jaue2016099: Review on Sludge Drying Reed Bed

Abstract

Sludge drying reed bed is a combination of constructed wetland and conventional sludge drying bed, which is researched and applied as a kind of new sludge treatment technology extensively. Wetland plant –reeds are planted in the packing layer and the sewage sludge is loaded on the surface of reed bed, the water in the sludge flows through sludge layer and packing layer, and enters into the collection pipe, and finally is discharged to the next unit. The solids in the sludge are retained on the surface of the bed, then dewatered and stabilized further through evaporation and plant evapo-transpiration. The operating cycles of the reed bed can get to eight to ten years under the conditions of reasonable design and operation, and then enters into the next cycle after the stabilized sludge is emptied. Sludge stabilized by reed bed shows obvious dewatering effect, total solid content in the sludge ranges from 20% to 65.7%, synthetic performance is better than centrifuge dewatering and filter- press dewatering. Raw sludge source, reed bed operation mode and time affect the removals of organic matter, nitrogen and phosphorus, thus the differences of the removals are relatively bigger. The maximum organic matter removal efficiency in sludge stabilization is up to 66.8%, while nitrogen removal efficiency from negative value to 65.5% and phosphate removal efficiency from negative value to 81%. Polycyclic aromatic hydrocarbons (PAHs) in raw sludge can be removed effectively in reed bed, average PAHs removal efficiency in the reed bed can get 29.86 percentages higher than that in the conventional sludge drying bed. Based on the summary of the main results reported in the literatures, the direction of following research and development about this technology is presented.