Water lilies (nymphaea) can be used to restore the purity of rivers and water sources polluted with poisonous heavy metals and as a means for treating waste water originating from household or industrial sources.

Experiments carried out at the Hebrew University of Jerusalem Faculty of
Agricultural, Food and Environmental Quality Sciences in Rehovot have shown that the water lily, generally thought of only as a decorative plant, is capable of absorbing great quantities of heavy, poisonous metals through its leaves and roots.

The researchers from the faculty's Department of Agricultural Botany are headed by Prof. Elisha Tel-Or and include doctoral student Noa Lavid and three master's degree students: Eldad Sokolovsky, Tamar Shor and Zvi Keilen.

The water lilies, which grow naturally in swampy areas, have in recent years become popular as decorative plants. Noa Lavid, a member of Kibbutz Hazorea, participated in the establishment of a water-lily farm, where the plants are grown in fresh water for export. In her doctoral studies at the Hebrew University, she has focused her research on testing the water lily's ability to purify waste and stagnant water of heavy metals.

She and the other researchers, under Prof. Tel-Or's direction, found that the special anatomical and physiological characteristics of the water lily made it especially suited for this task, without causing any harm to the plant. Indeed, they found that the plant actually thrives in water containing high concentrations of heavy metals, such as cadmium, and is capable of absorbing metals to up to 16% of its dry weight.

Last year, a pilot experiment was established at the Haifa municipal waste water treatment plant to test the purification capabilities of the water lily. Results showed a marked reduction of the amount of cadmium in the sludge following exposure to the water lilies. Other experiments with industrial sludge also showed promising results in removing heavy metals such as cadmium, mercury, nickel and cobalt.
Experimental work is still going on by the Hebrew University researchers to improve and optimize  the purification techniques.