High oxidation potential as well as other advantages over other tertiary wastewater treatments have led in recent years to a focus on the development of advanced oxidation processes based on sulfate ...radicals (SR-AOPs). These radicals can be generated from peroxymonosulfate (PMS) and persulfate (PS) through various activation methods such as catalytic, radiation or thermal activation. This review manuscript aims to provide a state-of-the-art overview of the different methods for PS and PMS activaton, as well as the different applications of this technology in the field of water and wastewater treatment. Although its most widespread application is the elimination of micropollutants, its use for the disinfection of wastewater is gaining increasing interest. In addition, the possibility of combining this technology with ultrafiltration membranes to improve the water quality and lifespan of the membranes has also been discussed. Finally, a brief economic analysis of this technology has been undertaken and the different attempts made to implement it at full-scale have been summarized. As a result, this review tries to be useful for all those people working in that area.
Contaminated water with landfill leachate (CWLL) with high salinity and high organic content (total organic carbon (TOC) = 649 mg/L and Chemical Oxygen Demand (COD) = 1175 mg/L) is a toxic and ...non-biodegradable effluent. The present research aimed to assess the treatment effectiveness of CWLL by electrocoagulation (EC)/oxidant process. The ferrous ions generated during the process were employed as coagulant and catalyst for the activation of different oxidants such as peroxymonosulfate (PMS), peroxydisulfate (PDS), hydrogen peroxide (HP), and percarbonate (PC) to decrease TOC in CWLL. Removal of ammonia, color, phosphorous, and chemical oxygen demand (COD) from CWLL effluent was explored at various processes. EC/HP had the best performance (∼73%) in mineralization of organic pollutants compared to others under the condition of pH 6.8, applied current of 200 mA, oxidant dosage of 6 mM, and time of 80 min. The oxidation priority was to follow this order: EC/HP > EC/PMS > EC/PDS > EC/PC. These processes enhanced the biodegradability of CWLL based on the average oxidation state and biochemical oxygen demand (BOD)/COD ratio. SUVA254 and E2/E3 indices were also investigated on obtained effluents. The phytotoxicity evaluation was carried out based on the germination index, indicating that the electro-activated oxidant was an effective system to reduce the toxicity of polluted waters. EC/HP showed supremacy compared to others in terms of efficiency, cost, and detoxification. Therefore, the electro-activated oxidant system is a good means for removing organic pollutants from real wastewater.
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•PC, HP, PDS, and PMS were used in EC to treat CWLL.•COD, ammonia, TOC, color, and phosphorous were monitored in different processes.•Phytotoxicity, biodegradability, and humification of each effluent were evaluated.•Economic analysis showed that EC/HP is the best option for the treatment.
The advancement of science has facilitated increase in the human lifespan, reflected in economic and population growth, which unfortunately leads to increased exploitation of resources. This ...situation entails not only depletion of resources, but also increases environmental pollution, mainly due to atmospheric emissions, wastewater effluents, and solid wastes. In this scenario, it is compulsory to adopt a paradigm change, as far as the consumption of resources by the population is concerned, to achieve a circular economy. The recovery and reuse of resources are key points, leading to a decrease in the consumption of raw materials, waste reduction, and improvement of energy efficiency. This is the reason why the concept of the circular economy can be applied in any industrial activity, including the wastewater treatment sector. With this in view, this review manuscript focuses on demonstrating the challenges and opportunities in applying a circular economy in the water sector. For example, reclamation and reuse of wastewater to increase water resources, by paying particular attention to the risks for human health, recovery of nutrients, or highly added-value products (e.g., metals and biomolecules among others), valorisation of sewage sludge, and/or recovery of energy. Being aware of this situation, in the European, Union 18 out of 27 countries are already reusing reclaimed wastewater at some level. Moreover, many wastewater treatment plants have reached energy self-sufficiency, producing up to 150% of their energy requirements. Unfortunately, many of the opportunities presented in this work are far from becoming a reality. Still, the first step is always to become aware of the problem and work on optimizing the solution to make it possible.
The degradation of acetaminophen (ACM) was comparatively studied by UV/chlorine and UV/H2O2 systems. An apparent reduction in the removal rate was observed above the optimum pH levels of 7.0 and 3.0 ...in UV/chlorine and UV/H2O2 processes, respectively. The relative contribution of each oxidizing agent in ACM removal using the two advanced oxidation processes (AOPs) was evaluated. Even though hydroxyl radicals, with the contribution percentage of 90.1%, were determined as the primary oxidizing species in ACM removal using the UV/H2O2 process, reactive chlorine species (RCS), with 43.8% of contribution percentage, were also found to play a pivotal role in ACM removal using the UV/chlorine process. For instance, dichlorine radical (Cl2•-) showed an acceptable contribution percentage of 32.2% in the degradation of ACM by the UV/chlorine process. The rate of ACM degradation significantly rose to 99.9% and 75.6%, as higher amounts of oxidants were used in the UV/chlorine and UV/H2O2 processes, respectively, within 25 min. The introduction of HCO3− ions and humic acid remarkably decreased the rate of ACM degradation in both techniques used in this study. The presence of NO3− and Cl− ions did not considerably affect the removal rate in the UV/chlorine process. The acute toxicity analysis revealed that a more pronounced reduction in the ACM solution toxicity could be achieved by the UV/H2O2 process compared to the UV/chlorine process, which should be ascribed to the formation of chlorinated products in the UV/chlorine treatment. Eventually, plausible oxidation pathways were proposed for each process.
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•Compared to UV/H2O2, UV/Cl2 was the more effective process for ACM degradation.•The hydroxyl radical was the dominant species for both systems.•Ferrous ions improved ACM degradation in both systems.•Compared to UV/Cl2, UV/H2O2 showed high efficiency in TOC removal & detoxification.
The purpose of this work is to offer a methodology for the introduction and consolidation of social indexes within a Life Cycle Sustainability Assessment for the evaluation of large-scale electricity ...production. This methodology is based on an interrelation of the UNEP subcategories with the global indicator framework for the Sustainable Development Goals, resulting in 9 categories of social impact quantified by 10 indexes. To evaluate the introduction of this methodology in an LCSA a study case is used. It is applied to obtain social indexes for the 2019, 2030 and 2050 Spanish electricity scenarios, which involve different electricity generation and storage technologies: involve coal, natural gas, nuclear, hydropower, wind, solar photovoltaic, concentrated solar, biomass and storage technologies. Within the study case, an environmental life cycle assessment is also conducted, while the impacts of the economic dimension are estimated by the levelized cost of energy. This study reveals that even before important qualitative information is brought to light, as should be done in any decision-making process, there are important gaps that can be filled in terms of quantitative information in an LCSA. To do so, it provides with a methodology to expand the number of social indexes normally used in this type of assessments with the purpose of contributing to decision processes with clarity and transparency. Labour rights, salary differences for the same position, diversity in executive positions, child labour, and R&D expenditure complement the previously used occupational injuries, fatalities due to large accidents, and direct employment. The proposed methodology is applied to a Spanish case study, demonstrating the benefits and disadvantages associated with the modification of the electricity mix. However, it also highlights significant information gaps in availability and transparency that need to be addressed in future research, as part of the path towards standardizing LCSA.
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•Sustainable development goals can be used for a crucial selection of social indexes.•The increase of social indexes is key in life cycle sustainability assessment.•Grounded quantitative social indexes broaden the objectivity of LCSA.•Life cycle sustainability assessments can optimize future electricity generation.
Wastewater recycling technologies are developed in areas where the necessity of water resources cannot be satisfied by natural sources. Nevertheless, nowadays trends and European Union Plans show an ...increasing interest on using these technologies to reduce environmental impacts. This manuscript aims to address the question of the real environmental results of using these technologies and the differences between each specific case using the Life Cycle Assessment (LCA) methodology. A real case study is analyzed to answer this question: the integral water cycle of a northern of Spain, comparing a traditional water supply system (system I), and an alternative wastewater regeneration plant (system II). System II presents a higher impact for all categories (between 1.2 and 37 times higher), except for land use, where it is reduced by 53 %. These results show a larger impact produced by the alternative system due to higher energy and chemical product consumption. Energy consumption is the main factor causing the highest impact in most of the impact categories for both studied systems, including the one associated to the water resource consumption. It accounts for at least 50 % of the total impact for each system in 7 of the 16 evaluated impact categories. In terms of climate change, energy consumption is not particularly significant in system I, but it is for system II, where it represents around 50 % of that impact. In the categories where the impact is not determined by energy consumption, chemical product consumption and waste and discharge treatment are the most relevant factors. In this sense, this paper highlights the importance of analysing each case specifically and underscores the usefulness of using LCA methodology as a tool to improve decision-making in resource management, with water resources emerging as a crucial focal point.
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•Application of LCA Methodology as a decision-making tool in water supply systems•The use of reclaimed water might increase environmental impact, except for land use.•The increases can range from 1.2 to 37 times, but it will depend on each case study.•Energy consumption in reclaimed water systems represents 50 % of the impact on climate change.•More similar studies would allow for an increase in knowledge about potential impacts.
Tetracycline is a broad-spectrum antibiotic largely found in the environment with many adverse effects on environmental and human health. Recently, the coupling of different advanced oxidation ...processes has been promised as the effective approach for the degradation of refractory pollutants. In this work, the magnetically separable Ag/CuFe2O4/CQDs photocatalyst was successfully synthesized and characterized by X-ray powder diffraction, Differential reflectance spectroscopy, Transmission Electron Microscopy, Field emission scanning electron microscopy, and Energy-dispersive X-ray spectroscopy analysis. The potential of different systems namely photocatalyst/light, photocatalyst/persulfate and photocatalyst/persulfate/light as well as operation parameters, reusability and involved radicals were evaluated for tetracycline degradation. The highest removal efficiency for the different systems was obtained as photocatalyst/persulfate/light (100%, 30 min) > photocatalyst/persulfate (100%, 55 min) > photocatalyst/light (100%, 75 min). The 47% total organic carbon removal was obtained in optimum condition and intermediate products were proposed based on results of liquid chromatography-mass spectrometry. The results indicated that reaction rate constant (Kobs) decreased from 0.1319 to 0.0270 min−1, 0.0332 min−1 and 0.0174 min−1 with increasing pH, initial tetracycline concentration and humic acid (HA), respectively. The inhibitory effect of inorganic ions was obtained as Cl− < NO3− < HCO3−. The nanocomposite showed high reusability after 5 consecutive cycles (91.5%). The results of the scavenger analysis suggest the superoxide and positive hole are the main species involved in tetracycline degradation.
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•Ag/CuFe2O4/CQDs nanocomposite was synthesized via hydrothermal process.•PS oxidation system was most effective than the photocatalytic process in TC degradation.•Nanocomposite containing Ag showed a high catalytic activity compared to other components.•Inorganic ions and humic acid have an inhibitory effect on the degradation process.•O2- and h+ are the main ROS in the TC degradation.
This research reports for the first time the full-scale application of different homogeneous Advanced Oxidation Processes (AOPs) (H2O2/UV-C, PMS/UV-C and PMS/Fe(II)/UV-C) for the removal of ...antibiotics (ABs) and antibiotic resistance genes (ARGs) from wastewater effluent at Estiviel wastewater treatment plant (WWTP) (Toledo, Spain).
AOPs based on the photolytic decomposition of H2O2 and peroxymonosulfate tested at low dosages (0.05–0.5 mM) and with very low UV-C contact time (4–18 s) demonstrated to be more efficient than UV-C radiation alone on the removal of the analyzed ABs. PMS (0.5 mM) combined with UV-C (7 s contact time) was the most efficient treatment in terms of AB removal: 7 out of 10 ABs detected in the wastewater were removed more efficiently than using the other oxidants. In terms of ARGs removal efficiency, UV-C alone seemed the most efficient treatment, although H2O2/UV-C, PMS/UV-C and PMS/Fe(II)/UV-C were supposed to generate higher concentrations of free radicals. The results show that treatments with the highest removal of ABs and ARGs did not coincide, which could be attributed to the competition between DNA and oxidants in the absorption of UV photons, reducing the direct photolysis of the DNA. Whereas the photolytic ABs removal is improved by the generation of hydroxyl and sulfate radicals, the opposite behavior occurs in the case of ARGs. These results suggest that a compromise between ABs and ARGs removal must be achieved in order to optimize wastewater treatment processes.
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•Wastewater treatment by Advanced Oxidation Processes studied at full-scale•Removal of antibiotic residues and antibiotic resistance genes assessed•Oxidants photolysis proved more efficient than UV-C alone for antibiotics removal•Sulfate radical based processes did not improve the ARGs removal reached by UV-C•Competition between DNA and oxidants for absorption of UV photons is hypothesized
•SODIS and solar-assisted oxidative treatments were assayed in large scale plastic bottles.•5-log bacterial inactivation was attained both in 25-L PET and 19-L polycarbonate bottles.•The choice of ...material influences the oxidative processes of E. coli inactivation pathways.•Testing of leachables showed no mutagenicity & estrogenicity was higher for polycarbonate.•The levels of estrogenic activity detected were not a threat to human health.
Solar disinfection (SODIS) in 2-L bottles is a well-established drinking water treatment technique, suitable for rural, peri‑urban, or isolated communities in tropical or sub-tropical climates. In this work, we assess the enlargement of the treatment volume by using cheap, large scale plastic vessels. The bactericidal performance of SODIS and two solar-Fe2+ based enhancements, namely photo-Fenton (light/H2O2/Fe2+) and peroxymonosulfate activation (light/PMS/Fe2+) were assessed in 19-L polycarbonate (PC) and 25-L polyethylene terephthalate (PET) bottles, in ultrapure and real water matrices (tap water, lake Geneva water). Although SODIS always reached total (5-logU) inactivation, under solar light, enhancement by or both Fe2+/H2O2 or Fe2+/PMS was always beneficial and led to an increase in bacterial elimination kinetics, as high as 2-fold in PC and PET bottles with tap water for light/H2O2/Fe2+, and 8-fold in PET bottles with Lake Geneva water. The toxicological safety of the enhancements and their effects on the plastic container materials was assessed using the E-screen assay and the Ames test, after 1-day or 1-week exposure to SODIS, photo-Fenton and persulfate activation. Although the production of estrogenic compounds was observed, we report that no treatment method, duration of exposure or material resulted in estrogenicity risk for humans, and similarly, no mutagenicity risk was measured. In summary, we suggest that SODIS enhancement by either HO•- or SO4•−-based advanced oxidation process is a suitable enhancement of bacterial inactivation in large scale plastic bottles, without any associated toxicity risks.
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The occurrence of micropollutants (MPs) in the aquatic environment poses a threat to the environment and to the human health. The application of sulfate radical-based advanced oxidation processes ...(SR-AOPs) to eliminate these contaminants has attracted attention in recent years. In this work, the simultaneous degradation of 20 multi-class MPs (classified into 5 main categories, namely antibiotics, beta-blockers, other pharmaceuticals, pesticides, and herbicides) was evaluated for the first time in secondary treated wastewater, by activating peroxymonosulfate (PMS) with UV-A radiation, without any pH adjustment or iron addition. The optimal PMS concentration to remove the spiked target MPs (100 μg L−1) from wastewater was 0.1 mM, leading to an average degradation of 80% after 60 min, with most of the elimination occurring during the first 5 min. Synergies between radiation and the oxidant were demonstrated and quantified, with an average extent of synergy of 69.1%. The optimized treatment was then tested using non-spiked wastewater, in which 12 out of the 20 target contaminants were detected. Among these, 7 were degraded at some extent, varying from 10.7% (acetamiprid) to 94.4% (ofloxacin), the lower removals being attributed to the quite inferior ratio of MPs to natural organic matter. Phytotoxicity tests carried out with the wastewater before and after photo-activated PMS oxidation revealed a decrease in the toxicity and that the plants were able to grow in the presence of the treated water. Therefore, despite the low degradation rates obtained for some MPs, the treatment effectively reduces the toxicity of the matrix, making the water safer for reuse.
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•The average extent of synergy obtained by PMS/UV-A LED was 69%.•80% average degradation of micropollutants (100 μg L−1) was achieved with PMS/UV-A.•Most of the removal of micropollutants occurred in the first 5 min of reaction.•Phytotoxicity reduction was observed after PMS/UV-A treatment.•Roots and shoots of germinated seeds were longer when fed with treated wastewater.
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