The treatment of industrial and domesticwastewaters by passage through bed containing plants of thecommon reed (Phragmites australis), reedmace (Typha latifolia),or other species, has been widely practised in recent years, withvarying degrees of success. Although many workers havedemonstrated good removal of organic components of effluentsand of suspended solids, poor removal of ammoniacal nitrogen is acommon finding. This has often been shown to limit the value ofreed beds for treatment of raw landfill leachates. Engineeredwetlands do however, have considerable capability for secondarypolishing of leachates that have been pretreated in aerobicbiological plants and for older leachates, this technology havingbeen widely used in the UK. This paper will deal in general and indetail with the design of engineered wetland systems, both for thetreatment of weaker and more-diluted leachates from older landfillsites, and also for the polishing of effluents from the pretreatmentof much stronger leachates in aerobic biological treatment plants.
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