Continuous bio-hydrogen production from citric acid wastewater via facultative anaerobic bacteria

Abstract

In this study, continuous biological hydrogen production using wastewater from citric acid factory as raw materials was investigated. And enrichment cultures from facultative hydrogen-producing anaerobe together with citric acid wastewater were utilized. For finding out the industrialized feasibility of continuous H 2 bio-production, the ability of H 2 -production via facultative anaerobe, optimum hydraulic retention time (HRT) and optimum volume loading rate (VLR) were also studied. The experimental results showed that facultative anaerobic bacteria could yield hydrogen as high as 0.84 mol H 2 / mol hexose consumed at the VLR of 38.4 kg COD / m 3 d . Butyric acid was the dominant product among volatile fatty acids (VFAs). An improved upward-flow anaerobic sludge blanket (UASB) reactor with a working volume 50 m 3 was used. Continuous hydrogen yield was 0.72 m 3 H 2 / m 3 reactor d under the following conditions: temperature at 35– 38 ∘ C , initial pH at 6.8–7.2, HRT = 12 h . The study also indicates that the reactor used has a better operational stability and the facultative anaerobe has an excellent adaptive capacity for organic loading rate. Furthermore, the chemical oxygen demand (COD) removal efficiency exceeded 60% and the total sugar degradation efficiency (TSDE) was close to or over 90%, even up to 96.6% at HRT of 12 h during the experiment.