11-32: Evaluation of biofuel potential through wastewater treatment using algae

The Logan City Environmental Department (Utah) operates a facility that consists of 460 acres of fairly shallow lagoons (up to 5’deep) for biological wastewater treatment that meets targets for primary and secondary treatments (solids, BOD and pathogen removal). Significant natural algal growth occurs in these lagoons, which improves BOD removal through oxygenation and also facilitates N removal through volatilization as ammonia at high pH conditions created by algal growth. Phosphorus, however, is non-volatile and stays in water and likely cycles in and out of algal cells as they grow and die in the lagoons.   Recently, the regulatory limits on phosphorus released from the Logan wastewater treatment facility have been significantly lowered to counter potential downstream eutrophication.  One way to potentially lower phosphorus levels in the wastewater effluent is through management of algal growth in the lagoons. As mentioned above, algae growth naturally occurs in the treatment lagoons and if the algal biomass is harvested when growth yields are highest, the phosphorus contained in the cells could be removed as well. The algal biomass could then be used for production of biodiesel, biomethane, and biohydrogen. We have collected pH, dissolved oxygen, temperature, nutrient, BOD, and suspended solids data from the lagoon system over several years.  Analysis of this data as it pertains to algal biomass productivity due to seasonal variation and treatment system operation will be presented. Strategies for management of the wastewater treatment system to improve algal productivity while achieving treatment goals will also be presented.