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Lapa, N., J. Morais, C. Borges, B. Mendes, and J. F. Santos Oliveira. "An integrated approach to assess the biodegradability of a wastewater containing chromium by using chemical and biological methods." Global Symposium on Recycling, Waste Treatment and Clean Technology, REWAS’2004. Eds. I. Gaballah, B. Mishra, R. Solozabal, and M. Tanaka. San Sebastián: TMS/INASMET, 2004. 1351-1362. Abstractrewas04_lapa_et_al.pdf

The Water Company of the North Alentejo (Águas do Norte Alentejano) (Portugal) has decided to implement a treatment plant to treat an urban wastewater with a significant influence of tannery effluents. The design of the wastewater treatment plant was attributed to a consortium coordinated by Sisaqua Company. Since the levels of the biodegradability and toxicity of the wastewater to be treated were unknown, Sisaqua Company asked the New University of Lisboa to develop and execute a monitoring plan to define the chemical composition and the levels of the biodegradability and toxicity of the wastewater.
A composite sampling procedure of the wastewater was performed during a daily working cycle of the tanneries. The composite sample was characterized for 19 chemical parameters. Five of these parameters were total Cr, Cr (VI), Zn, Cu and Al, which were determined in the dissolved and suspended fractions. The composite sample was also submitted to a biological test to assess its biodegradability degree. This assay was performed according to the methodology indicated in the test 301E of OECD [1], taking into account the amendment of 1992. A respirometric assay was carried out, to assess the toxic effect of the composite sample on the biological populations involved in the biological stabilization of organic compounds. This assay followed the “Sapromat” methodology developed by Brabander and Vandeputte [2]. Finally, the composite sample was submitted to a coagulation-flocculation process according to the methodologies proposed by Eckenfelder [3, 4] and Pereira [5]. The supernatants were characterized for the same chemical and biological parameters as it was described for the composite sample.
It was possible to conclude that the high levels of Cr present in the composite wastewater were mainly in the trivalent oxidation state. Since this oxidation state is less toxic for biological populations than the Cr (VI) and this metal was mainly in the suspended fraction, it was possible to obtain a biodegradability of the organic compounds quite similar to those observed for domestic wastewaters. The toxicity determined by the “Sapromat” method was slightly higher than those determined for domestic wastewaters. Nevertheless, this toxicity did not affect significantly the wastewater biodegradability. The Cr (III) was easily removed by a chemical coagulation-flocculation process.

Lapa, N., R. Barbosa, J. Morais, B. Mendes, J. Méhu, and J. Santos Oliveira. "Ecotoxicological assessment of leachates from MSWI bottom ashes." Waste Management. 22.6 (2002): 583-593. AbstractWebsite

In this paper, chemical and ecotoxicological data of leachates from bottom ashes collected in different Municipal Solid Waste Incinerators (MSWI) are shown. The bottom ashes were collected in Belgium (three incinerators—samples B1 to B3), France, Germany, Italy and United Kingdom (one incinerator in each country—samples F1, D1, I1 and UK1, respectively). Both chemical and ecotoxicological characterizations of leachates were done on the framework of the European Directive 91/689/EEC and the European Council Decision 94/904/EC. This work was carried out under the European project called Valomat, which was supported by the European Commission through Brite-Euram III program. Twenty-one inorganic parameters were analyzed. The ecotoxicological assays were done under standard laboratory conditions, using the bacterium Photobacterium phosphoreum, the freshwater alga Pseudokirchneriella subcapitata, the crustacean Daphnia magna and the vegetable Lactuca sativa. Chemical data varied from sample to sample. Similar results were obtained in biological assays. The samples can be classified as ecotoxic/hazardous according to the French proposal for a Criterion and Evaluation Methods of Waste Ecotoxicity (CEMWE) and the German regulation on Hazardous Waste Classification (HWC). However, samples B1, B2, B3 and D1 comply the maximum limits for direct valorization category defined in the French Classification of Bottom Ashes based on their Polluting Potential (CBAPP). Sample B1 presented the lowest level of ecotoxicity, being considered as the most interesting to be used in the development of new materials for civil engineering works.

Lapa, N., R. Barbosa, M. H. Lopes, B. Mendes, P. Abelha, I. I. Gulyurtlu, and J. Santos Oliveira. "Chemical and ecotoxicological characterization of ashes obtained from sewage sludge combustion in a fluidised-bed reactor." Journal of Hazardous Materials. 147.1-2 (2007): 175-183. AbstractWebsite

In 1999, the DEECA/INETI and the UBiA/FCT/UNL started a researching project on the partition of heavy metals during the combustion of stabilised sewage sludge (Biogran®), in a fluidised-bed reactor, and on the quality of the bottom ashes and fly ashes produced. This project was entitled Bimetal and was funded by the Portuguese Foundation for Science and Technology. In this paper only the results on the combustion of Biogran® are reported. The combustion process was performed in two different trials, in which different amounts of sewage sludge and time of combustion were applied. Several ash samples were collected from the bed (bottom ashes) and from two cyclones (first cyclone and second cyclone ashes). Sewage sludge, bed material (sand) and ash samples were submitted to the leaching process defined in the European leaching standard EN 12457-2. The eluates were characterized for a set of inorganic chemical species. The ecotoxicological levels of the eluates were determined for two biological indicators (Vibrio fischeri and Daphnia magna). The results were compared with the limit values of the CEMWE French Regulation. The samples were also ranked according to an index based on the chemical characterization of the eluates. It was observed an increase of the concentration of metals along the combustion system. The ashes trapped in the second cyclone, for both combustion trials, showed the highest concentration of metals in the eluates. Chemically, the ashes of the second cyclone were the most different ones. In the ecotoxicological point of view, the ecotoxicity levels of the eluates of the ashes, for both combustion cycles, did not follow the same pattern as observed for the chemical characterization. The ashes of the first cyclone showed the highest ecotoxicity levels for V. fischeri and D. magna. This difference on chemical and ecotoxicological results proves the need for performing both chemical and ecotoxicological characterizations of the sub-products of such type of thermal processes.

Lapa, N., R. Barbosa, B. Mendes, and J. F. Santos Oliveira. "Chemical and ecotoxicological long-term behaviour of new materials for quarry back-filling and underground constructions." International RILEM Conference on the Use of Recycled Materials in Building and Structures. Eds. E. Vázquez, Ch. F. Hendriks, and G. M. T. Janssen. Barcelona: RILEM, 2004. 373-382. Abstractpaper_186_final_version.pdf

The main aim of the Valomat project was the development of new materials for quarry back-filling and underground constructions, based on the reuse of bottom ashes from MSWI. Bottom ashes were collected in six incineration plants of Europe. Some of them were selected for the development of new materials.
One task of this project comprised the study of the long-term behavior of new materials, under simulated conditions of environmental exposure. Three different scenarios were studied. For each scenario, a pilot plant was constructed and the new materials were studied under laboratory conditions or natural weather. The long-term behavior of these materials was assessed through the characterization of chemical and ecotoxicological properties of the leachates.
The chemical contamination and the ecotoxicological levels of the leachates were relatively low, although different levels had been determined for the three different scenarios. The immersion in dechlorinated tap water (scenario S1) had shown the highest emission levels of chlorides, sulphates, DOC, and Al, especially for the materials B2/1 and B2/2. The lowest ecotoxicological and chemical levels were determined in the scenario in which the materials were buried in a sieved soil.

Lapa, N., J. F. Santos Oliveira, S. L. Camacho, and L. J. Circeo. "An ecotoxic risk assessment of residue materials produced by the plasma pyrolysis/vitrification (PP/V) process." Waste Management. 22.3 (2002): 335-342. AbstractWebsite

Plasma is the fourth state of matter, following the three states of solid, liquid and gas. Experience has amply demonstrated that solids exposed to the oxygen-deficient plasma flame are converted to liquid, and liquid exposed to the same flame is converted to gas. A low amount of vitrified solid residue material usually remains at the end of this process. Plasma pyrolysis/vitrification (PP/V) has been demonstrated as a safe, efficient, cost-effective technology for the treatment of wastes, including hazardous wastes. Besides the low amounts of gaseous byproducts that PP/V produces, the solid vitrified residue presents a low leachability of pollutants. Studies have been performed in many countries in order to assess the leachability of chemical substances. But from the results of identified studies, none has reported results on the ecotoxicological properties of the leachates. The aim of this study was to contribute to the assessment of ecotoxic risk of four different vitrified materials. Vitrified samples of contaminated soils, municipal solid wastes, and incinerator bottom ashes were submitted to the European leaching pre-standard test number prEN 12457-2. The leachates were analyzed for 22 chemical parameters. The biological characterization comprised the assessment of bioluminescence inhibition of Photobacterium phosphoreum bacterium, growth inhibition of Pseudokirchneriella subcapitata algae and the germination inhibition of Lactuca sativa vegetable. The chemical and ecotoxicological results were analyzed according to the French proposal of Criteria on the Evaluation Methods of Waste Toxicity (CEMWT) and a Toxicity Classification System (TCS). The chemical and ecotoxicological results indicated a low leachability of pollutants and a low toxicity level of leachates. All samples studied were as below the TCS class 1 level (no significant toxicity observed) and as non-ecotoxic for CEMWT. Therefore, the environmental ecotoxic risk of the analyzed vitrified samples was determined to be very low.

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.

Lapa, N., J. Morais, and J. F. Santos Oliveira. "A qualidade de vida em Portugal." Indústria e Ambiente. 5 (1995): 15-24.
Lapa, N., R. Barbosa, S. Camacho, R. C. C. Monteiro, M. H. Fernandes, and J. F. Santos Oliveira. "Leaching behaviour of a glass produced from a MSWI bottom ash." Advanced Materials Forum III, III International Materials Symposium Materiais 2005. Ed. Paula Vilarinho. Universidade de Aveiro, Aveiro: Trans Tech Publications Inc., 2005. 1736-1741. Abstractlapa_et_al_-_to10.o3.pdf

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 µm). 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.

Lapa, N., J. Morais, and J. F. Santos Oliveira. "Valorização de lamas de ETAR’s como fertilizantes dos solos." Indústria e Ambiente. 2 (1994): 4-10.
Lapa, N., R. Barbosa, and B. Mendes. "Intrinsic properties of new materials for civil engineering works based on the reuse of MSWI bottom ashes: chemical and ecotoxicological assessment." Urban Mining: A global cycle approach to resource recovery from solid waste. Eds. R. Cossu, V. Salieri, and V. Bisinella. Padova: CISA Publisher, 2012. 298-307.
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.