DVGW-Forschungsstelle am Engler-Bunte-Institut des Karlsruher Instituts für Technologie

Fenton chemistry encompasses reactions of hydrogen peroxide in the presence of iron to generate highly reactive species such as the hydroxyl radical and possibly others. In this review, the complex mechanisms of Fenton and Fenton-like reactions and the important factors influencing these reactions, from both a fundamental and practical perspective, in applications to water and soil treatment, are discussed. The review covers modified versions including the photoassisted Fenton reaction, use of chelated iron, electro-Fenton reactions, and Fenton reactions using heterogeneous catalysts. Sections are devoted to nonclassical pathways, by-products, kinetics and process modeling, experimental design methodology, soil and aquifer treatment, use of Fenton in combination with other advanced oxidation processes or biodegradation, economic comparison with other advanced oxidation processes, and case studies.

The Power-to-Gas (PtG) process chain could play a significant role in the future energy system. Renewable electric energy can be transformed into storable methane via electrolysis and subsequent methanation. This article compares the available electrolysis and methanation technologies with respect to the stringent requirements of the PtG chain such as low CAPEX, high efficiency, and high flexibility. Three water electrolysis technologies are considered: alkaline electrolysis, PEM electrolysis, and solid oxide electrolysis. Alkaline electrolysis is currently the cheapest technology; however, in the future PEM electrolysis could be better suited for the PtG process chain. Solid oxide electrolysis could also be an option in future, especially if heat sources are available. Several different reactor concepts can be used for the methanation reaction. For catalytic methanation, typically fixed-bed reactors are used; however, novel reactor concepts such as three-phase methanation and micro reactors are currently under development. Another approach is the biochemical conversion. The bioprocess takes place in aqueous solutions and close to ambient temperatures. Finally, the whole process chain is discussed. Critical aspects of the PtG process are the availability of CO₂ sources, the dynamic behaviour of the individual process steps, and especially the economics as well as the efficiency.

Partial nitritation/anammox (PN/A) has been one of the most innovative developments in biological wastewater treatment in recent years. With its discovery in the 1990s a completely new way of ammonium removal from wastewater became available. Over the past decade many technologies have been developed and studied for their applicability to the PN/A concept and several have made it into full-scale. With the perspective of reaching 100 full-scale installations in operation worldwide by 2014 this work presents a summary of PN/A technologies that have been successfully developed, implemented and optimized for high-strength ammonium wastewaters with low C:N ratios and elevated temperatures. The data revealed that more than 50% of all PN/A installations are sequencing batch reactors, 88% of all plants being operated as single-stage systems, and 75% for sidestream treatment of municipal wastewater. Additionally an in-depth survey of 14 full-scale installations was conducted to evaluate practical experiences and report on operational control and troubleshooting. Incoming solids, aeration control and nitrate built up were revealed as the main operational difficulties. The information provided gives a unique/new perspective throughout all the major technologies and discusses the remaining obstacles.

Abstract In natural waters arsenic concentrations up to a few milligrams per litre were measured. The natural content of arsenic found in soils varies between 0.01 mg/kg and a few hundred milligrams per kilogram. Anthropogenic sources of arsenic in the environment are the smelting of ores, the burning of coal, and the use of arsenic compounds in many products and production processes in the past. A lot of arsenic compounds are toxic and cause acute and chronic poisoning. In aqueous environment the inorganic arsenic species arsenite (As(III)) and arsenate (As(V)) are the most abundant species. The mobility of these species is influenced by the pH value, the redox potential, and the presence of adsorbents such as oxides and hydroxides of Fe(III), Al(III), Mn(III/IV), humic substances, and clay minerals.

The impact of COVID-19 on social life has been drastic and global. However, the different numbers of cases and different actions in different countries have been leading to various interesting yet unexplored effects on human behavior. In the present study, we compare the physical activity and recreational screen time of a representative sample of 1711 4- to 17-year-olds before and during the strictest time of the first COVID-19 lockdown in Germany. We found that sports activity declined whereas recreational screen time increased. However, a substantial increase in habitual physical activities leads to an overall increase in physical activity among children and adolescents in Germany. The effects differ in size but not in their direction between age groups and are stable for boys and girls. We conclude from this natural experiment that physical activity among children and adolescents is highly context-driven and mutual and does not act as a functional opposite to recreational screen time.

During the oxidative degradation of 2,4-dimethylaniline (2,4-xylidine) by means of the H2O2/UV method, a series of hydroxylated aromatic amines are formed, this result confirming the role of the hydroxyl radical as an initiator of the oxidative chain reaction. Thermal or photochemically enhanced Fenton reactions in the presence of 2,4-dimethylaniline (2,4-xylidine) yield primarily 2,4-dimethylphenol as an intermediate product, the genesis of which may only be explained by an electron transfer mechanism. Experimental evidence for such a mechanism is presented, and values for the quantum yields of the photochemically enhanced reduction of iron(III) to iron(II) in aqueous solutions of 2,4-xylidine are given.

Abstract In natural waters arsenic normally occurs in the oxidation states +III (arsenite) and +V (arsenate). The removal of As(III) is more difficult than the removal of As(V). Therefore, As(III) has to be oxidized to As(V) prior to its removal. The oxidation in the presence of air or pure oxygen is slow. The oxidation rate can be increased by ozone, chlorine, hypochlorite, chlorine dioxide, or H 2 O 2 . The oxidation of As(III) is also possible in the presence of manganese oxide coated sands or by advanced oxidation processes. Arsenic can be removed from waters by coprecipitation with Fe(OH) 3 , MnO 2 or during water softening. Fixed‐bed filters have successfully been applied for the removal of arsenic.The effectiveness of arsenic removal was tested in the presence of adsorbents such as FeOOH, activated alumina, ferruginous manganese ore, granular activated carbon, or natural zeolites. Other removal technologies are anion exchange, electrocoagulation, and membrane filtration by ultrafiltration, nanofiltration or reverse osmosis.

Abstract A detailed modeling study of the formation of polycyclic aromatic hydrocarbons in a burner-stabilized low-pressure sooting 23.6 % C2 H2-21.4% 02-Ar flame of Bockhorn and co-workers is reported. The model predicts the correct orders of magnitude and relative appearances of the concentration peaks, but overstates the decline of the species concentrations in the post-flame zone. Imprecise knowledge of the thermochemical data and unknown details of the oxidation of hydrocarbon radicals are the reasons identifed for the latter. The main reaction pathways for cyclization and growth of polycyclic aromatics and the results of the sensitivity tests are in close agreement with those of the previous modeling study of acetylene oxidation under shock-tube conditions. An additional factor that is important in the. flame environment is the diffusion of hydrogen atoms from the main reaction zone into a cooler preflame region

Municipal wastewater collected in areas with moderate climate is subjected to a gradual temperature decrease from around 20 °C in summer to about 10 °C in winter. A lab-scale moving bed biofilm reactor (MBBR) with carrier material (K3 from AnoxKaldnes) was used to test the tolerance of the overall partial nitritation/anammox process to this temperature gradient. A synthetic influent, containing only ammonium and no organic carbon was used to minimize denitrification effects. After stable reactor operation at 20 °C, the temperature was slowly reduced by 2 °C per month and afterward held constant at 10 °C. Along the temperature decrease, the ammonium conversion dropped from an average of 40 gN m(-3) d(-1) (0.2 gN kgTSS h(-1)) at 20 °C to about 15 gN m(-3) d(-1) (0.07 gN kg TSS h(-1)) at 10 °C, while the effluent concentration was kept <8 mg NH4-N l(-1) during the whole operation. This also resulted in doubling of the hydraulic retention time over the temperature ramp. The MBBR with its biofilm on 10 mm thick carriers proved to sufficiently sustain enough biomass to allow anammox activity even at 10 °C. Even though there was a minor nitrite-build up when the temperature dropped below 12.5 °C, reactor performance recovered as the temperature decrease continued. Microbial community analysis by 16S rRNA amplicon analysis revealed a relatively stable community composition over the entire experimental period.

Abstract In view of the growing importance of photochemically initiated reactions in industry, the use of free‐radical additions of thiols to unsaturated compounds also seems promising. The present article is intended to demonstrate the possibilities and limitations of reactions of this type in organic synthesis.

Abstract Fossil fuels have to be substituted by climate neutral fuels to contribute to CO 2 reduction in the future energy system. Pyrolysis of natural gas is a well‐known technical process applied for production of, e. g., carbon black. In the future it might contribute to carbon dioxide‐free hydrogen production. Production of hydrogen from natural gas pyrolysis has thus gained interest in research and energy technology in the near past. If the carbon by‐product of this process can be used for material production or can be sequestrated, the produced hydrogen has a low carbon footprint. This article reviews literature on the state of the art of methane / natural gas pyrolysis process developments and attempts to assess the technology readiness level (TRL).

The publication gives an overview of the production costs of synthetic methane in a Power-to-Gas process. The production costs depend in particularly on the electricity price and the full load hours of the plant sub-systems electrolysis and methanation. The full-load hours of electrolysis are given by the electricity supply concept. In order to increase the full-load hours of methanation, the size of the intermediate hydrogen storage tank and the size of the methanation are optimised on the basis of the availability of hydrogen. The calculation of the production costs for synthetic methane are done with economics for 2030 and 2050 and the expenditures are calculated for one year of operation. The sources of volume of purchased electricity are the short-term market, long-term contracts, direct-coupled renewable energy sources or seasonal use of surpluses. Gas sales are either traded on the short-term market or guaranteed by long-term contracts. The calculations show, that an intermediate storage tank for hydrogen, adjustment of the methanation size and operating electrolysis and methanation separately, increase the workload of the sub-system methanation. The gas production costs can be significantly reduced. With the future expected development of capital expenditures, operational expenditure, electricity prices, gas costs and efficiencies, an economic production of synthetic natural gas for the years 2030, especially for 2050, is feasible. The results show that Power-to-Gas is an option for long-term, large-scale seasonal storage of renewable energy. Especially the cases with high operating hours for the sub-system methanation and low electricity prices show gas production costs below the expected market prices for synthetic gas and biogas.

Power-to-Methane (PtM) can provide flexibility to the electricity grid while aiding decarbonization of other sectors. This study focuses specifically on the methanation component of PtM in 2050. Scenarios with 80–95% CO2 reduction by 2050 (vs. 1990) are analyzed and barriers and drivers for methanation are identified. PtM arises for scenarios with 95% CO2 reduction, no CO2 underground storage and low CAPEX (75 €/kW only for methanation). Capacity deployed across EU is 40 GW (8% of gas demand) for these conditions, which increases to 122 GW when liquefied methane gas (LMG) is used for marine transport. The simultaneous occurrence of all positive drivers for PtM, which include limited biomass potential, low Power-to-Liquid performance, use of PtM waste heat, among others, can increase this capacity to 546 GW (75% of gas demand). Gas demand is reduced to between 3.8 and 14 EJ (compared to ∼20 EJ for 2015) with lower values corresponding to scenarios that are more restricted. Annual costs for PtM are between 2.5 and 10 bln€/year with EU28’s GDP being 15.3 trillion €/year (2017). Results indicate that direct subsidy of the technology is more effective and specific than taxing the fossil alternative (natural gas) if the objective is to promote the technology. Studies with higher spatial resolution should be done to identify specific local conditions that could make PtM more attractive compared to an EU scale.

Imaging of biofilm systems is a prerequisite for a better understanding of both structure and its function. The review aims to critically discuss the use of optical coherence tomography (OCT) for the visualization of the biofilm structure as well as its dynamic behavior. A short overview on common and well-known, established imaging techniques for biofilms such as scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), Raman microscopy (RM), and magnetic resonance imaging (MRI) paves the way to imaging biofilms at the mesoscale, which is perfectly covered by means of OCT. Principle, resolution, imaging velocity, and limitations of OCT are subsequently presented and discussed in the context of biofilm applications. Examples are provided showing the strength of this technique with respect to the visualization of the mesoscopic biofilm structure as well as the estimation of flow profiles and shear rates. Common and new structural parameters derived from OCT datasets are presented. Additionally, the review shows the importance of OCT with respect to a better description of mechanical biofilm properties. Finally, the implementation of multi-dimensional OCT datasets in biofilm modelling is shown by several examples aiming on an improved understanding of mass transfer at the bulk-biofilm interface. Biotechnol. Bioeng. 2017;114: 1386-1402. © 2017 Wiley Periodicals, Inc.

Sulfonamide antibiotics undergo transformation in the aquatic environment through biodegradation, photolysis, or hydrolysis. In this study, the residual antibacterial activity of 11 transformation products (TPs) of sulfamethoxazole (SMX) was investigated with regard to their in vitro growth and luminescence inhibition on Vibrio fischeri (30 min and 24 h exposure). Two transformation products, 4-hydroxy-SMX and N(4)-hydroxy-acetyl-SMX, were synthesized in-house and confirmed by nuclear magnetic resonance and high-resolution mass spectrometry. Results of individual compound experiments showed that TPs modified at the para amino group still exhibit clear antibacterial effects, whereas TPs resulting from breakdown of the SMX structure lost this mechanism of action. 4-NO2- and 4-OH-SMX were found to inhibit growth to a clearly greater extent than the parent compound, SMX. In contrast, the N(4)-acetyl- and N(4)-hydroxy-acetyl-derivatives retain less than 10 and 5% of the effect of SMX on growth and luminescence inhibition, respectively. The effect of a mixture of para-modified TPs was observed to be additive. Considering the homologous series of sulfa drugs widely prescribed and their common mechanism of action, the potential environmental impact must consider the total amount of sulfonamide antibiotics and their derivative TPs, which might end up in a water body. Extrapolating the results obtained here for the para TPs of SMX to other sulfa drugs and determining the persistence and occurrence of these compounds in the aquatic environment is required for improved risk assessment.

The bioremediation of soil contaminated with polycyclic aromatic hydrocarbons (PAH) often is limited by a low bioavailability of the contaminants. The effect of two nonionic surfactants of the alkylphenolethoxylate type, Arkopal N-300 and Sapogenat T-300, on bioavailability of PAH in manufactured gas plant soil was evaluated in soil columns percolated by recirculating flushing water. Both surfactants enhanced the mass transfer rate of sorbed PAH into the aqueous phase due to solubilization. Solubilized PAH were available for biodegradation. Degradation of the surfactants themselves was monitored by counting cell numbers of surfactant degraders. It could be demonstrated that the rapid degradation of Arkopal N-300 resulted in a lack of oxygen and an inhibition of PAH degradation. Sapogenat T-300 was degraded more slowly, but a depletion of oxygen occurred after 54 d of incubation. Until then the surfactant-enhanced PAH mobilization resulted in an increased PAH degradation as compared to the treatment without surfactant. Therefore, biodegradability of the surfactants was shown to be one of the key functions for the use of surfactants in practice. Reduction of PAH content and toxicity of the contaminated soil was obtained in all cases. Decrease of soil toxicity as indicated by the bioluminescence test was most pronounced in case of the Sapogenat T-300-amended treatment. It is concluded that surfactants can be a useful tool for stimulating biodegradation of PAH in contaminated soil.

We measure the branching fraction of ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\tau}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\tau}}$ using the full $\ensuremath{\Upsilon}(4S)$ data sample containing $772\ifmmode\times\else\texttimes\fi{}{10}^{6}$ $B\overline{B}$ pairs collected with the Belle detector at the KEKB asymmetric-energy ${e}^{+}{e}^{\ensuremath{-}}$ collider. Events with $B\overline{B}$ pairs are tagged by reconstructing one of the $B$ mesons decaying into hadronic final states, and ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\tau}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\tau}}$ candidates are detected in the recoil. We find evidence for ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\tau}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\tau}}$ with a significance of 3.0 standard deviations including systematic errors and measure a branching fraction $\mathcal{B}({B}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\tau}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\tau}})=[{0.72}_{\ensuremath{-}0.25}^{+0.27}(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.11(\mathrm{syst})]\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$.

The exploitation of a lag phase in nitrate production after anoxic periods is a promising approach to suppress nitrite oxidizing bacteria, which is crucial for implementation of the combined partial nitritation-anammox process. An in-depth study of the actual lag phase in nitrate production after short anoxic periods was performed with varied temperatures and air flow rates. In monitored batch experiments, biomass from four different full-scale partial nitritation-anammox plants was subjected to anoxic periods of 5–60 min. Ammonium and the nitrite that was produced were present to reproduce reactor conditions and enable ammonium and nitrite oxidation at the same time. The lag phase observed in nitrite oxidation exceeded the lag phase in ammonium oxidation after anoxic periods of more than 15–20 min. Lower temperatures slowed down the conversion rates but did not affect the lag phases. The operational oxygen concentration in the originating full scale plants strongly affected the length of the lag phase, which could be attributed to different species of Nitrospira spp. detected by DGGE and sequencing analysis.

Abstract i-SANEX is a process for separating actinides(III) from used nuclear fuels by solvent extraction: Actinides(III) and lanthanides(III) are co-extracted from a PUREX raffinate followed by selective back extraction of actinides(III) from the loaded organic phase. This step requires a complexing agent selective for actinides(III). A hydrophilic sulfonated bis triazinyl pyridine (SO3-Ph-BTP) was synthesized and tested for selective complexation of actinides(III) in nitric acid solution. When co-extracting Am(III) and Eu(III) from nitric acid into TODGA, adding SO3-Ph-BTP to the aqueous phase suppresses Am(III) extraction while Eu(III) is extracted. Separation factors in the range of 1000 are achieved. SO3-Ph-BTP remains active in nitric acid up to 2 mol/L. As a result of this performance, buffering or salting-out agents are not needed in the aqueous phase; nitric acid is used to keep the lanthanides(III) in the TODGA solvent. These properties make SO3-Ph-BTP a suitable candidate for i-SANEX process development. Keywords: i-SANEXliquid-liquid extractionaqueous complexationhydrophilic BTPactinides(III)lanthanides(III)separationnitric acid ACKNOWLEDGMENT Financial support from the Commission of the European Community (project ACSEPT, FP7-CP-2007-211 267) and the German Federal Ministry of Education and Research (BMBF contract numbers 02NUK012A and 02NUK012E) is acknowledged. ESI-MS analysis of SO3-Ph-BTP was kindly performed by D. Girnt, Karlsruher Institut für Technologie, Institut für Anorganische Chemie.

Abstract In the context of our studies on ruthenium(II) complexes containing polyazaheterocyclic ligands, we have determined the rate constants of quenching by molecular oxygen ( k q ) of the metal‐to‐ligand charge‐transfer‐excited state of a series of homoleptic [RuL 3 ] complexes (where L stands for 2,2′‐bipyridine (bpy), 1,10‐phenanthroline (phen), 2,2′‐bipyrazine (bpz), 4,7‐diphenyl‐1,10‐phenanthroline (dip), diphenyl‐1,10‐phenanthroline‐4,7‐disulfonate (dpds), and 1, 10‐phenanthroline‐5‐octadecanamide (poda)) in H 2 O and in MeOH. These compounds are singlet‐oxygen (O 2 ( 1 Δ g )) sensitizers, and quantum yields of singlet‐oxygen production (Ψ Δ ) in both solvents are also reported. Values of k q and Ψ Δ depend on the nature of the ligand L and on the solvent, Ψ Δ values showing a large range of variation (0.2 to 1.0). In MeOH, the only pathway for quenching of the excited [RuL 3 ] complexes by molecular oxygen is energy transfer: the fraction of quenched excited states yielding singlet oxygen (ƒ ) is unity for all compounds in the series investigated. Changing from MeOH to H 2 O has several remarkable effects: higher k q and lower Ψ Δ values are observed; ƒ drops to ca. 0.5 except for [Ru(bpz) 3 ] 2+ . In fact, [Ru(bpz) 3 ] 2+ is by far the weakest reductant in the series and behaves differently from the other complexes, with lowest k q and Ψ Δ values and a ƒ equal to 1 in both solvents. Results are interpreted on the basis of the role played by charge‐transfer interactions between the sensitizer excited state and molecular oxygen in the quenching mechanism. Ru II Complexes based on the 4,7‐diphenyl‐1, 10‐phenanthroline (dip) ligand are very efficient and stable singlet‐oxygen sensitizers with Ψ Δ values close to unity in air‐saturated MeOH.