Phytoremediation: Marsh Plants that Clean Grey Water


Home / Phytoremediation: Marsh Plants that Clean Grey Water

The ubiquitous cattail can help clean grey water. Photo: Phil Roeder / CC by 2.0

A wetland full of reeds, fish, frogs, and ducks is a peaceful place. A marsh ecosystem is also an outstanding water treatment system.  Marsh plants are incredible plants, capable of recycling waste water or grey water.

What is Grey Water?

Everyone uses water. Some of this water is used in toilets and called black water and contains sewage. Although it contains organic matter and detergents, fifty to eighty percent of residential water is only gently used before it goes down the sewer.  This water might be from a shower, washing machine, or from the kitchen sink, and it’s called grey water.

Conserve Grey Water in Times of Drought 

In the heat of summer, plants need water. However, this is the time when gardeners must think of ways to conserve water. What is a gardener to do to accommodate thirsty plants? Rain barrels and water-wise gardening help conserve water in the garden, but reusing grey water is another way to conserve.

Many people collect water from the shower or bath in a bucket and use it to water plants. Some connect devices like the Aqus water saver to a sink to collect used water. A dishpan is also a handy, low tech option to save and reuse kitchen water. However, this household water may contain bacteria and organic matter. Creating a wetland full of plants that clean water is an excellent way to reuse grey water and have a thriving wetland garden.

What is Phytoremediation?

Wetlands are beautiful wildlife habitats, but they can also be designed as water treatment systems. This water filtration using plants is also called phytoremediation. Reeds and other wetland plants filter and recycle waste water through their roots.

Constructing Wetlands: Reed Bed Design

Constructed wetlands can be as simple as a rain garden in a low-lying part of a garden. You can use a small wetland to treat waste water collected manually, or larger wetlands can collect water from appliances that is held in a tank and released into the wetland.

Some wetland designs place water above ground, while others have subsurface flow. Keeping water below the gravel is preferable for the home wetland, since this reduces any odors and removes a potential mosquito habitat. One cubic foot of wetland is required for every gallon of water.  For a home, this might be a 1 foot deep and 120 cubic foot wetland.

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