Dewatering and Mineralization of Sludge from Secondary Sedimentation Tank in a Constructed Sludge Drying Reed Bed

The dewatering and mineralization of sludge in the constructed reed bed was investigated in this study.The sludge from the secondary sedimentation tank is from in the wastewater treatment plant in Yiyang city,Hunan province.Anaerobic pond and oxidation ditch biological treatment processes is accepted there.The performance of the system was monitored for one year. Total Solids (TS), Volatile Solids(VS), Chemical Oxygen Demand, nutrients (TKN) and Total Phosphorus(TP), heavy metals in the sludge were analysed.The removal rate of COD,NH4-N,and TP of the percolated fluid for the first cycle was also monitored. TS content reached 36.5% for the surface layer and 37.8% for the bottom layer at the end of the examination period.Sludge stabilization in the bed was also observed(VS content decreased to 31.3% and 13.4% respectively for the surface and bottom layer).Concentration of nutrients of the sludge accumulated in the bed also decreased. The heavy metal concentration meets the European Union standards for heavy metals in case of agricultural disposal of the treated sludge.