INFLUENCE OF HYDRAULIC RETENTION TIME ON HYDROGEN PRODUCTION BY TREATING CHEESE WHEY WASTEWATER IN ANAEROBIC FLUIDIZED BED BIOREACTOR - AN APPROACH FOR DEVELOPING COUNTRIES

Abstract This study assessed the effect of hydraulic retention time (HRT) on biohydrogen production by dark fermentation using an anaerobic fluidized bed reactor fed with cheese whey synthetic wastewater. The reactor of 1.2 L was operated with an approximate carbohydrate concentration of 2800 mg L-1, and HRTs of 6, 4, 2, 1 and 0.5 h. Acetic and butyric acids were the main metabolites produced in the reactor. The hydrogen production increased from 0.039 to 1.43 L-H2 h-1 L-1-reactor as the HRT decreased from 6 to 0.5 h. The best hydrogen yield (HY) (2.73 mol-H2 mol-carbohydrate-1) and carbohydrate consumption (81.02%) were achieved at a HRT of 6 h (12.34 kg-COD m-3 d-1) followed by the HY of 2.43 mol-H2 mol-carbohydrate-1 at a HRT of 0.5h (163.02 kg-COD m-3.d-1). An increase in the influent pH in the operational phase 05 (HRT of 0.5 h) favored hydrogen production despite the reduced carbohydrate conversion compared to phase 01 (HRT of 6 h). In both conditions, the reactor presented the highest amount of acetic acid, indicating that the acetate route favored the hydrogen yield production. The HRT reduction led to an increase in microbial diversity, as evidenced by the Shannon-Wiener coefficient of 2.586, which corresponds to the operational phase with a HRT of 2 h.

摘要 本研究评估了水力停留时间（hydraulic retention time, HRT）对以合成干酪乳清废水为进料的厌氧流化床反应器暗发酵生物制氢效果的影响。本研究所用的1.2 L反应器采用初始碳水化合物浓度约为2800 mg·L⁻¹的进料，水力停留时间分别设置为6、4、2、1和0.5 h。反应器内主要代谢产物为乙酸与丁酸。随着水力停留时间从6 h降至0.5 h，反应器的产氢速率从0.039提升至1.43 L-H₂·h⁻¹·L⁻¹（反应器容积）。当水力停留时间为6 h时，系统取得最优产氢率（hydrogen yield, HY）为2.73 mol-H₂·mol-碳水化合物⁻¹，碳水化合物去除率达81.02%，对应的容积有机负荷为12.34 kg COD·m⁻³·d⁻¹；其次为水力停留时间0.5 h时的产氢率2.43 mol-H₂·mol-碳水化合物⁻¹，其容积有机负荷为163.02 kg COD·m⁻³·d⁻¹。在运行阶段05（水力停留时间0.5 h）中，进水pH升高可促进产氢，尽管相较于阶段01（水力停留时间6 h），此时的碳水化合物转化率有所降低。在两种工况下，反应器内乙酸含量均为最高，表明乙酸代谢途径更利于提升产氢率。水力停留时间的缩短会提升微生物多样性，这一点可由对应水力停留时间2 h的运行阶段的香农-威纳指数（Shannon-Wiener coefficient）为2.586得到验证。