Composite conditioners in deep-dewatered sludge have an important influence on its drying characteristics. In order to obtain deep-dewatered sludge

the raw sludge was pretreated by four kinds of typical composite conditioners and then dewatered. At the N2 atmosphere and 473 K

the effects of the composite conditioners on the emission characteristics of moisture and pollutants

as well as the drying products properties of gas

liquid and solid phase

were investigated. The results showed that the composite conditioner could effectively reduce the water content of dewatered sludge and accelerate the water release

shorting the drying time as well. Conditioning process in the acid

alkali and strong oxidizing environment destroyed the organic structure of sludge so that the aromatic-or thiophene-S in sludge could transfer into more stable sulfonic acid-or sulfone-S. Also

the alkaline environment allowed the dissolved acidic sulfur-containing gas to be fixed

thereby reducing the amount of sulfur-containing gas released during drying. But the releasing rate of ammonia was accelerated. Because of the high concentration of sulfur-containing gases

nitrogen-containing gases and volatile organic compounds in the drying exhaust gas

the condensate had a high pH and COD accompanied by malodor

and thus needed to be disposed before it can be discharged. The lower heating value of sludge can be 6.79—13.18 kJ·g-1 of dry sludge and efficiently maintained under the drying temperature of 473 K so that the dried sludge can provide a kind of renewable energy.