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

Christine Lepine, Laura Elizabeth Christianson, John Davidson, Steven Summerfelt

Research output: Contribution to journalArticle

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

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aquaculture system
recirculating aquaculture systems
wood chips
bioreactors
bioreactor
wastewater
nitrogen
aquaculture
expenditure
cost
replacement
denitrification
wastewater aquaculture
trench
respiration
effluents
removal
effluent
nitrate
water quality

Keywords

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

ASJC Scopus subject areas

  • Aquatic Science

Cite this

Woodchip bioreactors as treatment for recirculating aquaculture systems’ wastewater : A cost assessment of nitrogen removal. / Lepine, Christine; Christianson, Laura Elizabeth; Davidson, John; Summerfelt, Steven.

In: Aquacultural Engineering, Vol. 83, 11.2018, p. 85-92.

Research output: Contribution to journalArticle

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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.",
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