Wood-chip filter (Filtres a Broyat de Bois, FBB)

Biological filter bed of wood chips, developed and tested specifically for treating greywater alone (as distinct from constructed wetlands typically sized for combined or blackwater flows) by INRAE and the Reseau Assainissement Ecologique. Passive, gravity-fed, no power needed; chips need periodic renewal as they break down.

Cost
Low
Upkeep
Seasonal
Skill to build
Basic
Lifespan
Structure/basin: 20-30 years; the wood-chip media itself needs periodic renewal as it breaks down (INRAE guidance doesn't specify an exact interval)
Embodied carbon
Low
Space / material use
Medium
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 for the filter bed

Inputs

Outputs

Sources

Tutorials

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.