Abstract: Methods for treatment of sludge with microwave irradiation for improving its dewatering are provided. In one embodiment, the method includes exposing the sludge to microwave irradiation at an absorbed power density of between about 7 W/ml and about 13 W/ml. Turbidity, total solids content and overall dewaterability are improved when the microwave irradiation treatment is combined with another method for dewatering sludge, such as enzyme treatment, conditioning with a flocculating agent and mechanical dewatering.