Process for chrome recovery from industrial waste and the like, as from chrome-ladened tannery waste, including pollution control of the same

摘要

This disclosure is concerned with a tannery primary treatment process that, in total combination, or as separate sub-process features, enables the reducing of BOD loading in such treatment, while increasing the efficiency of hexavalent chrome recovery therefrom by separating out alkaline sulfide solids from the normal unhairing beamhouse stage and utilizing the same to attain appropriate sedimentation tank sludge pH for oxidation of the chrome to the hexavalent state during incineration; and/or increasing the hexavalent chrome recovery by backwetting and roasting the ash again; and/or enabling use of such ash for recycling as a chrome tanning liquor with the side-production of an improved flocculating chrome water wash for waste treatment use.