Novel three-phase anaerobic digestion with cogeneration of bio-hydrogen and bio-methane.

Abstract

An investigation on anaerobic hydrogen production from carbohydrate in the leachate of solid fermentation reactor was conducted in serum bottles and continuous stirred tank reactor (CSTR) seeded with acclimated hydrogen producing inoculum to evaluate their performance under various conditions. The effects of hydraulic retention time (HRT), pH, dilution factor and inhibition of volatile fatty acid (VFA) on hydrogen production performance of the CSTR were assessed. The CSTR was operated in a thermostat-controlled temperature room of 30±1 C at a HRT of 6-10 h with an initial glucose concentration of 10-20 g/L and later fed with leachate of solid fermentation reactor (RSF). To define preliminary parameters for CSTR, it was found that the ideal pH influent was 6.5 and the dilution factor was 3 using 1 portion of extraction 1(RSF2 E1) and 2 portion of extraction 2 (RSF2 E2) using serum bottle tests. However, it was also observed that the acclimated sludge from CSTR controlled at pH 5.5 yielded the best result among all external inocula due to its ability to produce more butyrate, twice as much as the inhibitory level of 50mM at tested pH ranges. A postulation was suggested regarding the observation made during the experiment and verified during the operation of CSTR. HRT affected the hydrogen production rate and hydrogen yield. Hydrogen production rate was found to increase as HRT decreased from 8 h to 6 h during CSTR operation. The control of pH was imperative for hydrogen production and yield as pH more than 5.5 promoted methanogenic activity thus inhibiting acidogenesis. ENVIRONMENTAL ENGINEERING