A. Grey water treatement

Greywater is leftover water from baths, showers, hand basins and washing machines. Salt and soap residues can be toxic to microbial and plant life alike, but can be absorbed and degraded through constructed wetlands and aquatic plants such as sedges (Cyperacaea, Scirpus, Carex) rushes like (Juncus effusus), reedbed and grasses.
Plantings of reedbeds are popular in European constructed wetlands, and plants such as cattails (Typha spp.), sedges, Water Hyacinth (Eichhornia crassipes) and Pontederia spp. are used worldwide (although Typha and Phragmites are highly invasive). Recent research in use of constructed wetlands for subarctic regions has shown that buckbeans (Menyanthes trifoliata) and pendant grass (Arctophila fulva) are also useful for metals uptake.

A number of stages of filtration and microbial digestion can be used to provide water for washing or flushing toilets. Given that greywater may contain nutrients, pathogens, and is often discharged warm, it is very important to store it before use in irrigation purposes, unless it is properly treated first.

Slow filter can be constructed using graded layers of sand with the coarsest sand, along with some gravel, at the bottom and finest sand at the top.

Different plant species are necessary in each of four depth-zones.

  • 0–20 centimetres (0–7.9 in)
  • 40–60 centimetres (16–24 in)
  • 60–120 centimetres (24–47 in)
  • Greater than 120 centimeters (47 in)

Water purifying

Plants purify water by consuming excess nutrients and by de-acidifying it by removing carbon dioxide.


  • Stratiotes aloides, for temperate climates, depth 40-60cm, is one of the best options.
  • Hydrocharis morsus-ranae, temperate climates, depth 40-60cm is one of the best options. Extremely invasive and is listed on the Washington State Noxious Weeds list.
  • Acorus calamus, for temperate climates


Other organismes help purification like fishes and bacteria (they can be grown by submerging straw (or other plant material) in water for several days, the bacteria automatically populate the material)
For ecologic/self-purifying ponds, de-nutrified soil needs to be taken for the plants to prevent the possible growth of algae. Coconut fibre (maybe palm fibre?) growing medium is best used to prevent soil from being spread around and to sometimes to let the plants root in.
More info on contructed wetland

Species of Plants that Filter Water

"Cattail, bulrush, reed and sedge species are all common in constructed wetland ecosystems. They play various roles in a constructed wetland. Some remove heavy metals, while others are more skilled at removing organic matter.

Phragmites australis, the common reed, is often used in water treatment in Europe to remove nitrogen. However, it can be invasive in North America and Australia. Duckweed (Lemnoideae family) also removes nitrogen and phosphorus. Typha has shown promise for removing heavy metals, and for those who weave, its vegetation can be used for mats and baskets. Iris and water hyacinth can also remove heavy metals such as lead, copper, zinc, nickel and cadmium, but take care, as water hyacinth can also be invasive in many locales.

As with all choices of wetland plants for the garden, plant species should be chosen with local ecology in mind. Always check with local wetland plant experts to ensure that a species is not invasive in local wetlands. Many wetland species breed and spread easily! A wetland garden can be full of life. It can also add to the sustainability of a home by allowing a gardener to conserve and reuse gray water. Turn a pond or a wet garden into a place that works for the planet by reframing it as a water treatment system."[1]

Species of Plants that Tolerate Filtered Graywater

Pilerensning method: 1
B. Black water


  1. ^ Marsh Plants that Clean Grey Water