Direct sludge freezing using dry ice

Abstract Dry ice was used as the heat sink in sludge freeze/thaw treatment. Four distinct sludges were frozen at four thermal contact configurations with dry ice. Experimental results indicate that dry ice freezing can sufficiently condition the sludges and is an economically feasible alternative for sludge conditioning. With a properly designed thermal contactor, the freezing rate can range from 0.48–0.64 m daily.