The characteristics and treatment performance of water washing wastewater from an incineration bottom ash

• Main Authors: Chun-Chen Hsu, 許峻誠
• Other Authors: Kuei-Jyum Yeh
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/84636418087129901448

碩士 === 國立屏東科技大學 === 環境工程與科學系所 === 99 === This study evaluated the influent characteristics and performance of a wastewater treatment plant in a bottom ash recycling factory in southern Taiwan. This plant received bottom ashes from incinerators in Chiayi, Pingtung and Kaohsiung counties. The wastewater samples from influents, physical and chemical treatment units were sampled to explore the variation of wastewater characteristics and the removal efficiency of each units. The results show that the pH values of wastewaters influent are all above 12. The characteristics of wastewater generated among batches of bottom ash washing vary significantly. The average concentration of COD, chloride and SS is 5760 mg/L, 3029 mg/L, and 41666 mg/L, respectively The average removal efficiency of COD, chloride, SS and heavy metals by sedimentation is 82.0％、39.9％、99.7％及96.5％, respectively. Although parts of heavy metals in bottom ashes are washed out along with particles, the concentrations of heavy metals in the effluent are below the discharge limits. All the sludge of sedimentation units pass the heavy metal regulation of TCLP test. The coagulation process after the sedimentation further increases the removal efficiencies (98.2% for COD, 55.2% for chloride, and 99.9% for SS). These results indicate that COD and heavy metals in the wastewater from bottom ash washing are in the form of suspended solids. If the resident time is long enough; sedimentation can achieve good removal efficiencies of COD and SS. Satisfactory removal efficiency can be obtained using sedimentation followed by coagulation. In addition, the odor problem is significantly reduced. Water washing of the bottom ash could wash out chloride ion, however, at the wash water/bottom ash (L/S) ratio of 0.6, about of 37.6% of chloride in the bottom ash is removed, which still could not meet the requirement of less than 0.024% chloride as a type I construction materials. It is recommend that the chemical dosage should be adjusted based on the influent characteristics. Enough hydraulic retention time, routine sludge excavation from sedimentation units and improved mixing during coagulation will help to improve the wastewater treatment efficiency.