Thermal drying of sludge reduces the moisture content below that achievable by conventional dewatering methods. The minimum moisture content practically attainable with thermal drying depends on the design and operation of the dryer, moisture content of the sludge feed, and the chemical composition of the sludge. For ordinary municipal wastewater sludge, moisture content as low as 5% may be achievable. The advantages of thermal drying include reduced product transportation costs, further pathogen reduction, improved storage capability, and marketability. Disadvantages include high capital and operating costs and requirements for skilled operating personnel.
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