Effects of sludge pretreatment on sludge reduction in a lab-scale anaerobic/anoxic/oxic system treating domestic wastewater

Excess sludge disposal is one of the serious challenges in biological wastewater treatment. Reduction of sludge production would be an ideal way to solve sludge-associated problems rather than the post-treatment of the sludge produced. In this study, a new wastewater treatment process combining anaerobic/anoxic/oxic system with thermochemical sludge pretreatment was tested in a laboratory scale experiment. In this study, the effects of the sludge pretreatment on the excess sludge production in anaerobic/anoxic/oxic were investigated. The system was operated in two Runs (1 and 2). In Run 1, the system was operated as a reference and in Run 2, a part of the mixed liquid was pretreated thermochemically and was returned to the bioreactor. The average solubilization efficiency of pretreated sludge was found to be about 35 % during the study period of 220 days. Sludge production rate in Run 2 was less than that in Run 1 by about 52 %. Total phosphorous was removed by enhanced biological phosphorous removal with the removal efficiency of 83–87 % and 81–83 % for Run 1 and Run 2, respectively. Total nitrogen removal in Run 2 (79–82 %) was slightly higher than that in Run 1 (68–75 %). The mixed liquor suspended solids/mixed liquor volatile suspended solids ratio was identical after both runs in the range 78–83 %. The effluent water qualities were not significantly affected when operated with thermochemical pretreatment at pH 11 and 60 °C for 3 h during 7 months. From the present study it is concluded that thermochemical sludge pretreatment of anaerobic/anoxic/oxic process plays an important role in reduction of sludge production.     

Cordieritite and Leucogranite Formation during Emplacement of Highly Peraluminous Magma: the El Pilon Granite Complex (Sierras Pampeanas, Argentina)

Cordieritites and highly peraluminous granites within the ElPilón granite complex, Sierras Pampeanas, Argentina,were emplaced during a medium-P, high-T metamorphic event duringthe initial decompression of a Cambrian orogen along the southwesternmargin of Gondwana. Very fresh orbicular and massive cordierititebodies with up to 90% cordieritite are genetically associatedwith a cordierite monzogranite pluton and a larger body of porphyriticgranodiorite. The petrogenesis of this association has beenstudied using petrographical, mineralogical, thermobarometric,geochemical, geochronological and isotope methods. The graniticmagmas were formed by anatexis of mid-crustal metamorphic rocksformed earlier in the Pampean orogeny. The cordieritites appearat the top of feeder conduits that connected the source regionlocated at     

3d transition metal L-edge X-ray absorption studies of the dichalcogenides of Fe, Co and Ni

The X-ray absorption spectra of the transition metal L_3,2-edges of the dichalcogenides FeS₂ (pyrite), FeSe₂, FeTe₂, CoS₂, CoSe₂, CoTe₂, NiS₂, NiSe₂ and NiTe₂ have been studied. These spectra are compared with theoretical simulations make using the atomic multiplet approach assuming on octahedral site for the metal atoms. The Ni spectra can be closely simulated using this approach but the Fe and Co spectra show less good fits to the experimental data. The reasons for this and its implications for the use of L-edge spectra in the study of such minerals are discussed in terms of the covalency and the ground states of the compounds; these results indicate the mixing of the ground states increases in the order Ni<Co<Fe.     

Impact of quarrying gypsum in a semidesert karstic area (Sorbas,SE Spain)

The Messinian gypsum of Sorbas is intensively karstified, with hundreds of dolines and numerous, highly unusual exo- and endokarstic forms. Amongst these the tumuli are especially spectacular, as are the large caverns, adorned with numerous speleothems, some of which have not been described anywhere else in the World. The extraction of the gypsum has impacted practically all the elements of the environment (landscape, water, soil, subsoil, flora, fauna, etc.) and, in particular, all of the karstic forms. In addition to endangering the caves and the natural treasures that they contain, it affects the surface waters, markedly modifying the hydrographic network. Groundwaters, which now occur in the bottom of a quarry, are also affected.     

Characterization of permineralized kerogen from an Eocene fossil fern

The processes of organic maturation that occur during the permineralization of fossils and the detailed chemistry of the resulting products are incompletely understood. Primary among such processes is the geochemical alteration of biological matter to produce kerogen, such as that which comprises the cell walls of the fossils studied here: essentially unmetamorphosed, Eocene plant axes (specimens of the fossil fern Dennstaedtiopsis aerenchymata cellularly permineralized in cherts of the Clarno Formation of Oregon and the Allenby Formation of British Columbia). The composition and molecular structure of the kerogen that comprises the cell walls of such axes were analyzed using ultraviolet Raman spectroscopy (UV–Raman), solid state ¹³C nuclear magnetic resonance spectroscopy (¹³C NMR) and pyrolysis–gas chromatography–mass spectrometry (py–GC–MS).Cellularly well-preserved fern axes from both geologic units exhibit similar overall molecular structure, being composed primarily of networks of aromatic rings and polyene chains that, unlike more mature kerogens, lack large polycyclic aromatic hydrocarbon (PAH) constituents. The cell walls of the Allenby Formation specimens are, however, less altered than those of the Clarno chert, exhibiting more prevalent oxygen-containing and alkyl functional groups and comprising a greater fraction of rock mass.The study represents the first demonstration of the effectiveness (and limitations) of the combined use of UV–Raman, ¹³C NMR and py–GC–MS for the analysis of the kerogenous cell walls of chert-permineralized vascular plants.