A. Andrés

Assessment of Self-Organizing Map artificial neural networks for the classification of sediment quality.

The application of mathematical tools in initial steps of sediment quality assessment frameworks can be useful to provide an integrated interpretation of multiple measured variables. This study reveals that the Self-Organizing Map (SOM) artificial neural network can be an effective tool for the integration of multiple physical, chemical and ecotoxicological variables in order to classify different sites under study according to their similar sediment quality. Sediment samples from 40 sites of 3 estuaries of Cantabria (Spain) were classified with respect to 13 physical, chemical and toxicological variables using the SOM. Results obtained with the SOM, when compared to those of traditional multivariate statistical techniques commonly used in the field of sediment quality (principal component analysis (PCA) and hierarchical cluster analysis (HCA)), provided a more useful classification for further assessment steps. Especially, the powerful visualization tools of the SOM, which offer more information and in an easier way than HCA and PCA, facilitate the task of establishing an order of priority between the distinguished groups of sites depending on their need for further investigations or remediation actions in subsequent management steps.

Characterisation and management of incinerator wastes

Management of municipal and hospital wastes by means of incineration processes generates solid residues, such as bottom and fly ashes and air pollution control residues with high content of heavy metals, inorganic salts and other organic compounds. Characterisation of 24 ash samples, collected from four municipal solid waste incinerators (MSWI) and six hospital medical waste incinerators (HMWI) located in the Basque Country Region (Northern Spain), were carried out at the request of Spanish Regulations and European Economic Community guidelines. The ecotoxicity values, EC(50), of the TCLP leachates show a high variability ranging from 12,967 to 1,000,000mgl(-1) in MSWI samples and from 2917 to 333,150mgl(-1) in HMWI samples. Results from chemical characterisation of DIN 38414-S4 leachates show a high concentration of lead, sulphate and chloride in MSWI samples and chromium in HMWI samples.

Experimental study of the waste binder anhydrite in the solidification/ stabilization process of heavy metal sludges

Abstract An experimental study of the use of an industrial byproduct, anhydrite (CaSO 4 ), as inorganic binder in the solidification/stabilization (S/S) process of heavy metal sludges has been performed. The influence of the variables: binder:waste ratio, anhydrite particle size and water amount on the S/S process of a synthetic sludge containing Cd, Cr and Pb has been studied. Leaching of stabilized products using the Toxicity Characterization Leaching Procedure was used to evaluate the behaviour of heavy metals after treatment with anhydrite. Significant reductions of leached metal concentrations were achieved depending on the experimental variables. Therefore, it has been shown the possibility to use anhydrite as binder in S/S processes of wastes containing heavy metals and the influence of the main variables in the S/S process, in order to satisfy landfill disposal regulations.

Characterization of metal finishing sludges: influence of the pH

Metal finishing sludges are classified as metal hydroxide hazardous wastes due to the heavy metal release to the environment. This release, commonly determined by compliance lixiviation tests based on the equilibrium conditions at the end of the leaching experiment, is mainly dependent on the pH of the solution. In this work, the leaching behaviour of Cd, Cr, Cu, Fe, Ni, Pb and Zn, of the 32 metal finishing sludges coming from 16 European industrial facilities, and using the distilled water compliance test DIN 38414-S4, have been studied. The concentrations of chromium and copper in the leachates do not follow the solubility evolution of their hydroxide with the pH. The simple assumption of a heavy metal concentration in the leachate directly related to the solubility of the hydroxide is not in good agreement with the experimental results of the distilled water leaching test, probably due to the presence of different species, which can contribute to the metal mobility depending on the sludge composition. An experimental evaluation of the easily available amount of metals in real wastes seems to be necessary for disposal assessment. This paper contains valuable information, from orderly handling metal finishing wastes to the statistical studies of production and management of wastes suggested recently by the Commission of the European Community.

Valorization of Foundry Sand in Clay Bricks at Industrial Scale

In this article, foundry sand as waste material has been valorized in ceramic brick manufacturing at industrial scale. The employment of a waste coming from one industry as an input for another is one of the key concepts of industrial ecology. To study the environmental behavior of the ceramic bodies in different life cycle stages, three leaching tests have been developed. We used an EN 12457 equilibrium leaching test with distilled water and a Wastewater Technology Centre acid neutralization capacity (WTC-ANC) leaching test with different acidic leachates to carry out the environmental evaluation under different granular scenarios to ascertain the possibilities of the reuse or disposal of this granular material at the end of its useful life (end-of-life stage). Finally, we used a NEN 7345 diffusion leaching test for construction materials, with the aim of studying the environmental assessment at the use stage. Regulated pollutants in both stages have been evaluated. Furthermore, other soluble salts have been analyzed because they are closely related to the efflorescence phenomenon in bricks. Results indicate that core and green sand from the foundry industry can be used to replace clay content in construction materials, and that these foundry-sand-based ceramics improve some soluble salt results. Despite this fact, at the end-of-life stage in an inert waste landfill, lead, arsenic and chromium can be an environmental problem, both for commercial bricks and for foundry-sand-based bricks. This work can contribute to the determination of viability of sustainable processes of brick manufacturing that use foundry wastes as raw materials.

Physico-chemical and environmental characterisation of sediments from Cantabrian estuaries (Northern Spain)

Previous studies show that sediments of the Cantabrian estuaries (Northern Spain) contain significant concentrations of heavy metals and organic pollutants derived from intensive industrial, agricultural and urban activities. In the most polluted sediments of two estuaries (the bay of Santander and estuary of Suances), physico-chemical and environmental characterisation has been carried out. Water content, density, pH, specific surface, porosity and particle diameter distribution have been evaluated as physical parameters. Total metal contents have been analysed as inorganic parameters. Loss of ignition (LOI), phenol index and extractable organic halogens (EOX) have been determined as organic parameters. Two leachate assays have been carried out in order to evaluate the environmental behaviour of the sediments. Total availability has been analysed using the NEN 7341 test and the mobility of the pollutants has been determined using the EN 12457 leaching test at two liquid/solid ratios. The obtained results have been compared with European Union regulations. The physical parameters and inorganic compounds are very similar in the studied sediments. However, the sediments from Suances have high concentrations of LOI and EOX. The obtained correlation of the physical parameters with the particle size distribution is useful in the study of the sediment addition to ceramic process as a sediment management option. A comparison of the results obtained from the total, availability and mobility analysis of the inorganic pollutant concentrations of As, Ba, Ni, Pb and Zn present in sediments has been made, giving knowledge for the development of regulations and tools that would contribute to the integral management of the estuarine areas.

The influence of binder/waste ratio on leaching characteristics of solidified/stabilized steel foundry dusts

Abstract The influence of the binder/waste ratio (AG/WS) on the leaching characteristics of two solidified/stabilized (S/S) steel foundry dusts has been investigated. Leach testing of the solidified products using the Toxic Characterization Leaching Procedure was used to determine the levels of Cd, Pb, Cr and Zn in leachates. The results show that the waste/binder ratio significantly influence the ability of solidified dusts to pass US EPA regulations. For the two wastes investigated minimum waste/binder ratios of 0.37 and 0.25 are recommended for CSFD and SSFD dusts, respectively.

Stabilization/solidification of an alkyd paint waste by carbonation of waste-lime based formulations.

The application of solvent-based paints by spraying in paint booths is extensively used in a wide range of industrial activities for the surface treatment of a vast array of products. The wastes generated as overspray represent an important environmental and managerial problem mainly due to the hazardous characteristics of the organic solvent, rendering it necessary to appropriately manage this waste. In this paper a solidification/stabilization (S/S) process based on accelerated carbonation was investigated as an immobilization pre-treatment prior to the disposal, via landfill, of an alkyd solvent-based paint waste coming from the automotive industry; the purpose of this S/S process was to immobilize the contaminants and reduce their release into the environment. Different formulations of paint waste with lime, lime-coal fly-ash and lime-Portland cement were carbonated to study the effect of the water/solid ratio and carbonation time on the characteristics of the final product. To assess the efficiency of the studied S/S process, metals, anions and dissolved organic carbon (DOC) were analyzed in the leachates obtained from a battery of compliance and characterization leaching tests. Regarding the carbonation of paint waste-lime formulations, a mathematical expression has been proposed to predict the results of the leachability of DOC from carbonated mixtures working at water/solid ratios from 0.2 to 0.6. However, lower DOC concentrations in leachates (400mg/kg DOC in L/S=10 batch leaching test) were obtained when carbonation of paint waste-lime-fly-ash mixtures was used at 10h carbonation and water to solid ratio of 0.2. The flammability characteristics, the total contents of contaminants and the contaminant release rate in compliance leaching tests provide evidence for a final product suitable for deposition in non-hazardous landfills. The characterization of this carbonated sample using a dynamic column leaching test shows a high stabilization of metals, partial immobilization of Cl(-), SO(4)(2-), F(-) and limited retention of DOC. However, the obtained results improve the previous findings obtained after the paint waste S/S using uncarbonated formulations and would be a useful pre-treatment technique of the alkyd paint waste prior to its disposal in a landfill.

Influence of commercial and residual sorbents and silicates as additives on the stabilisation/solidification of organic and inorganic industrial waste.

An environmental problem of the foundry activities is the management of industrial waste generated in different processes. The foundry sludge from gas wet cleaning treatment that contains organic and inorganic compounds and a high content of water is an interesting example. Due to their characteristics, they can be managed using different stabilisation/solidification (S/S) technologies prior to land disposal. The purpose of this work is to study S/S formulations in order to improve the control of the mobility of the pollutants and the ecotoxicity of the samples. Different mixtures of cement or lime as binders and additives (foundry sand, silica fume, sodium silicate, silicic acid, activated carbon and black carbon) have been used in order to reduce the mobility of the chemical and ecotoxicological regulated parameters and to compare the results for commercial and residual additives. The best results have been obtained with sorbents (activated carbon and black carbon) or sodium silicate. The results of the foundry sand ash as additive can conclude that it can be used as replacement in the cement products. However, silica fume in the samples with lime and siliceous resin sand as additives gives products that do not fulfil the regulated limits. Finally, some linear expressions between the chemical parameters and the quantity of material used in the samples have been obtained.

Environmental Characterization of Metal Finishing Sludges

Metal finishing industries generate effluents with high contents of heavy metal, inorganic anions and minor amounts of organic compounds, which must be treated by specific physicochemical processes leading to complex sludges. The characterization of these wastes is necessary to assess their environmental impact and to establish management. In this work two different methods of characterization, based on the Spanish Regulations and European Economic Community suggestions, have been applied to 32 wastes from 16 metal finishing facilities. The ecotoxicity values, EC50, of the TCLP leachates show a high variability among different metal finishing activities and batches of the same activity, ranging from 1 000 mg l−1 to 1 000 000 mg l−1. Results of chemical characterization of leachates, according to the DIN 38414-S4 leaching procedure show a high concentration of SO4 2−, Cr and Ni. The paper establishes the characterization parameters of sludge wastes from the physicochemical treatment of metal finishing effl...