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The presence of microalgae affects water quality and beneficial uses of surface freshwaters. Chitosan with proven potential for harvesting specific microalgae species from their culture medium to produce biofuels and bioproducts also appears promising for efficient removal of mixed microalgae species from surface freshwaters. The main focus of the present study was on removal of mixed microalgae species using chitosan as a coagulant to help improve water quality. Important operational parameters were optimized for economical microalgae removal. The microalgae cells, chlorophyll-a, total nitrogen, and total phosphorous removal efficiency were 82.06%, 89.90%, 69.32%, and 44.01%, respectively, at an optimum chitosan dose of 10 mg/L, pH 8, slow mixing time 7 min, slow mixing rate 30 rpm, and settling time of 15 min. The results show that chitosan coagulation efficiently removed mixed microalgae species from surface freshwater with significant improvement in water quality and recovery of algal biomass for other beneficial applications. Key words: chitosan, microalgae harvesting, flocculation, water quality improvement, microalgal biomass. La presence de microalgues a une incidence sur la qualite de l'eau et les utilisations benefiques des eaux douces de surface. Le chitosane, avec un potentiel confirme en matiere de recolte d'especes precises de microalgues a partir de leur milieu de culture pour la production de biocarburants et de bioproduits, semble egalement prometteur pour l'elimination efficace des especes mixtes de microalgues des eaux douces de surface. L'objectif principal de la presente etude etait d'eliminer les microalgues mixtes en utilisant le chitosane comme coagulant pour ameliorer la qualite de l'eau. Des parametres operationnels importants ont ete optimises pour l'elimination economique des microalgues. L'efficacite d'elimination des cellules de microalgues, de chlorophylle-a, d'azote total et de phosphore total etaient 82.06, 89.90, 69.32 et 44.01 %, respectivement, a une dose optimale de chitosane de 10 mg/L, pH 8, temps de melange lent 7 min, vitesse de melange lente 30 rpm et temps de sedimentation de 15 min. Les resultats ont montre que la coagulation du chitosane a permis d'eliminer efficacement les microalgues mixtes des eaux douces de surface, ce qui a permis d'ameliorer considerablement la qualite de l'eau et de recuperer la biomasse algale pour d'autres applications benefiques. Mots-cles : chitosane, recolte de microalgues, floculation, amelioration de la qualite de l'eau, biomasse de microalgues., 1. Introduction Excessive growth of microalgae, especially cyanobacteria, in surface freshwaters forms unsightly surface scum, causes severe oxygen depletion and fish mortalities upon die-off, releases algal toxins, taste and odour, [...]

In this article, an algorithm for snow depth (SD) and snow water equivalent (SWE) retrieval is proposed based on a polarimetric synthetic aperture radar (SAR) decomposition model and field measured snow data. The field campaigns were conducted at the Dhundi observatory (in the Indian Himalaya) in January 2016 and 2018. The field-measured data are used here to build a linear regression between wetness (w) and the imaginary part of the snow permittivity (ε''), and the validation of retrieved SD and SWE. The snow density (ρs) and w are calculated with a generalized volume parameter derived using a theoretical model and SAR data (coherency matrix). These snow parameters and the field-based regression relating w and ε'' are eventually used for the SD and SWE retrieval. Three TerraSAR-X scenes of the quad-polarization X-band data acquired in January 2016 are used to study the effect of the snow conditions on the accuracy of the proposed algorithm. The mean absolute error (MAE), root-mean-square error (RMSE), and index of agreement (IOA) for SD are 4.84 cm, 5.12 cm, and 0.71, respectively. On the other hand, for SWE, it is 1.42 cm, 1.53 cm, and 0.71, respectively. [ABSTRACT FROM AUTHOR]

Various glass compositions were prepared in a glassy system [25BaCO3-(10-x) ZrO2-20TiO2-45SiO2-xCrO3] (x = 0, 2, 4, and 6) using melt-quenching technique. XRD patterns of glass and glass ceramics showed amorphous and crystalline nature. Density of glass and glass ceramics decreased from 3.4553 to 3.4381 g/cm3 and 3.7485 to 3.1977 g/cm3 with increasing concentration of CrO3. DTA of the glasses revealed a shift in base line which suggests a change in specific heat and attributed to the glass transition temperature, Tg. FTIR and Raman spectroscopic analysis indicated that an increasing doping of CrO3 changes structural network by increasing number of nonbridging oxygens (NBO) within glassy matrix. These results revealed that bands toward low frequency side endorsed to the vibration of Ba2+ metal cation, bending vibration of Si-O-Si and bonding formation of ZrO2. Concentration of CrO3, changed the microsture significantly and hence, a denser, fully developed mixed morphology was noticed with spherical grains of ZrO2, irregular shape of bazirite (BaZr0.97Ti0.03Si3O9) phase and TiO2 grains. Glass ceramic sample BZTS6C971 CrO3 (x = 6) retains high value of dielectric constant, ~4555 due to space charge polarization. Hence, these glass ceramics might be useful for diverse applications such as in optical devices, electronic circuits, and multilayer ceramic capacitors. [ABSTRACT FROM AUTHOR]