Influence of Cu2+ concentration on the biohydrogen production of continuous stirred tank reactor

In this paper, the effect of hydraulic retention time (HRT, 16 h–4 h) on fermentative hydrogen production by mixed cultures was firstly investigated in a sucrose-fed anaerobic continuous stirred tank reactor (CSTR) at 35 °C and initial pH 8.79. After stable operations at HRT of 16–6 h, the bioreactor became unstable when the HRT was lowered to 4 h. The maximum hydrogen yield reached 3.28 mol H2/mol-Sucrose at HRT 4 h. Supplementation of Cu2+ at HRT 4 h improved the operation stability through enhancement of substrate degradation efficiency. The effect of Cu2+ concentration ranging from 1.28 to 102.4 mg/L on fermentative hydrogen production was studied. The results showed that Cu2+ was able to enhance the hydrogen production yield with increasing Cu2+ concentration from 1.28 to 6.4 mg/L. The maximum hydrogen yield of 3.31 mol H2/mol-Sucrose and the maximum hydrogen production rate of 14.44 L H2/Day/L-Reactor were obtained at 6.4 mg/L Cu2+ and HRT 4 h Cu2+ at much higher concentration could inhibit the hydrogen production, but it could increase substrate degradation efficiency (12.8 and 25.6 mg/L Cu2+). The concentration of Cu2+ had effect on the distribution of soluble metabolite.