Most previous studies on continuous hydrogen fermentation were performed using simple hydrolysates (glucose and sucrose). However there are few reports on continuous operation using biopolymers like starch. In the research, effect of HRT on continuous hydrogen production in CSTR was investigated using corn starch as a substrate. The operation lasted for 128 days. Organic acid concentrations were observed on daily basis. VFA profile supported the fact that B/A ratio was the most important parameter to justify hydrogen yield at various HRTs. Highest hydrogen yield of 0.92 $mol.H_2/mol.hexose_{added}$ was observed at 12 hr HRT. Estimation modeling of homoacetogenism was also performed and quantification of hydrogen consuming acetate, at various HRTs, was evaluated. In addition, microbial characteristics at various HRTs were explored using PCR-DGGE analysis.
Sequencing batch reactor processes offer distinct advantages when compared with continuous processes, including a high degree of process flexibility and no requirement for a separate clarifier. The characteristics of the reactor should therefore be compared with CSTR in continuous hydrogen production. Besides, little is known about effect of process intensification to maintain higher biomass on hydrogen production using ASBR. Feasibility of continuous hydrogen fermentation with varying HRTs in ASBR was observed using starch as a substrate. It was concluded that continuous hydrogen production in ASBR was impossible with varying HRTs unless it was converted in to CSTR in between while varying HRTs. Therefore, unbiased effect of various HRTs on $H_2$ producing ASBR in continuous mode was evaluated. Maximum $H_2$ yield of 0.58 $mol.H_2/mol.glucose_{added}$ was witnessed at 12 hr HRT. Homoacetogenism was found to be the major factor for inefficient performance of ABSR producing $H_2$. ASBR was found very efficient in glucose removal. PCR-DGGE analysis was also performed to identify the competent species of microorganisms for substrate utilization at each HRT.
ASBR was found inefficient in $H_2$ production as compared to CSTR under continuous mode. Sludge characteristics of ASBR producing $H_2$ should therefore be explored to identify the reason of low $H_2$ productivity in ASBR. Effect of stratification in settling phase on $H_2$ producing ASBR was observed using batch experiment. It was found that specific $H_2$ activity of decanting non-settleable sludge is more as compared to settleable sludge. In addition, effect of settling time on settleable sludge in $H_2$ producing ASBR was also analyzed. Settling time was also found to be an important parameter in hydrogen producing ASBR besides R/S ratio. It was observed that the long the microorganisms were contained in the settling phase, the lower would be their specific hydrogen activity and vice versa.
기존연구는 대부분 간단한 기질(글루코스, 자당)을 이용한 실험이었으며, 녹말같이 복잡한 구조의 기질에 대한 연구는 미비하였다. 본 연구에서는 옥수수 녹말을 기질로 이용하여 CSTR 반응조의 수소발효에서 HRT의 영향을 고찰하였다. 총 128일동안 운전하였으며, 유기산의 조성을 분석한 결과 뷰틸산/아세트산의 비가 수소 생산과 매우 밀접한 관계를 보였으며, HRT 12시간에서 가장 높은 수소 전환율, 0.92 $mol H_2/mol hexose_{added}$ 가 관찰되었다. 수소를 소모하며 아세트산을 생성하는 기작과 미생물 분석이 각각의 조건에서 분석되었다.
SBR은 CSTR에 비하여 많은 장점을 지니고 있다고 알려져 있기 때문에 본 연구에서는 수소발효에서 SBR을 운전해 보았다. SBR로 운전할 경우는 CSTR 보다 더 낮은 수소 전화율을 보였다. 최대 수소생산율도 마찬가지로 HRT 12시간에 0.58 $mol H_2/mol hexose_{added}$ 이었다. 수소를 소모하며 아세트산을 생성하는 기작과 미생물 분석이 각각의 조건에서 분석되었으며, SBR운전은 CSTR에 비하여 기질 분해율이 훨씬 높았다.
ASBR은 CSTR보다 훨씬 수소생산에 불리하다고 판명되었으며, SBR에서 침전 시간에 따른 슬러지의 수소발효 성능을 관찰해본 결과 잘 침전하지 않는 미생물이 더 높은 수소생산 활성을 띄고 있었다.
