Immobilization of nannochloropsis sp. in calcium alginate bead for removing nutrient in aquaculture water

Abstract

Effluent from aquaculture is high in dissolved inorganic nitrogen and phosphorus. The effluent should be treated before discharge into the aquatic environment. Biological treatment by using microalgae is widely used to remove nutrient from wastewater. The major drawback of this treatment is the difficulties to regulate and harvest the microalgae from the culture system. Immobilization of microalgae by using calcium alginate is potential to overcome the problem. Immobilization also provides a more stable matrix and better protection to the microbe and enhances nutrient removal. This study aims to improve immobilization of Nannochloropsis sp. in calcium alginate for removing excessive nutrient from the aquaculture water. Optimal formulation for immobilizing Nannochloropsis sp. in calcium alginate was 5 % (w/v) alginate solution and hardens by 2 % (w/v) CaCl2 solution. Performance of the immobilized cell was boosted by addition of nutrient during the process of immobilization. As compared to the ordinary formulation, growth rate and ammonia uptake of the nutrient-enriched immobilized cell increased by 67.9 % and 42.7 %, respectively.