Cultivo de microalgas em fotobiorreatores de placas planas para a produção de biomassa e biorremediação de efluente da agroindústria de óleo de palma

Abstract

Currently the Brazilian production of palm oil exceeds 300,000 tons per year and it is expanding. The palm oil mill efluent (POME) is the main liquid effluent generated by the palm oil industry. For each ton of oil are needed from 5 to 7.5 tonnes of water and about 50% of this volume ends up as effluent. Conventionally, POME is treated in stabilization ponds, consisting of a series of anaerobic and aerobic tanks that may require up to 100 days for treatment. The use of microalgae for wastewater treatment is a biological low-cost process, which is capable to accelerate the removal of inorganic compounds, especially nitrogen and phosphorus. Furthermore, it is possible to use algal biomass produced (rich in commercially valuable molecules) for energy production, animal feed and pigments, for example. Thus, this study evaluated the bioremediation capacity and biomass production in effluent POME stabilization pond (ELE-POME) of microalgae strains Chlamydomonas biconvexa Embrapa|LBA 40 and Tetranephris sp. Embrapa |LBA 52 from the microorganisms and microalgae collection applied to Agroenergia e Biorrefinarias of Embrapa Agroenergia. Microalgae were cultivated in photobioreactors air lift flat plates with 15L capacity, using artificial lighting in cycles of 12 h/12 h light/dark and supplemental CO2. Independent batch cultivation were performed for 5, 10 and 15 days using as culture mediums ELE-POME and BBM (synthetic control medium). The three times were chosen in order to evaluate the influence of the cultivation time on cell growth rate and on the medium nutrient removal. Based on the results described in this work, we conclude that the ELE-POME can be used as a culture medium for the production of microalgae biomass of C. biconvexa Embrapa|LBA40 and Tetranephris sp. Embrapa|LBA52 without supplementation. The time of 5 days in BBM presented the best biomass productivity results 286.87 mgL-1day-1 to Tetranephris sp. Embrapa | LBA 52 and 164,67mgL-1day-1 Chlamydomonas biconvexa Embrapa | LBA 40. Regarding the bioremediation of wastewater, the tests showed that there is significant removal of nitrogen and phosphorus, ≥60% and ≥90%, respectively, mainly during the exponential growth phase of the cells, a period that coincides with the maximum productivity of algal biomass. These results are important because they increase the technical and economic feasibility of the integration of algal cultivation to the chain of palm oil in a context of biorefinery.