Woodchip bioreactors as treatment for recirculating aquaculture systems’ wastewater: A cost assessment of nitrogen removal

Christine Lepine, Laura Christianson, John Davidson, Steven Summerfelt

Research output: Contribution to journalArticlepeer-review

26 Scopus citations

Abstract

Denitrifying “woodchip” bioreactors are engineered systems, consisting of a carbon filled trench (e.g., with woodchips), designed to remediate nitrogen (N)-enriched water through naturally occurring denitrification, a process where microbes reduce nitrate into inert di-nitrogen gas during their respiration processes. Recent studies have demonstrated the feasibility of woodchip bioreactors for treating aquacultural wastewater, specifically the concentrated effluents generated from recirculating aquaculture (RAS), with the caveat that system lifespan can be reduced from clogging associated with high organic solids loading and bacterial overgrowth. Because this technology is relatively new, particularly for aquaculture applications, lifetime cost-efficiency has not been fully assessed. A cost-estimate of N removal over a one- to five-year anticipated lifespan was obtained by estimating initial capital, recurring, and operational expenditures of a full-scale bioreactor system designed for a RAS production facility, using N removal rates from previous pilot-scale aquaculture wastewater bioreactor research. Assumptions included static N removal rates of 6.06 or 11.75 kg of N removal per year for conservative and maximum sensitivities, respectively 49 and 71% N removal efficiency, and at least one woodchip replacement over the system lifetime across a ten-year planning horizon. Initial capital expenditure totaled $47,838 or roughly $139.88 per m3 installed with woodchip replacements each $19,469. Ten-year operational expenditure total present value costs included of $3737 for water quality work and $4666 for lifetime maintenance. Cost per kg of N removed per year ranged from $13.35 to $2.83, dependent on woodchip replacement scenarios of one- to five-years, respectively, which demonstrated denitrification bioreactors might offer a low-cost N treatment option for aquacultural farmers.

Original languageEnglish (US)
Pages (from-to)85-92
Number of pages8
JournalAquacultural Engineering
Volume83
DOIs
StatePublished - Nov 2018
Externally publishedYes

Bibliographical note

Funding Information:
Special thanks to Steve Atkinson and family and to the Taste of BC for their commitment to sustainability; Karen Schroyer, Susan Glenn, Natalie Redman, Brianna Taylor, and Christina Williams, for water chemistry analyses; to Kata Sharrer for engineering drawings; to Laura Bailey for RS Means assistance; and to Fred Ford, Shanen Cogan, and Scott Tsukuda for physical and technical assistance. This research was partially supported by Tides Canada, Vancouver, British Columbia and the USDA Agricultural Research Service under Agreement Numbers 59-1930-0-046 and 59-8082-5-001. Opinions, conclusions, and recommendations are of the authors and do not necessarily reflect the views of either Tides Canada or the USDA.

Publisher Copyright:
© 2018 The Conservation Fund's Freshwater Institute

Keywords

  • Cost-assessment
  • Denitrification
  • Recirculating aquaculture
  • Woodchip bioreactor

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