Extended Dewatering of Sewage Sludge in Solar Drying Plants Original Research Article

A solar drying process was implemented for extended dewatering, volume reduction and partial pathogen control of sewage sludge. The average sludge moisture content decreased from 85% to 6% within 7–12 d during summer, and to 10% within 9–33 days in autumn, resulting to a total volume reduction of 80–85%. Total and fecal coliforms were reduced during summer conditions by two orders of magnitude, resulting to a dry product with 2·104 CFU/g DS and 103 CFU/g DS, respectively. Incorporating a solar water heater, with water recirculation through the bottom of the plant, the drying process was accelerated by 1–9 d during winter conditions. Solar sludge drying was proved to be efficient for regions which receive high annual solar radiation such as Greece.