Investigation on specific evaporation rates during biosolid air drying process

Biosolids, inevitable by-products of wastewater treatment processes, can be potentially used as a biomass feedstock for energy and resource applications. These by-products have a high moisture content, which must be reduced before they can be used for further applications. Natural air drying is an energy saving and sustainable approach, but it highly depends on local climatic conditions. We conducted biosolid air drying experiments under room temperature and winter outdoor temperature. The biosolid air drying experiment under room temperature was designed to screen four factors: wind speed, solid content, layer thickness and pan location. Wind speed and solid content were identified as primary factors, and the specific evaporation rate increased as the wind speed increased and decreased as solid content increased. The developed regression model can effectively predict the specific evaporation rate. Under winter outdoor temperature, the results revealed the surrounding temperature has a great effect on the sublimation rate.