BEHAVIOR OF HEAVY METALS IN THE SEWAGE SLUDGE INCINERATION

RODRIGUEZ, R.; PALACIOS C., HEKTOR K.; UDAQUIOLA S.

Río de Janeiro

Congreso; ICHMET XIII INTERNATIONAL CONFERENCE ON HEAVY METALS IN THE ENVIRONMENT; 2005

Centro de Tecnologia Mineral - CETEM

The sewage sludge is the more important byproduct of wastewater treatments. The possible final disposition of sludge are: recycling as fertilizer, landfill, dumping in the sea and incineration. The incineration may be a very interesting process because its discharge to the environment is highly technically controllable while other alternatives have shown great problem by the treatment of metal emisssions. Considering the incineration processes, the fluidized bed presents one of the most interesting options. Important environmental aspects are the atmospheric emissions, especially the dioxins and furans, and the heavy metals emission in the different exit flow of the incinerator. Most heavy metals are found in in ash and powders (Werther et al., 1999). The heavy metals partition in the different exit flows, bottom ash, fly ashes, submicrometric particles and gaseous flow, is governed by a kinetics combination and diffusion with the fluid dynamics of the bed. The ash quantity leaving the fluidized bed is governed by the basic principles of the fluidization engineering. Due to the short residence times in the bed, the thermodynamic is not very important in the heavy metals partition of the because the equilibrium is not reached (Corella et al, 2000). Many heavy metals only appear in solid phase, such as Cr and As, but other metals also appear in gaseous flow, such as Hg, Cd and Pb. If the heavy metals are distributed homogeneously with the radius of the ash particle, their amount in each exit flow of ash will depend on the overall amount of each type of ash flow (Corella et al, 2000). This work is focused in the Cr and Pb behavior in the sewage sludge combustion in fluidized bed.