Organisms involved in water purification

However some processes, especially those involved in removing very low concentrations of contaminants, may use engineered eco-systems created by the introduction of specific plants and sometimes animals.

In other cases, the presence of specific chemical species may produce toxic effects limiting growth and abundance of living matter.

Saprophytic bacteria and fungi can convert organic matter into living cell mass, carbon dioxide, water and a range of metabolic by-products.

[5] Aquatic vegetation may provide similar surface habitat for purifying bacteria, protozoa, and rotifers in a pond or marsh setting; although water circulation is often less effective.

They also have the ability to translocate chemicals between their submerged foliage and their root systems and this is of significance in engineered wet-lands designed to de-toxify waste waters.

Plants that have been used in temperate climates include Nymphea alba, Phragmites australis, Sparganium erectum, Iris pseudacorus, Schoenoplectus lacustris and Carex acutiformis.

[citation needed] Where oxygenation is a critical requirement Stratiotes aloides, Hydrocharis morsus-ranae, Acorus calamus, Myriophyllum species and Elodea have been used.

Fish are frequently the top level predators in a managed treatment eco-system and in some case may simply be a mono-culture of herbivorous species.

They occur naturally in aerobic lagoons, activated sludge processes, in trickling filters and in final settlement tanks and are a significant factor in removing suspended bacterial cells and algae from the water column.

[6][7] Annelid worms are essential to the effective operation of trickling filters [8] helping to remove excess bio-mass and enhancing natural sloughing of the bio-film.