ABSTRACT
Many natural wetlands have received domestic wastewater pollution for a long time, and their productivity is increased as they have a large capacity for absorbing domestic wastewater. Constructed wetlands are the engineer-made equivalent of natural wetlands, and they are designed to reproduce and intensify the wastewater treatment processes that occur in natural wetlands. Thus rooted aquatic plants, often termed ‘macrophytes’, are grown either in soil or, now more commonly, gravel beds which receive domestic wastewater after primary treatment in, for example, an anaerobic pond. Constructed wetlands are also called ‘reedbeds’ after the aquatic macrophyte most commonly grown in them – Phragmites australis, the common reed. Other plants commonly used include Schoenoplectus lacustris (bulrush), Typha latifolia (cattail) and Juncus effusus (soft rush). Constructed wetlands are long, narrow, shallow (ie almost plug flow) reactors (Figure 17.1) in which the partially treated wastewater is treated further by natural wetland processes. Fully comprehensive reviews of constructed wetlands for wastewater treatment are given by IWA Specialist Group (2000) and Sundaravadivel and Vigneswaran (2001*).
