Treatment of Domestic Sewage by Using the Entrapped Mixed Anaerobes
Date Issued
2015
Date
2015
Author(s)
Lin, Shiou-Jing
Abstract
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.
Subjects
Anaerobic digestion
Domestic sewage
Immobilized cells
Entrapped mixed anaerobes
Methane
Type
thesis
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