Hydrogen Production by a Floating-Type Photobioreactor

Abstract

We have succeeded in continuously producing H-2 over three months using a floating-type photobioreactor, artificial light (halogen lamp), artificial raw waste water (identical to the effluent of an anaerobic pre-treatment process), and Rhodopseudomonas palustris R-l. The goal was to determine the specifications of artificial raw waste water, whose constituents compel bacteria to produce H-2. We eliminated nutrients such as P, K, N, Fe, Ca, vitamin, and yeast-extract, which caused bacteria to grow instead of producing H-2. The raw waste water contained 800 mg/L each of acetate, propionate, and butyrate and 400 mg/L of ethanol, which are the suitable electron donors for H-2 photoproduction. A thermostat controlled liquid temperature at 35 degrees C, and 24 halogen lamps illuminated the reactor surface for 24 h at 434 W/m(2). The raw waste water was fed at 0.8 L/day to the reactor. The bacteria separated from the pre-culture was added to the reactor several times during the experiment. We accumulated 85 L of gas during 1583 h. The H-2 content in the gas was nearly 85% and CH4 was less than 1%. N-2 was less than 6% and O-2 was not detected. The gas production rate was 100-300 mL/L.day during the early stage and 300-500 mL/L.day in the later stage. The efficiency of light conversion to H-2 was 0.308%.