A Dual Role of Marine Microalga Chlorella sp. (PSDK01) in Aquaculture Effluent with Emphasis on Initial Population Density

The marine microalga Chlorella sp. (PSDK01) was cultured in shrimp-cultured effluent under different initial population densities (IPDs) ranging from 0.25 to 12.0 g L-1 for dual purpose (excess nutrient consumption and biomass productivity). It was found that the IPD had affected the nutrient consumption and biomass significantly (P < 0.001). A higher biomass productivity compared to that of other IPDs was achieved in 0.5 g L-1 IPD, and the concentration had reached 0.78 g L-1 d(-1). In the same time, higher IPD derived higher biomass concentration (up to 5.5 g L-1) in 6 days growth, but at the end of the experiment (9th day), the biomass was slightly decreased (2 %). In the current observation, while starting IPDs 0.25-0.5 g L-1, with the increase in IPD, the biomass productivity also increased, when IPD exceed the 0.5 g L-1, the biomass productivity reversely decreased. The maximum nutrients consumption was recorded in 0.5 g L-1 IPD at the end of the experiment (9th day) as 96, 69, and 67 % for phosphate, nitrate, and nitrite, respectively. However, the highest consumption (63 %) was observed in 0.25 g L-1 on 9th day. Maximum ammonia consumption in other IPDs was resulted at 6th day, after that ammonia concentration was slightly increased from the previous concentration due to the decay of microalgae. Based on these results, to obtain the maximum nutrient consumption and biomass productivity of Chlorella sp. (PSDK01) in diverse wastewater on large-scale level, it is necessary to select a suitable IPD at around 0.5 g L-1.