Decreasing activated sludge thermal hydrolysis temperature reduces product colour, without decreasing degradability

Activated sludges are becoming more difficult to degrade in anaerobic digesters, due to the implementation of stricter nitrogen limits, longer sludge ages, and removal of primary sedimentation units. Thermal hydrolysis is a popular method to enhance degradability of long-age activated sludge, and involves pressure and heat treatment of the process fluid (150-160 degrees C saturated steam). However, as documented in this study, in a full-scale system, the use of thermal hydrolysis produces coloured, recalcitrant compounds that can have downstream impacts (e.g., failure of UV disinfection, and increased effluent nitrogen). The coloured compound formed during thermal hydrolysis was found to be melanoidins. These are coloured recalcitrant compounds produced by polymerisation of low molecular weight intermediates, such as carbohydrates and amino compounds at elevated temperature (Maillard reaction). By decreasing the THP operating temperature from 165 degrees C to 140 degrees C, THP effluent colour decreased from 12,677 mg-PtCo L(-1) to 3837 mg-PtCo L(-1). The change in THP operating temperature from 165 degrees C to 140 degrees C was shown to have no significant impact on anaerobic biodegradability of the sludge. The rate and extent of COD biodegradation remained largely unaffected by the temperature change with an average first order hydrolysis rate of 0.19 d(-1) and conversion extent of 0.43 g-COD(CH4)g-COD(-1).     

Influence of combined doping of tricalcium silicate with MgO, Al2O3 and Fe2O3: synthesis, grindability, X-ray diffraction and 29Si NMR

Tricalcium silicate is the major component of ordinary Portland cement and as recently demonstrated is an alternative to ceramic implant material for clinical applications, because of its good biocompatibility. It is known, that the crystal structure of tricalcium silicate depends on the kind and amount of foreign oxides incorporated into the lattice that correlates with materials properties like hydration activity. Up to now, the correlation between structure and materials properties was only quantified for single oxide doping, but nothing is known about combined doping, which is the standard for industrial applications of tricalcium silicate. In this study the influence of single and multiple doping with MgO, Al₂O₃ and Fe₂O₃ on the crystal structure and materials properties was quantified. This first part deals with the synthesis, grindability, X-ray diffraction with Rietveld refinement and ²⁹Si nuclear magnetic resonance of the unhydrated compound, a second paper deals with the hydration reaction.

Presence of cancerostatic platinum compounds in hospital wastewater and possible elimination by adsorption to activated sludge

Platinum originating from the excreted cancerostatic platinum compounds (CPC) cisplatin, carboplatin and oxaliplatin was monitored over a period of 28 days in the wastewater of the oncologic ward of the Vienna University Hospital. Concentration levels ranging from 4.7 to 145 microg L(-1) were measured by inductively coupled plasma mass spectrometry (ICP-MS). An average ratio of weekly drug emission/drug consumption of 0.27+/-0.12 was assessed. Model studies were carried out for fundamental understanding of CPC interaction with the solid phases present at different stages of the water cycle. Wastewater and activated sludge were spiked with CPC at concentration levels as found in the sewer of the oncologic ward. The platinum concentration remaining in the tested solution was measured after 24 h of incubation. Depending on pH, the three substances exhibited considerably different adsorption rates in wastewater. At pH 7, cisplatin was adsorbed by 88%, whereas only 26% of carboplatin and 54% of oxaliplatin were removed from the aqueous phase. Adsorption by activated sludge was higher, less affected by pH variation and comparable for all investigated CPC (96% for cisplatin, 70% for carboplatin and 74% for oxaliplatin at pH 6.8). In a next step, the dependence of CPC adsorption was tested for wastewater and activated sludge of different sampling sites. Strong variations were found only for wastewater, whereas activated sludge showed more consistent elimination rates (average values: cisplatin 92%, carboplatin 72%, and oxaliplatin 78%). These findings indicate that the major part of the excreted CPC is adsorbed by the solid phase in the water cycle and is thus expected to be removed from the wastewater by sewage treatment plants.     

Neural network modelling of the inductively coupled RF plasma synthesis of silicon nanoparticles

The synthesis of silicon nanopowders by an inductively coupled plasma (ICP) process is investigated. The specific surface area (SSA) of the elaborated particles is determined by nitrogen absorption (BET) as a function of the quenching gas flow rate and the precursor feeding rate. Nanopowders with specific surface areas varying from 69 to 194 m² g^− 1, corresponding to equivalent particle sizes of 37 and 13 nm respectively, could be produced. The correlation between these two input parameters and the output SSA has been numerically modelled with linear regression and artificial neural networks approaches. It has been demonstrated that with the available data set, a regression model with quadratic regressors and a neural network modelling give a similar response.     

Real-Time Analysis of Alarm Pheromone Emission by the Pea Aphid (<Emphasis Type="Italic">Acyrthosiphon Pisum</Emphasis>) Under Predation

Upon attack by predators or parasitoids, aphids emit volatile chemical alarm signals that warn other aphids of a potential risk of predation. Release rate of the major constituent of the alarm pheromone in pea aphids (Acyrthosiphon pisum), (E)-b-farnesene (EBF), was measured for all nymphal and the adult stage as aphids were attacked individually by lacewing (Chrysoperla carnae) larvae. Volatilization of EBF from aphids under attack was quantified continuously for 60 min at 2-min intervals with a rapid gas chromatography technique (zNose) to monitor headspace emissions. After an initial burst, EBF volatilization declined exponentially, and detectable amounts were still present after 30 min in most cases. Total emission of EBF averaged 16.33 +/- 1.54 ng and ranged from 1.18 to 48.85 ng. Emission was higher in nymphs as compared to adults. No differences between pea aphid life stages were detected for their speed of alarm signal emission in response to lacewing larvae attack. This is the first time that alarm pheromone emission from single aphids has been reported.     

Biosynthesis of (3<Emphasis Type="Italic">Z</Emphasis>,6<Emphasis Type="Italic">Z</Emphasis>,9<Emphasis Type="Italic">Z</Emphasis>)-3,6,9-Octadecatriene: The Main Component of the Pheromone Blend of <Emphasis Type="Italic">Erannis bajaria</Emphasis>

The hydrocarbons (3Z,6Z,9Z)-3,6,9-octadecatriene (3Z,6Z,9Z-18:H) and (3Z,6Z,9Z)-3,6,9-nonadecatriene (3Z,6Z,9Z-19:H) constitute the pheromone of the winter moth, Erannis bajaria. These compounds belong to a large group of lepidopteran pheromones which consist of unsaturated hydrocarbons and their corresponding oxygenated derivatives. The biosynthesis of such hydrocarbons with an odd number of carbons in the chain is well understood. In contrast, knowledge about the biosynthesis of even numbered derivatives is lacking. We investigated the biosynthesis of 3Z,6Z,9Z-18:H by applying deuterium-labeled precursors to females of E. bajaria followed by gas chromatography–mass spectrometry analysis of extracts of the pheromone gland. A mixture of deuterium-labeled [17,17,18,18-²H₄]-3Z,6Z,9Z-18:H and the unlabeled 3Z,6Z,9Z-18:H was obtained after topical application and injection of (10Z,13Z,16Z)-[2,2,3,3-²H₄]-10,13,16-nonadecatrienoic acid ([2,2,3,3-²H₄]-10Z,13Z,16Z-19:acid) or (11Z,14Z,17Z)-[3,3,4,4-²H₄]-11,14,17-icosatrienoic acid ([3,3,4,4-²H₄]-11Z,14Z,17Z-20:acid). These results are consistent with a biosynthetic pathway that starts with α-linolenic acid (9Z,12Z,15Z-18:acid). Chain elongation leads to 11Z,14Z,17Z-20:acid, which is shortened by α-oxidation as the key step to yield 10Z,13Z,16Z-19:acid. This acid can be finally reduced to an aldehyde and decarbonylated or decarboxylated to furnish the pheromone component 3Z,6Z,9Z-18:H. A similar transformation of 11Z,14Z,17Z-20:acid yields the second pheromone component, 3Z,6Z,9Z-19:H.     

Caged capsaicins: New tools for the examination of TRPV1 channels in somatosensory neurons

The vanilloid capsaicin, N-(4-hydroxy-3-methoxybenzyl)-8-methylnon-6-enamide, is the pungent ingredient of chili peppers and is used in pain research as an activating ligand of heat-sensitive transduction channels in nociceptive neurons. Here we describe the synthesis and application of two capsaicin derivatives modified at the hydroxy function of the vanillyl motif: alpha-carboxy-4,5-dimethoxy-2-nitrobenzyl-caged (CDMNB-caged) capsaicin and {7-[bis(carboxymethyl)amino]coumarin-4-yl}methoxycarbonyl-caged (BCMACMOC-caged) capsaicin. These compounds show dramatically reduced pungency, but release active capsaicin upon irradiation with UV light. CDMNB-caged capsaicin can be used to perform concentration-jump experiments, while BCMACMOC-caged capsaicin is membrane-impermeant and can be applied selectively to the intracellular or extracellular sides of a plasma membrane. Both compounds can serve as valuable research tools in pain physiology.     

Bioconcentration factor hydrophobicity cutoff: an artificial phenomenon reconstructed

The debate on whether highly hydrophobic organic chemicals (with log Kow > 5-6) bioconcentrate less than may be expected from their hydrophobicity is still not settled. The often-observed hydrophobicity "cutoff" might either be explained by artifacts occurring during bioconcentration factor (BCF) measurements or by a true mechanism, i.e., reduced uptake of larger molecules due to decreased membrane permeation. In this paper, we advocate there is no hydrophobicity cutoff, at least not for compounds with log Kow of up to 7.5. Data are presented on the uptake of polycyclic aromatic hydrocarbons (PAHs) in the aquatic worm Lumbriculus variegatus. For this combination of chemicals/organism, BCFs were measured using several approaches, including traditional batch uptake kinetics measurements and alternative ones, involving solid-phase microextraction (SPME), polyoxymethylene solid-phase extraction (POM-SPE), field exposures, and the substitution of living worms by dead worm material or liposomes. A hydrophobicity cutoff was observed at two levels during the traditional approach only, whereas for the other approaches it was absent. The data were used to demonstrate the presence and impact of artifacts due to so-called "third phase effects" and nonequilibrium conditions that can obscure "true uptake". The experiments suggest that previously observed cutoff effects can be ascribed to artifacts, and that current risk assessment (often incorporating a BCF cutoff) as well as BCF measurement techniques of very hydrophobic chemicals should be revised.     

2‐Aminopyridines as an α‐Bromination Shuttle in a Transition Metal‐Free One‐Pot Synthesis of Imidazo[1,2‐a]pyridines

A wide range of imidazo[1,2‐a]pyridines are accessible from cheap and readily available 2‐aminopyridines and 1,3‐dicarbonyl compounds using a unique CBrCl₃/2‐aminopyridine system for bromination at the α‐carbon. 2‐Aminopyridine is not only the substrate but also acts as a bromination shuttle, transferring the bromine atom from CBrCl₃ to the α‐carbon of the 1,3‐dicarbonyl. The reaction mechanism involves a series of reversible steps, including an addition reaction with cyclic transition state, to form a bromo‐hemiaminal intermediate. Isolated yields of up to 97% were obtained under mild conditions and at short reaction times in this transition metal‐free, one‐pot synthesis.