Study of pre-fabricated Sewage Treatment Plant under Steady State and Unsteady State Operating Conditions

• Main Authors: Pi-Shuang Hsu, 徐碧霜
• Other Authors: Tzu-Yi Pai
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/62x5f7

碩士 === 朝陽科技大學 === 環境工程與管理系碩士班 === 92 === Abstract This study evaluated a pre-fabricated sewage treatment plant located in Chaoyang University of Technology (Taichung, Taiwan). The plant was designed with the separated contact stablilizaton process at a treatment capacity of 10 persons (2.5 m3/day). The evaluation was separated into four phases: clean water tracer study, acclimation study, steady state study, and unsteady state study for a period of 111 days. Results of the tracer study showed that the actual hydraulic detention time was deviated from the theoretica value by -24.9 and -25.4 % for the first chamber (primary settling tank) and for the aeration tank followed by the final settling tank as a whole, respectively, suggesting a serious short circuiting for the small scale modual plant. Short circuiting was not evidenced for the second chamber (primary settling tank), implying that the first chamber served as a function to prevent the second chamber from short circiting. During the steady state study (63 days), influent concentration of BOD5, COD, and SS in average was 127, 313, 153 mg/L, while efflent was 29.7, 108, and 21.4 mg/L, respectly. The effluent well complied with the current dischage standard (80, 250, 80 mg/L). However, effluent quality flucrtuated with a variation coefficient (Cv) of 60.7, 46.8, 54.9 %, indicating a wide variation for the small scale treatment system. The first period of dynamic study was conducted for 13 days and in average the effluent concentration of BOD5, COD, SS was 47.1, 136, and 40.7 mg/L, respectively. The average removal efficiency of BOD5 and COD was 73.9 and 65.4%, respectively. This suggest that treatment performance was not deteriated by the dynamic loading. The settled sludge blanket was estimated for 6 months to be accumulated up to 55.7 and 62.4 cm for the first chamber and secondary chamber (primary settling tank), epectively. The would make the sludge blanket exceeding the outlet tip of the secondary chamber, required to be extended into the water depth by one-half of the total water depth. The effluent water quality was likely to be deteriated due to the sludge blanket disturbance after 6 months of operation. The settlied sludge retained in the primary settling tank will be disgeted and the reduction is estimated to be 71.8% by weight after 4 months of operation.