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Abstract Scenedesmus obliquus biomass was used as a feedstock for comparing the biological production of hydrogen by two different types of anaerobic cultures: a heat-treated mixed culture from a wastewater treatment plant and Clostridium butyricum DSM 10702. The influence of the incubation temperature and the carbon source composition were evaluated in order to select the best production profile according to the characteristics of the microalgal biomass. C. butyricum showed a clear preference for monomeric sugars and starch, the latter being the major storage compound in microalgae. The highest H 2 production reached by this strain from starch was 468 mL/g, whereas the mixed culture incubated at 37 °C (LE37) produced 241 mL/g. When the mixed culture was incubated at 58 °C (LE58), a significant increase in the H 2 production occurred when xylose and xylan were used as carbon and energy source. The highest H 2 yield reached by the LE37 culture or in co-culture with C. butyricum was 1.52 and 2.01 mol/mol of glucose equivalents, respectively. However, the ratio H 2 /CO 2 (v/v) of the biogas produced in both cases was always lower than the one produced by the pure strain. In kinetic assays, C. butyricum attained 153.9 mL H 2 /L h from S. obliquus biomass within the first 24 h of incubation, with a H 2 yield of 2.74 mol/mol of glucose equivalents. H 2 production was accompanied mainly by acetate and butyrate as co-products. In summary, C. butyricum demonstrated a clear supremacy for third generation bioH 2 production from S. obliquus biomass.

Abstract This paper presents a new methodology for impact assessment—SIAM (Spatial Impact Assessment Methodology)—which is based on the assumption that the importance of environmental impacts is dependent, among other things, on the spatial distribution of the effects and of the affected environment. The information generated by the use of Geographical Information Systems (GIS) in impact identification and prediction stages of Environmental Impact Assessment (EIA) is used in the assessment of impact significance by the computation of a set of impact indices. For each environmental component (e.g., air pollution, water resources, biological resources), impact indices are calculated based on the spatial distribution of impacts. A case study of impact evaluation of a proposed highway in Central Portugal illustrates the application of the methodology and shows its capabilities to be adapted to the particular characteristics of a given EIA problem.

A methodology for the sizing of domestic hot water heating and storage systems is defined, by assuming an extreme operating condition cycle composed of only two parts, a water consumption period and a system repositioning period. In both parts to respond to the extreme hot water demanding conditions, the heating is always on. The subsequent exergy analysis of this domestic hot water production system compares the irreversibility and the exergy efficiency of the water storage and the tankless situation. To carry out such analysis, some basic assumptions were made: a constant temperature heat source, a short duration operating cycle and a constant thermal energy supply. Under these circumstances it is shown that the hot water storage system leads to lower exergy losses while the tankless system is more exergy efficient, but requiring a higher instantaneous thermal power input. The use of the joule effect electricity, as the system heat source, be it a water storage one or a tankless one, maximizes the system irreversibility losses and minimizes the system exergy efficiency. The tankless system, with the joule effect electricity heat source is the worst situation.

Water is a scarce resource in the Mediterranean region where adverse climatic conditions promoting water shortages tend to increase with climate change. Under water scarcity conditions and high atmosphere evaporative demand, the risks of decreased water quality, and land salinization are major threats to the sustainability of irrigated agriculture in this region. The assessment of the quality of irrigation water is increasingly important to ensure the maintenance of long-term salt balance at a crop, farm, and regional scale. This study is focused on the spatial and temporal variability of water quality for irrigation in the Alqueva reservoir (Southern Portugal). The assessment was performed every 2 months during a distinctive drought year (2017) and included inorganic ions (Na+, Ca2+, Mg2+, K+, NH4+, Cl-, F-, SO42-, NO3-, and NO2-), pH, and electric conductivity (ECW) of water. Sodium adsorption ratio (SAR) was calculated, and potential soil permeability problems were estimated. The assessment showed significantly higher values of the physicochemical parameters in the most upstream sites, located near tributaries inflows, and an upward trend in ion concentrations throughout the year, with significantly higher concentrations of Na+, Mg2+, Cl-, and SO42, registered through May to November, reflecting the severe drought felt in the summer, autumn, and winter. The evaluation of water quality for irrigation indicated a slight to moderate risk of reduced infiltration rates, which should be considered whenever sprinkler irrigation is used, mainly in fine-textured soils, which are prevalent in the irrigated area. The multivariate statistical approach, using principal component analysis and factor analysis, identified two principal components related to salinity and nutrient concentrations. The cluster analysis revealed three groups of similarity between samples pointing to a more time- than space-controlled pattern. Overall, the temporal dynamics of the water physicochemical parameters could indicate that an abnormal annual distribution of precipitation and temperature may distort seasonal differences. To prevent water and soil degradation, a more frequent assessment of the water quality should be considered, allowing for the selection of appropriate soil and water management measures in irrigated areas.

The intensive agricultural practices are increasing the demand for chemical fertilizers, being currently produced from a non-environmental friendly way. Besides the environmental impacts, the nutrient uptake efficiency by the crops is very low, representing huge losses into the fields. Therefore, it is crucial to study alternatives for the current chemical fertilizers, which simultaneous improve nutrient efficiency and minimize environmental impacts. A sustainable solution is to recover nutrients from wastewater streams with microalgal cultures and the biomass conversion into bio-char for soil amendment. Wastewaters are loaded with nitrogen and phosphorus and can be used as culture medium for microalgae. Thus, nutrients can be recycled, reducing the requirement of chemical fertilizers. This paper aims to review nutrient recovery from wastewater using microalgae and the biomass conversion into bio-char. This process promotes nutrient recycling and the bio-char (when added to soil) improves the nutrient uptake efficiency by crops.

The partitioning behaviours of CO2 with three kinds of common impurities, i.e., N2, CH4 and H2S, in the formation brine are investigated by numerical simulations. The results indicate that the effects of N2, CH4 or the mixture of N2 and CH4 at the same concentrations are generally similar. The leading gas front is usually made up of less soluble impurities, such as N2, CH4 or the mixture of N2 and CH4, while more soluble species such as H2S has dissolved preferentially in the formation brine. The separations between different gas species increase as the gas displacement front migrates forwards and contacts more of the aqueous phase. Compared with the partitioning results of the 98% CO2 and 2% H2S mixture, the results indicate that the inclusion of less soluble N2 and/or CH4 results in an earlier gas breakthrough and a longer delay between the breakthrough times of CO2 and H2S. The early breakthrough of the gas phase is mainly because that the addition of N2 and/or CH4 lowers the viscosity of the gas phase, resulting in a higher gas velocity than that of the CO2–H2S mixture. Meanwhile, the mobility ratio is higher and the gas mixture contacts the formation brine over a larger area, giving rise to more efficient stripping of the more soluble gas species like H2S and thus larger separations. In the meantime, with the same total concentrations of impurities (12%), when 2% H2S is contained in the CO2 streams, gas phase flows slower and thus the breakthrough time is later. Furthermore, the effects on the partitioning phenomenon are weaker with decreasing concentrations of N2 and/or CH4 (from 10% to 2%) with fixed concentrations of other impurity like H2S (2%). The migration distances and the separations between different gas species change linearly with time on the whole, as confirmed by a simulation in a longer model.

Photocatalytic oxidation is promising technology for removal of recalcitrant pollutants from water. Solar energy can be an interesting radiation source since the operating costs can be lower. However, the use of powder photocatalyst is a major drawback of the technology since suitable separation technologies are required and catalysts recovery is difficult. This work aims to test the suitability of using polymeric supports to immobilize TiO 2 in the reactor and apply it for parabens removal from water by solar photocatalytic oxidation. Polyurethanes (PU) and polydimethylsiloxane (PDMS) membranes were prepared and modified with TiO 2. While PU materials are only able to adsorb (35% in 1 h) parabens whichever the modification applied, modified PDMS was able to promote parabens photocatalytic oxidation removing 20% in 1 h under solar energy. Plasma/UV modification was able to active PDMS membranes (16% of methyl paraben (MP) removal) and further entrapment of TiO 2 in the polymeric matrix did not improve the process (18% of MP removal). Thus, only the superficial TiO 2 was active. Results show that PDMS is suitable material to support TiO 2 aiming photocatalytic wastewater treatment process using the Sun as a clean and renewable energy source.