Use of constructed wetlands in water pollution control: historical development, present status, and future perspectives

Abstract

During the last two decades the multiple functions and values of wetlands have been recognized not only by the scientists and managers working with wetlands, but also by the public. The ability of wetlands to transform and store organic matter has been exploited in constructed wetlands. This paper summarizes the state-of-the-art of the uses of constructed wetlands in water pollution control by reviewing the basics of the technology, the historical development, and the performance expectations with focus on the use of free water surface and subsurface flow constructed wetlands for municipal wastewater treatment. Performance data from a total of 104 subsurface flow systems and 70 free water surface flow systems are reviewed. The present state of knowledge is sufficient to apply constructed wetlands as a tool for improving water quality. The potential applications range from secondary treatment of municipal and various types of industrial wastewaters to polishing of tertiary treated waters and diffuse pollution. In many situations constructed wetlands is the only appropriate technology available. The treatment capacity of subsurface flow systems can be improved by selecting vertical flow systems with intermittent loading, by proper media selection, and by recycling of the wastewater. Further research is needed to help define and optimize engineering design criteria and the long-term performance capabilities and operational problems.

Purification capacity of a highly loaded laboratory scale tidal flow reed bed system with effluent recirculation

“…A high hydraulic loading of 0.04 m 3 /m 2 d was reported in the literature for the treatment of pig farm wastewater using combined vertical and horizontal flow reed bed system . It is well recognized that the hydraulic loading rate is one of the most important factors affecting the purification process; the value has been recommended in the range between 0.025-0.050 m 3 /m 2 d (Brix, 1994). Clearly, the hydraulic loading rate used in this study is higher by one order of magnitude than those reported.…”

“…It is reported that the recirculation of effluent can enhance pollutants-microorganisms interaction by allowing a longer retention time without significantly changing the operation of the beds. It is well known that reed bed technology works on the principle that biofilms attached onto the bed medium break down pollutants in wastewater passing through the bed (Brix, 1994). Reeds have the ability to transfer a certain amount of oxygen to their roots, stimulating microbial activities and enhancing the breaking down of pollutants (Brix, 1994;IWA, 2000).…”

“…It is well known that reed bed technology works on the principle that biofilms attached onto the bed medium break down pollutants in wastewater passing through the bed (Brix, 1994). Reeds have the ability to transfer a certain amount of oxygen to their roots, stimulating microbial activities and enhancing the breaking down of pollutants (Brix, 1994;IWA, 2000). It is believed that effluent recirculation benefits the purification capacity of reed bed systems, especially in the case of treating high strength wastewaters.…”

Removal of ammoniacal-nitrogen from an artificial landfill leachate in downflow reed beds

“…It involves a series of physical, chemical and biological processes such as adsorption in the bed matrix, filtration, pollutant sedimentation, ion exchange, plant sorption and microbiological reactions (Brix, 1994). Results from this study do not show a complete picture for the complicated transformations of NH 4 -N. Nevertheless, this study provides useful information to identify the fate of soluble NH 4 -N removed in downflow reed bed systems, particularly regarding the initial adsorption and retaining of NH 4 -N inside the bed matrices.…”

Nutrient Removal From Waste Water by Macrophytes – An Eco-Friendly Approach to Waste Water Treatment and Management

“…Nutrient diversion through constructed wetlands have become an important tool in developed countries for efficient management of wastewater during the last decade (Brix, 1994;Kadlec & Knight, 1994;Knight, Kadlec, & Reed, 1992). However, economic feasibility of such systems limits their application, especially in developing countries (Sun & Qu, 1998).…”