The effects of substrate and C:N ratio on water quality in denitrification systems for brackish water aquaculture
Recirculating aquaculture systems (RAS) accumulate dissolved nitrate in the water, which can harm animals. Denitrification can be used to remove nitrate, although some strategies can be expensive and difficult to operate. The purpose of this project was to help simplify denitrification techniques to...
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| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Elsevier
2025-03-01
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| Series: | Aquaculture Reports |
| Subjects: | |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S2352513425000109 |
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| Summary: | Recirculating aquaculture systems (RAS) accumulate dissolved nitrate in the water, which can harm animals. Denitrification can be used to remove nitrate, although some strategies can be expensive and difficult to operate. The purpose of this project was to help simplify denitrification techniques to facilitate long-term water reuse. Two experiments were conducted: one to testing various substrates in denitrification reactors (Experiment 1), and another to investigate lower carbon: nitrogen ratios on suspended growth denitrification systems (Experiment 2). The results of these experiments were then applied to on-farm demonstrations. Experiment 1 had a control with no media, and three treatments containing either plastic bio-media, expanded clay pellets, or woodchips. Experiment 2 had a control receiving no carbon (0:1) and three treatments with varying C:N ratios (0.2:1, 0.5:1, and 1:1). For experiment 1, nitrate was reduced in all treatments even without media; this fact provided motivation for Experiment 2. In Experiment 2, all of the treatments had significantly lower nitrate-N than the control. The 0.5:1 and 0.2:1 treatments had almost complete removal of N, while the 1:1 had high nitrite-N. The initial nitrate-N was 298.1 mg L−1; the final concentrations in each treatment were: 0.2:1 = 2.3, 0.5:1 = 2.3, and 1:1 = 15.5 mg L−1. Subsequent tests at shrimp farms using the 0.2:1 C:N ratio resulted in almost complete removal of nitrate-N. In one case, nitrate-N was reduced from 493 to 1.4 mg L−1 in 7 days. These results demonstrate that simple, suspended growth denitrification can be highly effective at nitrate removal. |
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| ISSN: | 2352-5134 |