Evaluation of an anaerobic baffled reactor (ABR) – downflow hanging sponge (DHS) system in treatment of black wastewater from a closed recirculating aquaculture system

• Published in: Aquacultural engineering Vol. 100; p. 102303
• Main Authors: Kotcharoen, Wilasinee, Watari, Takahiro, Adlin, Nur, Tran P., Thao, Satanwat, Penpicha, Pungrasmi, Wiboonluk, Powtongsook, Sorawit, Takeuchi, Yutaka, Hatamoto, Masashi, Yamazaki, Shinichi, Yamaguchi, Takashi
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-02-2023
• Subjects: Anaerobic baffled reactor; Denitrification; DHS; Nitrification; Nitrogen removal; Recirculating aquaculture system; Nitrogen removal; Denitrification; Recirculating aquaculture system; Anaerobic baffled reactor; DHS; Nitrification
• ISSN: 0144-8609; 1873-5614
• DOI: 10.1016/j.aquaeng.2022.102303

This study focused on evaluating the nitrogen and solids removal performance of a laboratory-scale anaerobic baffled reactor (ABR) – downflow hanging sponge (DHS) system for treating black wastewater from a closed recirculating aquaculture system (RAS) under a salinity of 15‰. The system was investigated under a controlled temperature (35 °C) with total organic carbon/total nitrogen (TOC/TN) ratios of 1.8, 2.5, 0.3, and 3.0, which corresponded to Phases 1, 2, 3, and 4, respectively, for 500 days. The ABR achieved a nitrate removal efficiency of 95–99 % at TOC/TN ratios higher than 1.8. The nitrate removal efficiency significantly decreased from 98 % to 12 % when the TOC/TN ratio decreased from 3.0 to 0.3. The highest TN removal efficiency (94 ± 4 %) was achieved with a TOC/TN ratio of 3.0. The ABR could remove 97 ± 6 % of the suspended solids during the entire experimental period. The DHS reactor achieved a nitrification efficiency of 70 % with short hydraulic retention times of 0.11–0.28 min. Total ammonia nitrogen in the DHS effluent was less than 1.0 mg N/L in the stable condition. The denitrifying Thauera genera predominant in the ABR reactor led to a high degree of denitrification. Methanogenic organisms such as Methanobacterium and Methanosaeta contributed to methane production of 0.8 ± 0.4 L/d in the ABR at a TOC/TN ratio of 3.0. Microbial community structure analysis showed that nitrifying microorganisms, such as Nitrosomonas, Nitrospira, and Candidatus Nitrosopumilus, were detected in the DHS-retained sludge. These results indicate that the ABR–DHS system evaluated could be applied for the removal of nitrogen and solids from RAS derived black wastewater to meet the water quality level needed for production-scale RAS.
•ABR-DHS system applied in treatment of RAS-black wastewater under salinity 15‰.•The ABR-DHS effluent met the water quality levels for RAS.•ABR performed 95–99 % of nitrate removal efficiency with TOC/TN ratio over 1.8.•DHS reactor achieved 70 % of TAN removal efficiency with short HRTs 0.11–0.28 min.•TOC/TN changes from 0.3 to 3.0 affects microbial community greatly.