Performance of rice husk biocarrier on ammonia nitrogen removal in the MBBR treating aquaculture wastewater using biological attached growth process: Performance and kinetic study
Fereshteh Alitaleshi, Allahyar Daghbandan, Alireza Pendashteh
Abstract
This study investigates the feasibility of using rice husk (RH) as a cost-effective and environmentally friendly bio-carrier for immobilizing isolated microorganisms to treat synthetic recirculating aquaculture system (RAS) wastewater. Two moving bed biofilm reactors (MBBR) inoculated with indigenous microorganisms were operated simultaneously for 391 days under various cycle times and compared. The RH and Kaldnes-3 (K3) bio-carriers were placed in reactors R1 and R2, respectively. The results indicated that at constant influent TAN, with increases in cycle time from 6 to 24 h, TAN and COD removal efficiencies increased in both bioreactors ; but at an optimum cycle time of 6 h, the TAN and COD removal efficiencies were 82 ± 1.5% and 77.9 ± 1.7% for the R1 and, 89.9 ± 3.3% and 84 ± 1.2% for the R2, respectively. Also, at a constant cycle time, the performance of R2 was better compared to R1 filled with RH. Microbial identification confirmed the presence of four dominant genera, including Arthrobacter , Bacillus , Rhodococcus , and Staphylococcus, which were heterotrophic nitrification bacteria (HNB). The TAN removal kinetics were investigated using a Modified Stover-Kincannon (MSK) model. In reactors R1 and R2, the biokinetic constants were determined to be U max : 0.116 and 0.149 g/Lday, and K B : 0.158 and 0.182 g/Lday, respectively. The correlation coefficients (R 2 ) of the MBBRs were higher than 0.97, indicating that the model adequately described the experimental data.