Reed-Bed versus slow sand filtration: A cost comparison

This article models the economic cost of establishing and maintaining reed bed filtration for the production of potable water compared to a slow sand filtration (SSF) system capable of purifying an equivalent volume of water. Reed bed filtration has been used for potable water filtration at Clear Water Lagoon (CWL) in Mount Isa, northwest Queensland since 1968. The system requires minimal maintenance and filters 60 ML of catchment runoff each day to a standard that complies with the Australian Drinking Water Guidelines (NHMRC, 2004). Although comparative analyses reveal minimal differences in the quality of water produced or the operating costs of the two systems, the capital outlay for establishing a reed bed system equivalent to CWL amounts to less than half that of an SSF system. A 100-year life cycle analysis found the cumulative expenses of CWL to be approximately $19.5 million compared to $32.1 million for a SSF facility. Economic evaluation has confirmed the absolute value of CWL to the Mount Isa water supply system. There are also several environmental benefits that arise from harnessing the free ecosystem services of a reed bed structure. These include relatively low maintenance requirements, lower energy consumption and running costs and the provision of substantial wetland habitat for biota.