Sharma Mona

Hydrogen production and metal-dye bioremoval by a Nostoc linckia strain isolated from textile mill oxidation pond

Biohydrogen production by Nostoc linckia HA-46, isolated from a textile-industry oxidation-pond was studied by varying light/dark period, pH, temperature and ratio of carbon-dioxide and argon in the gas-mixture. Hydrogen production rates were maximum under 18 h of light and 6 h of darkness, pH 8.0, 31°C, a CO(2):Ar ratio 2:10. Hydrogen production of the strain acclimatized to 20 mg/L of chromium/cobalt and 100 mg/L of Reactive red 198/crystal violet dye studied in N-supplemented/deficient medium was 6-10% higher in the presence of 1.5 g/L of NaNO(3). Rates of hydrogen production in the presence of dyes/metals by the strain (93-105 μmol/h/mg Chlorophyll) were significantly higher than in medium without metals/dyes serving as control (91.3 μmol/h/mg Chlorophyll). About 58-60% of the two metals and 35-73% of dyes were removed by cyanobacterium. Optimal conditions of temperature, pH and metals/dyes concentration for achieving high hydrogen production and wastewater treatment were found practically applicable as similar conditions are found in the effluent of regional textile-mills.

Integrating photobiological hydrogen production with dye–metal bioremoval from simulated textile wastewater

The study reports production of hydrogen in photobioreactors with free (PBR(Fr)) and immobilized (PBR(Imm)) Nostoc biomass at enhanced and sustained rates. Before running the photobioreactors, effects of different immobilization matrices and cyanobacterial dose on hydrogen production were studied in batch mode. As hydrogen production in the PBRs declined spent biomass from the photobioreactors were collected and utilized further for column biosorption of highly toxic dyes (Reactive Red 198+Crystal Violet) and metals (hexavalent chromium and bivalent cobalt) from simulated textile wastewater. Breakthrough time, adsorption capacity and exhaustion time of the biosorption column were studied. The photobioreactors with free and immobilized cyanobacterium produced hydrogen at average rates of 101 and 151 μmol/h/mg Chl a, respectively over 15 days, while the adsorption capacity of the spent biomass was up to 1.4 and 0.23 mg/g for metals and 15 and 1.75 mg/g for the dyes, respectively in continuous column mode.