Abstract
The denitrifying woodchip bioreactor is designed to remediate nitrate-rich water, including those produced from aquaculture effluents. Reuse of treated bioreactor outflows in recirculating aquaculture would offer considerable water savings and valuable alkalinity recuperation. However, such bioreactors may leach detrimental wood-bound contaminants, preventing outflow reuse. To determine water reuse potential, woodchip media from two hardwood species (white ash, Fraxinus americana; Norway maple, Acer platanoides) were evaluated for 206 d under a range of operating conditions (start-up, steady-state, reducing conditions, and drying-rewetting cycles) for a spectrum of potentially harmful dissolved contaminants. Aerated outflows also were evaluated for acute and chronic toxicity to the biologically sensitive invertebrate Ceriodaphnia dubia. Dissolved metal leaching subsided within the first few weeks of operation, though initial concentrations of copper and zinc were detected at concentrations of concern. Elevated concentrations of tannins-lignin and total ammonia nitrogen were detected throughout the study and were influenced by operational phase. Acute toxicity was not generally detected, though chronic toxicity was observed during drying-rewetting cycles in the maple outflows. The measured toxicity was not correlated with water chemistry, indicating an additive effect of several toxicants. Overall, significant differences in outflow water quality between ash and maple wood species were negligible. Results indicated that bioreactor outflows may be applicable for aquacultural reuse, though reusing outflows immediately following start-up or restarting after a dry period would not be recommended.
Original language | English (US) |
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Article number | 102129 |
Journal | Aquacultural Engineering |
Volume | 93 |
DOIs | |
State | Published - May 2021 |
Externally published | Yes |
Bibliographical note
Funding Information:This research was supported by the USDA Agricultural Research Service under Agreement Number 59-8082-5-001 . Opinions and conclusions are of the authors and do not necessarily reflect the views of the USDA. The Conservation Fund and the USDA are equal opportunity providers/employers.
Publisher Copyright:
© 2020
Keywords
- Aquatic life
- Effluent
- Recirculating aquaculture systems
- Salmonid