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

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. 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 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 de l oxydation. La première partie de ce travail est consacrée à la compréhension des interactions entre l ozone et les adsorbants. La décomposition de l ozone est favorisée en présence de charbon actif mésoporeux mais au prix de la dégradation de la structure poreuse. En revanche, la structure de la faujasite n est pas modifiée sous l action de l ozone mais l effet sur la formation de radicaux hydroxyles est très faible. 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 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 des charbons actifs d un facteur 2,1 à 2,7 selon le charbon actif utilisé. Dans une dernière partie, une application avec un effluent industriel a été réalisée. L adsorption 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 adsorptionIndustrial 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. 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 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. 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. Moreover, the sequential mode (adsorption followed by regeneration with ozone) allows increasing 2 to 3 fold the activated carbon lifetime. 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 stepTOULOUSE-INSA (315552106) / SudocSudocFranceF

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 by three 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 part. 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 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 BET and 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

Abatement of Polychoro-1,3-butadienes in Aqueous Solution by Ozone, UV Photolysis, and Advanced Oxidation Processes (O-3/H2O2 and UV/H2O2)

The abatement of 9 polychloro-1,3-butadienes (CBDs) in aqueous solution by ozone, UV-C(254 nm) photolysis, and the corresponding advanced oxidation processes (AOPs) (i.e., O-3/H2O2 and UV/H2O2) was investigated. The following parameters were determined for 9 CBDs: second-order rate constants for the reactions of CBDs with ozone (k(O3)) (50% at specific ozone doses of 0.5 gO(3)/gDOC to similar to 100% at >= 1.0 gO(3)/gDOC) were achieved for tetra-CBDs followed by (Z)-1,1,2,3,4-penta-CBD and hexa-CBD. This is consistent with the magnitude of the determined k(O3) and k.(OH). The formation of bromate, a potentially carcinogenic ozonation byproduct, could be significantly reduced by addition of H2O2. For a typical UV disinfection dose (400 J/m2), various extents of phototransformations (10-90%) could be achieved. However, the efficient formation of photoisomers from CBDs with E/Z configuration must be taken into account because of their potential residual toxicity. Under UV-C(254 nm) photolysis conditions, no significant effect of H2O2 addition on CBDs abatement was observed due to an efficient direct phototransformation of CBDs

MEMBRO₃X, a Novel Combination of a Membrane Contactor with Advanced Oxidation (O₃/H₂O₂) for Simultaneous Micropollutant Abatement and Bromate Minimization

Ozonation is a water treatment process for disinfection and/or micropollutant abatement. However, ozonation of bromide-containing water leads to bromate (BrO₃^–) formation, a potential human carcinogen. A solution for mitigating BrO₃^– formation during abatement of micropollutants is to minimize the ozone (O₃) concentration. This can be achieved by dosing ozone in numerous small portions throughout a reactor in the presence of H₂O₂. Under these conditions, O₃ is rapidly consumed to form hydroxyl radical (^<b>•</b>OH), which will oxidize micropollutants. To achieve this goal, a novel process (“MEMBRO₃X”) was developed in which ozone is transferred to the water through the pores of polytetrafluoroethylene (PTFE) hollow fiber membranes. When compared to the conventional peroxone process (O₃/H₂O₂), the MEMBRO₃X process shows better performance in terms of micropollutant abatement and bromate minimization for groundwater and surface water treatment. For a groundwater containing 180 μg/L bromide, a 95% abatement of the ozone-resistant probe compound <i>p</i>-chlorobenzoic acid yielded <0.5 μg/L BrO₃^–, whereas in the conventional peroxone process, 8 μg/L BrO₃^– was formed. In addition, the efficacy of the MEMBRO₃X process was demonstrated with river water and lake water