Heavy metal speciation and acid treatment of activated sludge developed in a membrane bioreactor.

The aim of this study was to identify the heavy metals forms (exchangeable and bound to carbonate, Fe/Mn oxides, bound to organic matter and sulphide, and residual) associated with different fractions of excess sludge produced by a membrane bioreactor (MBR). Furthermore, the release of metals from the sludge to the liquid was investigated by applying acid treatment using 10% (v/v) H2SO4 (T = 25 degrees C, solid-liquid ratio 1:5 w/v) for contact time ranging from 15 min to 4 h. Metal partitioning in sludge, as determined by the sequential chemical extraction showed that the dominant form of both Ni and Zn was bound to the exchangeable and carbonate fraction; the latter were very unstable and sensitive to environmental conditions. The dominant Cu fraction was bound to organic matter and sulphide, while Pb was found to be mainly in the residual fraction which is very stable. Metal speciation after acidification with H2SO4 indicates changes of metal content in sludge and an increase of the exchangeable and bound to carbonate fraction for all metals except Cu. Acidification resulted in removal of 82% for Ni, 78% for Zn, 47% for Cu and 45% for Pb.

Leaching properties of slag generated by a gasification/vitrification unit: the role of pH, particle size, contact time and cooling method used.

The environmental impact from the operation of thermal waste treatment facilities mainly originates from the air emissions, as well as the generated solid residues. The objective of this paper is to examine the slag residue generated by a demonstration plasma gasification/vitrification unit and investigate the composition, the leaching properties of the slag under different conditions, as well as the role of the cooling method used. The influence of pH, particle size and contact time on the leachability of heavy metals are discussed. The main outcome is that the vitrified slag is characterized as inert and stable and can be safely disposed at landfills or used in the construction sector. Finally, the water-cooled slag showed better resistance in relation to heavy metal leachability compared to the air-cooled slag.

Copper removal from sludge permeate with ultrafiltration membranes using zeolite, bentonite and vermiculite as adsorbents.

The aim of this work is to examine copper removal from sludge permeate with the use of low-cost minerals of Mediterranean origin combined with ultrafiltration membranes. The minerals used were zeolite (clinoptilolite), bentonite and vermiculite. Activated sludge was enriched with 0.01 N (317.7 ppm) of Cu(II). Fixed concentrations of minerals were added to sludge and the pH value was adjusted at 5.5. The mixture was agitated for 2 hours at 800 rpm at room temperature and was then filtered through a batch ultrafiltration system for 1 hour. This experiment was repeated, for comparison purposes, with sludge enriched with 0.01 N of Cu(II) with no mineral addition. The results showed that ultrafiltration membranes with no mineral addition were able to remove a significant amount of copper with removal efficiencies ranging from 59.4-78.3%. The addition of 10 g/l and 20 g/l of bentonite combined with ultrafiltration membranes resulted in removal efficiencies of 94.9% and 99.4% respectively and that of 10 g/l and 20 g/l of vermiculite in removal efficiencies of 93.8% and 96.8%, respectively. The ion exchange capacity of minerals followed the order bentonite > vermiculite > zeolite. Furthermore, membrane fouling was investigated. The addition of zeolite and bentonite reduced membrane fouling, while the addition of vermiculite did not impact on fouling. The use of low-cost minerals in combination with ultrafiltration membranes can be employed to treat industrial wastewater, resulting in a final effluent with very low copper concentrations.

Preliminary study for the management of construction and demolition waste.

This paper refers to the management of the construction and demolition (C&D) waste since, according to the EU Waste Strategy, C&D waste is considered to be one of the priority waste streams and appropriate actions need to be taken with respect to its effective management. Initially, the paper presents the state-of-the-art of the problem of C&D waste, including the amount and composition of C&D waste in EU countries, differences in the characteristics of this waste stream depending on its origin, as well as collection and management practices that are applied. A methodology is described for the estimation of the quantities of the waste stream under examination, since in most cases quantitative primary data is not available. Next, the fundamentals for the development of an integrated scheme for the management of C&D waste are presented and discussed, such as appropriate demolition procedures and location of waste management (off-site waste management, on-site waste management, direct on-site recovery, centralized on-site recovery). Finally, taking into consideration all relevant parameters, alternative systems that could be applied for the management of the C&D waste are suggested.

Analysis of results from the operation of a pilot plasma gasification/vitrification unit for optimizing its performance.

Plasma gasification/vitrification is an innovative and environmentally friendly method of waste treatment. A demonstration plasma gasification/vitrification unit was developed and installed in Viotia region in order to examine the efficiency of this innovative technology in dealing with hazardous waste. The preliminary results from the trial runs of the plasma unit, as well as the study of the influence of certain parameters in the system performance are presented and analyzed in this paper, contributing to the improvement of the operation performance. Finally, data on the final air emissions and the vitrified ash toxicity characteristic leaching procedure (TCLP) results are provided in order to assess the environmental performance of the system. The produced slag was found to be characterized by extremely low leaching properties and can be utilized as construction material, while the values of the polluting parameters of the air emissions were satisfactory.

Development of guidelines on best practices for the slaughter of animals in Cyprus.

Cyprus is one of the candidate countries to become a full member of the European Union. In order to access formally to the EU, Cyprus has to follow an implementation process and take into account all the obligations that the fifteen Member States have to respect. A large number of obligations derive from the European Integrated Pollution Prevention and Control (IPPC) Directive 96/61/EC, which intends to result in the protection of the environment as a whole and the public health as well. This will be the outcome of determining ways of pollution prevention and control for several industrial sectors, which are covered by the IPPC Directive and then taking action so that all operators act according to the Directive's demands. In this framework, the National Technical University of Athens, after thorough examination of a large number of documents relevant to the Best Available Techniques (BATs), developed guidelines for the application of BATs for 14 categories of the industry of Cyprus. This paper concerns the developed guidelines for slaughterhouses.

Cement-based stabilization/solidification of metal plating industry sludge.

This study examines the cement-based Stabilization/Solidification (S/S) technique of sludge produced from a metal plating industry. The sludge samples were characterized in terms of pH and heavy metal content (Cr, Cu, Fe, Ni, Pb and Zn). The leachability of the sludge was estimated using the Toxicity Characteristic Leaching Procedure (TCLP). Two binder mixtures were used for the S/S process, fly ash/cement and zeolite/cement. The weight ratio of the binder mixtures was optimized to achieve the highest strength. The optimum ratio binder mixtures was mixed with sludge samples of different weight ratios and cured for 28 days in order to find the S/S products with the highest strength and the lowest leachability.

Removal of heavy metals from sewage sludge by acid treatment.

Sludge samples were found to contain significant amounts of heavy metals (Cr, Cu, Ni, Pb and Zn) and were subjected to acid treatment using either hydrochloric, sulfuric, nitric or phosphoric acid. The optimum combination, in terms of metal removal efficiency and environmental impacts was sought through a variety of tests by applying a ratio of 1:5 of sludge quantity (g) per volume of acid (ml). The concentrations of the different acids used, were in the range of 5%-20% and the contact times ranged between 15 and 60 minutes. The optimum combination was achieved when the sludge samples were in contact with H2SO4 20% v/v for 60 minutes. In order to estimate the metal leachability, the heavy metal content as well as the metal distribution in the residue were investigated and it was found that most of the heavy metal content was extracted while the remaining was removed from the initial mobile phases to the more stable ones.