Design/operating Experience on a Utility Boiler Wash Treatment System

It might not appear at first that this paper has sig­ nificance in the field of Solid Waste Processing, since it applies to cleaning wash water from cleaning the fireside surfaces of utility boilers burning gas and oil. It is generally believed that systems which burn mu­ nicipal solid waste (MSW) do not require treatment of boiler wash water, since this can be used to quench the ash and thus be discharged into the ash before the ash residues are trucked to landfill. However, the wash water from boilers burning MSW when tested would probably fail the EPA toxicity test for heavy metals such as lead, cadmium and chromium if it were not discharged into the ash. Upon further thought, it might make the ash residue itself fail the test if too much was added in a short time. With the controversy about the toxicity of ash res­ idues, and local opposition trying to close WTE plants on the basis of the ash residues, or with high costs of ash disposal, it behooves us to look at alternatives such as described by the authors. The system installed at PG&E at Contra Costa is fundamentally simple, although the prohibition of stor­ ing hazardous wastes on site forced the inconvenient use of portable storage containers rather than simple