The suitability of using dimethyl ether (DME) in dewatering coal for the treatment of sewage sludge has been found empirically to be highly effective. We investigated the effectiveness of a method involving the use of DME for dewatering electroplating sludge and tried to clarify the mechanism and characteristics of the dewatering process. Two zinc-containing sludge samples were examined and the effect of the volume of liquefied DME on the dewatering process was assessed. During the initial dewatering phase, the dewatering ratio is dependent only on the saturation degree of water in liquefied DME. In the later phase, it depends proportionally on the water concentration in the sludge and has a pattern that reduces the dewatering rate as dewatering is proceeded. Moreover, the dewatering pattern can be expressed using one dewatering rate constant, k .   The water contained in the sludge samples was analyzed using thermogravimetry/differential thermal analysis and the evaporation temperature range was determined. The water remaining in the samples after dewatering was found to be thermally stable and tightly bound. We further determined the amounts of total carbon and metal elements in the dewatered water and compared the concentrations to those specified in the Japan Water Pollution Quality Control Act. An important observation is that the dewatered water from the samples requires further processing before it can be discharged into the drainage system due to the presence of large amounts of Cu, Pb and Zn.