Improvements in drying beds for non-concentrated sludge

Abstract We planned to dry sludge directly from a secondary clarifier or batch reactor in drying beds in order to remove sludge thickeners and digesters from wastewater treatment processes in small facilities, although fresh sludge is not generally suitable for drying beds. Such non-concentrated sludge as in a secondary clarifier or batch reactor separates into water and solids easily in drying beds. The water separated from sludge is drained from the beds very slowly, thus, preventing the solids from drying. To solve this problem, we buried an aerator in the sand layer of a laboratory-scale drying bed model to provide aeration while the water separated from sludge drained from the drying bed. Although it took 73 min to drain 8 cm of water without aeration of the drainage time was decreased by approximately 30% with continuous aeration. Fifteen seconds of aeration every 2 min decreased the drainage time from 73 to 30 min. We concluded that drying beds could be used for non-concentrated sludge by this method of intermittent aeration.