Solar Energy Application for Sewage Sludge Drying Process

Studies were carried out in summer (28.07 divided by 28.09.2009) on sewage sludge primarily dewatered on a belt press and subsequently dried by solar energy on a ferroconcrete plate covered with foil in a solar dryer ventilated gravitationally. No raking of the sludge was applied during the process. Experiments were carried out on plots of 2 x 2 m area and sludge layer depths of 30, 40 and 50 cm, and in plastic boxes. The purpose of the study was to determine the content of sludge dry matter after the solar drying. The dry matter amount changed from the original 14.6% to 55 divided by 65% after drying, but only in the top part of the layer reaching about 10 cm, independent of the layer depth. Below the 10 cm layer, the drying effect occurred in a minimal degree. From the energetic point of view, the studied sewage sludge after dehydration on the belt press contained 10.13 MJ/kg of dry matter and after the experiment termination, it reached the value of 18.03 MJ/k d. m. The required demand for heat energy was fully satisfied by the solar energy.