Enhanced bio-recalcitrant organics removal by combined adsorption and ozonation

Removal of bio-recalcitrant and toxic compounds from wastewaters has been a major objective of industrial manufacturers for a few years. Due to the potential risk toward public health,regulations are becoming increasingly strict and classical treatments like biological treatments are not efficient. Other techniques such as incineration, oxidation or adsorption provide higher levels of removal but with a high energy and capital cost. A coupled process involving adsorption and oxidation is studied. Four adsorbents are tested and compared according to two objectives,their adsorption capacity and their capability to decompose ozone into powerful hydroxyl radicals. Two model compounds were chosen: 2,4-dichlorophenol and nitrobenzene.Experimental results allow comparing coupled process with results obtained during ozonation alone. Zeolite (Faujasite Y) gave disappointing results in term of both adsorption kinetics and ozone decomposition. On the contrary, activated carbons showed fast adsorptions and important capabilites to decompose ozone into radicals, almost in nitrobenzene experiments. S-23 activated carbon proved to be the most interesting adsorbent for better mechanical and chemical stabilities over time. Sequential adsorption/ozonation experiments were conducted,showing a strong loss of adsorption efficiency after the first operation, but the positive point is that the adsorption capacity remains almost constant during further cycles

Influence of activated carbons on the kinetics and mechanisms of aromatic molecules ozonation

Companies have been looking for new methods for treating toxic or refractory wastewaters; which can mainly be used prior to or after or in connexion with biological treatment processes.This paper compares conventional ozone oxidation with activatedcarbon (AC) promoted ozone oxidation, which helps developing a mechanism involving HOradical dot radical. For a compound which is quite easy to oxidise, like 2,4-dichlorophenol (2,4-DCP) conventional ozonation is efficient enough to remove the initial molecule. The mechanism involved mainly consists of an electrophilic attack on the aromatic ring, which is activated by the donor effect of the –OH group, then followed by a 1,3 dipolar cycloaddition (Criegee mechanism) that leads to aliphatic species, mainly carboxylic acids. Yet, the addition of AC, through the presence of HOradical dot radical, enhances the removal of these species which are more refractory.For a refractory compound like nitrobenzene (NB), with a de-activatedaromatic ring because of the attractive effect of –NO2, conventional ozonation is inefficient. On the contrary, this molecule can be quite easily removed with AC promoted oxidation and it is found that the mechanism (electrophilic attack followed by a 1,3 dipolar cycloaddition) is quite similar to the one corresponding to conventional ozonation, but with less selectivity.For both molecules, a mass balance has established that the by-products accounting for more than 75% of the remaining COD can be quantified. A significant part is composed of carboxylic acids (acetic, oxalic, etc.), which could afterwards be easily removed in an industrial wastewater treatment process followed by a final biological treatment step

Whole Farm Economic Evaluation of No-Till Rice Production in Arkansas

Rice in Arkansas is typically produced using intensive tillage. No-till rice has been studied, but the research focus has been limited to impacts on yields and per acre net returns. This analysis evaluates the profitability of no-till rice at the whole-farm level using both enterprise budget analysis and linear programming.Crop Production/Industries,

Couplage des procédés d’adsorption et d’ozonation pour l’élimination de molécules bio-récalcitrantes

Les molécules organiques bio-récalcitrantes ou toxiques issues des eaux résiduaires industrielles ne peuvent être traitées par des procédés conventionnels tels que la dégradation biologique.\ud Pour cela, des techniques plus poussées et coûteuses doivent être utilisées comme par exemple l’incinération, l’oxydation ou l’adsorption. Ici, un procédé d’oxydation avancé original a été étudié : un couplage utilisant à la fois l’adsorption et l’oxydation de la matière organique. En\ud effet il a été montré que la présence de charbon actif ou de zéolithes hydrophobes, comme la faujasite, favorise la décomposition de l’ozone en radicaux hydroxyles. Ces radicaux hydroxyles (HO° : E°=2,8 V) ont un pouvoir oxydant plus important que la molécule d’ozone elle-même (O3 : E°=2,07 V) et présentent une faible sélectivité. Ils permettent donc d’augmenter l’efficacité\ud de l’oxydation.\ud La première partie de ce travail est consacrée à la compréhension des interactions entre l’ozone\ud et les adsorbants. La décomposition de l’ozone est favorisée en présence de charbon actif\ud mésoporeux mais au prix de la dégradation de la structure poreuse. En revanche, la structure\ud de la faujasite n’est pas modifiée sous l’action de l’ozone mais l’effet sur la formation de radicaux\ud hydroxyles est très faible.\ud Le nitrobenzène et le 2,4-dichlorophénol ont ensuite été utilisés comme molécules modèles pour tester le procédé. Les essais d’adsorption ont mis en évidence que les charbons actifs sont de meilleurs adsorbants que la faujasite. Le couplage ozone/adsorbant s’avère être efficace avec les charbons actifs pour traiter les molécules difficilement ozonables comme le nitrobenzène. En\ud revanche, il est peu efficace pour éliminer des molécules facilement ozonable comme le 2,4-dichlorophénol ou lorsque la faujasite est utilisée comme matériau. Enfin, une utilisation en mode séquentiel, adsorption puis régénération à l’ozone, permet d’augmenter la durée de vie\ud des charbons actifs d’un facteur 2,1 à 2,7 selon le charbon actif utilisé.\ud Dans une dernière partie, une application avec un effluent industriel a été réalisée. L’adsorption\ud des matières organiques contenues dans cet effluent est compromise car la taille des espèces est trop importante par rapport à celle des pores des charbons actifs : l’adsorption n’a donc lieu que sur la surface externe. De plus, le couplage simultané ozone/charbon actif n’améliore pas les rendements d’élimination. Par contre, l’utilisation du procédé en mode séquentiel permet d’augmenter la durée de vie du charbon actif par rapport à une simple adsorption.------------------------------------------------------------------------------------------------------------------------------------------Industrial wastewaters often contain bio-recalcitrant compounds which cannot be removed with conventional processes such as biological treatments. Thus sophisticated and expensive techniques have to be used, such as incineration, adsorption or oxidation. In this study, an original advanced oxidation process is studied: a hybrid process that combines the performances of adsorption and oxidation. Indeed, previous studies have showed that activated carbons or hydrophobic zeolites, like faujasite, improve ozone decomposition into hydroxyl radicals. These hydroxyl radicals (E° = 2.8 V) have a higher oxidation capacity than the ozone molecule (E° = 2.07 V) and thus increase the oxidation efficiency.\ud First the interaction between the ozone molecules and the adsorbents is analysed. Ozone decomposition is mostly favoured when a mesoporous activated carbon is used but the\ud degradation of the material’s structure is important. On the other hand, the faujasite structure is not modified by ozone oxidation but the ability of this medium to decompose ozone is weak.\ud Nitrobenzene and 2,4-dichlorophenol are then used as model target molecules. It appears that the adsorption capacity is higher for activated carbons than for faujasite. The hybrid process, which simultaneously combines activated carbon and ozone, is efficient to remove the compounds that are weakly oxidized by ozone alone, such as nitrobenzene, but it is not efficient for 2,4-dichlorophenol oxidation because this molecule is too easily removed by single ozone.\ud Moreover, the sequential mode (adsorption followed by regeneration with ozone) allows increasing 2 to 3 fold the activated carbon lifetime.\ud Finally, an industrial effluent was studied. Organic matter is not well adsorbed onto activated carbon since the molecules sizes are larger than the media micropores. Thus, the adsorption phenomenon only occurs onto the external surface. Moreover, the simultaneous ozone/activated carbon process does not improve the treatment yield but the sequential application allows increasing the activated carbon lifetime compared to a classical adsorption\ud step

Comparison of Activated Carbon and Hydrophobic Zeolite Efficiencies in 2,4-Dichlorophenol Advanced Ozonation

This study aims at comparing the removal of 2,4-dichlorophenol (2,4-DCP) by 3 methods; adsorption using hydrophobic zeolite (faujasite) or activated carbon (S-23 and L-27), conventional ozonation and hybrid adsorption/ozonation treatment. On the one hand, the three materials correctly adsorb 2,4-DCP; however the adsorption kinetics using zeolite is very low. On the other hand, ozonation totally removes 2,4-DCP after 1 h experiment and the simultaneous combination of adsorbent and ozone does not change the 2,4-DCP degradation. But, though ozonation and hybrid process appear to be equivalent for 2,4-DCP removal, activated carbons are able to decompose ozone and to improve chemical oxygen demand (COD) removal, whereas the zeolite does not show this catalytic effect. Similar results were also observed in a former study with nitrobenzene. Adsorbent degradation is evaluated by Brunauer, Emmet and Teller (BET) and differential thermogravimetric (DTG) analysis, which evidence that Faujasite and S-23 activated carbon are resistant to ozone exposure whereas the pore volume and the surface area of L-27 activated carbon decrease during ozonation

Effectiveness of seasonal malaria chemoprevention (SMC) treatments when SMC is implemented at scale: Case-control studies in 5 countries.

BACKGROUND: Seasonal malaria chemoprevention (SMC) has shown high protective efficacy against clinical malaria and severe malaria in a series of clinical trials. We evaluated the effectiveness of SMC treatments against clinical malaria when delivered at scale through national malaria control programmes in 2015 and 2016. METHODS AND FINDINGS: Case-control studies were carried out in Mali and The Gambia in 2015, and in Burkina Faso, Chad, Mali, Nigeria, and The Gambia in 2016. Children aged 3-59 months presenting at selected health facilities with microscopically confirmed clinical malaria were recruited as cases. Two controls per case were recruited concurrently (on or shortly after the day the case was detected) from the neighbourhood in which the case lived. The primary exposure was the time since the most recent course of SMC treatment, determined from SMC recipient cards, caregiver recall, and administrative records. Conditional logistic regression was used to estimate the odds ratio (OR) associated with receipt of SMC within the previous 28 days, and SMC 29 to 42 days ago, compared with no SMC in the past 42 days. These ORs, which are equivalent to incidence rate ratios, were used to calculate the percentage reduction in clinical malaria incidence in the corresponding time periods. Results from individual countries were pooled in a random-effects meta-analysis. In total, 2,126 cases and 4,252 controls were included in the analysis. Across the 7 studies, the mean age ranged from 1.7 to 2.4 years and from 2.1 to 2.8 years among controls and cases, respectively; 42.2%-50.9% and 38.9%-46.9% of controls and cases, respectively, were male. In all 7 individual case-control studies, a high degree of personal protection from SMC against clinical malaria was observed, ranging from 73% in Mali in 2016 to 98% in Mali in 2015. The overall OR for SMC within 28 days was 0.12 (95% CI: 0.06, 0.21; p < 0.001), indicating a protective effectiveness of 88% (95% CI: 79%, 94%). Effectiveness against clinical malaria for SMC 29-42 days ago was 61% (95% CI: 47%, 72%). Similar results were obtained when the analysis was restricted to cases with parasite density in excess of 5,000 parasites per microlitre: Protective effectiveness 90% (95% CI: 79%, 96%; P<0.001), and 59% (95% CI: 34%, 74%; P<0.001) for SMC 0-28 days and 29-42 days ago, respectively. Potential limitations include the possibility of residual confounding due to an association between exposure to malaria and access to SMC, or differences in access to SMC between patients attending a clinic and community controls; however, neighbourhood matching of cases and controls, and covariate adjustment, attempted to control for these aspects, and the observed decline in protection over time, consistent with expected trends, argues against a major bias from these sources. CONCLUSIONS: SMC administered as part of routine national malaria control activities provided a very high level of personal protection against clinical malaria over 28 days post-treatment, similar to the efficacy observed in clinical trials. The case-control design used in this study can be used at intervals to ensure SMC treatments remain effective

The Wide-field Spectroscopic Telescope (WST) Science White Paper

The Wide-field Spectroscopic Telescope (WST) is proposed as a new facility dedicated to the efficient delivery of spectroscopic surveys. This white paper summarises the initial concept as well as the corresponding science cases. WST will feature simultaneous operation of a large field-of-view (3 sq. degree), a high multiplex (20,000) multi-object spectrograph (MOS) and a giant 3x3 sq. arcmin integral field spectrograph (IFS). In scientific capability these requirements place WST far ahead of existing and planned facilities. Given the current investment in deep imaging surveys and noting the diagnostic power of spectroscopy, WST will fill a crucial gap in astronomical capability and work synergistically with future ground and space-based facilities. This white paper shows that WST can address outstanding scientific questions in the areas of cosmology; galaxy assembly, evolution, and enrichment, including our own Milky Way; origin of stars and planets; time domain and multi-messenger astrophysics. WST's uniquely rich dataset will deliver unforeseen discoveries in many of these areas. The WST Science Team (already including more than 500 scientists worldwide) is open to the all astronomical community. To register in the WST Science Team please visit this https URL<br/

The Wide-field Spectroscopic Telescope (WST) Science White Paper

The Wide-field Spectroscopic Telescope (WST) is proposed as a new facility dedicated to the efficient delivery of spectroscopic surveys. This white paper summarises the initial concept as well as the corresponding science cases. WST will feature simultaneous operation of a large field-of-view (3 sq. degree), a high multiplex (20,000) multi-object spectrograph (MOS) and a giant 3x3 sq. arcmin integral field spectrograph (IFS). In scientific capability these requirements place WST far ahead of existing and planned facilities. Given the current investment in deep imaging surveys and noting the diagnostic power of spectroscopy, WST will fill a crucial gap in astronomical capability and work synergistically with future ground and space-based facilities. This white paper shows that WST can address outstanding scientific questions in the areas of cosmology; galaxy assembly, evolution, and enrichment, including our own Milky Way; origin of stars and planets; time domain and multi-messenger astrophysics. WST's uniquely rich dataset will deliver unforeseen discoveries in many of these areas. The WST Science Team (already including more than 500 scientists worldwide) is open to the all astronomical community. To register in the WST Science Team please visit this https URL (https://www.wstelescope.com/for-scientists/participate)

The PLATO mission

PLATO (PLAnetary Transits and Oscillations of stars) is ESA’s M3 mission designed to detect and characterise extrasolar planets and perform asteroseismic monitoring of a large number of stars. PLATO will detect small planets (down to <2REarth) around bright stars (<11 mag), including terrestrial planets in the habitable zone of solar-like stars. With the complement of radial velocity observations from the ground, planets will be characterised for their radius, mass, and age with high accuracy (5%, 10%, 10% for an Earth-Sun combination respectively). PLATO will provide us with a large-scale catalogue of well-characterised small planets up to intermediate orbital periods, relevant for a meaningful comparison to planet formation theories and to better understand planet evolution. It will make possible comparative exoplanetology to place our Solar System planets in a broader context. In parallel, PLATO will study (host) stars using asteroseismology, allowing us to determine the stellar properties with high accuracy, substantially enhancing our knowledge of stellar structure and evolution. The payload instrument consists of 26 cameras with 12cm aperture each. For at least four years, the mission will perform high-precision photometric measurements. Here we review the science objectives, present PLATO‘s target samples and fields, provide an overview of expected core science performance as well as a description of the instrument and the mission profile towards the end of the serial production of the flight cameras. PLATO is scheduled for a launch date end 2026. This overview therefore provides a summary of the mission to the community in preparation of the upcoming operational phases

Effect of IX dosing on polypropylene and PVDF membrane fouling control

The performance of ion exchange (IX) resin for organics removal from wastewater was assessed using advanced characterisation techniques for varying doses of IX. Organic characterisation using liquid chromatography with a photodiode array (PDA) and fluorescence spectroscopy (Method A), and UV254, organic carbon and organic nitrogen detectors (Method B), was undertaken on wastewater before and after magnetic IX treatment. Results showed partial removal of the biopolymer fraction at high IX doses. With increasing concentration of IX, evidence for nitrogen-containing compounds such as proteins and amino acids disappeared from the LC-OND chromatogram, complementary to the fluorescence response. A greater fluorescence response of tryptophan-like proteins (278nm/343nm) for low IX concentrations was consistent with aggregation of tryptophan-like compounds into larger aggregates, either by self-aggregation or with polysaccharides. Recycling of IX resin through multiple adsorption steps without regeneration maintained the high level of humics removal but there was no continued removal of biopolymer. Subsequent membrane filtration of the IX treated waters resulted in complex fouling trends. Filtration tests with either polypropylene (PP) or polyvinylidene fluoride (PVDF) membranes showed higher rates of initial fouling following treatment with high IX doses (10mL/L) compared to filtration of untreated water, while treatment with lower IX doses resulted in decreased fouling rates relative to the untreated water. However, at longer filtration times the rate of fouling of IX treated waters was lower than untreated water and the relative fouling rates corresponded to the amount of biopolymer material in the feed. It was proposed that the mode of fouling changed from pore constriction during the initial filtration period to filter cake build up at longer filtration times. The organic composition strongly influenced the rate of fouling during the initial filtration period due to competitive adsorption processes, while at longer filtration times the rate of fouling appeared to depend upon the amount of biopolymer material in the feed water