Browsing by Issue Date, starting with "2025-05"
Now showing 1 - 7 of 7
Results Per Page
Sort Options
- Design optimisation of five pilot-scale two-stage vertical flow-constructed wetlands for piggery wastewater treatmentPublication . Karan, N.; Gogoi, Jayanta; Ganguly, Anasuya; Brito, António; Marques dos Santos, C.; de Oliveira Corrêa, Diego; Gouveia, Luisa; Mutnuri, SrikanthABSTRACT: With growing pig farming, sustainable piggery wastewater treatment methods are essential for environmental protection. This study evaluated five pilot-scale two-stage vertical flow-constructed wetlands (VFCWs) with varying configurations of aeration, plantation, and saturation zones. Three VFCW configurations (1VFCW, 2VFCW, and 3VFCW) were unsaturated, while 4VFCW and 5VFCW were saturated in the second stage (up to 60 and 90 cm, respectively). The 5VFCW featured a stacked configuration with no space between its two stages. Passive aeration was selectively applied in 2VFCW, 3VFCW, 4VFCW, and 5VFCW, while plants were present in most configurations except the control. Saturated 4VFCW achieved the highest removal efficiency for TN (77.03 ± 16.24%) and NO3− (46.06 ± 45.96%), while the stacked 5VFCW showed the highest removal for chemical oxygen demand (COD) (94.17 ± 4.85%) and Total ammoniacal nitrogen (TOC) (86.35 ± 6.78%). Unsaturated 1VFCW excelled in TAN removal (98.89 ± 0.33%), and the control system (C) showed the highest removal efficiency for PO43− (90.38 ± 6.52%) and TOC (87.52 ± 9.83%). Overall, 4VFCW emerged as the most balanced and effective system, supported by an optimal combination of aerobic and anaerobic conditions that facilitated sequential nitrification and denitrification, along with an extended hydraulic retention time due to saturation.
- Reappraisal of active tectonics of the Porto Alto buried fault zone (Portugal) considering new geophysical shallow studiesPublication . Carvalho, João; Cabral, João; Ghose, Ranajit; Borges, José Fernando; Dias, RubenABSTRACT: The Lower Tagus Valley area (LTV), where Lisbon is located, has been affected by several destructive, M 6+ earthquakes whose sources remain to be determined. The identification of expectable surface or near surface ruptures in the area is a challenging task that requires a multidisciplinary analysis that includes geophysical techniques, as the source faults are mainly buried despite likely to deform Upper Pleistocene to Holocene alluvial cover of the Tagus River. This paper focuses on the characterization of the Porto Alto fault zone for seismic hazard mitigation purposes. The Porto Alto fault zone was recognized in oil-industry P-wave 1980’s seismic reflection data as an important, Miocene reactivated, deep structure in the LTV. Highresolution P-wave seismic reflection data were later acquired in the early 2000’s to investigate related Holocene fault activity, leading to the identification of a shallow fault zone near the surface. However, the vertical resolution of the acquired P-wave seismic reflection data was considered insufficient to corroborate any presumably small vertical offset related to fault rupture in the ca. 50 m thick alluvium cover. Trenching for the recognition and characterization of surface faulting was previously tested in the study region but it proved to be a challenging and poorly efficient methodology due to the very shallow water table (at ~1 m) and low cohesion of the sediments. Due to these constraints, we revisited the former fault study site to acquire higher resolution S-wave seismic and ground penetrating radar (GPR) data. The new seismic profiles show interruption of the reflectors in the stacked sections. Diffracted energy, changes in amplitude/shape of the reflection hyperbolae in the shot gathers and spatially coincident low velocity anomalies, also indicate the presence of several shallow fault strands deeper than 10 m. The GPR profile, overlapping and extending the seismic profiles in 30 m reaches a maximum investigation depth of about 15 m and shows the presence of deformation at three locations, one of which matches with one of the fault strands detected in the high resolution S-wave seismic data. In this profile, sediment disruption was detected extending upwards to a depth as shallow as ca. 3.5 m, corresponding to alluvium with a poorly constrained age of ca. 2,300 yrs. Slip rate, maximum earthquake magnitude and recurrence, and other parameters are also estimated for the Porto Alto fault zone. These recently acquired seismic and GPR datasets indicate that there were at most three to five maximum earthquakes generated by the fault in the last 13,100 years, with an average recurrence of approximately 4,400 to 2,600 years respectively. However, the data show a grouping of these earthquakes in time, the first two in the period 13,100-12,300 years, separated by about 800 years, and the third or the last grouped three having occurred in the past 2,300 years with a similar average recurrence time of ca. 800 years. However, the regional historical and instrumental seismicity does not show an obvious link of any known major earthquake with the Porto Alto fault zone.
- Detailed in-depth mapping of the world largest anorthositic complex: Magnetic anomalies, 2.5-3D modelling and emplacement constraints of the Kunene Complex (KC), SW AngolaPublication . Merino-Martínez, E.; Rey-Moral, Carmen; Machadinho, Ana; Carvalho, João; Represas, Patricia; García-Lobón, J. L.; Feria, María Carmen; Martín-Banda, Raquel; López-Bahut, T.; Alves, Daniela; Ramalho, Elsa; Manuel, José; Cordeiro, DomingosABSTRACT: The Kunene Complex (KC) represents a very large Mesoproterozoic igneous body, mainly composed of anorthosites and gabbroic rocks that extends from SW Angola to NW Namibia (outcropping 18,000 km2 , NE-SW trend, and ca. 350 km long and up to 50 km wide). Little is known about its structure at depth. Here, we use recently acquired aerogeophysical data to accurately determine its hidden extent and to unravel its morphology at depth. These data have been interpreted and modelled to investigate the unexposed KC boundaries, reconstructing the upper crustal structure (between 0 and 15 km depth) overlain by the thin sedimentary cover of the Kalahari Basin. The modelling reveals that the KC was emplaced in the upper crust and extends in depth up to ca. 5 km, showing a lobular geometry and following a large NE-SW to NNE-SSW linear trend, presumably inherited from older Paleoproterozoic structures. The lateral continuation of the KC to the east (between 50 and 125 km) beneath the Kalahari Cenozoic sediments suggests an overall size three times the outcropping dimension (about 53,500 km2 ). This affirmation clearly reinforces the economic potential of this massif, related to the prospecting of raw materials and certain types of economic mineralization (Fe-Ti oxides, metallic sulphides or platinum group minerals). Up to 11 lobes have been isolated with dimensions ranging from 135.5 to 37.3 km in length and 81.9 to 20.7 km in width according to remanent bodies revealed by TMI mapping. A total volume of 65,184 km3 was calculated only for the magnetically remanent bodies of the KC. A long-lasting complex contractional regime, where large strike-slip fault systems were involved, occurred in three kinematic pulses potentially related to a change of velocity or convergence angle acting on previous Paleoproterozoic inherited sutures. The coalescent magmatic pulses can be recognized by means of magnetic anomalies, age of the bodies as well as the lineations inferred in this work: (i) Emplacement of the eastern mafic bodies and granites in a stage of significant lateral extension in a transtensional context between 1500 Ma and 1420 Ma; (ii) Migration of the mantle derived magmas westwards with deformation in a complex contractional setting with shearing structures involving western KC bodies and basement from 1415 Ma to 1340 Ma; (iii) NNW-SSE extensional structures are relocated westwards, involving mantle magmas, negative flower structures and depression that led to the formation of late Mesoproterozoic basins from 1325 Ma to 1170 Ma. Additionally, we detect several first and second order structures to place the structuring of the KC in a craton-scale context in relation to the crustal structures detected in NW Namibia. (c) 2025 China University of Geosciences (Beijing) and Peking University. Published by Elsevier B.V. on behalf of China University of Geosciences (Beijing).
- Strategic Bidding to Increase the Market Value of Variable Renewable Generators in New Electricity Market DesignsPublication . Algarvio, Hugo; Sousa, VivianABSTRACT: Electricity markets with a high share of variable renewable energy require significant balancing reserves to ensure stability by preserving the balance of supply and demand. However, they were originally conceived for dispatchable technologies, which operate with predictable and controllable generation. As a result, adapting market mechanisms to accommodate the characteristics of variable renewables is essential for enhancing grid reliability and efficiency. This work studies the strategic behavior of a wind power producer (WPP) in the Iberian electricity market (MIBEL) and the Portuguese balancing markets (BMs), where wind farms are economically responsible for deviations and do not have support schemes. In addition to exploring current market dynamics, the study proposes new market designs for the balancing markets, with separate procurement of upward and downward secondary balancing capacity, aligning with European Electricity Regulation guidelines. The difference between market designs considers that the wind farm can hourly bid in both (New 1) or only one (New 2) balancing direction. The study considers seven strategies (S1-S7) for the participation of a wind farm in the past (S1), actual (S2 and S3), New 1 (S4) and New 2 (S5-S7) market designs. The results demonstrate that new market designs can increase the wind market value by 2% compared to the optimal scenario and by 31% compared to the operational scenario. Among the tested approaches, New 2 delivers the best operational and economic outcomes. In S7, the wind farm achieves the lowest imbalance and curtailment while maintaining the same remuneration of S4. Additionally, the difference between the optimal and operational remuneration of the WPP under the New 2 design is only 22%, indicating that this design enables the WPP to achieve remuneration levels close to the optimal case.
- Strategies to Incentivize the Participation of Variable Renewable Energy Generators in Balancing MarketsPublication . Algarvio, Hugo; Sousa, VivianABSTRACT: Balancing markets (BMs) play a crucial role in ensuring the real-time equilibrium between electricity demand and supply. The current requirements for participation in BMs often overlook the characteristics and capabilities of variable renewables, limiting their effective integration. The increasing penetration of variable renewables necessitates adjustments in the design of BMs to support the transition toward carbon-neutral power systems. This study examines the levels of active market participation for a wind power producer (WPP) in the Iberian Electricity Market and the Portuguese BMs. In addition to exploring current market dynamics, the study tests one methodology proposed by the Danish Transmission System Operator to support the participation of variable renewables in BMs, the P90, and two new methods based on the full cost balancing concept. These methodologies incentivize WPPs to minimize imbalances by allowing market participation only if imbalances remain within a 10% deadband of annual hours (P90), hourly offers (D90), or both (DP90). The results indicate that participating in the secondary capacity market, particularly for downward capacity, is the most profitable strategy. This participation enhances the value of wind power by over 42%. However, in most methodologies, the WPP failed to deliver nearly 100% of its allocated capacity approximately 1% of the time. In contrast, the D90 approach limited the maximum deviation to 10%, demonstrating the highest reliability among the evaluated methods.
- Strawberry Tree Fruit Residue as Carbon Source Towards Sustainable Fuel Biodesulfurization by Gordonia alkanivorans Strain 1BPublication . Paixão, Susana M.; Silva, Tiago; Salgado, Francisco; Alves, LuísABSTRACT: Biodesulfurization (BDS) is a clean technology that uses microorganisms to efficiently remove sulfur from recalcitrant organosulfur compounds present in fuels (fossil fuels or new-generation fuels resulting from pyrolysis and hydrothermal liquefaction). One of the limitations of this technology is the low desulfurization rates. These result in the need for greater amounts of biocatalyst and lead to increased production costs. To mitigate this issue, several approaches have been pursued, such as the use of alternative carbon sources (C-sources) from agro-industrial waste streams or the co-production of high-added-value products by microorganisms. The main goal of this work is to assess the potential of strawberry tree fruit residue (STFr) as an alternative C-source for a BDS biorefinery using Gordonia alkanivorans strain 1B, a well-known desulfurizing bacterium with high biotechnological potential. Hence, the first step was to produce sugar-rich liquor from the STFr and employ it in shake-flask assays to evaluate the influence of different pretreatments (treatments with 1-4% activated charcoal for prior phenolics removal) on metabolic parameters and BDS rates. Afterwards, the liquor was used as the C-source in chemostat assays, compared to commercial sugars, to develop and optimize the use of STFr-liquor as a viable C-source towards cost-effective biocatalyst production. Moreover, the high-market-value bioproducts simultaneously produced during microbial growth were also evaluated. In this context, the best results, considering both the production of biocatalysts with BDS activity and simultaneous bioproduct production (carotenoids and gordofactin biosurfactant/bioemulsifier) were achieved when strain 1B was cultivated in a chemostat with untreated STFr-liquor (5.4 g/L fructose + glucose, 6:4 ratio) as the C-source and in a sulfur-free mineral-minimized culture medium at a dilution rate of 0.04 h-1. Cells from this steady-state culture (STFr L1) achieved the highest desulfurization with 250 mM of dibenzothiophene as a reference organosulfur compound, producing a maximum of approximate to 213 mM of 2-hydroxibyphenil (2-HBP) with a corresponding specific rate (q2-HBP) of 6.50 mu mol/g(DCW)/h (where DCW = dry cell weight). This demonstrates the potential of STFr as a sustainable alternative C-source for the production of cost-effective biocatalysts without compromising BDS ability. Additionally, cells grown in STFr L1 also presented the highest production of added-value products (338 +/- 15 mu g/g(DCW) of carotenoids and 8 U/mL of gordofactin). These results open prospects for a future G. alkanivorans strain 1B biorefinery that integrates BDS, waste valorization, and the production of added-value products, contributing to the global economic viability of a BDS process and making BDS scale-up a reality in the near future.
- Friedrich Welwitsch’s prolegomena of Angolan geologyPublication . Brandão, José Manuel Moraes Vale; Mesquita Soares, SofiaABSTRACT: Recent work at the drill core library of LNEG at Alfragide has brought to light a small collection of rocks and fossils gathered by the Austrian physician and botanist Friedrich Welwitsch during his prolific expedition to Angola (Iter Angolense, 1853-1860) on behalf of the Portuguese crown. The samples were seen and mentioned by Paul Choffat, in 1889, but have remained completely forgotten ever since. Revisiting the samples, this article, which extends the evocation of 150 years of Welwitsch's passing, recalls the scientific partnership with the French naturalist Arthur Morelet, who studied mollusk faunas, and reviews the geological notes taken during the years of herborisations. Considering those notes and samples, it can be said that these pioneering elements in the study of the geology of Angola are, in essence, consistent with the recent knowledge and geological mapping of that territory.