Discharge management in fresh and brackish water RAS: Combined phosphorus removal by organic flocculants and nitrogen removal in woodchip reactors |
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| Institution: | 1. Department of Biological and Environmental Science, University of Jyväskylä, P.O. Box 35, 40014Jyväskylä, Finland;2. Natural Resources Institute Finland (LUKE), Survontie 9A, 40500Jyväskylä, Finland;1. Fisheries and Oceans Canada, Gulf Fisheries Centre, 343 Université Ave., Moncton, NB, E1C 9B6, Canada;1. Korea Institute of Ocean Science and Technology, Busan, Republic of Korea;2. Sekwang Engineering Consultants CO., LTD, Seoul, Republic of Korea;1. Craft & Hawkins, Department of Petroleum Engineering, Louisiana State University, 3207 Patrick F. Taylor Hall, Baton Rouge, LA, 70803, USA;2. Department of Biological & Agricultural Engineering, Louisiana State University, 149 E. B. Doran Building, Baton Rouge, LA, 70803, USA;3. Aquatic Germplasm and Genetic Resources Center, School of Renewable Natural Resources, Louisiana State University Agricultural Center, 2288 Gourrier Avenue, Baton Rouge, LA, 70820, USA;1. North Carolina State University, Department of Biological and Agricultural Engineering, Raleigh, NC, United States;2. North Carolina State University, Department of Civil, Construction, and Environmental Engineering, Raleigh, NC, United States;1. CAS Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, 7 Nanhai RD, Qingdao, 266071, PR China;2. University of Chinese Academy of Sciences, 19(A) Yuquan Road, Beijing, 100049, PR China;3. Center for Ocean Mega-Science, Chinese Academy of Sciences, 7 Nanhai RD, Qingdao, 266071, PR China;1. Department of Biology and Centre for Coastal Studies and Aquaculture, University of New Brunswick, Ganong Hall, P. O. Box 5050, Saint John, New Brunswick E2L 4L5, Canada;2. School of Fisheries, Aquaculture and Aquatic Sciences, Auburn University, Auburn, Alabama, USA;3. Department of Fisheries Science, Faculty of Natural Resources, University of Kurdistan, Sanandaj, Iran;4. National Institute of Aquatic Resources, Technical University of Denmark, Lyngby, Denmark;5. Billund Aquaculture, Montanavej 2, DK-7190 Billund, Denmark;6. Mount Allison University, 62 York Street, Sackville, New Brunswick E4L 1E2, Canada |
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| Abstract: | The current study combined P and N removal using organic flocculant chemicals and woodchip bioreactors in both freshwater and brackish water (7 ppm) recirculating aquaculture systems (RAS). The use of carbon (C) containing flocculant chemicals in the process was hypothesized to further stimulate C-demanding N removal (denitrification) in bioreactors. The trial of combined P and N removal consisted of four treatments: freshwater and brackish water RAS with and without the addition of supernatant from flocculation process to the woodchip reactor. Duplicate woodchip reactors were used per treatment and the trial was run for six weeks. 56% and 49% of P was removed from fresh and brackish sludge water, respectively. The nitrate-N (NO3-N) removal rate was improved in the treatment when supernatant from flocculation process was used together with RAS discharge water when compared against the control. In brackish water RAS, the improvement was more pronounced (from 6.6–16.5 g NO3-N m−3 d-1) than in freshwater RAS (from 5.1–6.5 NO3-N m−3 d-1). In the freshwater bioreactors using supernatant, N was largely discharged as a nitrite-N (NO2-N). High NO2-N concentrations in freshwater reactors allude to incomplete denitrification reactions taking place. The results suggest that the organic flocculants did provide an additional C source for denitrification, which improved the N-removal process. However, in freshwater RAS this might have been partly due to untargeted processes such as DNRA (dissimilatory nitrate reduction to ammonium), and/or insufficient denitrification reactions taking place (excessive NO2-N production). |
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| Keywords: | Woodchip bioreactor Recirculating aquaculture Wastewater Flocculation |
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