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The treatment of wastewater, financed through environmental taxes, is key to the development of a sustainable economy. The objective of this study is to verify whether the tax loads on wastewater discharges applied in Spain are effective, allowing the costs of secondary and tertiary treatments to be financed. First, the revenues collected from taxes related to the discharge of wastewater in the different Spanish regions, which reach an average value of 0.72 €/m3, are analysed. Second, the costs of secondary wastewater treatment, prolonged aeration, activated sludge with nutrient removal, and activated sludge without nutrient removal are studied. Additionally, the costs of tertiary treatments, with environmental objectives and for reuse purposes, are considered. The analysis carried out reveals high heterogeneity in the amounts collected through taxes in the different Autonomous Communities. In some cases, these amounts do not cover the costs of the treatments. An urgent review is therefore required of the financing systems applied in order to secure a level of income that can cover all the exploitation and investment costs incurred.

Laundry sector consumes a huge amount of water which is usually discharged as wastewater instead of being reused. The application of biological treatment of laundry wastewater coupled with post-treatment utilizing advanced oxidation processes creates a possibility to recycle water to the washing process. However, the investigations on such systems are very limited. In the present work, a novel approach of post-treatment of laundry wastewater utilizing solar photo-Fenton operated at a pilot scale in a compound parabolic collector (CPC) photoreactor is proposed. Sodium dodecyl sulfate (SDS) was used as a representative of surfactants applied in the laundry system. The effect of feed matrix was investigated using distilled water as a reference matrix and synthetic wastewater simulating the composition of biologically pre-treated laundry wastewater. Different concentrations of H 2 O 2 (50–400 mg/L) and ferrous iron (2.75–10 mg/L) were assayed. For comparison purpose, experiments at neutral pH using ethylenediamine-N,N′-disuccinic acid (EDDS) as an iron complexing agent were carried out. A high SDS removal efficiency was obtained under both neutral and acidic pH, reaching 89% and 96%, respectively, in just 8 min. However, the remaining organic load originating from EDDS needs application of further post-treatment steps. Therefore, the solar photo-Fenton operated under acidic pH was found to be a more promising approach of post-treatment of laundry wastewater aimed at its reuse.

Benzophenone-3, fipronil and propylparaben are micropollutants that are potential threats to ecosystems and have been detected in aquatic environments. However, studies involving the investigation of new technologies aiming at their elimination from these matrices, such as advanced oxidation processes, remain scarce. In this study, different iron complexes (FeCit, FeEDTA, FeEDDS and FeNTA) were evaluated for the degradation of a mixture of these micropollutants (100 µg L−1 each) spiked in municipal wastewater treatment plant (MWWTP) effluent at pH 6.9 by solar photo-Fenton. Operational parameters (iron and H2O2 concentration and Fe/L molar ratio) were optimized for each complex. Degradation efficiencies improved significantly by increasing the concentration of iron complexes (1:1 Fe/L) from 12.5 to 100 µmol L−1 for FeEDDS, FeEDTA and FeNTA. The maximum degradation reached with FeCit for all iron concentrations was limited to 30%. Different Fe/L molar ratios were required to maximize the degradation efficiency for each ligand: 1:1 for FeNTA and FeEDTA, 1:3 for FeEDDS and 1:5 for FeCit. Considering the best Fe/L molar ratios, higher degradation rates were reached using 5.9 mmol L−1 H2O2 for FeNTA and FeEDTA compared to 1.5 and 2.9 mmol L−1 H2O2 for FeEDDS and FeCit, respectively. Acute toxicity to Canton S. strain D. melanogaster flies reduced significantly after treatment for all iron complexes, indicating the formation of low-toxicity by-products. FeNTA was considered the best iron complex source in terms of the kinetic constant (0.10 > 0.063 > 0.051 > 0.036 min−1 for FeCit, FeNTA, FeEDTA and FeEDDS, respectively), organic carbon input and cost-benefit (USD 327 m−3 > USD 20 m−3 > USD 16 m−3 > USD 13 m−3 for FeEDDS, FeCit, FeEDTA and FeNTA, respectively) when compared to the other tested complexes.

In this work, the activated persulfate oxidation of ciprofloxacin (CIP) using a low-grade titanium ore under sunlight or simulated sunlight were conducted to analyze the CIP degradation efficiency and to identify the transformation products (TPs) generated during oxidation under both types of irradiation sources by using liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-QTOF-MS). All advance oxidation process experiments were performed in a 2700-mL raceway reactor at a pH value of ~ 6.5 and an initial CIP concentration of 1 mg/L, during 90 min of reaction time. The control experiments carried out under simulated sunlight achieved a 97.7 ± 0.6% degradation efficiency, using 385 W/m 2 of irradiation with an average temperature increase of 11.7 ± 0.6 °C. While, the experiments under sunlight reached a 91.2 ± 1.3% degradation efficiency, under an average irradiation value of 19.2 ± 0.3 W/m 2 in October–November 2019 at hours between 11:00 am and 3:00 pm with an average temperature increase of 1.4 ± 0.8 °C. Mass spectrometry results indicated that 14 of the 108 possible TPs reported in the literature were detected. The calculated exact mass, measured accurate mass, and its characteristic diagnostic fragment ions were listed, and two new TPs were tentative identified. The TP generation analysis showed that some specific compounds were detected in different time intervals with kinetic variations depending on the irradiation used. Consequently, two CIP degradation pathways were proposed, since the type of irradiation determines the CIP degradation mechanism. Graphical abstract

In arid Mediterranean countries, such as Tunisia, wastewater often has high salinity, being an obstacle to the elimination of microcontaminants for the reuse of water in agriculture. In this paper, the photo-Fenton process in raceway pond reactors (RPRs) has been successfully applied to a simulated secondary effluent from a Tunisian urban wastewater treatment plant (WWTP), with high chloride load. A mixture of three contaminants of emerging concern (CECs) was used as model pollutants at 50 μg/L each (one antibiotic, sulfamethoxazole and two pesticides, pyrimicarb and imidacloprid). All the assays were conducted at neutral pH with 0.1 mM Fe(III):EDDS at 1:1 molar ratio. The effect of hydrogen peroxide initial concentration (20, 30, and 90 mg/L) on microcontaminant removal was studied. Different liquid depths (5 and 15 cm) were selected to assess the relationship between the microcontaminant removal and the volumetric rate of photon absorption (VRPA). Although the reaction rate was initially photo-limited, after a short reaction time of 15 min, the final yield (≈ 80% of CEC removal) was limited by the photo-degradation of the Fe(III):EDDS complex and excess H 2 O 2 was found at all concentrations used. Therefore, treatment times below 15 min should be used. The treatment capacity was three times higher when the liquid depth was increased from 5 to 15 cm. For the first time, these results show that the operation of a 15 cm-deep RPR in continuous flow mode would be suitable for large-scale implementation of the solar photo-Fenton process.

Background: Water is a scarce resource and is considered a fundamental pillar of sustainable development. The modern development of society requires more and more drinking water. For this cleaner wastewater, treatments are key factors. Among those that exist, advanced oxidation processes are being researched as one of the sustainable solutions. The main objective of this manuscript is to show the scientific advances in this field. Methods: In this paper, a systematic analysis of all the existing scientific works was carried out to verify the evolution of this line of research. Results: It was observed that the three main countries researching this field are China, Spain, and the USA. Regarding the scientific collaboration between countries, three clusters were detected—one of Spain, one of China and the USA, and one of Italy and France. The publications are grouped around three types of water: industrial, urban, and drinking. Regarding the research, 15 clusters identified from the keywords analyzed the advanced oxidation process (alone or combined with biological oxidation) with the type of wastewater and the target pollutant, removal of which is intended. Finally, the most important scientific communities or clusters detected in terms of the number of published articles were those related to the elimination of pollutants of biological origin, such as bacteria, and of industrial nature, such as pesticides or pharmaceutical products.

The presence of persistent and toxic pollutants in waters has encouraged the development of new water treatment technologies, such as the solar photocatalysis process, solar photo-Fenton, which uses the Sun as renewable source of energy to diminish process costs. The market failure associated to the pollution originated by industrial wastewater discharges is corrected with the establishment of environmental taxes. The heterogeneity in the design of these taxes affects both the considered pollution parameters and their specific weight in the calculation of the tax to be paid. In this paper, it is discussed the capability of the environmental taxes to correct the water pollution as market failure, and as an incentive to invest in sustainable technologies and water treatment processes.

Determining the effects of local and landscape drivers on endangered species and predicting potential suitable habitats for their persistence is crucial for effective conservation management. Here, we applied a multi-scale approach to disentangle the effects of host resources, local, and landscape variables on the occurrence pattern of Phengaris (= Maculinea) nausithous in semi-natural upland grasslands. Our approach comprised the assessment of host parameters (plant cover, density, height, flower heads density, ant nest density, ant colony size), local grassland management (pasture, meadow), site conditions (area, shape, terrain attributes), and landscape variables (landscape composition, connectivity). We used ensemble of small models based on bivariate generalized linear models for explaining and predicting the butterfly occurrence pattern. Bivariate models revealed that host ant nest density, plant cover and height, local grassland management type (pasture), slope and eastness, landscape forest cover and grassland connectivity had a positive effect on the occurrence of P. nausithous (average explained deviance 20.5%). Host ant density, host plant cover, and local grassland management were the most influential factors on the ensemble predictions. The presence of P. nausithous in upland grasslands is not only determined by host resources, but also by local and landscape factors. Such factors proved to be relevant for identifying and predicting suitable grassland sites for this endangered species. Consequently, we recommend that conservation actions should include a landscape perspective to promote connectivity by facilitating coherent grazing networks enabling dispersal between semi-natural upland grasslands and thus species persistence.

Nowadays, the increased agro-industrial activities and the inability of traditional wastewater treatment plants (WWTPs) to eliminate recalcitrant organic contaminants are raising a potential worldwide risk for the environment. Among the various advanced water treatment technologies that are lately proposed for addressing this challenge, the development and optimization of an innovative hybrid photocatalytic nanofiltration reactor (PNFR) prototype emerges as a prominent solution that achieves synergistic beneficial effects between the photocatalytic degradation activity and size exclusion capacity for micropollutant molecules. Both these features can be contemporarily endued to a multitude of membrane monoliths. The physicochemical and the photoinduced decontamination properties of the titania materials were firstly determined in the powder form, and subsequently, the structural and morphological characterization of the obtained titania-modified membrane monoliths were accomplished. The PNFR unit can operate at high water recovery and low pressures, exhibiting promising removal efficiencies against Acetamiprid (ACT) and Thiabendazole (TBZ) pesticides and achieving the recycling of 15 m3/day of real agro-wastewater. The obtained results are very encouraging, demonstrating the integration of titania photocatalysts in a photocatalytic membrane reactor as a feasible technological solution for the purification of agricultural wastewater.

“Ensure access to water for all”, states Goal 6 of the UN’s Sustainable Development Goals. This worldwide challenge requires identifying the best water disinfection method for each scenario. Traditional methods have limitations, which include low effectiveness towards certain pathogens and the formation of disinfection byproducts. Solar-driven methods, such as solar water disinfection (SODIS) or solar photocatalysis, are novel, effective, and financially and environmentally sustainable alternatives. We have conducted a critical study of publications in the field of water disinfection using solar energy and, hereby, present the first bibliometric analysis of scientific literature from Elsevier’s Scopus database within the last 20 years. Results show that in this area of growing interest USA, Spain, and China are the most productive countries in terms of publishing, yet Europe hosts the most highly recognized research groups, i.e., Spain, Switzerland, Ireland, and UK. We have also reviewed the journals in which researchers mostly publish and, using a systematic approach to determine the actual research trends and gaps, we have analyzed the capacity of these publications to answer key research questions, pinpointing six clusters of keywords in relation to the main research challenges, open areas, and new applications that lie ahead. Most publications focused on SODIS and photocatalytic nanomaterials, while a limited number focused on ensuring adequate water disinfection levels, testing regulated microbial indicators and emerging pathogens, and real-world applications, which include complex matrices, large scale processes, and exhaustive cost evaluation.