Removal of contaminants of emerging concern by Wolffia arrhiza and Lemna minor depending on the process conditions, pollutants concentration, and matrix type.

Research was carried out on the removal of a group of six contaminants of emerging concern: bisphenol A, N,N-diethyl-m-toluamide, diethylstilbestrol, triclosan, estrone and estradiol from the water matrix during contact with small floating macrophytes Wolffia arrhiza and Lemna minor. The optimal conditions for the process, such as pH, light exposure per day, and plant mass, were determined using the design of experiments chemometric approach based on central composite design. Experiments conducted under the designated optimal conditions showed that after 7 days, the removal efficiency equals 88-98% in the case of W. arrhiza and 87-97% in the case of L. minor, while after 14 days of the experiment, these values are 93-99.6% and 89-98%, respectively. The primary mechanism responsible for removing CECs is the plant uptake, with the mean uptake rate constant equal to 0.299 day-1 and 0.277 day-1 for W. arrhiza and L. minor, respectively. Experiments conducted using municipal wastewater as a sample matrix showed that the treatment efficiency remains high (the average values 84% and 75%; in the case of raw wastewater, 93% and 89%, and in the case of treated wastewater, for W. arrhiza and L. minor, respectively). Landfill leachate significantly reduces plants' ability to remove pollutants (the average removal efficiency equals 59% and 56%, for W. arrhiza and L. minor, respectively).

Revamping of a Full-Scale Membrane Plant for Landfill Leachate Pretreatment Using Partial Nitritation.

This paper describes a case study involving a revamping of a full-scale membrane bioreactor that treats landfill leachate and other liquid wastes. The main change was the introduction of nitritation/denitritation in alternating cycles instead of the classic denitrification/nitrification process, together with the installation of fine bubble diffusers, a reduction in the volume of the biological compartment, and an increase in the equalization volume. The most significant results were obtained for the biological compartment, with a decrease in the specific energy consumption of 46.6%. At the same time, the removal efficiency of COD, BOD, and TN substantially remained the same before and after plant revamping, while the removal efficiency of TP increased over the years, reaching an average value of almost 71%. Regarding the ultrafiltration unit, the specific flux (or permeability) was characterized by an increasing trend. At the same time, the specific energy consumption of this section decreased by 9.4%. These results led to the conclusion that the changes introduced with the revamp led to a more stable process, a reduction in membrane fouling, and important energy savings.

A picture of pharmaceutical pollution in landfill leachates: Occurrence, regional differences and influencing factors.

Municipal solid waste (MSW) landfill sites have been identified as a significant source of pharmaceuticals in the environment because unused or expired pharmaceuticals are discarded into MSW, which eventually percolate into leachates. However, the contamination of pharmaceuticals in landfill leachate in China is not comprehensively understood. Previous research into factors influencing pharmaceutical concentrations focused on a limited number and type of target pollutants or restricted study area. In the present study, 66 pharmaceuticals were analyzed (including 45 antibiotic and 21 non-antibiotic pharmaceuticals, also categorized as 59 prescription and 7 non-prescription pharmaceuticals) in leachate samples from landfill sites with various characteristics in different regions of China. The results indicated that non-antibiotic pollutants were present at significantly higher concentrations than antibiotic pollutants, with median concentrations of 1.74 µg/L and 527 ng/L, respectively. Non-antibiotic pollutants also presented a higher environmental risk than antibiotic pollutants, by 2 to 4 orders of magnitude, highlighting that non-antibiotic pharmaceuticals should not be overlooked during the assessment of landfill leachate. Pharmaceutical concentrations in landfill leachate samples exhibited regional differences; the population size served by the landfills was the dominant factor contributing to the observed differences. In addition, landfill characteristics such as the solid waste composition and MSW loading can also affect pharmaceutical concentrations in landfill leachate. Despite the implementation of the classification and disposal policy of MSW in Shanghai, China since July 2019, specifying that unused or expired pharmaceuticals should be discarded as hazardous waste, high levels of pharmaceutical contaminations were detected in leachate from the main components of classified MSW (i.e., residual and food waste). These findings emphasize the importance of pharmaceutical management in solid waste systems.

The Chickahominy T.R.U.T.H. (Trust, Research, Understand, Teach, and Heal) Project-A Tribal Community-Academic Partnership for Understanding the Impact of Structural Factors on Perceived Cancer Risk in Rural Virginia.

In 2022, the Virginia Chickahominy Indian Tribe partnered with Virginia Commonwealth University Massey Comprehensive Cancer Center to investigate concerns about a potential cancer cluster near a local landfill. While investigating cancer clusters is complex due to long latency and multifactorial causes, the community's concerns about structural factors driving cancer risk warrant exploration. Thus, the Chickahominy T.R.U.T.H. (Trust, Research, Understand, Teach, and Heal) Project was created as a community-academic partnership to (1) identify structural factors and barriers associated with perceived cancer risk and care; (2) assess cancer knowledge, care access gaps, and perceived risks, including testing private and community water sources; (3) develop and deploy culturally tailored cancer education and resource navigation, including groundwater safety education, policies, and remediation. We will conduct 150 in-person interviews and water tests among residents within a four-mile radius of the landfill, and deploy 1000 structured questionnaires among Charles City County residents. In this paper, we provide an overview of the ongoing project design, development, and progress in support of the project's objectives. This collaborative investigation aims to address cancer health disparities, enhance research and health policy advocacy, and honor the sacred knowledge of an underserved community, laying the groundwork for a long-term partnership to guide future research questions.

Beta-Lactam-Resistant Enterobacterales Isolated from Landfill Leachates.

Antibiotic resistance is one of the main challenges worldwide due to the high morbidity and mortality caused by infections produced by resistant bacteria. In Colombia, this problem has been studied mainly from the clinical perspective; however, it is scarcely studied in the leachates produced in landfills. The objective of this study was to detect, identify and determine the antibiotic sensitivity profile of Enterobacterales isolated from a leachate treatment plant located in Cali, Colombia. Detection was performed using selective culture media, bacterial identification using Matrix-Assisted Laser Desorption/Ionization-Time-Of-Flight (MALDI-TOF, bioMérieux) and by sequencing the gene coding for the 16S ribosomal RNA subunit when discrepancies were observed between phenotypic characteristics and MALDI-TOF. Antibiotic sensitivity profiling was determined using the automated VITEK®2 system (bioMérieux). Twenty-one isolates were obtained, of which Klebsiella pneumoniae was the most frequent (23.8%), and 34% of the isolates showed decreased sensitivity to beta-lactam antibiotics such as cefoxitin, ampicillin/sulbactam and piperacillin/tazobactam. These findings suggest that leachates from landfills could be a reservoir of pathogenic bacteria carrying antibiotic resistance determinants, so periodic microbiological characterization of these effluents should be performed, promoting the One Health approach.

Continuous monitoring of dissolved inorganic nitrogen (DIN) transformations along the waste-vadose zone - groundwater path of an uncontrolled landfill, using multiple N-species isotopic analysis.

Landfill leachates contain a heavy load of dissolved inorganic nitrogen (DIN), posing a threat to water resources. Therefore, it is highly important to understand the processes that control its evolution (speciation, accumulation, or attenuation) during the percolation of leachates through the unsaturated zone, finally affecting the groundwater. However, tracking DIN transformations in this complex and inaccessible environment is challenging, and knowledge concerning this important topic under field conditions is scarce. The presented study used a unique monitoring system that allows sampling of repetitive samples from within the waste and the unsaturated zone. An array of 8 wells penetrating the underlying aquifer completed the spatial observation. Multiple N-species isotopic approach was applied to discern the dominating N-involving processes over the continuum - from the waste mound through the unsaturated zone and the underlying aquifer. Despite the considerable heterogeneity observed throughout the profile, the results provided a cohesive and valuable reflection of the evolution of the inorganic nitrogen pool in this highly contaminated environment. Leachates inside the waste had reducing characteristics with high accumulation of ammonium (up to 360 mg/l NH4+-N), and a distinct δ15N-NH4+ range (-3‰ to +10‰). The upper layers of the unsaturated zone underneath the landfill margins found to be aerated, promoting N oxidation which resulted in the accumulation of nitrate in the leachates (up to 490 mg/l NO3-N). Exceptionally high concentrations of nitrite (up to 126 mg/l NO2-N) were found as oxygen levels decreased in deeper sections of the vadose zone. Enrichment of δ15N-NO2- compared to δ15N-NO3- indicated the significance of autotropic nitrite reduction, controlling the DIN composition, correlated with NO2- accumulation and net DIN attenuation. The δ15N: δ18O ratio implied co-occurrence of denitrification in the leachates, even in the more oxidized sections, further contributing to N-attenuation in the unsaturated zone. In the aquifer, δ15N-NH4+ values and δ15N: δ18O ratio linked N contamination to the leachates source. The encounter with the oxidized groundwater promoted intensive nitrification. δ15N-NO2- values in the groundwater were lighter than both δ15N-NH4+ and δ15N-NO3- by 22‰ to 62‰, implying the co-occurrence of nitrification-denitrification processes. The effect of denitrification grew with decreasing dissolved oxygen (DO) levels below 0.5 mg/l towards the center of the plume, contributing to net DIN attenuation in the plume. The findings are significant for any consideration of the risk posed by DIN, as well as remediation measures, in a landfill environment and other sites with a heavy load of degrading organic matter.

Electrochemical oxidation of landfill leachate using boron-doped diamond anodes: pollution degradation rate, energy efficiency and toxicity assessment.

Electrochemical oxidation (EO), due to high efficiency and small carbon footprint, is regarded as an attractive option for on-site treatment of highly contaminated wastewater. This work shows the effectiveness of EO using three boron-doped diamond electrodes (BDDs) in sustainable management of landfill leachate (LL). The effect of the applied current density (25-100 mA cm-2) and boron doping concentration (B/C ratio: 500 ppm, 10,000 ppm and 15,000 ppm) on the performance of EO was investigated. It was found that, of the electrodes used, the one most effective at COD, BOD20 and ammonia removal (97.1%, 98.8% and 62%, respectively) was the electrode with the lowest boron doping. Then, to better elucidate the ecological role of LLs, before and after EO, cultivation of faecal bacteria and microscopic analysis of total (prokaryotic) cell number, together with ecotoxicity assay (Daphnia magna, Thamnocephalus platyurus and Artemia salina) were combined for the two better-performing electrodes. The EO process was very effective at bacterial cell inactivation using each of the two anodes, even within 2 h of contact time. In a complex matrix of LLs, this is probably a combined effect of electrogenerated oxidants (hydroxyl radicals, active chlorine and sulphate radicals), which may penetrate into the bacterial cells and/or react with cellular components. The toxicity of EO-treated LLs proved to be lower than that of raw ones. Since toxicity drops with increased boron doping, it is believed that appropriate electrolysis parameters can diminish the toxicity effect without compromising the nutrient-removal and disinfection capability, although salinity of LLs and related multistep-oxidation pathways needs to be further elucidated.

Concentration profiles of per- and polyfluoroalkyl substances in major sources to the environment.

A review of published literature was conducted to present the concentrations and composition profiles of per- and polyfluoroalkyl substances (PFAS) from significant sources to the environment. The major sources of PFAS to the environment are categorized under direct and indirect sources. The characteristic compounds and concentrations are summarized as found from direct sources such as manufacturing facilities, aqueous film-forming foam (AFFF) applications, metal coating operations, and textile and paper coating operations; and from indirect sources such as landfills and wastewater treatment plants (WWTPs). The major findings are: 1) among the aqueous matrices for which data were reviewed, groundwater impacted by AFFF contamination showed the highest median concentrations for both perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), while the second-highest median concentrations were associated with landfill leachates for PFOA and metal-plating sources for PFOS; 2) many of the unknown polyfluorinated precursors present in AFFF-impacted sites could potentially convert to persistent PFAS by abiotic or biotic transformation, and therefore could act as the long-term source of contamination to the environment; 3) part per billion (ppb) concentrations of PFAS were detected in water bodies surrounding fluorochemical manufacturing plants; 4) in consumer products such as textile, paper, and personal care products, PFOA concentrations were an order of magnitude higher compared to other PFAS; 5) biotransformation products such as fluorotelomer carboxylic acids (FTCAs) and perfluoroalkyl acids (PFAAs) are detected in landfill leachates and WWTP effluents; and 6) many studies have shown increased PFAA concentrations in WWTP effluents compared to influents. This work provides a comprehensive review of the literature on the PFAS concentration and composition trends of select non-polymeric PFAS in different sources.

Sonoelectrochemical activation of peroxymonosulfate: Influencing factors and mechanism of FA degradation, and application on landfill leachate treatment.

In this work, sonoelectrochemically activated peroxymonosulfate (US-EC/PMS) was used to degrade fulvic acid (FA) in water. Compared with other technologies, the US-EC/PMS system can achieve higher FA decolorization in a short time. Moreover, the benefits of synergy are more prominent in the US-EC/PMS system. The effects of operating parameters on the sonoelectrochemical degradation of FA were investigated, including initial pH, initial FA concentration, current density, ultrasonic power, PMS dosage. The results showed the initial FA concentration and current density were critical to the degradation of FA. Under optimized parameters: initial pH of 2, 50 mg L-1 initial FA concentration, 30 mA cm-2 current density, 50 W ultrasonic power, 1 mM PMS dosage, the US-EC/PMS system can achieve 93% FA decolorization. The calculation results of current efficiency and energy consumption indicate that the introduction of PMS into the US-EC system has economic applicability. Scavenger experiments and electron paramagnetic resonance suggest that hydroxyl radicals, sulfate radicals, and singlet oxygen were the main ROS produced in the US-EC/PMS system. Accordingly, the possible mechanism of FA degradation by sonoelectrochemical activation PMS was proposed. Finally, the US-EC/PMS system was used to treat the aged landfill leachate. Three-dimensional fluorescence analysis showed that most of the humic substances (Hss) were effectively removed, and the biodegradability of the leachate was considerably improved. In addition, the effective removal of COD, chroma, and ammonia nitrogen were observed, proving that this technology is a powerful means to treat organic wastewater contaminated by Hss.

Antibiotic and metal resistance genes are closely linked with nitrogen-processing functions in municipal solid waste landfills.

Landfilled antibiotics and metals were related to the occurrences of their resistance genes, whose decade-long development in leachates with the dynamic landfilling environmental conditions, especially with the varying nitrogen contents, has yet to be studied. Here, we sampled leachates from five representative municipal solid waste landfills in China. The total concentrations of antibiotics (5000 - 50000 ng/L) and metals (10 - 60 mg/L) in leachates were significantly different among different sites and they were only closely related to sulfonamide and tetracycline resistance genes (P < 0.05). Regarding the abundance of subtype resistance genes, sul1 and ermB were dominant antibiotic resistance genes (ARGs) and terc, arsc, and mer were dominant heavy metal resistance genes (HMRGs); and meanwhile the observed huge variations of these genes appeared to be related to environmental factors like nitrate and pH (P < 0.05). The GeoChip results further indicated that more than 85% of sequenced ARGs/HMRGs and nitrogen processing genes, particularly of the denitrification genes, were hosted by the same bacterial species, such as Pseudomonas sp. and Bacillus sp., which belonged to the predominant phylum in leachates. These results extended our knowledge about the linkages among ARGs, HMRGs and nitrogen-processing functions in leachates.

Electrochemical determination of nitroaromatic explosives at boron-doped diamond/graphene nanowall electrodes: 2,4,6-trinitrotoluene and 2,4,6-trinitroanisole in liquid effluents.

The study is devoted to the electrochemical detection of trace explosives on boron-doped diamond/graphene nanowall electrodes (B:DGNW). The electrodes were fabricated in a one-step growth process using chemical vapour deposition without any additional modifications. The electrochemical investigations were focused on the determination of the important nitroaromatic explosive compounds, 2,4,6-trinitrotoluene (TNT) and 2,4,6-trinitroanisole (TNA). The distinct reduction peaks of both studied compounds were observed regardless of the pH value of the solution. The reduction peak currents were linearly related to the concentration of TNT and TNA in the range from 0.05-15 ppm. Nevertheless, two various linear trends were observed, attributed respectively to the adsorption processes at low concentrations up to the diffusional character of detection for larger contamination levels. The limit of detection of TNT and TNA is equal to 73 ppb and 270 ppb, respectively. Moreover, the proposed detection strategy has been applied under real conditions with a significant concentration of interfering compounds - in landfill leachates. The proposed bare B:DGNW electrodes were revealed to have a high electroactive area towards the voltammetric determination of various nitroaromatic compounds with a high rate of repeatability, thus appearing to be an attractive nanocarbon surface for further applications.

Do high levels of PPCPs in landfill leachates influence the water environment in the vicinity of landfills? A case study of the largest landfill in China.

Landfill leachates are identified as a significant source of pharmaceutical and personal care products (PPCPs), which might pose a threat to groundwater and surface water nearby the landfill. However, knowledge of PPCP contamination in the surrounding water environment of landfills is very limited. Here we investigated eighteen PPCPs in water environment near the largest landfill in China, focusing on their occurrences and spatial distribution, as well as the environmental risks. The results showed the concentration of target PPCPs was below the limit of quantification (

Characterization and treatment of landfill leachates by electro-Fenton process: A case study in Algeria.

The feasibility of the electro-Fenton (EF) process to improve the biodegradability of Algerian leachates was examined, in order to prepare this kind of flux for conventional biological treatment. This work also included, for the first time in Algeria, the control and monitorization of a landfill-the "Hamici" landfill. Several physicochemical parameters were determined allowing its classification into an intermediate degradation phase, namely considering their alkaline pH (8.7), high ammonium concentration (3,120 mg/L), low content in heavy metals, and biodegradability (BOD5 /COD = 0.22). The effects of important parameters such as current intensity, treatment time, and temperature on COD removal have been studied and optimized by using response surface analysis of a central composite design, where 91.1% of COD was removed with a treatment time of 285 min, a current intensity of 3 A, and a temperature of 20°C. A biodegradability test, which was performed on a solution electrolyzed with 120 min, 2 A, and 20°C, allowed to improve the leachates biodegradability from 0.2 to 0.42, with a removal rate of COD and TOC of 53.35% and 34.5%, respectively. However, the current efficiency declined from 137% to 76.6% when the current intensity was rise from 0.5 to 2 A. These results showed the relevance of EF process applied on raw intermediate leachates and its possible benefit in the Algiers leachates treatment processes. Thus, it was concluded that biological treatment can be combined with EF process for optimal mineralization of leachates with clear advantages in this studied location. PRACTITIONER POINTS: Characterization and treatment of leachates by electro-Fenton (EF) process were carried out. The leachates are intermediate type and therefore biologically recalcitrant. The operating parameter for EF process were modeled and optimized by the central composite design. Current intensity of 2 A reduces COD and TOC of 53.35% and 34.5%, respectively. The ratio BOD5 /COD increased from 0.2 to 0.42 after 120 min of electrolysis time.

Landfill leachates and wastewater of maritime origin as possible sources of endocrine disruptors in municipal wastewater.

In this study, wastewater from municipal services, such as a port wastewater reception facility (PRF-WW) and a municipal solid waste plant (MSWP), was tested for the presence of the suspected endocrine-disrupting compounds phthalates (PAEs) and bisphenol A (BPA). PAEs and BPA were found in this study in high concentrations in raw wastewater obtained from passenger ships (RMT-WWs) (up to 738 µg/L and 957 µg/L, respectively) collected in the Port of Gdynia and in landfill leachates (LLs) (up to 536 µg/L and up to 2202 µg/L, respectively) from a MSWP located near Gdynia. In particular, the presence of reprotoxic di(2-ethylhexyl) phthalate (DEHP, up to 536 µg/L in LLs and up to 738 µg/L in RMT-WWs) requires further action because if this compound, as well as other PAEs and BPA, is not degraded by activated sludge microorganisms, it may reach receiving waters and adversely impact aquatic organisms. Therefore, PAEs and BPA should be removed either during the onsite pretreatment of tested industrial wastewater or during tertiary treatment at municipal wastewater treatment plants (WWTPs, representing end-of-pipe technology). Graphical abstract.

Organophosphate flame retardants in leachates from six municipal landfills across China.

With the phasing out of brominated flame retardants, organophosphate flame retardants (OPFRs) have been widely used and further detected in multiple environmental media. However, municipal landfill leachates, an important source of contamination of OPFRs to aquatic environment, have not been fully understood, especially in a developing country like China. Thus, the occurrence, aqueous removal efficiency, environmental emission, and risk assessment of 10 OPFRs were investigated in leachates from six municipal landfills across China. The results indicated that except triethyl phosphate (TEP), the remaining 9 OPFRs were detected in both raw and final leachates with different frequencies higher than 33.3%. The range of total concentrations of OPFRs (ΣOPFRs) across China was 29.0-437 and 0.652-32.4 µg L-1 in raw and final leachates, respectively. Tris(2-chloroethyl) phosphate (TCEP) was the dominant species and accounted for 78.5% and 85.8% of average ΣOPFR concentration in raw and final leachates, respectively. This may be because TCEP is the most prevalently used OPFR in China. The overall aqueous removal efficiency of ΣOPFRs across China ranged from 57.7% to 99.8%. Tris(2-butoxyethyl) phosphate was the most removed species (98.8%), whereas TCEP was the least removed species (91.5%). The annual emissions of ΣOPFRs discharged into the aquatic environment from municipal landfills across China were estimated to be between 170 and 7094 g. Further risk assessment based on risk quotient values in the final leachates showed that most OPFRs posed negligible risk except TCEP (medium and high risk) and tributyl phosphate (medium risk).

Measurement and monitoring of anions, cations and metals in landfill leachate in Iranian metropolises.

Leachate generation is a major problem for municipal solid waste (MSW) landfills and causes significant threat to surface and groundwater. Samples were collected from the landfills of Iranian metropolises (Ahwaz, Mashhad, Tehran (before and after treatment plant), Isfahan, Tabriz, Hamedan, Rasht, Sanandaj and Qazvin) based on the standard sampling methods and transferred to the laboratory. Cr, Cd, Hg, Pb, Ni, As, Ca, Mg, Fe, Mn, Na, K, Zn, Al, Ba, Li, Sr, Ti and V were analyzed. The pH values for the ten leachate samples obtained from 4.57 to 8.95. The results showed the amount of some metals in Iranian landfill sites higher than the DOE standards for agricultural irrigation and surface water.

Oscillating membrane photoreactor combined with salt-tolerated Chlorella pyrenoidosa for landfill leachates treatment.

In this study, a novel oscillating membrane (OM) photoreactor combined with salt-tolerated Chlorella was developed for old landfill leachates treatment, in which harvesting of highly-active algae was easily performed on large scale. Compared with control membrane photo-bioreactor (CMPBR), OM-MPBR exhibited excellent NH3-N removal efficiency as high as 94.0%. With light time prolonged, an increase in biomass production and NH3 removal rates was observed due to more energy provided for Chlorella cells. By comparison, it was found the highest membrane flux (99.6 L/m2 h bar) was obtained in OM-MPBR, which was attributed to strong shear stress on interface of liquid/membrane effectively reducing bio-foulants. It was clear that energy consumptions of OM-MPBR on biomass productivity (0.68 kWh/kg cell) and NH3 removal (0.0151 kWh/kg NH3-N) were lower than CMPBR. The new coupling system opens a door to scalable development of promising and economical MBR for environmental pollution control and biomass energy production.

Otimização multivariada do processo foto-Fenton solar na remoção da demanda química de oxigênio em lixiviados de aterros sanitários / Multivariate optimization of solar photo-Fenton process for chemical oxygen demand removal in landfill leachate treatment

RESUMO A presente pesquisa objetivou otimizar o processo foto-Fenton solar no tratamento de lixiviados de aterros sanitários. O Delineamento Composto Central Rotacional associado à Metodologia de Superfície de Resposta foi aplicado para investigar três variáveis operacionais: razão de reagentes [H2O2]/[FeSO4.7H2O], fator de H2O2 e pH inicial, a fim de maximizar a remoção de matéria orgânica, em termos da demanda química de oxigênio (DQO). De acordo com os resultados, obteve-se elevada redução da DQO em 3 horas de fotocatálise solar (70,97 a 84,74%). Com base na análise de variância (ANOVA), a variável reposta pode ser descrita por um modelo quadrático, com elevado coeficiente de explicação, R2=0,9894. A análise das superfícies de resposta indicou que as condições ótimas foram: faixa de pH inicial entre 2,5 e 3,5; com pico em 2,79; e razões de reagentes [H2O2]/[FeSO4.7H2O] a partir de 6 até o nível máximo estudado (7,36). Calculou-se a concentração de peróxido de hidrogênio com base no fator de H2O2, atingindo o ponto crítico em 143,77% da quantidade estequiométrica de H2O2 necessária para a oxidação completa da matéria orgânica, isto é, 11.751,05 mg H2O2.L-1 para estabilizar uma DQO de 3.845,55 mg O2.L-1.

ABSTRACT This research aimed to optimize the solar photo-Fenton process in landfill leachate treatment. Central Composite Rotatable Design associated with the Response Surface Methodology was applied to investigate three operational factors: reagents ratio [H2O2]/[FeSO4.7H2O], H2O2 factor and initial pH, in order to maximize the organic matter removal, in terms of chemical oxygen demand (COD). According to the results, high COD reduction was obtained in three hours of solar photocatalysis (70.97 to 84.74%). Based on the analysis of variance (ANOVA), the response variable can be described by a quadratic model, with a high coefficient of determination, R2=0.9894. The analysis of response surfaces indicated that the optimum conditions were: initial pH range between 2.5 and 3.5, with a peak at 2.79, and reagents ratio range from 6 to the maximum level studied (7.36). Hydrogen peroxide concentration was calculated from the H2O2 factor, reaching the critical point at 143.77% of the stoichiometric amount of H2O2 needed for the complete oxidation of organic matter, that is, 11,751.05 mg H2O2.L-1 to stabilize a COD of 3,845.55 mg O2.L-1.

Mineralization of humic acids (HAs) by a solar photo-Fenton reaction mediated by ferrioxalate complexes: commercial HAs vs extracted from leachates.

The mineralization of bio-recalcitrant humic acids (HAs) by a solar photo-Fenton (SPF) process was investigated in aqueous system, in order to understand its abatement in real high-HA content matrices, such as sanitary landfill leachates. SPF reactions were performed in tubular photoreactors with CPCs at lab-scale (simulated solar light) and pilot-scale (natural sunlight). Considering the experimental conditions selected for this work, the formation of insoluble HA-Fe3+ complexes was observed. Thus, to avoid HA precipitation, oxalic acid (Ox) was added, since Fe3+-Ox complexes present a higher stability constant. The effect of different process variables on the performance of SPF reaction mediated by ferrioxalate complexes (SPFF) was assessed with excess of H2O2 (50-250 mg L-1), at lab-scale: (i) pH (2.8-4.0); (ii) initial iron concentration (20-60 mg Fe3+ L-1); (iii) iron-oxalate molar ratio (Fe3+-Ox of 1:3 and 1:6); (iv) temperature (20-40 °C); (v) UV irradiance (21-58 WUV m-2); and (vi) commercial-HA concentration (50-200 mg C L-1). At the best lab conditions (40 mg Fe3+ L-1, pH 2.8, 30 °C, 1.6 Fe3+-Ox molar ratio, 41 WUV m-2), commercial HAs' mineralization profile was also compared with HAs extracted from a sanitary landfill leachate, achieving 88 and 91% of dissolved organic carbon removal, respectively, after 3-h irradiation (8.7 kJUV L-1). Both reactions followed the same trend, although a 2.1-fold increase in the reaction rate was observed for the leachate-HA experiment, due to its lower humification degree. At pilot-scale, under natural sunlight, 95% HA mineralization was obtained, consuming 42 mM of H2O2 and 5.9 kJUV L-1 of accumulated UV energy. However, a pre-oxidation during 2.8 kJUV L-1 (12 mM H2O2) was enough to obtain a biodegradability index of 89%, showing the strong feasibility to couple the SPFF process to a downstream biological oxidation, with low chemicals and energetic demands. Graphical abstract ᅟ.

Simulated discharge of treated landfill leachates reveals a fueled development of antibiotic resistance in receiving tidal river.

Around 350 million tons of solid waste is disposed of in landfills every year globally, with millions of cubic meters of landfill leachates released into neighboring environment. However, to date, little is known about the variations of antimicrobial resistance (AMR) in on-site leachate treatment systems and its development in leachate-receiving water environment. Here, we quantified 7 subtypes of antibiotic resistance genes (ARGs), 3 types of culturable antibiotic resistant bacteria (ARB) and 6 subtypes of mobile genetic elements (MGEs) in the effluents from a combined leachate treatment process, including biological treatment (MBR), physical separation (UF), ultraviolet (UV) disinfection and advanced oxidation process (AOP). The contents of ARGs, ARB and MGEs were generally enriched by the MBR, but then decreased significantly along with the tertiary treatment process. However, in the effluent-receiving water samples, the abundance of dominant ARGs (i.e. ermB, sul1, blaTEM) increased by 1.5 orders of magnitude within 96 h, alongside a general increase of MGEs (~10.0 log10(copies/mL) and total ARB (~1100 CFU/mL). Structural correlation analyses reveal that target ARGs were closely associated with MGEs, particularly in effluent-receiving samples (Procrustes test; M2 = 0.49, R = 0.71, P = 0.001); and occurrences of ARB were majorly affected by ARG's distribution and environmental conditions (e.g. nitrogen speciation) in effluent and recipient groups, respectively. This study indicates that current treatment technologies and operation protocols are not feasible in countering the development of AMR in effluent-receiving water environment, particularly in tidal rivers that are capable of retaining contaminants for a long residence time.