Macrophytes to clean water?

Abstract

The capacity of macrophytes to produce organic matter are increasingly used to extract nutrients from domestic wastewater in order to reduce the impacts of partially purified water discharges on the natural environment. Improved knowledge in this area has played an important role in the design of new water treatment systems inspired by natural processes, called «constructed wetlands". Brix (1993) proposed a classification of the various «constructed wetlands" according to the types of macrophytes used, i.e. rooted and emergent, rooted and submerged and free-floating on the water surface. After an assessment of the knowledge on the uses of these three types of macrophytes to purify effluents, we will develop a rationale to better clarify the role of plants in purification as well as the constraints induced by their deliberate or involunatry presence. Acting as a support for plant purifying microorganisms, these plants also turn out to be attractive landscape elements. However, the biomass they produce must be regularly exported to allow the sustainable operation of wastewater treatment facilities.