Bioreactors

Bioreactors

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• Overview
• Key considerations
• Planning and design
• Construction and operation
• Links and references

Other name/s

Woodchip bioreactor, denitrifying bioreactor, denitrifying wall, bioreactor wall, denitrifying bed, bioreactor bed

Description

Bioreactors convert nitrate in groundwater or surface water to nitrogen gas using microbes and a carbon source (typically woodchip) under anoxic* conditions.

Bioreactor walls consist of a trench filled with woodchips or another carbon source, located perpendicular to the groundwater flow. Denitrification (the conversion of nitrates to nitrogen gas) is enhanced in the presence of carbon and anoxic conditions and occurs as the groundwater passes through the wall[1][3][4].

Bioreactor beds consist of a bed of woodchips or other carbon source through which water from subsurface pipes (e.g. tile drains, mole drains) or an open drain is passed. They are either inline (within a drain) or offline (water is diverted into the bioreactor via an offtake). An inlet and outlet structure is required in either instance. Excess flow is bypassed. A sediment trap is required upstream to prevent clogging of the bioreactor bed[1][3][4].

Bioreactors work by passing irrigation tailwater, stormwater runoff, deep drainage, or shallow groundwater containing nitrates through the carbon source (e.g. woodchips). As water passes through the bioreactor, denitrification occurs, thereby removing nitrates from the water.

Bioreactors can be used to treat nitrate in groundwater or surface waters. They are a relatively inexpensive technology for the removal of nitrate provided the site conditions are suitable (i.e. shallow groundwater, subsurface drainage network etc.)[2].

The main services that bioreactors provide include:

• Water treatment (nitrogen reduction)

References

1. ^ a b Addy, K, Gold, AJ, Christianson, LE, David, MB, Schipper, LA & Ratigan, NA (2016), 'Denitrifying Bioreactors for Nitrate Removal: A Meta-Analysis', Journal of Environmental Quality, vol. 45, pp. 873-881.
2. ^ Christianson, L, Tyndall, J & Helmers, M (2013), 'Financial comparison of seven nitrate reduction strategies for Midwestern agricultural drainage', Water Resources and Economics, vol. 2-3, pp. 30-56.
3. ^ a b Christianson, LE & Schipper, LA (2016), 'Moving Denitrifying Bioreactors beyond Proof of Concept: Introduction to the Special Section', Journal of Environmental Quality, vol. 45, pp. 757-761.
4. ^ a b Schipper, L, Robertson, WD, Gold, AJ, Jaynes, DB & Cameron, SC (2010), 'Denitrifying bioreactors—An approach for reducing nitrate loads to receiving waters', Ecological Engineering, vol. 36, pp. 1532-1543.
5. ^ Stormwater Australia (2009), Glossary of Terms used in the Stormwater Industry. [online], Stormwater Industry Association, Canberra, ACT. Available at: https://www.stormwater.asn.au/images/publications/Stormwater_Glossary.pdf.

Last updated: 5 October 2018