ABSTRACT
The concept of treating wastewaters with emergent aquatic macrophytes (the root-zone process) was introduced in Denmark in 1983. All Danish systems are constructed as subsurface flow systems designed to percolate sewage horizontally through the macrophyte rhizosphere. Sewage is mechanically pretreated in septic tanks, sedimentation tanks, or stabilization ponds before it is led into the beds. Bed dimensions vary because different construction companies use different design criteria with little or no input from researchers or regulatory review by federal agencies. In general, systems receiving sewage from combined drainage systems or dilute sewage, with relatively high hydraulic loading rates, are built as relatively short and wide beds to prevent overland flow. However, as most Danish reed beds are constructed on sites with no requirement for nutrient removal, we conclude that generally reed bed function is satisfactory for fulfilling quality criteria set by authorities for the specific sites.
