Production of concentrated solar collector for drying treatment sludes

Treatment sludge are concentrated wastes including organic and inorganic solid matters with water and resulted from separation process of wastewater treatment plants. Although the sludge is separated from water by dewatering processes, it still contains a large amount of water. The water content of the sludge cake from the centrifugal dewatering unit varies between 82% and 78% in the Konya wastewater treatment plant. This high-water content in the sludge is a problem that needs to be overcome in the implementation of final disposal or reuse alternatives. It is necessary to increase the solid matter content of the sludge in order to burn, landfilling or to use as fertilizer. Therefore, drying is a mandatory process for these reuse or disposal options. Thermal dryers operated by fossil fuel could be achieve high drying rates, but its implementation and operational cost is disadvantage. Greenhouse type indoor or outdoor drying plants, where the sludge is laid on the floor in a thin layer to benefit from solar energy, have relatively low cost but requires large areas. Concentrated solar energy systems are promising alternative to overcome these problems. Parabolic trough types solar collectors where the heat generated at high temperatures is used for industrial application such as production of electricity by steam power. In this study, a mechanism of direct sludge passing through the tube located at the focal point of the parabolic collector was installed to concentrate solar energy on the lower area. The moisture was removed by means of ventilation while the sludge was heated in the metal tube. Drying experiment were carried out at Konya Wastewater Treatment Plant in autumn and summer season. The solid matter content increased from 18% to 47% on a day where the average solar radiation is 882 W/m2 and the sludge flow rate of 33 g/min. On another day when the radiation and the flow rate were 1047 W/m2 and 28.6 g/min, respectively, the solids content increased from 21% to 64%. In summer season, solid mater of raw sludge increased from 20% to 96% in 5 hours when the average solar radiation was 946 W/m2.