Nutrient removal from swine wastewater using a thermotolerant strain of Chlorella sp. grown under outdoor conditions

BACKGROUND Recently, wastewater effluents from animal farms have been treated using microalgae for the removal of organic and inorganic compounds. Swine wastewater (SW) and wastewater treated by anaerobic digestion (TW) were used as culture media for a wild strain of microalga, Chlorella sp. (Chlorophyta), previously isolated for our research group. This was cultivated under laboratory conditions in a batch culture, and then inoculated in a cascade thin-layer reactor under outdoor conditions. The kinetic behavior, nutrient removal (COD, NH4+-N, NO3--N and PO34--P) efficiency and biochemical composition of the microalga biomass were evaluated. RESULTS SW supported the highest growth (339 x 10(6) cells mL(-1) and mu = 0.42 d(-1)) and the maximal removal of COD (91%), nitrates (87%), ammonium (45%) and phosphate (70%) in a batch culture. Whereas, in continuous cultivation, an adequate operation was achieved at temperatures up to 42 degrees C, with removals greater than 80% of COD, 70% of nitrates, 90% of ammonium and 60% of phosphates. Also, the produced biomass achieved the highest content of proteins (386 mg g(-1) dry weight), carbohydrates (291.49 mg g(-1) dry weight) and saturated and monounsaturated fatty acids, reaching 74.76% of total fatty acids. CONCLUSIONS The SW medium showed greater growth of Chlorella than TW using the outdoor thin-layer cascade reactor. This is an opportunity to use wastewater as nutrient to obtain biomass enriched in compounds with various possibilities for application. (c) 2019 Society of Chemical Industry