Abstract

For decades, microalgae have received a lot of attention because of their capability of using inorganic carbon (carbon dioxide, CO2) as carbon source and wastewater components as nutrients while producing biomass. On the other hand, disposal of wastewater often results in high nutrient loading into aquatic environments, which may lead to favorable conditions for undesirable phytoplankton blooms. Microalgae are efficient in removing nitrogen, phosphorus, and toxic metals from wastewater under controlled environments. During the Antarctic summer, the population in Antarctic stations tend to increase significantly, causing high stress on wastewater treatment systems. Usually, these systems are not designed for the removal of nutrients and therefore low-quality effluent are obtained. Because of this, the use of algae obtained from Antarctic becomes an interesting alternative to supplement the wastewater treatment. This alternative does not introduce species in antarctic environmental and it in summer could complement existing treatment systems. Also problems, such as resistance to long periods of low temperatures and high solar light, could be minimized. This research worked with Chlorella sp isolated from Fildes Bay on King George Island, archipelago of the South Shetland Islands. The reasons C: N: P ideals for the growth of algae were determined in synthetic media under controlled laboratory conditions. In addition, experiments with raw wastewater (pretreated) and synthetic wastewater were performed (simulating an effluent of a secondary treatment with and without disinfection). Testing wastewater were developed in two conditions of temperature and light: 15 ° C and light periods of 12 hours and uncontrolled environmental conditions, corresponding to the city of Punta Arenas in Chilean Patagonia, variable temperature between 7 and 20 ° C and exposure to typical summer light (about 16 hours). Wastewater trials were performed in one-liter reactors of methacrylate, agitated by injecting air. Samples were taken every two days for measuring total nitrogen, organic matter (COD) and phosphorus. The pH was monitored daily. Results of growth rate assay, using synthetic medium with different N:P ratios, revealed that higher values of growth rate was obtained on N:P (6:1) ratio that is similar to those found in urban wastewater. Preliminary results from tests on three types of wastewater (raw wastewater and synthetic secondary effluent with and without disinfection), showed that the system is able to maintain an approximately constant pH for 15 days. The maximum removal efficiencies of nitrogen were observed in raw wastewater under uncontrolled conditions, reaching an elimination of 55% and 85% on day 8 and 13 respectively. For the same conditions, the removal of organic matter (measured as COD filtered) peaked at 87% (8th). Phosphorus removal was not significant in all tests performed. The results show that the inclusion of Antarctic algae in wastewaters treatments represent an opportunity to improve the quality of effluent and the possible valorization of them.