open access

https://hdl.handle.net/2115/45460

Removal of residual dissolved methane gas in an upflow anaerobic sludge blanket reactor treating low-strength wastewater at low temperature with degassing membrane

英語

Low-strength wastewater

2011

Elsevier

Water Research

45(11)

3533-3540

In this study, we investigated the efficiency of dissolved methane (D-CH4) collection by degasification from the effluent of a bench-scale upflow anaerobic sludge blanket (UASB) reactor treating synthetic wastewater. A hollow-fiber degassing membrane module was used for degasification. This module was connected to the liquid outlet of the UASB reactor. After chemical oxygen demand (COD) removal efficiency of the UASB reactor became stable, D-CH4 discharged from the UASB reactor was collected. Under 35°C and a hydraulic retention time (HRT) of 10 h, average D-CH4 concentration could be reduced from 63 mg COD L–1 to 15 mg COD L–1; this, in turn, resulted in an increase in total methane (CH4) recovery efficiency from 89% to 97%. Furthermore, we investigated the effects of temperature and HRT of the UASB reactor on degasification efficiency. Average D-CH4 concentration was as high as 104 mg COD L–1 at 15°C because of the higher solubility of CH4 gas in liquid; the average D-CH4 concentration was reduced to 14 mg COD L–1 by degasification. Accordingly, total CH4 recovery efficiency increased from 71% to 97% at 15°C as a result of degasification. Moreover, degasification tended to cause an increase in particulate COD removal efficiency. The UASB reactor was operated at the same COD loading rate, but different wastewater feed rates and HRTs. Although average D-CH4 concentration in the UASB reactor was almost unchanged (ca. 70 mg COD L–1) regardless of the HRT value, the CH4 discharge rate from the UASB reactor increased because of an increase in the wastewater feed rate. Because the D-CH4 concentration could be reduced down to 12 ± 1 mg COD L–1 by degasification at an HRT of 6.7 h, the 3 CH4 recovery rate was 1.5 times higher under degasification than under normal operation.

学術雑誌論文

Accepted Manuscript

0043-1354

AA00886427