Inverse Estimation of Temperature Profiles in Landfills Using Heat Recovery Fluids Measurements

In addition to leachate and gas emission analysis, temperature variations in municipal solid waste landfills are routinely monitored for safety and health reasons, such as the increased production of biogas or the danger of spontaneous combustion phenomena if the temperature exceeds 70–75°C. The increasing constraints on greenhouse gas emissions and the convenience of fuel and heat recovery have helped develop a global approach to landfills' operation and maintenance, generally referred to as bioreactor landfill management. The heat recovery piping we are presently designing can be a significant part of this approach. The heat gained by a fluid circulated in a closed network through the landfill is transferred to an external heat exchanger or used directly as warm water. Additionally, it can help reduce landfill temperature levels and control biogas generation. Since the pipes diameter is large enough to allow for a radial temperature gradient, this information can be used for an inverse estimation of the temperature profile in the landfill which constitutes the boundary conditions of the resulting heat transfer problem. In this paper, we describe an algorithm for regularising the resulting ill-posed free boundary estimation problem using sampled data of the heat recovery fluid on exiting the landfill

Microalgae growth in winery wastewater under dark conditions

open6noWine-making process leads to large amounts of wastewater. Winery wastewaters (WWW) are produced from different activities of wine production: washing, transferring and storage operations. Tank cleaning and filtration equipment are responsible for the release of the largest amount of wastewater, whose polluting power is mainly due to both the large volumes produced and the high organic load. Because of the latter problem, biological WWW treatments are particularly appropriate. Microalgae, often used to treat civil and different industrial wastewaters, are unicellular organisms that can be grown either in autotrophic or heterotrophic mode using various organic and inorganic carbon sources. Their importance is related to their high growth rate, use to produce different biofuels, use in human or animal nutrition, and extraction of chemicals and pharmaceuticals. Purposes of this work were to reduce WWW environmental impact and to find a cheap growth medium able to reduce the microalgae production costs. In this study, three different wastewaters were used, namely WWW from first (1W) and second (2W) washing tanks, and WWW from filtration apparatus (3W). They were 20:80 (v/v) diluted with Bold Basal medium and treated batchwise with a co-culture of Arthrospira platensis and Chlorella vulgaris. Microalgae were grown under dark conditions in 0.5-L flasks with continuous air supply for 15 days. Biomass concentration was quantified daily by measurements of cell dry weight and optical density at 625 nm and expressed in grams of microalgae per liter (g/L). Chemical Oxygen Demand (COD) and total polyphenols content (by the Folin-Ciocalteu method) of WWWs were quantified daily, in order to evaluate the degradation capability of the co-culture. At the end of cultures, the lipid content of microalgal biomass was also quantified. Biomass grown in the presence of WWW reached final concentrations three times higher than the control. In general, COD was reduced by more than 90 % after 15 days, polyphenols concentration was reduced by 40, 90 and 100 % in 1W, 2W and 3W, respectively, while lipid content of biomass grown in 1W and 3W increased from 7 to 11 and 15 %, respectively. In conclusion, the results of this study demonstrate that microalgae can grow efficiently under dark conditions in media enriched with WWW, hence reducing its environmental impact.openSpennati E.; Casazza A.A.; Perego P.; Solisio C.; Busca G.; Converti A.Spennati, E.; Casazza, A. A.; Perego, P.; Solisio, C.; Busca, G.; Converti, A

Use of the microalga Scenedesmus obliquus to remove cadmium cations from aqueous solutions

The ability of a wild strain of Scenedesmus obliquus, isolated from a heavy metal-contaminated environment, to remove Cd2+ from aqueous solutions was studied at several initial concentrations. Viable biomass removed metal to a maximum extent of 11.4 mgCd/g at 1 mgCd/l, with most Cd2+ being adsorbed onto the cell surface. A commercially available strain (ACOI 598) of the same microalga species was also exposed to the same Cd concentrations, and similar results were obtained for the maximum extent of metal removal. Heat-inactivated cells removed a maximum of 6.04 mgCd/g at 0.5 mgCd/l. The highest extent of metal removal, analyzed at various pH values, was 0.09 mgCd/g at pH 7.0. Both strains of the microalga tested have proven effective in removing a toxic heavy metal from aqueous solutions, hence supporting their choice for bioremediation strategies of industrial effluents.info:eu-repo/semantics/acceptedVersio

Physiological responses of Porphyra haitanesis to different copper and zinc concentrations

In the present study, several physiological responses of the red marine alga Porphyra haitanesis to elevated concentrations of copper (up to 50 μM) and zinc (up to 100 μM) were investigated. Our results showed that the effects of Cu2+ and Zn2+ on growth, photosynthetic pigments (chlorophylls and carotenoids), phycobiliprotein and metabolism (the fluorescence emission spectra and the activities of photosystemII) did not follow the same pattern. The relative growth rate was inhibited by different concentrations of Cu2+, and was slightly increased at lower concentrations (up to 10 μM) and inhibited at higher Zn2+concentrations. On the other hand, the phycoerythrin contents were slightly increased at relatively low concentrations (up to 1 μM Cu2+ or 20 μM Zn2+) and inhibited by high Cu2+ and Zn2+ concentrations. Moreover, photosynthesis and respiration showed an increase in the amount of oxygen exchange in response to relatively low Cu2+ (up to 1 μM) and Zn2+ concentrations (up to 10 μM), and a reduction to relatively high Cu2+ and Zn2+ concentrations. Oxygen evolution was more sensitive than oxygen uptake to Cu2+ and Zn2+. In addition, the photoreductive activities and fluorescence emission of photosystem II (PS II) were enhanced by lower concentrations of Cu2+ (up to 0.1 μM) and Zn2+ (up to 10 μM) and inhibited by higher concentrations. Furthermore, the intensity of chlorophyll a fluorescence and the active PSII reaction centers followed a similar pattern in response to elevated concentrations of Cu2+ and Zn2+. These results suggest that lower concentrations of Cu2+ and Zn2+ affected the metabolism of P. haitanesis, which was inhibited by higher concentrations of these metals.No presente estudo foram investigadas as respostas fisiológicas da alga vermelha Porphyra haitanesis às elevadas concentrações de cobre (acima de 50 μM) e de zinco (acima de 100 μM). Os resultados mostram que os efeitos de Cu2+ e Zn2+ sobre o crescimento, pigmentos fotossintéticos (clorofilas e carotenóides), ficobiliproteína e metabolismo (o espectro de emissão de fluorescência e as atividades do fotossistema) não seguem o mesmo padrão. A taxa de crescimento relativo foi inibida por diferentes concentrações de Cu2+ e, em presença de Zn2+, aumentou ligeiramente em baixas concentrações (abaixo de 10 μM) e foi inibida em altas concentrações. Por outro lado, os teores de ficoeritrina apresentaram leve aumento em concentrações relativamente baixas de Cu2+ e Zn2+ (até 1 μM Cu2+ e até 20 μM Zn2+, respectivamente) e foram inibidas por altas concentrações. Além disso, tanto a fotossíntese quanto a respiração mostraram aumento nas trocas de oxigênio em resposta às concentrações relativamente baixas de Cu2+ (até 1 μM) e de Zn2+ (até 10 μM), além da redução em concentrações relativamente altas desses metais. Adicionalmente, as atividades fotoredutoras e as emissões de fluorescência do fotossistema II (PSII) foram incrementadas em baixas concentrações de Cu2+ (até 0,1 μM) e de Zn2+ (até 10 μM) e inibidas por altas concentrações. Desta forma, a intensidade da fluorescência da clorofila-a e dos centros de reação ativa PSII seguiram um padrão semelhante em resposta às elevadas concentrações de Cu2+ e Zn2+. Esses resultados sugerem que baixas concentrações de Cu2+ e Zn2+ afetam o metabolismo de P. haitanesis, que se torna inibido por altas concentrações desses metais