Reduction Of Ecotoxicity Research Articles

Enhanced removal of chiral emerging contaminants by an electroactive biofilter

50% of pharmaceuticals and 25% of herbicides used worldwide are chiral. Each enantiomer has a unique toxicity and biodegradation profile, affecting differently to organisms. Chirality plays a key role in the behavior of these emerging contaminants (ECs) in terms of their pharmacological or herbicidal activity, but this peculiarity is often overlooked in environmental research. The complexity of chiral ECs is underestimated, as the varying sensitivity of biological systems to enantiomers is rarely considered. Biofilters can promote the activity of specific microbial communities, facilitating the degradation of ECs, due to the greater interaction between water and microorganisms and their compact design. Here, we show that an electroactive biofilter can alter the chirality of drugs and herbicides in wastewater treatment, impacting their removal and toxicity. The electrochemical biofilter (BioeF) removed 80% of pharmaceuticals and 50–75% of herbicides, outperforming the conventional filter (ConF). BioeF also showed greater chiral alterations and lower ecotoxicity. This work provides the first evidence of a relationship between changes in contaminant chirality and detoxification capacity, enhanced by electroactive systems. The increased microbial activity observed in the BioeF suggests that bioelectrochemical systems offer a valuable advance for ECs removal and ecotoxicity reduction, addressing the environmental challenge posed by ECs.

Highly efficient and secure recycling of neomycin fermentation residue by optimum temperature: Nutrients release, neomycin degradation and safety evaluation

The neomycin fermentation residues (NFR) are a solid waste during neomycin production, possessing high recycling value due to their rich organic content. However, the environmentally friendly use of NFR was hindered by its rigid matrix structure and residual neomycin. In this study, the effect of temperature on the structure and bioresource properties of NFR were investigated. Meanwhile, the effect of temperature on the degradation of residual neomycin, the toxicity of neomycin degradation products, and the safety of NFR were assessed. The results indicated that the content of soluble organic matter was increased by appropriate temperature treatment through the disruption of the rigid matrix structure of the NFR. However, excessively high temperatures led to the mineralization of organic matter. Simultaneously, appropriate temperature facilitated the transformation of organic substances to humic-like acids. The neomycin in NFR was effectively degraded with the increasing temperature, and the degradation efficiency exceeded 99 % under 220 °C for 120 min. In addition, the applicability of using appropriate temperatures to degrade antibiotics in similar other AFR has been demonstrated. Neomycin degradation occurred primarily through the cleavage of the glycosidic bond and ring ether, the detachment of the amino group, and the addition of hydroxyl groups. Meanwhile, the developmental toxicity and acute toxicity of neomycin were effectively mitigated by the appropriate temperature, and a significant reduction in ecotoxicity was observed. As a result, optimum temperature treatment proved to be an efficient method for the secure recycling of NFR.

Anaerobic treatment removing tetrabromobisphenol A and biota safety: How do tropical aquatic species respond to effluent toxicity over short- and long-term exposures?

Wastewater containing tetrabromobisphenol A (TBBPA), a commonly used flame retardant found in wastewater, can present significant toxic effects on biota, yet its impact on tropical freshwater environments is not well understood. This study explores the effectiveness of two independent anaerobic treatment systems, the acidogenic reactor (AR) and the methanogenic reactor (MR), for the ecotoxicity reduction of TBBPA-rich wastewater in four tropical freshwater species. Despite presenting good physicochemical performance and reduced toxicity of the influent for most species, AR and MR treatments remain acute and chronic toxicity. Overall, MR exhibited greater efficacy in reducing influent toxicity compared with AR. TBBPA bioaccumulation was observed in Chironomus sancticaroli after short-term exposure to 100% MR effluent. Multigenerational exposures highlighted changes in the wing length of C.sancticaroli, showing decreases after influent and AR exposures and increases after MR exposures. These findings underscore the need for ecotoxicological tools in studies of new treatment technologies, combining the removal of emerging contaminants with safeguarding aquatic biota. PRACTITIONER POINTS: Acidogenic and methanogenic reactors reduced the acute and chronic toxicity of wastewater containing tetrabromobisphenol A. Both treatments still exhibit toxicity, inducing short- and long-term toxic effects on four native tropical species. The aquatic species Pristina longiseta was most sensitive to effluents from acidogenic and methanogenic reactors. TBBPA concentrations recovered from Chironomus sancticaroli bioaccumulation analysis ranged from 1.07 to 1.35 μg g-1. Evaluating new treatment technologies with multiple species bioassays is essential for a comprehensive effluent toxicity assessment and ensuring aquatic safety.

Degradation of veterinary antibiotics by the ozonation process: Product identification and ecotoxicity assessment

The purpose of the study was to evaluate the effects of using of ozonation to remove antibiotics used, among others, in veterinary medicine, from the aqueous environment. The effect of this process on the degradation, mineralisation and ecotoxicity of aqueous solutions of ampicillin, doxycycline, tylosin, and sulfathiazole was investigated. Microbiological MARA® bioassay and two in silico methods were used for the ecotoxicity assessment. Ozonation was an effective method for the degradation of the antibiotics studied and the reduction in ecotoxicity of the solutions. However, after ozonation, the solutions contained large amounts of organic products, including compounds much less susceptible to ozonation than the initial antibiotics. Structures of 14, 12, 40 and 10 degradation products for ampicillin, doxycycline, tylosin, and sulfathiazole, respectively, were proposed. It was confirmed that ozone plays a greater role than hydroxyl radicals in the degradation of these antibiotics, with the exception of TYL. The use of ozonation to obtain a high degree of mineralisation is unfavourable and it is suggested to combine ozonation with biodegradation. The pre-ozonation will cause decomposition of antibiotic pharmacophores, which significantly reduces the risk of spread of antimicrobial resistance in the active biocenosis of wastewater treatment plants.

Innovative bioremediation of dexamethasone in aquatic ecosystems using Rhodococcus sp. D32: Pathway discovery and reduction of ecotoxicity

In response to the widespread environmental concern of endocrine disruptors, our research investigated the aerobic biodegradation of dexamethasone (DEX), a widely used synthetic glucocorticoid with endocrine-disrupting properties, by strain Rhodococcus sp. D32. This innovative strain showcases remarkable DEX-degrading capabilities, with the half-life for degrading 500 μg/L DEX in MH broth being just 7.56 h. Utilizing high-resolution mass spectrometry, we identified six transformation products (TPs) and revealed a unique steroid nucleus-opening pathway marked by A-ring lactonization and subsequent lactone hydrolysis. This newly discovered pathway deviates from the classical steroid 9,10-seco pathways and previous transformations that preserved the intact steroid nucleus, thus expanding our knowledge of microbial steroid transformations. Additionally, the degradation process progressively converts the parent DEX into less ecotoxic products, significantly reducing the overall ecotoxicity of the system. This reduction remains evident when considering the combined toxicity of DEX and its TPs, indicating a promising approach for lessening environmental harm. Strain D32 also proved effective in various authentic aquatic environments, including fishpond water, urban sewage, river water, and reservoir water, where its introduction markedly expedited the dissipation of DEX. Our findings underscore the potential of strain D32 as a powerful tool for the bioremediation of DEX, presenting an efficient and eco-friendly strategy to alleviate the effects of this endocrine disruptor in aquatic ecosystems.

A two dimensional Co(OH)2 catalytic gravity-driven membrane for water purification: a green and facile fabrication strategy and excellent water decontamination performance.

Cobalt-based materials are reported to be the most efficient catalysts in sulfate radical advanced oxidation processes (SR-AOPs). A green and facile method was developed in this work to prepare uniform Co(OH)2 hexagonal nanosheets, which was void of any organic solvents via mere ambient temperature stirring. The obtained nanosheets were assembled into a catalytic gravity-driven membrane, through which the removal efficiency of a typical pharmaceutical contaminant, ranitidine (RNTD), could reach ∼100% within 20 min. Meanwhile, the catalytic membrane also demonstrated effective removal performance towards various pollutants. In order to augment the long-term stability of catalytic membranes, Co(OH)2/rGO composites were fabricated using the same strategy, and a Co(OH)2/rGO catalytic membrane was prepared correspondingly. The Co(OH)2/rGO membrane could maintain a ∼100% removal of RNTD over a constant reaction period lasting for up to 165 hours, which was approximately 11 times that of the sole Co(OH)2 membrane (15 h). Analysis of element chemical states, metal ion concentration in filtrates, and quenching experiments suggested that the combination with rGO could promote the electron transfer to accelerate the Co(II) regeneration, restrain the cobalt dissolution to alleviate the active site loss, and contribute to the production of 1O2via synergistic effects of oxygen-containing groups in rGO. Toxicity assessment was performed on RNTD and its degradation intermediates to confirm the reduction in ecotoxicity of the treated feed. Overall, this work not only offered guidance for the application of nanosheets in AOP membranes, but also had implications for the environmentally-friendly preparation protocol to obtain functional metal hydroxides.

Electro-oxidative removal of five antibiotics of different classes and their mixture using Ti/Sb-SnO2/PbO2 anode: Kinetics, degradation pathway, and toxicity evaluation

In this study, electro-oxidation of representative antibiotics of five different classes viz. sulfonamides (sulfamethoxazole), penicillin (ampicillin), tetracycline (tetracycline), aminoglycoside (streptomycin), macrolide (erythromycin), and the mixture of representative antibiotics by Ti/Sb-SnO2/PbO2 anode were studied. Ti/Sb-SnO2/PbO2 anode was synthesized and characterized by SEM, EDAX, XRD, CV, and LSV analysis. The physical characterization revealed the compact nature of the PbO2 crystals, composition, and crystal arrangement in β-planes. Further, CV and LSV confirmed the electrode stability under the operating condition with high oxygen evolution potential. The in situ generated reactive oxygen species, such as hydroxyl radicals, hydrogen peroxide, and sulfate radicals, were quantified. Sulfamethoxazole was used as a model antibiotic to study the effect of current density (10–40 mA cm−2), initial concentration (100–1000 μg L−1), and water matrix (25 mM sodium sulfate and secondary effluent). The kinetic constants were determined by adopting a non-linear regression model and curve fitting. The optimum current density was 30 mA cm−2 with k1 = 0.4162 min−1. Under the optimum conditions, degradation of antibiotics was >99 % irrespective of the antibiotic class. The intermediates were identified by LC-MS/MS analysis, and a complete electro-oxidation pathway was proposed for five antibiotics of different classes. The toxicity of the representative antibiotics and mixture was evaluated by V. fischeri bioluminescence inhibition. Overall, the toxicity was found to decrease, and extending the treatment time ensures effective eco-toxicity reduction by allowing safe discharge of the treated water. The observed results confirm that the electro-oxidation with Ti/Sb-SnO2/PbO2 anode is an effective and a low-cost alternative for BDD.

Reducing the environmental impact of offshore H2S scavenging wastewater via hydrothermal oxidation

The discharge of H2S scavenging wastewaters, containing spent and unspent scavengers (SUS), into the marine environment is a large contributor to the environmental impact of offshore oil and gas production. Hydrothermal oxidation (HTO) can be a viable method for on-site treatment of the SUS before discharge, but the effect of the process on the ecotoxicity of the effluent has not been investigated so far. The aim of this study was to investigate the potential of the HTO technology in reducing the environmental impact by linking the chemical process design with ecotoxicity reduction. For this, we combined HTO experiments on a SUS sample from an oil and gas platform in the North Sea with whole effluent ecotoxicity evaluation before and after the treatment. The HTO process was carried out under excess of oxygen, for temperatures and pressures in the range 199 to 350°C and 83 to 228 bar, respectively, and for reaction times of 5 to 360 min. Initially, the SUS sample exhibited very high ecotoxicity, which was drastically reduced by the HTO process. More specifically, the ecotoxicity towards bacteria was reduced more than 90% for all HTO conditions, while the reduction in algal toxicity was in the range 48% to 66%, 59% to 86% and 60% to 82% at reaction temperatures of 199°C, 279°C, and 350°C, respectively. Furthermore, this work shows how typical wastewater chemical analyses, such as COD and TOC, and ecotoxicity tests towards different organisms provide complementary information, which should be used in combination to optimize operating conditions of the HTO process.

Oxidative treatment of bisphenol A by Fe(VI) and Fe(VI)/H2O2 and identification of the degradation products

Bisphenol A (BPA) is classified as a xenoestrogen compound and has caused adverse effects in humans and animals. Ferrate(VI) (Fe(VI)) and the combination of Fe(VI) and hydrogen peroxide ( H 2 O 2 ) were investigated to degrade BPA in water. This study evaluated the impact of BPA initial concentration (50, 200, and 1, 000 μ g L −1 ) and background anions ( Cl − , PO 4 3 − , and NO 3 − ) on the degradation efficiency of the combined oxidants. The results showed that Fe(VI)/H 2 O 2 performed significantly better than Fe(VI) or H 2 O 2 alone. BPA degradation ( 50 μ g L −1 ) using Fe(VI)/H 2 O 2 was recorded at 99.8% within 60 min at pH 8.0 with [Fe(VI)]/[H 2 O 2 ] molar concentration ratio of 250:2,500. At the same initial concentration of BPA and pH condition, the degradation of BPA using Fe(VI) and H 2 O 2 was recorded as 89% ([Fe(VI)]/[BPA]=5) and 33.5% ([H 2 O 2 ]=2, 500 μ g L −1 ), respectively. BPA degradation using Fe(VI)/H 2 O 2 was 99.8%, 85.3%, and 43.8% for an initial concentration of 50, 200, and 1, 000 μ g L −1 , respectively. The presence of Cl − and NO 3 − ions had no obvious effects on BPA degradation; however, a considerable reduction in the degradation efficiency was observed for PO 4 3 − ( 350 μ g L −1 ) due to the complexation between PO 4 3 − ion and ferric oxy/hydroxides. There were eleven intermediates detected in BPA degradation using Fe(VI)/H 2 O 2 , and three degradation pathways were proposed, including hydroxylation, cleavage of the C-C bond, and oxidation to form ring opening products. A reduction in ecotoxicity was observed after 60 min of reaction for both Fe(VI) and Fe(VI)/H 2 O 2 . • Bisphenol A (BPA) degradation using Ferrate(VI) (Fe(VI)) and Fe(VI)/H 2 O 2 was studied. • Nearly a complete degradation of BPA in water was achieved with Fe(VI)/H 2 O 2 . • BPA degradation by Fe(VI)/H 2 O 2 was affected by PO 4 3 − , but not by Cl − and NO 3 − . • Eleven intermediates in the BPA degradation were detected. • BPA degradation pathways during the oxidative treatments were proposed.

Evaluation of a bioelectrochemical reductive/oxidative sequential process for chlorinated aliphatic hydrocarbons (CAHs) removal from a real contaminated groundwater

In the present study, the sequential reductive/oxidative bioelectrochemical process has been tested with real groundwater from a contaminated site in Northern Italy for chlorinated aliphatic hydrocarbons (CAHs) removal. The sequential system was developed by connecting in series two membrane-less microbial electrolysis cells (MECs) equipped with an internal graphite counter electrode. The first MEC aimed at the CAHs reductive dechlorination (RD) and was constituted of a granular graphite working electrode. In the second MEC, a mixed metal oxide working electrode stimulated the oxidative dechlorination of the low chlorinated RD's by-products through oxygen production. The sequential process allowed complete mineralization of the CAHs contained in the real groundwater. A complete reduction of the perchloroethylene into vinyl chloride (VC) was observed in the first MEC polarized at −450 mV vs SHE, while the resulting VC was oxidized with a 92 ± 2 % efficiency in the second MEC due to the HRT increment from 0.7 to 1.7 days. Biomarkers of the reductive (Dehalococcoides mccartyi 16S rRNA and reductive dehalogenase genes) and oxidative (etnE, etnC genes) dechlorination have been monitored in the two MECs along with the ecotoxicity tests. Overall, they provide information on the efficiency of the applied technology and allow to assess the potential adverse effects. According to the Tetrahymena pyriformis reproduction inhibition test and Panagrellus redivivus mortality tests, showed a significant ecotoxicity reduction with respect its initial inhibitory effect at the tested concentrations.

Transformation and stabilization of heavy metals during pyrolysis of organic and inorganic-dominated sewage sludges and their mechanisms

Improperdisposal of sludge will release heavy metals contained in sludge into soils or waters which could further move through the food chain, posing a risk to human health. Understanding the transformation and stabilization of heavy metals (HMs) during pyrolysis is of great value for safe disposal of sludge. Herein, municipal sewage sludge (MSS, organic-dominated) and pharmacy sludge (PS, inorganic-dominated) were pyrolyzed to investigate the effects of organic and inorganic components and temperature on the stabilization of HMs in sludges. The results showed that pyrolysis can promote the transition of HMs from mobile fractions to stable fractions. Compared to MSS and PS, the potential ecological risk index of biochar derived from MSS and PS decreased by 95.51% and 85.05%, respectively, after pyrolysis at 800 °C. The stabilization of HMs in MSS was mainly due to the complexation reactions between metals and amide functional groups (-CO-NH-) during pyrolysis. Moreover, the mechanism of HMs stabilization in PS lied in the formation of a stable crystal-structure such as copper iron oxide (Cu6Fe3O7) and copper iron phosphate (Cu2Fe5(PO4)6, Cu3Fe4(PO4)6) with iron-containing minerals after high-temperature pyrolysis. The results of this study indicated that the organic and inorganic components of sludge play different roles in the stabilization and transformation of HMs during pyrolysis, which provided a scientific basis for the ecotoxicity reduction of HMs and safe disposal of sludge.

Micropollutant transformation and toxicity: Electrochemical ozonation versus biological metabolism

Environmental water sources are constantly polluted by anthropogenic compounds, not always minimized by conventional water treatment methods to remove these compounds at the micro- and nano-range. The absolute concentrations of a suite of seven representative environmental micropollutants were compared pre- and post-treatment with both ozone and microbial biofilms, in terms of removal efficiencies and toxicity assays. Both synthetic micropollutant mixes and environmental water samples were evaluated. The study started with two representative micropollutants (carbamazepine, CBZ, and sulfamethoxazole, SMX), and broadened into a suite of pollutants, evaluating whole-sample eco-toxicological footprints. An ozone concentration of 4.24 ± 0.27 mg/L in tap water, resulted in an 87.9% and 96.5% removal of CBZ and SMX, respectively, within 1 min. Despite almost immediate removal of parent micropollutants by oxidation, endocrine disruption potential (anti-estrogenicity) of CBZ and SMX required up to 240 min of ozone treatment to show no assay effect. A broader suite of micropollutants in more complex environmental matrices showed scavenging of ozone (2.95 ± 0.17–0.25 ± 0.03 mg/L) and varying micropollutant recalcitrance to oxidation. Lower matrix pollution led to lower reduction in eco-toxicity. Microbial degradation of CBZ and SMX (56% and 70% versus 19% and 79%, respectively, in duplicate biofilms) by nutrient-limited biofilms showed less removal than ozonation, with marked variation due to the stochastic nature of biofilm sloughing. Microbial degradation of CBZ and SMX resulted in an increase of >90% in both estrogenicity and Aliivibrio inhibition. The results obtained from this study address a gap in understanding the removal efficiency of micropollutants, where the removal process often receives more attention than the comparative reduction of toxicological effects. This shift from a controlled laboratory environment to real-world scenarios also provided comparative insights into the removal of micropollutants and the eco-toxicity of the transformation by-products of each process.

Reuse of Textile Dyeing Wastewater Treated by Electrooxidation

Wastewater reuse has been addressed to promote the sustainable water utilization in textile industry. However, conventional technologies are unable to deliver treated wastewater with the quality required for reuse, mainly due to the presence of dyes and high salinity. In this work, the feasibility of electrooxidation, using a boron-doped diamond anode, to provide treated textile dyeing wastewater (TDW) with the quality required for reuse, and with complete recovery of salts, was evaluated. The influence of the applied current density on the quality of treated TDW and on the consecutive reuse in new dyeing baths was studied. The ecotoxicological evaluation of the process towards Daphnia magna was performed. After 10 h of electrooxidation at 60 and 100 mA cm−2, discolorized treated TDW, with chemical oxygen demand below 200 (moderate-quality) and 50 mg L−1 (high-quality), respectively, was obtained. Salt content was unchanged in both treatment conditions, enabling the consecutive reuse without any salt addition. For the two reuse cycles performed, both treated samples led to dyed fabrics in compliance with the most restrictive controls, showing that an effective consecutive reuse can be achieved with a moderate-quality water. Besides the water reuse and complete salts saving, electrooxidation accomplished an ecotoxicity reduction up to 18.6-fold, allowing TDW reuse without severe ecotoxicity accumulation.

Sustainable iron-olive stone-based catalysts for Fenton-like olive mill wastewater treatment: Development and performance assessment in continuous fixed-bed reactor operation

Iron oxide catalysts supported on activated carbon prepared from olive stones (OSAC–Fe) were used for the catalytic wet peroxide oxidation of refractory polyphenolic solutions and real olive mill wastewater (OMW) in a fixed-bed reactor (FBR). Catalysts were prepared with different precursors and Fe-loadings. The resulting catalysts were essentially microporous materials with well-developed surface areas (SBET = 588–689 m2/g), whereas the nature and distribution of metallic nanoparticles were found to be strongly dependent on the precursor used.The stability and catalytic performance were screened in a batch reactor using a synthetic solution and the most promising catalyst – prepared at 5 wt.% Fe using Fe(NO3)3 as the precursor – was selected for the operation of a continuous FBR. Different operational conditions were evaluated through a parametric study. At 60 °C, [H2O2]feed = 1.5 g/L and Q = 0.75 mL/min, 87% total phenolic content removal (TPh), 28% mineralization and 88% H2O2 conversion were achieved at steady-state. Real OMW samples were then treated at a fixed [H2O2]/[COD] in the feed, and TPh removals of 57–71% and COD (chemical oxygen demand) reductions of 26–34% were attained. The resulting effluents showed an overall reduction of eco-toxicity and improvement of biodegradability indices.

Selecting the most environmentally friendly oxidant for UVC degradation of micropollutants in urban wastewater by assessing life cycle impacts: Hydrogen peroxide, peroxymonosulfate or persulfate?

The quality of water bodies has been decreasing over time. Urban wastewater treatment plants (UWWTPs) are key players to avoid that potentially toxic micropollutants reach the environment, and advanced treatment processes are being applied to address this issue. However, several variables have to be taken into account, particularly environmental sustainability. The aim of this study is to assess the life cycle impacts of combining UVC with different oxidants – hydrogen peroxide (H2O2), peroxymonosulfate (PMS) and persulfate (PS) –, considering different concentrations (0.05, 0.20 and 0.50 mM) and UVC dosages of 42, 63 and 170 J/L, corresponding to UV contact times of 4, 7 and 18 s in a specific industrial equipment. UVC/PMS was the worst performing process (despite being able to achieve removals similar to UVC/H2O2), followed by UVC/PS. Both would only be preferred relatively to H2O2 if much lower concentrations of PMS or PS could be used to achieve the same removal of micropollutants (10 times lower was not enough). Additionally, PMS and PS production contributes more to the environmental footprint than the electricity use, unlike H2O2. Therefore even if considering lower treatment times when using sulfate-based oxidants, these will still be more impactful than using H2O2 at the studied conditions. Based on both avoided and generated impacts, H2O2 is the best option environmentally. In this case, the environmental impacts are more affected by an increase in treatment time rather than by an increase in the H2O2 concentration. It is thus best to opt for a higher concentration and the lowest treatment time possible for a significant ecotoxicity reduction. Electricity is a relevant parameter in all cases and its impact can be reduced in nearly all endpoint categories by opting for cleaner energy sources.

Enhanced pilot bioremediation of oily sludge from petroleum refinery disposal under hot-summer Mediterranean climate

Large pilot scale bioremediation approaches were implemented for the treatments of oily sludge (OS) characterised by alkaline pH (pH > 9), high concentration of metals (3% dry weight) and high total petroleum hydrocarbons content (TPH) rangingbetween 22,000 and 67,300 mg kg −1 from a Tunisian petroleum refinery. The treatments included bioaugmentation and biostimulation approaches with autochthonous isolated bacterial strains and consortia. Chemical, microbial, and ecotoxicological analyses were performed over a period of 180 days incubation. The bioremediation treatments favoured the development of Proteobacteria , Firmicutes and Bacteroidetes following an ecological succession of specialist bacterial groups, first associated to hydrocarbon degradation (e.g. Marinobacter and Alcanivorax ) that resulted in a greater extent of TPH-degradation (up to 80%), and the selection of metal resistant bacteria including Hyphomonas , Phaeobacter , and Desulfuromusa . The best performances were obtained when bioaugmentation and biostimulation were combined. Over 90% of the TPH initial concentration was degraded over 180 days, which was accompanied with a 3-fold reduction of ecotoxicity. Our study demonstrates the efficacy of large pilot scale bioremediation of highly contaminated oily sludge, providing the evidence that the management of autochthonous microbial communities is of paramount importance for the success of the bioremediation process. • Effective oil sludge bioremediation by managing bacterial community. • Optimal treatment combining bioaugmentation and biostimulation. • Bacterial community plasticity evidenced through ecological succession.

Phytoremediation mechanisms and plant eco-physiological response to microorganic contaminants in integrated vertical-flow constructed wetlands

Vegetations play a vital role in the ecological function of constructed wetlands (CW), but the systemic phytoremediation mechanism of CW is still unclear. An integrated vertical-flow constructed wetland (IVCW) was established to elucidate the phytoremediation mechanisms and plants eco-physiological response to an emerging contaminant, sulfamethoxazole (SMX). Attenuation of SMX in IVCW with and without vegetation (Acorus calamus) are comparatively analyzed. The results showed significant enhancement of removal efficiencies of total nitrogen (via intensified denitrification) and SMX by up to 10% respectively with vegetation. A unique micro-rhizo environment was created by stimulating the denitrifiers, Clostridium_sensu_stricto, Ignavibacterium, Rhodanobacter, and Geobacter. Free-living plant growth-promoting bacteria, unclassified_Burkholderiales and unclassified_Betaproteobacteria, proliferated in the rhizosphere, protecting the growth mechanism of A. calamus and, consequently, promoting performance of the IVCW. Overall, A. calamus exhibited tolerance to SMX, maintaining its photosynthesis rate and stabilizing the plant cell structure by an effective antioxidant system. The growth and defense mechanisms of A. calamus appeared to positively correlate with the IVCW performance, whereby the photosynthetic rate and antioxidant enzymes activities peaked together with the maximum removal efficiency of TN (77.81%) and SMX (99.88%). The contribution of vegetation to ecotoxicity reduction in CW might be underrated as absorbed SMX could be phytodegraded into less toxic metabolites via specific enzymes.

Diclofenac Toxicity Abatement in Wastewater with Solar Disinfection: A Study in the Rural Area of Brazil’s Central−West Region

Domestic wastewater has been targeted for the presence of emerging contaminants such as antibiotics, of which diclofenac is one of the most frequently detected. Many studies have focused on the removal of these emerging pollutants. However, the legislation has focused on toxicity monitoring. In search of simplified solutions for rural areas, and to guarantee the safe reuse of effluent in agriculture, this study evaluated the efficiency of a decentralized solar disinfection (SODIS) system regarding the reduction of ecotoxicity, phytotoxicity, and pathogens in domestic wastewater after adding diclofenac potassium. For this purpose, the bioindicators Artemia sp., Allium cepa L. and Lactuca sativa were used, after 1, 2, and 3 h of exposure to solar radiation. After 3 h of exposure to solar radiation, toxicity was reduced and root growth inhibition was noted, which indicates low effluent toxicity after treatment by the SODIS system. It was achieved a reduction of 3 and 2 log units in the concentration of total coliforms and Escherichia coli, respectively.

Floating treatment wetland for nutrient removal and acute ecotoxicity improvement of untreated urban wastewater

Wastewater treatments are often expensive, and the resulting effluent can still harm the environment. Floating treatment wetland is an alternative low-cost eco-technology in which a hydroponic root network remediates polluted waters. This system has been broadly studied as a secondary treatment to remove nutrients and pollutants, but its application to improve raw wastewater quality is still incipient. Moreover, few studies have assessed acute ecotoxicity toward fish after treatment. Thus, this study aimed to evaluate the efficiency of a mesocosm floating treatment wetland to improve the raw wastewater quality from a university campus in South Brazil. Efficiency was assessed based on the improvement of physicochemical parameters (conductivity, pH, turbidity, color), nutrients (nitrogen and phosphorus), and heavy metals (zinc, chromium, copper, lead, and cadmium); Typha domingensis adaptability; and acute fish ecotoxicity reduction after wastewater treatment. Influent was treated with macrophytes tanks and their respective controls. T test was used to compare influent versus effluent samples, and macrophytes tanks versus controls. A Principal Component Analysis identified the main explanatory variables on the system, and a Two-way Cluster Analysis grouped samples before and after treatment. The results show floating mats efficiency in reducing most parameters compared to the influent, except phosphorus and zinc. Control tanks were also effective in improving wastewater quality due to microalgae and duckweed proliferation. In conclusion, floating treatment wetlands with Typha domingensis have the potential to treat raw wastewater. Further nitrogen removal in wastewater might improve acute ecotoxicity toward fish.

Ternary TiO2/WO3/CQDs nanocomposites for enhanced photocatalytic mineralization of aqueous cephalexin: Degradation mechanism and toxicity evaluation

A highly solar active nanocomposite with sheet-like WO3 skeleton and evenly loaded TiO2 and carbon quantum dots (CQDs) was synthesized by facile hydrothermal-calcining process, which showed 3.1- and 46.6- times activity on antibiotic (cephalexin) degradation than TiO2 and WO3, respectively. The construction of TiO2/WO3 heterojunction narrowed the band gap and facilitated the electrons-holes separation. The π conjugated CQDs was found to further improve the charge separation and extend the visible light response by photosensitization. However, the promoted charge separation predominantly contributed to the improved photocatalytic activity. The contributions of detected reactive species follows the order of: O2–>1O2>OH>h+. The cephalexin degradation mechanism and pathway were proposed based on DFT (density functional theory) calculation and experimental analysis. The photocatalytic mineralization efficiency can reach 92.4% in 4 h, indicating the efficient reduction of ecotoxicity of cephalexin and its intermediates. This new composite proved to have great potentials for emerging contaminants degradation in water.