Characterization of a mineral waste resulting from the melting treatment of air pollution control residues.

Air pollution control (APC) residues which are generated by municipal solid waste (MSW) incineration show a high-level of pollution potential. In order to stabilize such APC residues, the French power supply company (EDF) is developing a thermal treatment process which leads to the production of a vitrified material. A structural characterization of the vitrified product was carried out by applying complementary investigation methods: XRD, SEM, Raman spectroscopy, EPMA, and data interpretation methods such as mineralogical analysis and principal component analysis (PCA). The major phase of the material was a solid solution of melilite type composed of five end-members: gehlenite (44%), åkermanite (25%), ferri-gehlenite (5%), sodamelilite (14%) and hardystonite (11%). The minor phases identified were spinels and pyroxenes. An ANC leaching test was performed in order to observe the treatment effect on pollutant release. The natural pH was close to 10, and the major element release was less than in the case of untreated APC. This was a consequence of melilite formation. The effect of pH was fundamental for heavy metals release: lower solubilization occurs at pH 10 than at APC's natural pH (11-12).

Coupling ultrafiltration with an activated carbon cloth for the treatment of highly coloured wastewaters: a techno-economic study.

This work investigates the coupling of a membrane technique, ultrafiltration, with a recent adsorbent, activated carbon cloth for the treatment of industrial highly coloured wastewaters. A first experimental part shows the high treatment ability of this process for fountain-pen inks effluents arising from the rinsing of vats in which inks were produced. Whereas ultrafiltration enables more than 97% of colour removal, COD and DOC are not completely retained and a residual value of 1,700 mg l(-1) of DOC is obtained in the permeate. The second step of the process, activated carbon cloth, allows residual organic matter to be removed and a complete discolouring of the permeate. Adsorption capacities of COD and DOC are high, equal to 500 and 250 mg g(-1) respectively. Furthermore, this adsorbent induces a complete removal of glycol compounds (acting as antifreeze) which were not retined by a nanofiltration technique. A second part is an evaluation of the economic feasibility of such an integrated process. Only direct costs are considered at this phase of the study, and are divided into fixed costs (equipment, depreciation, maintenance), variable costs (electricity and consumption) and labour costs. The technical-economic study is carried out for two configurations: a low capacity unit (the UF membrane area is 2.4 m2) and an industrial capacity unit (with a 100 m2 UF membrane). Costs per treated m3 are respectively 111 and 32 euros, with costs partitioning which are dependent on the unit capacity.