An unplanted drying bed is a simple, permeable bed that, when loaded with sludge, collects percolated leachate and allows the sludge to dry by evaporation. Approximately 50% to 80% of the sludge volume drains off as liquid or evaporates. The sludge, however, is not effectively stabilized or sanitized. Unplanted drying beds need to be desludged regularly. The percolate or leachate needs to be collected and treated before reuse or disposal. See also planted drying beds.