Moisture sorption characteristics of waste activated sludge

Nowadays the treatment of activated sludge often includes a thermal drying step. Data such as water vapour sorption isotherms and heat of sorption are required for good design and control of the drying processes. An equilibri um method was used to measure these data on domestic activated sludge, betw een 39 degreesC and 80 degreesC. The experimental investigation indicated t hat the nature of the sludge and its evolution (bulking sludge, anaerobic s torage) ilo not affect the sorption isotherms. Experimental data were fitte d to different well-known models; the Oswin relationship gave the better fi t. Based on sorption data the heat of sorption as a function of moisture co ntent was determined. (C) 2001 Society of Chemical Industry.