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Consider a constructed wetland or reed bed

A constructed wetland is a lined cell of gravel, sand and wetland plants where microbes, plants and media treat settled wastewater. It can polish septic tank effluent or greywater.

How

1. Always settle solids first, usually in a septic tank, before the wetland.
2. Use an impermeable liner so untreated water cannot reach groundwater, and choose plants that tolerate permanently wet conditions (US EPA).
3. Decide on gravity flow or pressure dosing based on your site levels and power.
4. Plan where the treated water goes next: often to a drainfield, as wetland effluent may still need dispersal.
5. For a first idea of size only: Akvopedia, summarising the Eawag compendium, gives about 5 to 10 m2 of horizontal subsurface flow wetland per person, with a 0.5 to 1 m deep bed of 3 to 32 mm gravel and the water kept 5 to 15 cm below the surface. Your designer sets the final size.
6. Keep the required separation distance from wells (for example 50 ft in Minnesota).
7. Get a qualified designer to size the cell, since sizing depends on flow, climate and local rules.

Safety: Open water attracts children. Use subsurface flow designs or fence the area.

Sources

1. Types of Septic Systems. US Environmental Protection Agency, accessed 2026-11
2. Isolation Distances from a Well. Minnesota Department of Health, accessed 2026-11
3. Horizontal Subsurface Flow Constructed Wetland. Akvopedia (summarising the Eawag Compendium of Sanitation Systems and Technologies), accessed 2026-11

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