Drying of ferric chloride water treatment plant residuals have been studied in two experimental sand drying beds. One bed was open and the other was covered with glass to study respectively the open bed drying of residuals under normal weather conditions and passive solar energy drying. The covered bed was fabricated, with a view, to simulate the solar distillation stills. A weather station was used to monitor the dynamic weather conditions in order to study their effect on the drying process. Solids content, drainage water volumes and distillate from the covered bed were measured on a daily basis. The aim of the study was to accelerate the drying process of residuals using passive solar energy drying technique. The study showed that the residuals dry faster in the open bed. The passive solar bed design was altered several times during the study in order to improve the bed performance. However no significant improvements were found in the performance. A reduction of 33% in drying time was achieved when the solar drying bed was provided with a fan heater. The operating conditions of both beds and their effect on the drying process are studied to understand the operation of sand drying process.