Optimization of pilot high rate algal ponds for simultaneous nutrient removal and lipids production

Special attention is required to the removal of nitrogen and phosphorous in treated wastewaters. Although, there are a wide range of techniques commercially available for nutrient up-take, these processes entail high investment and operational costs. In the other hand, microalgae growth can simultaneously remove inorganic constituents of wastewater and produce energy rich biomass. Among all the cultivation technologies, High Rate Algae Ponds (HRAPs), are accepted as the most appropriate system. However, the optimization of the operation that maximizes the productivity, nutrient removal and lipid content in the biomass generated has not been established. In this study, the effect of two levels of depth and the addition of CO₂ were evaluated. Batch essays were used for the calculation of the kinetic parameters of microbial growth that determine the optimum conditions for continuous operation. Nutrient removal and lipid content of the biomass generated were analyzed. The best conditions were found at depth of 0.3m with CO₂ addition (biomass productivity of 26.2gTSSm^-2d^-1 and a lipid productivity of 6.0glipidsm^-2d^-1) in continuous mode. The concentration of nutrients was in all cases below discharge limits established by the most restrictive regulation for wastewater discharge.