Constructed wetland / reed bed filtration

Plants and gravel media biologically filter greywater; low-tech, no powered parts in the bed itself. Gravity-fed and genuinely passive where the site gives enough fall; on flat ground or where flow has to rise, a pump is needed and it is no longer passive.

Cost

Low

Upkeep

Seasonal

Skill to build

Intermediate

Lifespan

15-25 years before media/gravel bed needs partial renewal; the basin structure itself can last far longer

Embodied carbon

Low

Space / material use

High

Output timing

Continuous process

Skill to repair

Basic

Regulation (FR example)

On-site sanitation (assainissement non collectif): the installation must be declared to and approved by the local SPANC before work starts, and is subject to periodic inspection. Arrete du 7 septembre 2009 modifie.

Note: Cost, carbon and footprint are rated against the other options for this same need, not in absolute terms.

What your site needs

Land area available for the wetland bed (a real footprint cost, cross-ref Relative Space/Material Footprint), and enough fall from the source to the bed to run on gravity

Inputs

• Greywater

Outputs

• Treated Effluent
• Nutrients

Sources

• Constructed-wetland treatment performance literature (NCBI vertical-flow constructed wetland studies)

Tutorials

• https://wiki.lowtechlab.org/wiki/Phytoépuration_des_eaux_grises
• https://wiki.lowtechlab.org/wiki/Phytoépuration_eaux_usées

What this page does not tell you

No sizing or quantities: how much a technique yields, and how much a household needs, both depend on the build and the people, so the catalogue compares options rather than dimensioning them. It carries no bill of materials and no build sequence, and it is written for an oceanic, clay-soil climate (Normandy, France). Regulatory notes are indicative and need confirming locally.