초록
<P>The potential of a pilot high rate algal pond (HRAP) interconnected via liquid recirculation with an external absorption column for the simultaneous removal of H<SUB>2</SUB>S and CO<SUB>2</SUB> from biogas using an alkaliphilic microalgal-bacterial consortium was evaluated. A bubble column was preferred as external absorption unit to a packed bed column based on its ease of operation, despite showing a comparable CO<SUB>2</SUB> mass transfer capacity. When the combined HRAP-bubble column system was operated under continuous mode with mineral salt medium at a biogas residence time of 30 min in the absorption column<SUB>,</SUB> the system removed 100% of the H<SUB>2</SUB>S (up to 5000 ppm<SUB>v</SUB>) and 90% of the CO<SUB>2</SUB> supplied, with O<SUB>2</SUB> concentrations in the upgraded biogas below 0.2%. The use of diluted centrates as a free nutrient source resulted in a gradual decrease in CO<SUB>2</SUB> removal to steady values of 40%, while H<SUB>2</SUB>S removal remained at 100%. The anaerobic digestion of the algal-bacterial biomass produced during biogas upgrading resulted in a CH<SUB>4</SUB> yield of 0.21–0.27 L/gVS, which could satisfy up to 60% of the overall energy demand for biogas upgrading. This proof of concept study confirmed that algal-bacterial photobioreactors can support an integral upgrading without biogas contamination, with a net negative CO<SUB>2</SUB> footprint, energy production, and a reduction of the eutrophication potential of the residual anaerobic effluents.</P><P><B>Graphic Abstract</B><BR><IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/esthag/2014/esthag.2014.48.issue-1/es403596m/production/images/medium/es-2013-03596m_0001.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/es403596m'>ACS Electronic Supporting Info</A></P>