Regarding resource recovery from mixed sludge, acceptance conditions are not strict except for the phosphorus content. The recovery of heavy metals from sludge at smelters is currently very rare. One of the main reasons is that plating plants are small and the amount of sludge produced at one plating plant is limited. Few plating plants classify wastewater according to the variety of plating, so that metals are mixed in sludge, which largely varies in metal type and amount. Sludge from plating plants can hardly be processed at smelters, which smelt ores in a mass-production basis.
Values are of dry sludge.
Acceptable hexavalent-chromium content is as obtained by an elution test conducted according to Environment Agency Announcement No. 13.