Low algal diversity systems are a promising method for biodiesel production in wastewater fed open reactors

Abstract

Planktivorous fish which limit zooplankton grazing have been predicted to increase algal biodiesel production in wastewater fed open reactors. In addition, tanks with higher algal diversity have been predicted to be more stable, more productive, and to more fully remove nutrients from wastewater. To test these predictions, we conducted a 14-week experiment in Houston, TX using twelve 2,270-L open tanks continuously supplied with wastewater. Tanks received algal composition (monocultures or diverse assemblage) and trophic (fish or no fish) treatments in a full-factorial design. Monocultures produced more algal and fatty acid methyl ester (FAME) mass than diverse tanks. More than 80% of lipids were converted to FAME indicating potentially high production for conversion to biodiesel (up to 0.9 T ha -1 y -1). Prolific algal growth lowered temperature and levels of total dissolved solids in the tanks and increased pH and dissolved oxygen compared to supply water. Algae in the tanks removed 91% of nitrate-N and 53% of phosphorus from wastewater. Monocultures were not invaded by other algal species. Fish did not affect any variables. Our results indicated that algae can be grown in open tank bioreactors using wastewater as a nutrient source. The stable productivity of monocultures suggests that this may be a viable production method to procure algal biomass for biodiesel production.

Biodiversity improves the ecological design of sustainable biofuel systems

“…In particular, large outdoor cultures of algae exhibit sudden catastrophic population “crashes” due to environmental fluctuations, disease, pests, and invasive species. Several studies have demonstrated the feasibility of growing algal polycultures in open outdoor ponds (Beyter et al., ; Bhattacharjee & Siemann, ; Cho et al., ; Sturm, Peltier, Smith, & deNoyelles, ), but because these studies did not simultaneously evaluate the performance for each of those same species when grown as monocultures, it is not possible to isolate the effect of species richness (as opposed to species identity) on the performance of the cultures. As a result, the hypothesis that biodiversity improves several aspects of algal biofuel cultivation remains untested under outdoor conditions.…”

Seasonal Assessment of Biomass and Fatty Acid Productivity by Tetraselmis sp. in the Ocean Using Semi-Permeable Membrane Photobioreactors

“…[10,11,19,26,30]. Thus, microalgal culture strategies combined with treatment of wastewaters and utilization of flue gas have been recognized as costeffective and eco-friendly strategies [2,9,12,14,29].…”

Comparative study for the treatment of domestic wastewater using Chlorella Vulgaris

“…The most eco-friendly and economical technique for wastewater treatment is with biological methods, where chemical break down and treatment of residues is done by microorganisms also with the production of value-added compounds [10,11]. Many studies have proposed microalgae as an alternative biological treatment that e ciently removes nutrients from wastewater even when nutrient concentrations are high [12,13,14,15,16] as municipal wastewater is enriched with essential nutrients which support algal biomass production [17,18].…”

“…Literature has been reported with nitrogen (>90%) and phosphorus (>50%) removal using microalgae [11]. Chlorella Vulgaris can effectively remove nitrogen (up to 81-85%) and phosphorus (32-36%), respectively [19], Galdieria sulphuraria when used removed ammoniacal nitrogen (63-89%) and phosphorus (71-95%), respectively [20].…”