Operational Performance Evalutation of Fixed-Bed Biological Filter and Sludge Blanket Clarifier for the Removal of Dissolved Organics

• Main Authors: Tinlai Lee, 李丁來
• Other Authors: Chihpin Huang
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/17914867447113307898

博士 === 國立交通大學 === 環境工程系所 === 95 === Abstract Organic matters and ammonia nitrogen are serious contaminants of surface water in Taiwan. These contaminants can interfere with the water treatment process and cause biological instability in the finished water. One solution is to employ a biological treatment stage prior to the conventional water treatment process. A continuous flow biological filter packed with reticulated PU foam was used to remove ammonia nitrogen and organic matters before the conventional water treatment practice. The effect of its operation mode, namely, empty bed contact time (EBCT) and backwash, on the removal efficiencies of ammonia nitrogen and dissolved organic matter was examined. Also, sludge blanket clarifiers（SBC）are presently an important unit of the water treatment process in Taiwan. Most studies concerning SBC have revolved around the treatment efficiency on turbidities. In Taiwan, most of the raw water sources for water treatment plants are contaminated with organic substances, which often interferes the operation of SBC. The effects of organic materials on the formation of sludge blanket and its performance, were also examined in this study. The results of the continuous flow biological filter suggested that organic matters and ammonia nitrogen can be effectively removed up to 30 ％ and 95％, respectively, by controlling the operation mode of the biological fixed bed. Efficient ammonia nitrogen removal was achieved upon the combination of backwash mode with short EBCT or extended EBCT without backwash. Efficient organic nitrogen and DOC removals were observed at short EBCT without backwash. The optimal pH for turbidity and DOC removal of biofilter effluent water coagulated with Alum is around 6.5-7.5 and 5.5-6.5, respectively. This study provides insights into the function of biofiltration, which benefits the design of fixed-bed bioreactor for the treatment of polluted surface water. Humic acid and salicylic acid were added in water to simulate natural waters polluted with organic materials of high and low molecular weights. The addition of humic acid accelerated the formation of stable sludge blanket, however, the sludge blanket so formed contained less solid. Opposite effects were discovered with salicylic acid. Nevertheless, both organics enhanced the efficiency of turbidity removal by SBC. Large organic molecules were more easily removed by SBC. Coagulant addition had no significant effect on turbidity removal although the formation time for sludge blanket was shortened. To successfully operate SBC, the occurrence and types of organic materials must be monitored.