Microalgae are one of the most effective biological sources for renewable energy production. They can be produced at rates that can be 50 times more than that of the conventional crops. They have a production capacity throughout the year. Comparing with other biomass sources such as terrestrial, agricultural and solid waste, algal biomass provides a more stable and manageable energy production system. However, there are some constraints for efficient microalgae production such as the need for large quantities of nutrients, high cost of installations and operation of production systems. For these reasons, using wastewaters obtained from different processes as a medium to grow microalgae has attracted new research interest. In the present study, the aqueous phase obtained from hydrothermal carbonization of orange pomace was utilized as a nutrient source in Chlorella minutissima growth. Different dilution rates (50x, 100x, 200x and 400x) were used to observe the effect of aqueous phase concentration on algal growth during 30 days. According to the results of microalgae cultivation, the medium with the lowest dilution rate was determined as the optimum medium because of giving the best growth value compared to other dilution rates.