No abstract

No abstract

No abstract

BACKGROUND: In the presence of light, micro-algae convert CO 2 and nutrients to biomass that can be used as a biofuel. In closed photo-bioreactors, however, light and CO 2 availability often limit algae production and can be difficult to control using traditional diffuser systems. In this research, a hollow fiber membrane photo-bioreactor (HFMPB) was investigated to: (1) increase the interfacial contact area available for gas transfer, (2) treat high nutrient strength (412 mg NO 3 − -N L −1 ) wastewater, and (3) produce algal biomass that can be used as a biofuel.

Sulfur-utilizing perchlorate (ClO 4 -)-reducing bacteria were enriched from a denitrifying wastewater seed with elemental sulfur (S 0 ) as an electron donor. The enrichment was composed of a diverse microbial community, with the majority identified as members of the phylum Proteobacteria. Cultures were inoculated into bench-scale packed bed reactors (PBR) with S 0 and crushed oyster shell packing media. High ClO 4 concentrations (5-8 mg/L) were reduced to <0.5 mg/L at an empty bed contact time (EBCT) of 13 h. Low ClO 4concentrations (60-120 µg/L), more typical of contaminated groundwater sites, were reduced to <4 µg/L at an EBCT of 7.5 h. PBR performance decreased when effluent recirculation was applied or when smaller S 0 particle sizes were used, indicating that mass transfer of ClO 4 to the attached biofilm was not the limiting mechanism in this process, and that biofilm acclimation and growth were key factors in overall reactor performance. The presence of nitrate (6.5 mg N/L) inhibited ClO 4 reduction. The microbial community composition was found to change with ClO 4availability from a majority of Beta-Proteobacteria near the influent end of the reactor to primarily sulfur-oxidizing bacteria near the effluent end of the reactor.