Sulfidogenesis process to strengthen re-granulation for biodegradation of methanolic wastewater and microorganisms evolution in an UASB reactor.
A lab-scale methanolic wastewater-fed (3000 mg COD L-1) UASB reactor was operated for 235 days to evaluate the influence of the sulfidogenesis process on metabolic routes, the re-granulation of dispersed granules and long-term process performance. Various sulfidogenesis scenarios were created by stepwise decreasing the influent COD/SO42-ratio from 20 to 0.5 at a fixed organic loading rate (OLR) of 12 g COD L-1d-1. It was shown that the conversion of methanol to methane was stable at a wide COD/SO42-range of ≥2, attaining high biogas production rate of 3.78 ± 0.32 L L-1d-1with efficient concurrent removal of the total COD (96.5 ± 4.4%) and sulfate (56.3 ± 13.0%). The methane content in biogas remained relatively stable at 81.5 ± 1.6% for all COD/SO42-ratios tested. The particle size of the granules was shown to clearly increase as the COD/SO42-ratios decreased. A slight linear decline was noted in the number of electrons utilized by methane producing archaea (MPA) (from 98.5 ± 0.5% to 80.0 ± 2.4%), whereas consumption by sulfate reducing bacteria (SRB) increased (from 1.5 ± 0.5% to 20.0 ± 2.4%) with the decreasing COD/SO42-ratio. According to the results of activity tests and microbial community analysis, the conversion of methanol to methane at a low COD/SO42-ratio, except from Methanomethylovorans sp., depends not only on low levels of acetoclastic and hydrogenotrophic methanogens, but also on incomplete oxidizer SRB species (e.g. Desulfovibrio sp.) that utilize H2-CO2with acetate to mineralize the methanol. This serves to diversify the metabolic pathway of methanol. Further analysis through scanning electron microscopy (SEM) revealed that a lower COD/SO42-ratio favored the sulfidogenesis process and diversified the microbial community inside the reactor. The benefical sulfidogenesis process subsequently invoked the formation of a sufficient, rigid [-Fe-EPS-]nnetwork (EPS: extracellular polymeric substances), binding and immobilizing the sludge, and resulting in the re-granulation of the dispersed granules.
Department of Civil and Environmental Engineering, Graduate School of Engineering, Tohoku University, Sendai, Miyagi 980-8579, Japan. Electronic address: luxueqin0220@126.com.
Xueqin
X
Lu
Department of Civil and Environmental Engineering, Graduate School of Engineering, Tohoku University, Sendai, Miyagi 980-8579, Japan. Electronic address: zhenguangyin@163.com.
Guangyin
G
Zhen
Department of Civil and Environmental Engineering, Graduate School of Engineering, Tohoku University, Sendai, Miyagi 980-8579, Japan.
Jialing
J
Ni
Department of Civil and Environmental Engineering, Graduate School of Engineering, Tohoku University, Sendai, Miyagi 980-8579, Japan.
Kengo
K
Kubota
Department of Civil and Environmental Engineering, Graduate School of Engineering, Tohoku University, Sendai, Miyagi 980-8579, Japan; Graduate School of Environmental Studies, Tohoku University, Sendai, Miyagi 980-8579, Japan. Electronic address: gyokuyu.ri.a5@tohoku.ac.jp.
Yu-You
YY
Li
D019149:Bioreactors; D008697:Methane / Q000378:metabolism; D000432:Methanol / Q000378:metabolism*; D012722:Sewage / Q000737:chemistry; D014865:Waste Disposal, Fluid; D062065:Wastewater / Q000737:chemistry*
D008697:Methane; D000432:Methanol; D012722:Sewage; D062065:Wastewater
Extracellular polymeric substances (EPS); Granular sludge; Methane; Methanol; Microbial community shift; Sulfidogenesis