Aspects of design, structure, performance and operation of reed beds--eight years' experience in northeastern New South Wales, Australia.
Reed beds (horizontal subsurface flow constructed wetlands) have been employed as secondary treatment devices in on-site and decentralised wastewater management systems in the northeast of the Australian state of New South Wales (NSW) for over a decade. This paper summarises some of the practical and research findings that have come to light in that time. Experience with various aspects of reed bed structure is discussed. A study of the evaporative performance of four small beds planted with Phragmites australis yielded an annual crop factor of 2.6. A total of 28 studies on reed beds treating a variety of commonly encountered wastewater streams yielded the following mean pollutant removal efficiencies: total suspended solids (TSS) 83%, biochemical oxygen demand (BOD) 81%, total nitrogen (TN) 57%, total phosphorus (TP) 35% and faecal coliforms (FC) 1.9 logs. The reed bed is becoming the preferred on-site technology for removing TN and BOD and polishing TSS from primary settled domestic wastewater. Sizing beds for a residence time of approximately five days has become standard practice. A study of six reed beds found six different species of earthworm present, mainly Perionyx excavatus (Indian Blue). A mesocosm experiment subsequently showed that the worms were translocating clogging material from the substrate interstices to the surface of the bed thereby indicating a possible method for prolonging reed bed life.
Davison
L
L
Centre for Ecotechnology, Southern Cross University, P.O. Box 157, Lismore, 2480, Australia. ldavison@scu.edu.au
Headley
T
T
Pratt
K
K
D000818:Animals; D001673:Biodegradation, Environmental; D017753:Ecosystem; D005160:Facility Design and Construction; D009517:New South Wales; D009835:Oligochaeta; D006109:Poaceae; D014865:Waste Disposal, Fluid / Q000379:methods*; D018508:Water Purification / Q000379:methods*