Scale-up of algae growth system to cleanse wastewater and produce oils for biodiesel production

Biofuels are a currently a very hot topic with significant interest in both ethanol and biodiesel production. These fuels can be used in current internal combustion engines with little or no modification. Biodiesel can be produced from a variety of sources. One of the most promising sources is microalgae. In some species of algae, oil or lipids can account for as much as 70% of their total biomass. Unfortunately, the cost to produce biodiesel from algae is much too high to compete with petroleum-based fuels. To reduce the production cost of algae, wastewater has been discovered to be an excellent growth media. For this study, Chlorella sp., Scenedesmus sp., and Chlamydomonas sp. were selected to test their ability to grow on wastewater growth media while cleansing the water of contaminants and producing oil. Lab tests in 10L tanks showed that all three species grow well and provide excellent treatment of municipal wastewater by reduction of ammonia, nitrate, and phosphate at levels of 99%, 87%, and 99%, respectively. After successful lab tests, a 230L (60 gal.) pilot tank was constructed to demonstrate scalability of the growth system. Scenedesmus was selected for growth tests at the pilot scale. Six growth tests of one week each were conducted at two light levels and three temperatures to investigate the effects these parameters have on the growth rate and nutrient uptake. In the pilot scale tests, Scenedesmus was shown to cleanse the water as efficiently as at the lab scale achieving nutrient reductions of over 99% for ammonia and phosphate. Biomass production was also shown to be very high at the pilot scale with accumulations of biomass greater than the predicted yield for five of the six tests