Effect of compound fertilizer on anaerobic fermentation types in hydrogen bio-production reactor

Effect of compound fertilizer (nitrogen, phosphor) on anaerobic fermentation types in hydrogen bioproduction (HBP) from CST reactor was studied. The organic load rate (OLD) was maintained at 21.8 kg COD/m³·d during the experiments. The compound fertilizer of N/P dosing was 40, 20, 10 and 0 mg/L, respectively. After 20 days operation, the fermentation type was converted from butyric type to ethanol type. During the period, the biogas production kept steady, while hydrogen yield was increased. The results indicated that nutrition was one of the most important factors which affected the fermentation types. In the experiments, adding N, P-compound fertilizer more than 10 mg/L conduce to the establishment of butyric-type fermentation, lower than 10 mg/L, the ethanol-type fermentation would come into being. The ORP and pH was not affected obviously by the nutrition dosage. In the HBP reactor, special microbe was the precondition of the fermentation type, but the other factors such as nutrition also have significant effects on the formation of ethanol-type fermentation.