acetaminophen) by the Fenton, photo-Fenton and radiation/H₂O₂ process with UVC, UVA and natural solar radiation at neutral pH with low concentrations of Fe²⁺ and H₂O₂. The UVC/H₂O₂ process was efficient in the degradation of nicotine (74%), the photo-Fenton process was more efficient in the degradation of 2,4-D (82%), diazepam (27%) and paracetamol (85%) using solar radiation, UVA and UVC respectively. The toxicity and total organic carbon (TOC) tests showed a reduction in the toxicity of the compounds after treatment, except for diazepam, which was more resistant to the process, leading to a higher mortality of Artemia salinas (92%) and less relative seed germination of Lactuca sativa (40%).