Electrodialytic remediation of two types of air pollution control residues and their applicability in construction materials

Dissertação para obtenção do Grau de Mestre em Engenharia do Ambiente Perfil de Engenharia de Sistemas Ambientais

Air pollution control (APC) residues from municipal solid waste incineration are classified as hazardous waste and disposed of, although it contains potential resources. Due to the different fuel gas cleaning system designs (wet or semi-dry), the APC residues present distinct chemical and physical characteristics that influence the remediation success and their possible reuse. Electrodialytic (ED) process was applied to two types of APC residues aiming their remediation. The characteristics of raw residues and upgraded APC and a broad range of ED experimental conditions were studied (ED cell with – 3 and 2 compartments; 5 or 50 mA of direct current; 3, 7 and 14 days of remediation time). Obtained results showed that remediation was very difficult but the use of low level direct current promoted the immobilization of the heavy metals. The leaching behaviour, for instance, of Pb was avoided in wet system, while the remaining values were kept below the Danish regulation thresholds, with a few exceptions. Still, after 14 days of ED process the best removal rates achieved were: 84% of Cd, 67% of Pb, 67% of Zn, 30% of Cu and 21% of Cr. Thus, 5% of Ordinary Portland Cement was replaced by APC residues in mortars, with or without ED pre-treatment. Porosity, density, compressive strength, heavy metals leaching and chloride were tested. After analysing the parameters, it is possible to say that for the wet gas cleaning systems use a pre-treatment before the reuse in building materials is the best option, since the values for heavy metals leaching tests decrease after, and compressive strength are comparable to material without residue. However, for semi-dry cleaning gas systems, the heavy metals leaching after pre-treatment appears to increase, so for this type of APC it is thus possible to aggregation only of the raw residue. The results of this study suggest new possibilities for this APC waste reuse, presenting great advantages in the waste management system as well as for resource conservation.

ELECTROACROSS - Electrokinetics across disciplines and continents: an integrated approach to finding new strategies for sustainable development (FP7-PEOPLE- 2010-IRSES-269289) and PTDC/ECM/111860/2009 - Electrokinetic treatment of sewage sludge and membrane concentrate: phosphorus recovery and dewatering