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Lapa, N., R. Barbosa, S. Camacho, R. C. C. Monteiro, M. H. V. Fernandes, and J. S. Oliveira. "Leaching behaviour of a glass produced from a MSWI bottom ash." Materials Science Forum. 514-516 (2006): 1736-1741. AbstractWebsite

This paper is mainly focused on the characterisation of a glass material (GM) obtained from the thermal treatment of a bottom ash (BA) produced at the Municipal Solid Waste (MSW) incineration plant of Valorsul. By melting the BA at 1400ºC during 2 hours, and without using any chemical additives, a homogeneous black-coloured glass was obtained. The thermal and mechanical properties of this glass were characterised. The thermal expansion coefficient, measured by dilatometry, was 9-10 x 10-6 per ºC and the modulus of rupture, determined by four-point bending test, was 75±6 MPa, which are similar values to those exhibited by commercial soda-lime-silica glasses used in structural applications. The chemical and the ecotoxicological leaching behaviour of the GM were also analysed. The GM was submitted to a leaching procedure composed of 15 sequential extraction cycles. A liquid/solid (L/S) ratio of 2 l/kg was applied in each cycle. The leachates were filtered through a membrane of PTFE (porosity: 0.45 8m). The filtered leachates were characterised for different chemical parameters and for an ecotoxicological indicator (bacterium Vibrio fischeri). The GM was also submitted to a microwave acidic digestion for the assessment of the total metal content. The crude BA was also submitted to the same experimental procedures. The GM showed levels of chemical emission and ecotoxicity for V. fischeri much lower than those determined for the crude BA. Similar characterisation studies will be pursued with the glass-ceramics produced by adequate thermal treatment of the glass, in order to investigate the effect of the crystallization on the final properties.

Lopes, M. H., P. Abelha, N. Lapa, J. S. Oliveira, I. Cabrita, and I. Gulyurtlu. "The behaviour of ashes and heavy metals during the co-combustion of sewage sludges in a fluidised bed." Waste Management. 23.9 (2003): 859-870. AbstractWebsite

Co-combustion tests of dry sewage sludges with coal were performed in a pilot bubbling FBC aiming at the characterization of ashes and determining the behaviour of heavy metals in the process. The tests showed compliance with the regulatory levels as far as heavy metal emissions were concerned. The bottom ashes, which accounted for about 70% of the total ash production, were obtained in a granular form, with diameters ranging from 0.5 to 4 mm. The heavy metals were distributed in ashes obtained from different locations of the installation and their concentrations were found to vary depending on the location of capture. The increase in heavy metals content in bottom ashes was not found to lead to higher leachability and ecotoxicity compared to sewage sludges, suggesting that there could be opportunities for their further use. Mercury suffered vaporisation inside the reactor, thus leaving bottom ashes free of contamination by it. However, there was observed a strong retention of mercury in cyclone ashes due to the presence of unburned carbon which probably acted as an adsorbent. The effluent mercury was also found to be mostly associated with the particulate fraction, being less than 20% emitted in gaseous forms. The results suggested that the combustion of the sewage sludge could successfully be carried out and the amount of unburned carbon leaving the combustor but captured in cyclone was large enough to ensure substantial retention of mercury at low temperatures, hence could contribute to an improvement of the mercury release which still remains an issue of great concern to resolve during combustion of waste materials.

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Mahiout, A., R. Damann, J. Pera, A. Luonsi, M. Kolari, J. Siivinen, J. F. Santos Oliveira, N. Lapa, G. Pourcelly, and F. Aslan. "Industrial liquid effluents in the pulp and paper industry." Industrial Liquid Effluents - A Guide Book on the Treatment of Effluents from the Mining/Metallurgy, Paper, Plating and Textile Industries. Eds. M. Cox, P. Négré, and L. Yurramendi. Donostia - San Sebastián: INASMET-Tecnalia and European Commission, 2006. 33-73.
Mendes, B. S., M. J. Nascimento, M. I. Pereira, G. Bailey, N. Lapa, J. Morais, and J. F. Santos Oliveira. "Efficiency of removal in stabilization ponds. I - Influence of climate." Water Science and Technology. 31.12 (1995): 219-229. AbstractWebsite

Owing to the existing or predictable water deficiencies in the South of Portugal, it is necessary to carry out the appropriate management of water resources, by reducing and/or minimizing the negative impacts of untreated/treated domestic effluents in the aquatic environment. As Portugal has a great diversity of ecoclimatic areas, five different stabilization pond systems were chosen to carry out a control study during one year (from March 1991 to March 1992). According to Pina Manique & Albuquerque the ecological classification of these stations is different, varying from Ibero-mediterranean (continental) up to mediterranean (maritime). The physical and chemical parameters studied were: temperature, pH, dissolved oxygen, conductivity, BOD, COD, nitrates, nitrites, ammonia and total nitrogen, total suspended and volatile solids, total phosphorus and orthophosphates. The microbiological parameters studied were: total and faecal coliforms, faecal Streptococci, Clostridium perfringens and Pseudomonas aeruginosa. The correlations between climatic parameters and the efficiency of the removal of organic matter were analysed.

Mendes, B., P. Urbano, C. Alves, J. Morais, N. Lapa, and J. F. Oliveira. "Fungi as environmental microbiological indicators." Water Science and Technology. 38.12 (1998): 155-162. AbstractWebsite

An evaluation of the mycological quality of the sand beaches of the Lisboa and Vale do Tejo coastal area in Portugal was undertaken in May-October 1994. The keratinolytic fungi, yeasts, potential pathogenic and allergic and/or environmental saprophytic fungi were analysed. The results for the yeast Candida were evaluated according to the “Proposed Guidelines for the Microbiological Quality of Sand” (Mendes et al., 1993). The data showed good/satisfactory quality of the sand beaches for the genus Candida. The results indicate that the allergic and/or environmental saprophytic fungi were the most common in sand beaches. The fungi Scopulariopsis and the yeast Candida could be used as specific indicator organisms of sand beaches quality. A new quality objective is introduced that will contribute to improve the sand beaches quality.

Mendes, B. S., M. J. Nascimento, M. I. Pereira, G. Bailey, N. Lapa, J. Morais, and J. F. Santos Oliveira. "Ecoclimatic influence on waste stabilization ponds (WSP) efficiencies: the case study of the Sesimbra system." Water Science and Technology. 30.8 (1994): 269-279. AbstractWebsite

Portugal has a great diversity of ecoclimatic areas and Sesimbra was chosen to carry out a study on WSP efficiencies over five years (1989 to 1993). According to Pina Manique & Albuquerque (1954), the climate is classified as Atlantic Mediterranean (AM). Some environmental and climatic parameters have been studied in order to define the area. The treatment system at Sesimbra has three ponds: anaerobic, facultative and maturation. The physical and chemical parameters studied in the WSP system were: Temperature, pH, Dissolved Oxygen, Conductivity, BOD5, COD, nitrates, nitrites, ammonia and total nitrogen, total and volatile suspended solids, total phosphorus and orthophosphates. Algal populations and the following microbiological parameters were studied: total and fecal coliforms, fecal Streptococci, Clostridium perfringens, Pseudomonas aeruginosa and some Enterobacteriaceae. The K and K20 kinetic parameters were studied and derived for the three ponds utilizing the seasonal regional characteristics from the surrounding area. These values were then correlated with temperature and the subsequent removal efficiencies for each pond deduced. The data obtained indicate a necessity to determine the seasonal fluctuations of the K and K20 kinetic parameters for the WSP systems.

Mendes, B. S., M. J. Nascimento, M. I. Pereira, G. Bailey, N. Lapa, J. Morais, and J. F. Santos Oliveira. "Efficiency of removal in stabilization ponds. II - Statistical analysis of K values." Water Science and Technology. 31.12 (1995): 231-238. AbstractWebsite

The analytical values obtained from five WSP systems located in different ecoclimatic zones in the centre and South of Portugal, were subjected to a statistical analysis of K and K20 values (as used in the van Hoff-Arrhenius equation) utilizing an analysis of variance and a vectorial analysis of principal components. Significant differences between K and K20 values in facultative, maturation ponds and in the whole system were verified. The projection of the first principal components of eigenvectors made possible the classification of the stations, showing the existence of similarities and discrepancies in their removal BOD kinetics behaviour. The K20 value must be estimated and taken into account for the design of waste stabilization ponds.

Morais, J., R. Barbosa, N. Lapa, B. Mendes, and I. Gulyurtlu. "Environmental and socio-economic assessment of co-combustion of coal, biomass and non-hazardous wastes in a power plant." Resources, Conservation & Recycling. 55 (2011): 1109-1118. AbstractWebsite

Under the framework of the European project named COPOWER, the possibility to partially substitute coal used in a 243 MWth Power Plant by biomass and non-hazardous wastes for the production of electricity and steam was assessed. Three combustion scenarios were studied, based on the combustion tests performed in a Power Plant located in Duisburg (Germany): Scenario 0 (Sc0) – combustion of coal; Scenario 1 (Sc1) – combustion of coal + sewage sludge (SS) + meat and bone meal (MBM); Scenario 2 (Sc2) – coal + SS + wood pellets (WP). An environmental and socio-economic assessment of these three scenarios was performed. In the environmental point of view, Sc0 was the worst scenario, mainly due to the emission of greenhouse gases (GHG). Sc1 was the best scenario, mainly due to the reduction of GHG emission, eutrophication chemical species and ozone depletion gases. In the socio-economic point of view, Sc0 was the worst scenario, mainly due to the absence of GHG abatement, and Sc1 was the best scenario due to the best cost of electricity production and negative cost of avoided emissions.

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Paradela, F., F. Pinto, I. Gulyurtlu, I. Cabrita, and N. Lapa. "Study of the co-pyrolysis of biomass and plastic wastes." Clean Technologies and Environmental Policy. 11.1 (2009): 115-122. AbstractWebsite

This work aimed to study the recovery of two types of waste by the process of pyrolysis. The obtained results show that the adding of a plastic mix improves the overall efficiency of the slow pyrolysis of pine. Therefore, it was possible to achieve higher liquid yields and less solid product than in the classic slow pyrolysis carbonization of biomass. The obtained liquids showed heating values similar to that of heating fuel oil. The gas products had energetic contents superior to that of producer gas, and the obtained solid fractions showed heating values higher than some coals. There were also identified some typical products of fast biomass pyrolysis used as raw material in several industries. The effects of experimental conditions in product yield and composition were also studied. The parameters that showed higher influence were (with its increase): reaction time on gas product composition (increase of the alkane content) and on liquid composition (increase in aromatics content); reaction temperature on product yield (decrease of liquid yield with increase of solids and gases) and on gas product composition (increase in alkane content); initial pressure on liquid composition (increase in the aromatics content) and mainly the pine content of the initial mixture on products yield (increase of gas and solid yield with a decrease in liquids) and on the gas product composition (favouring CO and CO2 formation).

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Santos, Susana, Nuno Lapa, Andreia Alves, João Morais, and Benilde Mendes. "Analytical methods and validation for determining trace elements in red wines." Journal of Environmental Science and Health, Part B: Pesticides, Food Contaminants, and Agricultural Wastes. 48.5 (2013): 364-375. AbstractWebsite

The objective of this work is to quantify As, Hg, Cd, Ni and Pb in Portuguese red wines. First, the methods for the quantification of trace elements in red wines were validated. Several pre-treatments were compared, namely a pre-digestion process with HNO3, a pre-oxidation step with H2O2, and a spiking step of wine samples with a known concentration of the trace elements analyzed. Except for As, it was determined that the quantification of the trace elements does not require a pre-digestion process with HNO3. For all of the trace elements analyzed, a pre-oxidation step with H2O2 may enable an accurate quantification. The techniques chosen for the quantification of trace elements were hydride generation atomic absorption spectrometry (HGAAS) for As and Hg, electrothermal atomic absorption spectrometry (ETAAS) for Cd, and flame atomic absorption spectrometry (FAAS) for Ni and Pb. In the second stage of this work, 25 Portuguese red wines spanning all of the red wine-producing regions were analyzed for all of the five trace elements referred to above. Only Cd and Pb have shown concentrations above the limit values defined by the “Organization Internationale de la Vigne et du Vin.” The Target Hazard Quotient (THQ) equation was used to determine in which wine-producing regions that wine consumption can be a problem for public health in terms of the concentrations of the five trace elements analyzed. THQ values have indicated that for the universe of the 25 red wines analyzed no region produces wines that can pose problems for public health, when the Portuguese red wine standard consumption is considered.

Santos, Susana, Débora Azeitona, Nuno Lapa, João Morais, Helena Lopes, and Benilde Mendes Study on the effect of thermal pre-treatments in the thermophilic anaerobic digestion of a potato peel waste. Proceedings of the International Anaerobic Digestion Symposium within the BioGasWorld 2013. Berlin, Germany: German Society for Sustainable Biogas and Bioenergy Utilisation, 2013. Abstractbiogas_world_2013_santos_et_al_2013.pdf

This work aimed to study the effect of different pre-treatments applied to a potato peel residue, in a thermophilic Anaerobic Digestion (AD) process. All samples were subjected to a mechanical pre-treatment through milling to a particle size below 2 mm. The thermal pre-treatments applied consisted of autoclaving the residue at a gauge pressure of 1.2 bar, under a temperature of 122°C, and for 20, 35 and 55 minutes: assays E122.20, E122.35 and E122.55, respectively. The control assay was performed on a ground residue, which was not submitted to any thermal pre-treatment. All pre-treated residues were subjected to an AD process in a CSTR reactor at 49±1°C. The experimental data showed that the highest methane percentages were very similar (about 92% v/v) for all samples submitted to the thermal pre-treatments. For the control assay, the highest percentage of methane was 87.9% (v/v). The highest biogas yields were recorded in the trial E122.35 (646±50 cm3.g-1 CODremoved), against only 250±20 cm3.g-1 CODremoved for the control assay. The highest biogas yields for VSremoved were attained in the assays E122.55 and E122.35, with values of 646±48 cm3.g-1 VSremoved and 634±59 cm3.g-1 VSremoved, respectively. Globally, the yields registered for the assay E122.35 were similar to those determined in the assay E122.55. Due to the lower energy consumption during the pre-treatment performed in the assay E122.35, this was considered to be the most suitable pre-treatment for this type of residue.

Santos Oliveira, J. F., B. Mendes, and N. Lapa Resíduos: Gestão, Tratamento e sua Problemática em Portugal. Lisboa: Lidel, 2009.Website
Santos Oliveira, J. F., N. Lapa, and J. Morais Eutrofização: a flor da água. Lisboa: IPQ/EPAL, 1999.Website
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Teixeira, Paula, Helena Lopes, Ibrahim Gulyurtlu, and Nuno Lapa. "Uncertainty estimation to evaluate mass balances on a combustion system." Accreditation and Quality Assurance. 17.2 (2012): 159-166. AbstractWebsite

Mass balances of ash and potassium for a fluidized bed combustor were performed incorporating measurement uncertainties. The total output mass of ash or a chemical element should be equal to the mass in the input fuel; however, this is not often achieved. A realistic estimation of recovery uncertainty can support the reliability of a mass balance. Estimation of uncertainty helps to establish a reliable evaluation of the recovery ratio of ash mass and elemental mass. This may clarify whether any apparent lack in closing the mass balance can be attributed to uncertainties. The evaluation of measurement uncertainty for different matrices, namely coal, biomass, sand and ashes from different streams was based on internal quality control data and external quality control data, namely analysis of samples from proficiency tests or use of a certified reference material. The evaluation of intermediate precision and trueness allowed the estimation of measurement uncertainty. Due to the different physic and chemical characteristics of the studied matrices, the uncertainty of precision was evaluated using R-charts of data obtained from the analysis of duplicates for the majority of samples. This allowed evaluating sample heterogeneity effects. The instrumental acceptance criterion was also considered and included in the combined uncertainty. The trueness was evaluated using data from several proficiency tests and from analysis of a certified reference material or sample spiking. Statistically significant bias was included.

Teixeira, P., H. Lopes, I. Gulyurtlu, and N. Lapa. "Use of chemical fractionation to understand partitioning of biomass ash constituents during co-firing in fluidized bed combustion." Fuel. 101 (2012): 215-227. AbstractWebsite

Three species of biomass origin (straw pellets, olive cake and wood pellets) and two coals from different countries (Coal Polish and Coal Colombian) have been studied to understand the fate of their ash forming matter during the combustion process and to investigate the influence of co-firing biomass with coal. Three different approaches to investigate the ash behaviour were employed: (1) chemical fractionation analysis to evaluate the association/reactivity of ash forming elements in the fuels as a prediction tool, (2) establishment of elements partitioning in ash streams produced in the combustion and co-combustion trials, and (3) evaluation of enrichment factors of elements in the ash streams. The chemical fractionation analysis was applied to all fuels used to evaluate how the association/reactivity of elements making up ash may influence their behaviour during combustion. Combustion tests were carried out on a pilot scale fluidized bed combustor (FBC). Four ash streams were obtained at different locations. The uncertainty of measurements was estimated allowing a critical evaluation of mass balances over the combustion system and the partitioning of elements in the ash streams. The enrichment factors of elements in the several ash streams were estimated, incorporating uncertainties associated with analytical measurements. Results obtained showed that for FBC the relation between the chemical fractionation and the experimental partitioning is strongly affected by elutriation of particles. The element enrichment factor estimated for each ash stream, using Al as a reference element, revealed better correlations with the elements reactivity obtained by chemical fractionation because it overcomes particles elutriation effects. Nevertheless, it was observed that the reactivity estimated by chemical fractionation could not be solely interpreted as tendency of the elements to volatilize on FBC system, as reaction in bed zone of boiler may also occur retaining reactive elements.

Teixeira, Paula, Helena Lopes, Ibrahim Gulyurtlu, Nuno Lapa, and Pedro Abelha. "Evaluation of slagging and fouling tendency during biomass co-firing with coal in a fluidized bed." Biomass & Bioenergy. 39 (2012): 192-203. AbstractWebsite

Over the last decades, several indices based on ash chemistry and ash fusibility have been used to predict the ash behaviour during coal combustion, namely, its tendency for slagging and fouling. However, due to the physical–chemical differences between coals and biomass, in this work only the applicability of an ash fusibility index (AFI) to the combustion and co-combustion of three types of biomass (straw pellets, olive cake and wood pellets) with coals was evaluated. The AFI values were compared with the behaviour of ash during combustion in a pilot fluidized bed and a close agreement was observed between them. For a better understanding of the mechanisms associated with bed ash sintering, they were evaluated by SEM/EDS and the elements present on the melted ash were identified. Evidences of different sintering mechanisms were found out for the fruit biomass and herbaceous biomass tested, depending on the relative proportions of problematic elements. The particles deposited on a fouling probe inserted in the FBC were analyzed by XRD and the differences between the compounds identified allowed concluding that the studied biomasses present different tendencies for fouling. Identification of KCl and K2SO4 in the deposits confirmed the higher tendency for fouling of fruit biomass tested rather than wood pellets.