Functions of Macrophytes in Constructed Wetlands

Abstract

Macrophytes have several intrinsic properties that makes them an indispensable component of constructed wetlands. The most important functions of the macrophytes in relation to the treatment of wastewater are the physical effects brought about by the presence of the plants. The macrophytes stabilise the surface of the beds, provide good conditions for physical filtration, prevent vertical flow systems from clogging, insulate against frost during winter, and provide a huge surface area for attached microbial growth. Contrary to earlier belief, the growth of macrophytes does not increase the hydraulic conductivity of the substrate in soil-based subsurface flow constructed wetlands. The metabolism of the macrophytes affects the treatment processes to different extents depending on the design of the constructed wetland. Plant uptake of nutrients is only of quantitative importance in low-loaded systems (surface flow systems). Macrophyte-mediated transfer of oxygen to the rhizosphere by leakage from roots increases aerobic degradation of organic matter and nitrification. The macrophytes have additional site-specific values by providing habitat for wildlife and making wastewater treatment systems aesthetically pleasing.

Utilisation des plantes aquatiques enracinées pour le traitement des eaux usées urbaines : cas du roseau

“…En effet, le choix d'un substrat convenable avec une bonne conductivité hydraulique et un temps de % séjour adéquat, est égale-ment nécessaire pour un bon fonctionnement de ces systèmes. Ces conditions réunies permettent un meilleur contact sol-eau usée (BRIX, 1994). En effet, en utilisant un substrat sableux, WATHUGALA étal.…”

“…En effet, les macrophytes aquatiques tel que le roseau sont dotés d'un espace d'air interne bien développé (aerenchyme) à travers les tissus de la plante qui assure le transfert de l'oxygène vers les racines et les rhizomes (BRIX, 1994). L'oxygène qui diffuse à travers les racines stimule la croissance des bactéries nitrifiantes au niveau de la rhizosphère (GESBERG et ai, 1986 ;ARMS-TRONG et ARMSTRONG, 1988.…”

Comparison of microbiological parameters in experimental and conventional recirculation aquaculture systems

“…Fish contaminated with E. coli should be treated with antibiotics and purged in clean water [11]. In this study the quantity of E. coli / Coliform was in the range from 1.65x10 3 to 18.20 x10 3 (Fig. 2).…”

“…The presence of toxic nitrogenous compounds can be assimilated by higher plants and zeolites [2]. The macrophytes uptake nutrients directly, provide good conditions for physical filtration and reduce water flow [3]. The macrophytes in pond systems performed very well in the removal of coliforms and enterobacteria [4].…”

Analysis of clogging in constructed wetlands using magnetic resonance

“…Retention of solids is aided by the gravel substrate and the root network of the reeds, which provide surface area to trap particulates and support biofilms. Removal of organic matter, pathogens and nutrients is mainly achieved by biofilms; whilst chemical compounds may be absorbed or precipitated according to the physicochemical conditions of the wastewater and filter environment [3]. Over time these processes result in the pore volume between the gravel becoming clogged, which leads to undesirable hydraulic short-circuiting and flow surfacing.…”