Freeze/thaw treatment of oily sludge from petroleum refinery plant

A petroleum refinery plant in Taiwan generates approximately 2.8 x 10(4) to ns of oily sludge, including the residual from storage tanks, and the scum sludge and waste-activated sludge from the wastewater treatment plant. Expe rimental results indicate that freezing and thawing can transform the flocs into large and compact aggregates and significantly enhance the sludge del iquorability for scum and waste-activated sludges. The results are attribut ed to the advance of an ice front during freezing that expels oil phases fr om the sludge body. Cationic polyelectrolyte conditioning only slightly inf luences sludge with a high oil content because the chemical conditioner lar gely binds to oily droplets on the sludge flocs. However, neither freeze/th aw treatment nor polyelectrolyte conditioning, can satisfactorily condition the tank residual. Underlying mechanisms of oily sludge conditioning are d iscussed.