Study on cultivating Chlorella in RO brine and wastewaters

In order to reduce the cost of cultivating microalgae and reclaiming of wastewaters, wastewaters from different locations within a wastewater treatment plant were selected and blended with reverse osmosis (RO) concentrate and used as a culture media. In this study, Chlorella sp. was grown to evaluate 6 different waters as culture media; primary effluent, secondary effluent, digester supernatant and then each of these blended with a RO discharge concentrate. These tests were used to determine which culture medium blend could provide the best growing conditions. Growing occurring at different temperatures was also investigated. Results showed that the chlorella biomass growth was stimulated and increased when blending the RO concentrate and its minerals with the wastewaters. The digester supernatant -RO concentrate blend was found to be the best of the different media combinations evaluated. After 15 days of incubation, the chlorella biomass growth in the 0%~90% (by volume) RO concentrate blends increased from 315% to 780% above the initial biomass levels. The 30% RO concentrate blend was found to be the most favorable. Overall, growth of the 0%~90% RO concentrate blends evaluated at 10℃, 20℃ and 30℃ demonstrated biomass increases from 140% to 570%. The temperature where better growth of Chlorella in the 0%~90% RO concentrate blends occurred was 20℃.