Comments about birefringence dispersion, with group and phase birefringence measurements in polarization-maintaining fibers

A recent JEOS-RP publication proposed Comments about Dispersion of Light Waves, and we present here complementary comments for birefringence dispersion in polarization-maintaining (PM) fibers, and for its measurement techniques based on channeled spectrum analysis. We start by a study of early seminal papers, and we propose additional explanations to get a simpler understanding of the subject. A geometrical construction is described to relate phase birefringence to group birefringence, and it is applied to the measurement of several kinds of PM fibers using stress-induced photo-elasticity, or shape birefringence. These measurements confirm clearly that the difference between group birefringence and phase birefringence is limited to 15–20% in stress-induced PM fibers (bow-tie, panda, or tiger-eye), but that it can get up to a 3-fold factor with an elliptical-core (E-core) fiber. There are also surprising results with solid-core micro-structured PM fibers, that are based on shape birefringence, as E-core fibers

Individual and combined effect of salinity and nitrite on freshwater Anammox bacteria (FAB)

Anaerobic ammonium oxidation (Anammox) based technology has potential for nitrogen removal from wastewater with high salinity, but both salt and nitrite (a substrate for Anammox) have negative effect on microbial activity. In order to achieve Anammox in saline wastewater treatment, it is essential to understand the combined effect of these two components. In this study, the individual and combined effect of salinity and nitrite on fixed film freshwater Anammox bacteria (FAB, mainly belonging to the Ca. Brocadia genus), enriched on carriers from a 1500 L pilot scale one-stage (PN/Anammox) moving bed bioreactor (MBBR), were systematically investigated by 57 pre-designed batch tests. The combined inhibition of nitrite and salinity was determined by comparing with additive and independent inhibition models. With salinity only, the specific Anammox activity (SAA) decreased with increasing salinity: 14.6 mS/cm (about 9.1 g NaCl/L) of salinity caused 50% inhibition (IC). With nitrite only, SAA started to decrease when nitrite concentration was above 450 mg N/L (threshold) and decreased with increased nitrite (IC = 666 mg N/L) thereafter. Significantly, when both salinity and nitrite were elevated, both the threshold and IC of nitrite were reduced, with inhibition enhanced. Analysis showed that at high salinity (>14.6 mS/cm) and nitrite concentration (>666 mg N/L), inhibition was close to that predicted by simulation of additive and independent inhibition models. Within a salinity range of 4–14.6 mS/cm and nitrite concentration range of 50–666 mg N/L, the combined inhibition was more severe than prediction (p < 0.05) based on the additive and independent inhibition models and therefore it was determined to be synergistic inhibition

Performances of protease and amylase cleaning for microporous membranes used in wastewater applications

Enzymes have been successfully applied to clean fouled membranes, especially those affected by the deposition of protein- and lipid-based compounds. In the water and wastewater industries, enzymatic cleaners are increasingly considered as potential alternatives from conventional chemical agents. Their very specific targeted actions and environmental impact are indeed some of the drivers for using enzymes in microporous membrane processes. This paper aims to assess the cleaning performance of two types of enzyme (protease and amylase) to remove typical fouling materials found in wastewater treatment (protein and carbohydrate modeled in this study by bovine serum albumin and sodium alginate, respectively). Under the experimental conditions used in this study, results showed relatively low cleaning efficiencies, with optimum efficiencies of 68% and 73%, for protease and amylase, respectively. Although enzymes are not known to cause membrane ageing/deterioration, this type of cleaners was expected to potentially foul the membrane, as residual enzyme may attach to the membrane during the cleaning process. To assess this potential, cyclical cleanings were performed in addition to single cycle cleaning. Results showed that fouling occurred four times faster after membrane was re-used for 16 cycles. The sequential use of the two enzymatic cleaners in series did not provide any improvement in efficiency compared to the use of single enzyme. However, analysis of residual foulants indicated the lower amount of material found on the membrane

Investigating the role of adsorption and biodegradation in the removal of organic micropollutants during biological activated carbon filtration of treated wastewater

Municipal water recycling may expose humans and the environment to trace organic contaminants. We assessed biological activated carbon (BAC) filtration for removal of organic micropollutants (MPs). Adsorption experiments were carried out in batch reactors containing secondary effluent and new granular activated carbon (GAC) and preloaded BAC media. Results show that BAC has good potential for removal of dissolved organic carbon (40%) and MPs (60–95%). The primary objective was to better understand removal mechanisms of representative MPs at environmentally relevant concentrations. Adsorption and biodegradation of 20 compounds of varying physico-chemical properties were investigated by inhibiting the biomass with azide. Average removal of compounds by adsorption on GAC was 88 ± 5% with no influence of azide. Average BAC removal was 72 ± 15%, reduced to 59 ± 20% after azide addition, showing that biological activity is important for MP removal. Comparison of MP removal by BAC and BAC + azide showed a more important impact of the inhibition on the removal of negatively charged compounds. Sustained removal of recalcitrant compounds showed that BAC maintained sorption capacity. These results highlight the advantage of a combination of adsorption and biodegradation as compared to other biofiltration techniques for the long-term attenuation of MPs

Calcul du biais thermique dans une bobine de fibre optique par un modèle thermomécanique homogénéisé

International audienc

Développement d’un Modèle Thermomécanique Homogénéisé pour la Conception Optimisée deGyromètres à Fibre Optique

International audienceLes Gyromètres à Fibre Optique (FOG) sont intégrés dans des centrales inertielles de haute précision. La pièce maîtresse de ce type de capteur est une bobine de fibre optique dont les déformations, d’ori- gine thermique notamment, peuvent générer un biais de mesure. Des modélisations numériques fines, mais coûteuses, permettent d’estimer ce biais et ainsi, d’optimiser la conception de la structure bobinée (matériau et géométrie). L’objectif de ce travail est de proposer un modèle homogénéisé de bobinage et d’évaluer sa pertinence au regard des quantités d’intérêt nécessaires au calcul du biais