and maintenance requirements causing higher operating costs. Constructed wetlands are designed to improve water quality by supporting rooted vegetation arranged to physically remove solids and particulate material while removing soluble nutrients in the water by uptake into plant tissue and supplying oxygen to the water to reduce BOD. Retention basins are used to manage stormwater runoff to prevent flooding and downstream erosion, and improve water quality in an adjacent river, stream, lake or bay. Detention basins are similar but are "dry ponds" designed to temporarily hold runoff as a flood control measure. Infiltration basins are ponds designed to percolate their contents into underlying permeable soils. Settling basins are designed to separate solids from wastewaters without provision for treatment of those solids. See also Industrial wastewater treatment Lagoon List of waste water treatment technologies Natural swimming pond Organisms used in water purification References External links Publications on ponds in the library of the Sustainable Sanitation Alliance Stabilization pond pictures: Enter "pond" into search field of SuSanA photo database on Flickr Anaerobic digestion Ponds Sanitation Sewerage infrastructure Water management Water treatment