Patama Lerksasen and Chalermraj Wantawin

pp. 1675 - 1683

Abstract

Spirulina platensis strain BP immobilized on fibrous polyester mat was applied for nitrogen removal from simulated shrimp pond water. Different S. platensis mass on mat was built up during immobilizing process by varying the amount of batch fed suspended S. platensis cells. During immobilization, 0.2 OD₅₆₀ S. platensis was replenished to reactor and chlorophyll-a in the solution was monitored. The immobilized S. platensis mass was 63, 49 and 19 g dw-S. platensis/m² for Sp V-1, Sp IV-1 and Sp II-1 mat reactors adding five, four and two times of 0.2 OD₅₆₀ S. platensis respectively. In accordance with statistic, the results of nitrogen removal tests by applying those immobilized mats in circulated batch system reactors loaded with 1.94 gN/m² -d showed that there were significant differences on ammonia removal among the different initial S. platensis mass on mats (ANOVA; P≤0.05). The Sp V-1, Sp IV-1 and Sp II-1 mats could reduce the ammonia nitrogen concentration from 1 mg-N/L to the level as low as 0.18 mg-N/L within 2 weeks. Transformation of 75-81% ammonia nitrogen to organic nitrogen in microalgal cells, of which 27-43% were detached to solution, resulted to 44-58% total nitrogen removed from the system.