Browsing by Author "Silva, Elisabete"
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- Characterization of MSW rejected fractions to fulfill RDF requirements and utilizationPublication . Brás, Isabel; Silva, Elisabete; Lobo, Germana; Faria, Miguel; Lemos, Luís Teixeira deIn order to fulfil European and Portuguese legal requirements, adequate alternatives to traditional municipal waste landfilling must be found namely concerning organic wastes and others susceptible of valorisation. According to the Portuguese Standard NP 4486:2008, refuse derived fuels (RDF) classification is based on three main parameters: lower heating value (considered as an economic parameter), chlorine content (considered as a technical parameter) and mercury content (considered as an environmental parameter). The purpose of this study was to characterize the rejected streams resulting from the mechanical treatment of unsorted municipal solid waste, from the plastic municipal selective collection and from the composting process, in order to evaluate their potential as RDF. To accomplish this purpose six sampling campaigns were performed. Chemical characterization comprised the proximate analysis – moisture content, volatile matter, ashes and fixed carbon, as well as trace elements. Physical characterization was also done. To evaluate their potential as RDF, the following parameters established in the Portuguese standard were also evaluated: heating value and chlorine content. As expected, results show that the refused stream from mechanical treatment is rather different from the selective collection rejected stream and from the rejected from the compost screening in terms of moisture, energetic matter and ashes, as well as heating value and chlorine. Preliminary data allows us to conclude that studied materials have a very interesting potential to be used as RDF. In fact, the rejected from selective collection and the one from composting have a heating value not very different from coal. Therefore, an important key factor may be the blending of these materials with others of higher heating values, after pre-processing, in order to get fuel pellets with good consistency, storage and handling characteristics and, therefore, combustion behavior.
- Co-Composting of Poultry Manure with Different Organic AmendmentsPublication . Silva, Elisabete; Brás, IsabelTo study the influence of different organic amendments on the quality of poultry manure compost, three pilot composting trials were carried out with different mixes: poultrymanure/carcasse meal/ashes/grape pomace (Pile 1), poultry manure/cellulosic sludge (Pile 2) and poultry manure (Pile 3). For all piles, wood chips were applied as bulking agent. The process was monitored, over time, by evaluating standard physical and chemical parameters, such as, pH, electric conductivity, moisture, organic matter and ash content, total carbon and total nitrogen content, carbon/nitrogen ratio (C/N) and content in mineral elements. Piles 1 and 2 reached a thermophilic phase, however having different trends. Pile 1 reached this phase earlier than Pile 2. For both, the pH showed a slight alkaline character and the electric conductivity was lower than 2 mS/cm. Also, the initial C/N value was 22 and reached values lower than 15 at the end of composting process. The total N content of the Pile 1 increased slightly during composting, in contrast with the others piles. At the end of composting process, the phosphorus content ranged between 54 and 236 mg/kg dry matter, for Pile 2 and 3, respectively. Generally, the Piles 1 and 3 exhibited similar heavy metals content. This study showed that organic amendments can be used as carbon source, given that the final composts presented parameters within the range of those recommended in the 2nd Draft of EU regulation proposal (DG Env.A.2 2001) for compost quality.
- Comparison of the bacterial composition of two commercial composts with different physicochemical, stability and maturity propertiesPublication . Silva, Elisabete; Lopes, Ana; Cunha-Queda, Ana; Nunes, OlgaPreviously, two municipal solid waste commercial composts (MSW1 and MSW2) were characterized. Although sharing the same type of raw material, most of their physicochemical, stability and maturity properties differed. The present study aimed to characterize them at a microbiological level, and to infer on possible relationships between the composts properties and the structure of their bacterial communities. Both the 16S rRNA gene-based PCR-DGGE profiling and 454-pyrosequencing technology showed that the structure of the bacterial communities of these composts was distinct. The bacterial community of MSW1 was more diverse than that of MSW2. Multivariate analyses revealed that the high electrical conductivity, Cu content as well as the low phytotoxity of compost MSW1, when compared to MSW2, contributed most to shape its bacterial community structure. Indeed, high abundance of halophilic (Halomonadaceae and Brevibacteriaceae) and metal resistant organisms (Brevibacteriaceae and Bacillaceae) were found in MSW1. In addition, Pseudonocardiaceae, Streptomycetaceae, Bacillaceae, and Brevibacteriaceae may have contributed to the high humic-like acids content and low phytotoxicity of MSW1. In contrast, the high organic matter content and the high density of the cultivable fungi population were the parameters most correlated with the structure of the bacterial community of compost MSW2, dominated by Corynebacteriaceae and mainly Aerococcaceae, taxonomic groups not commonly found in composts.
- Influence of the composition of the initial mixtures on the chemical composition, physicochemical properties and humic-like substances content of compostsPublication . Silva, Elisabete; Lemos, Luís Teixeira de; Nunes, Olga C.; Cuhna-Queda, Ana CristinaThe influence of the proportion of C- and N-rich raw materials (initial C/N ratio) and bulking agent on the chemical functional groups composition, humic-like substances (HS-like) content and physicochemical properties of composts was assessed. To achieve these goals, seven initial mixtures (BA1–6 and C1) of dog food (N-rich raw material) were composted with wheat flour (C-rich raw material). Composts were analyzed in terms of chemical functional groups, physicochemical, maturity and stability parameters. The C-rich raw material favored the formation of oxidized organic matter (OM) during the composting process, as suggested by the variation of the ratios of the peaks intensity of FT-IR spectra, corresponding to a decrease of the polysaccharides and an increase of aromatic and carboxyl-containing compounds. However, although with high proportion of C-rich raw material, mixtures with low initial C/N seems to have favored the accumulation of partially oxidized OM, which may have contributed to high electrical conductivity values in the final composts. Therefore, although favoring the partial transformation of OM into stabilized HS-like, initial mixtures with high proportion of C-rich raw material but with low initial C/ N led to unstable composts. On the other hand, as long as a high percentage of bulking agent was used to promote the structure of biomass and consequently improve of the aeration conditions, low initial C/N was not a limiting factor of OM oxidation into extractable stabilized humic-like acids.
- Irrigation with Treated Wastewater: Potential Impacts on Microbial Function and Diversity in Agricultural SoilsPublication . Lopes, Ana Rita; Becerra-Castro, Cristina; Vaz-Moreira, Ivone; Silva, Elisabete; Nunes, Olga; Manaia, CéliaThe reuse of treated wastewater could be a promising measure to attenuate the water scarcity burden. In agriculture, irrigation with wastewater may contribute to improve production yields, reduce the ecological footprint and promote socioeconomic benefits. However, it cannot be considered exempt of adverse consequences in environmental and human health. Apart from the introduction of some biological and chemical hazardous agents, the disturbance of the indigenous soil microbial communities and, thus, of vital soil functions impacting soil fertility may occur. The consequences of these disturbances are still poorly understood. This chapter summarises the physicochemical and microbiological alterations in soil resultant from irrigation with treated wastewater that are described in scientific literature. These alterations, which involve a high complexity of variables (soil, wastewater, climate, vegetal cover), may have impacts on soil quality and productivity. In addition, possible health risks may arise, in particular through the direct or indirect contamination of the food chain with micropollutants, pathogens or antibiotic resistance determinants. The current state of the art suggests that irrigation with treated wastewater may have a multitude of long-term implications on soil productivity and public health. Although further research is needed, it seems evident that the analysis of risks associated with irrigation with treated wastewater must take into account not only the quality of water, but other aspects as diverse as soil microbiota, soil type or the cultivated plant species.
- A Life Cycle Assessment Study on a New Countertop MaterialPublication . Silva, Luiza; Silva, Elisabete; Brás, Isabel; Domingos, Idalina; Wessel, Dulcineia; Ferreira, JoséThe Life Cycle Assessment (LCA) is one of the most important analytical tools available to provide the scientific basis of engineering solutions for sustainability. The focus of this study was a LCA (cradle to gate) of a product intended to be used in countertops. The functional unit chosen was 1 m2 of finished panel (countertop) and the boundary system involved the study of raw materials and product packaging and the panel’s production process. The chosen method for impact assessment was EPD (2018) available in SimaPro PhD software and Acidification, Eutrophication, Global Warming, Photochemical Oxidation, Abiotic Depletion (elements), Abiotic Depletion (fossil fuels), Water Scarcity and Ozone Layer Depletion were the impact categories considered. Results showed that the panel’s manufacturing is the process that presented the highest influence in all categories analyzed ranging from 88% on Abiotic Depletion to approximately 101% on Water Scarcity. Polyvinylchloride (PVC) is the greatest contributors to all impact categories except to Photochemical Oxidation that is the Polyester.
- Potential valorization as fertilizers of Humic Substances extracted from landfill leachatePublication . Silva, Elisabete; Brás, IsabelIn this study, four leachates samples from 3 different landfills localized in the north of Portugal were characterized and fractionated, to understand the decomposition degree and to evaluate their potential as an agent for fertilization. Humic substances (HS) were extracted, quantified, chemical characterized and further fractionated in humic acid (HA) and fulvic acid (FA). Keeping in mind the purpose to use these fractions as fertilizers, the phytotoxicity of HS, HA and FA solutions was evaluated on cress seed germination. The HS concentration was similar for all the leachates evaluated and was higher than 780 mg/L of total organic carbon. All the leachates analysed registered higher FA concentration than HA. The chemical characterization indicated that HA had a relatively higher aromatic character than the FA obtained from same sources. These results suggest that the HS from landfill leachates were in an early stage of humification, once the degree of humification increase as the landfilling age increase. Overall, the HS extracts showed absence of phytotoxicity, with germination index greater than 80% for samples treated to achieve low electric conductivity values. This suggests that the HS from the leachate may be used to produce liquid organic fertilizers.
- The role of compost properties in sorption of heavy metalsPublication . Martinho, João; Campos, Bruno; Brás, Isabel; Silva, ElisabeteThe feasibility of various composts to operate as sorbents for heavy metals (Cu and Zn) removal from wastewater has been evaluated. Three commercial composts obtained from municipal solid wastes (MWS), sludge sewage (SS) and poultry manure (PM) were selected as potential sorbents. Kinetic and equilibrium tests were conducted in order to assess the equilibrium conditions to remove metals from aqueous samples. For all composts, the maximum time necessary to reach the equilibrium was 240 min. The Freundlich and Langmuir isotherm models were found to fit the sorption data. The SS compost proved to be the one with highest removal capability for both assessed metals, while MWS compost showed to be the less suitable for this purpose. These results can be explained in terms of the compost surface properties, namely, with the cation exchange capacity.
- Wastewater reuse in irrigation: A microbiological perspective on implications in soil fertility and human and environmental healthPublication . Becerra-Castro, Cristina; Lopes, Ana Rita; Vaz-Moreira, Ivone; Silva, Elisabete; Manaia, Célia; Nunes, OlgaThe reuse of treated wastewater, in particular for irrigation, is an increasingly common practice, encouraged by governments and of fi cial entities worldwide. Irrigation with wastewater may have implications at two different levels:alterthephysicochemicalandmicrobiologicalpropertiesofthesoiland/orintroduceandcontributetothe accumulation of chemical and biological contaminants in soil. The fi rst may affect soil productivity and fertility; the second may pose serious risks to the human and environmental health. The sustainable wastewater reuse in agriculture should prevent both typesofeffects,requiring a holisticand integratedrisk assessment. Inthis article wecriticallyreviewpossible effects of irrigation with treatedwastewater, with special emphasison soil microbi- ota. The maintenance of a rich and diversi fi ed autochthonous soil microbiota and the use of treated wastewater with minimal levels of potential soil contaminants are proposed as sine qua non conditions to achieve a sustain- able wastewater reuse for irrigation.