ABSTRACT
Both natural and constructed wetlands have been used as wastewater treatment systems; it is generally found that both systems may act as efficient water purification systems and nutrient sinks. The possibility of achieving better treatment performance in improved designs of macrophyte-based systems is discussed. Emergent macrophyte-based wastewater treatment systems can be constructed with different designs. The concept of treating wastewater in constructed wetlands with subsurface flow was developed in Germany in the 1970s. A design consisting of several beds laid out in parallel with percolation flow and intermittent loading will increase soil oxygenation several-fold compared to horizontal subsurface flow systems. The applicability of the different macrophyte-based wastewater treatment systems depends, among other things, on climatic conditions, effluent quality required, wastewater characteristics, availability and price of land, conservation regulations, etc. Water hyacinth-based systems can, for instance, only be used in warm climates, as the plant does not tolerate frost.
