應用包埋式混合厭氧菌處理生活污水

Abstract

生活污水的處理傳統上多使用好氧程序，然而好氧程序在曝氣時會有消耗大量能源的缺點。和好氧程序比較，厭氧程序具有三個顯著的優點：產生的污泥量較少、省去曝氣的成本以及產生可燃之甲烷氣體。厭氧程序一般用於處理有機濃度較高的廢水，且由於厭氧菌生長較慢，過去很少用於處理流量較大且濃度較低的生活污水。此外，近年來固定化細胞(Immobilized cells)技術的應用已相當廣泛，其作用係將菌種限制在特定空間內，使菌種不會隨出流水流失，因而提高反應槽的固體停留時間(Solids retention time, SRT)，並可保護菌種較不會受環境變化而影響其活性(Liu and Chou, 2010)。 為節省能源以及有效處理低有機濃度的生活污水，本研究應用固定化包埋式混合厭氧菌，探討生活污水的處理及生成甲烷之可行性，並找出反應槽的最佳操作參數。實驗的菌種使用取自民間豬場廢水處理系統的厭氧污泥，製成固定化細胞後，以37.5%的填充率置入工作體積為3 L的反應槽，並以水浴將槽體溫度控制於37±1°C，系統採連續式進流。反應槽起動時，以475 mg TCOD/L之人工廢水進流，操作在水力停留時間(Hydraulic retention time, HRT)12小時，待TCOD去除率達93%以及甲烷比例達70%時，進流開始加入生活污水。以上起動階段結束後，即進行設訂之試驗，進流完全換成生活污水，濃度為381±102 mg TCOD/L，HRT由12逐漸降至6、4、3、2.4以及2小時。每天至少取樣2次，進行水質之化學分析，同時記錄總產氣量及分析氣體的組成。結果顯示，整個實驗過程的TCOD去除率皆在92%以上，其中又以HRT為4小時的試驗有最佳的產氣，其甲烷產率及甲烷比例分別達到0.230 L CH4/L/d 及59.8%。由本研究的結果證實，應用固定化包埋式混合厭氧菌可成功地處理生活污水同時產生甲烷，明顯達到節能的效果。

Traditionally, aerobic process has been adopted mostly in treatment of domestic sewage. However, its intensive energy input for aeration is a major disadvantage need be considered. Compared to the former, anaerobic process owns three advantages: first, it produces less sludge than the activated sludge process, second, it does not need the cost for aeration, and the last, it can produce the combustible gas, methane. Anaerobic process has been applied to treat the highly organic wastewater, and seldom used to treat the high flow rate and low concentration domestic sewage for its slow growth rate. Additionally, the immobilized-cells technology has been widely applied in many fields, with the function to contain the inoculum within a specified space and so that may efficiently retain the bacteria and able to protect the bacteria for not affecting its activity when varying the ambient environment (Liu and Chou, 2010). In order to save energy and efficiently treat the low organic domestic sewage, immobilized entrapped mixed anaerobes was utilized in this study to investigate the feasibility of treating the domestic sewage and producing the methane, and to find the optimal operational parameters. The inoculum used was the anaerobic sludge of wastewater treatment system in a pig farm. After being fabricated as the immobilized cells, it was then placed in a reactor of 3 L working volume with a packing ratio of 37.5%. The reactor was fed continuously and its temperature was controlled at 37±1°C with a water bath. In start-up stage, the reactor was fed the synthetic wastewater of 475 mg TCOD/L as influent and operated at an HRT of 12 hours. The real domestic sewage was added in the influent stream till the TCOD removal efficiency of 93% and methane content of 70% were observed. Following the start-up stage, designated tests of different HRTs from 12, 6, 4, 3, 2.4 to 2 hours were conducted and were fed the real domestic sewage with concentration of 381±102 mg TCOD/L. Samples of influent and effluent were collected and analyzed at least twice everyday. Daily gas production was recorded and the gas was sampled for component analysis. Results showed the TCOD removal efficiency was all 92% up during the whole experiment. The optimal gas production was observed in the test of HRT 4 hours, in which the methane production rate and methane content of 0.230 L CH4/L/d and59.8% were achieved, respectively. According to the experimental results, applying the immobilized entrapped mixed anaerobes could treat the domestic sewage and produce methane successfully, so as to save energy efficiently.