PERFORMANCE OF TWO-PHASE UASB REACTOR IN ANAEROBIC TREATMENT OF WASTEWATER
WITH SULFATE

Oh, Sae Eun

doi:2007.12.1.8

Environmental Engineering Research 2007;12(1): 8-15. DOI: https://doi.org/10.4491/eer.2007.12.1.008

PERFORMANCE OF TWO-PHASE UASB REACTOR IN ANAEROBIC TREATMENT OF WASTEWATER WITH SULFATE

Sae Eun Oh^†

Dept. of Environmental Engineering, Hanbat National University, San 16-1, Dukmyung-dong, Yuseong-gu, Daejeon, 305-719

Corresponding Author: Sae Eun Oh ,Tel: +82-42-821-1263, Fax: : +82-42-821-1476, Email: saeun@hanbat.ac.kr

Received: January 5, 2007; Accepted: January 22, 2007.

ABSTRACT

Two phase UASB reactors for treating wastewater with sulfate were operated to assess the performance and competition of organics between sulfate reducing bacteria(SRB) and methane producing bacteria(MPB), and the change of characteristics of microorganisms. The reactors were fed in parallel with a synthetic wastewater of 4,000-5,000 mgCOD/L and sulfate concentration of 800-1,000 mgS0<sub>4</sub>/L. In the MPR(methane producing reactor) and CR(control reactor), COD removal efficiencies were 90% and 60%, respectively, at the OLR(organic loading rate) of 6 gCOD/L, while the amount of biogas and methane content were 6.5 L/day and 80%, and 3 L/day and 50%, respectively. However, the portion of electron flow used by SRB at the OLR of 6 gCOD/L • day in MPR and CR was 3% and 26%, respectively. This indicated that the increase of OLR of wastewater containing high sulfate like CR resulted in activity decrease and cell decay of MPB, while SRB was adapted immediately to new environment. The MPB activities in MPR and CR were 2 and 0.38 kgCH<sub>4</sub>-COD/gVSS • day at the OLR of 6 gCOD/L ■ This indicated hat SRB dominated gradually over MPB during long-term operation with wastewater containing sulfate as a consequence of outcompeting of SRB over MPB. In addition, the solution within AFR was maintained around pH 5.0, the MPB such as Methanothrix spp. which was very important to formation of granules was detached from the surface of granules due to the decrease of activity by limitation of substrate transportation into MPB. Therefore, a significant amount of sludge was washed out from the reactor.

Keywords: Anaerobic treatment | UASB | Sulfate reducing bacteria | Methanogens | Sulfate