As stated before, Government regulation requires that all effluent must be contained on the property and must not run onto the nature strip into the kerb and channel. However, on-site sewerage facilities (OSSF) on properties that are not connected to the municipal sewage system remain a concern. Owners of those non-sewered properties can reduce the amount of pollutants running off their properties by installing reed beds. The name reed beds, refers to a specific type of plants in use. The technology was developed in Germany in the 1950s by Dr. Käthe Seidel. A better term to use however is ‘horizontal sub-surface flow constructed wetlands’ as it does not imply a specific plant species. As the name suggests, the water runs through the soil underneath the surface and is not exposed. This minimises the risk for the establishment of mosquito breeding grounds, which are related to mosquito-borne diseases. However, that does not mean, that a surface flow wetland does not necessarily promote mosquito breeding. These wetlands support a diversity of aquatic animals which are crucial for the ecosystem and the predator-prey relationship is usually a sufficient mosquito control.
Plants like reeds and rushes are traditionally the preferred choice to remove pollutants from wastewater in reed beds in any climate. In the subtropical north-eastern area of NSW Schoenoplectus validus (river club rush), Thypha orientalis (bull rush), Bolboscoenus fluviatilis (marsh club rush) and Baumea articulata (jointed twig rush) have been used successfully but other plants can work equally well or even better. Iris pseudacorus (Yellow Flag) and Lythrum salicaria (purple loosestrife), which is native to southeastern Australia,show even more improved growth rate and performance of nutrient removal but almost any freshwater wetland plant can be used. The selection of plants found in the garden pond section of the local nursery gives an idea of what to choose to suit any style of garden. The selection of a larger variety of plants can not only improve the uptake of nutrients in horizontal sub-surface flow constructed wetlands but can also add aesthetic appeal. Many councils encourage the use of reed beds on non-sewered properties. For the majority of the last 15 years reed beds are part of the wastewater management system in the Lismore, Byron and Richmond River Shires in north-eastern NSW.
During periods of low rainfall people on smaller properties are inclined to collect the water from their washing machine. It makes a viable option for watering the garden, as many homes use top-loading washing machines to wash their clothes. Whereas a front loader washing machines use between 50 and 65L per wash, their top-loading counterparts use about double the amount, although some of the newer models can use as little as the front-loaders.
Due to the small size of the blocks greywater used for above surface application can easily cause problems due to the close proximity. Even though greywater from the laundry usually has low concentrations of pollutants it can still cause problems in surrounding areas when entering neighbouring properties or even waterways. Therefore it should always be treated for re-use. A small horizontal sub-surface flow constructed wetland should be the preferred option and can become a focal point in the garden. A word of warning, though when connecting to the washing machine directly to such a system the manual should be checked or the manufacturer consulted to avoid loss of warranty.
As a benefit, with every sub-surface flow constructed wetland bed comes as a bonus a hideaway for birds and other animals.
References:
• Camacho JV, Martinez ADL, Gomez RG, et al. (2007). A comparative study of five horizontal subsurface flow constructed wetlands using different plant species for domestic wastewater treatment. Environmental Technology, 28 (12), 1333-1343.
• Davison L, Headley T, Pratt K (2005). Aspects of design, structure, performance and operation of reed beds – eight years’ experience in northeastern New South Wales, Australia. Conference Information: 6th International Conference on Small Water and Wastewater Systems/1st International Conference on Onsite Wastewater Treatment and Recycling, FEB 11-13, 2004, Freemantle, AUSTRALIA. Water Science and Technology, 51 (10), 129-138.
• Domayne (2010). Half-year sales catalogue, December 2010.
• Greenway M, Dale P, Chapman H (2003). An assessment of mosquito breeding and control in four surface flow wetlands in tropical-subtropical Australia. Water Science and Technology, 48 (2), 121-128.
• Jeppesen, B (1996). Domestic greywater re-use: Australia’s challenge for the future. Conference Information: International Water Specialists Conference, DEC 01-02, 1994 Murdoch University, Perth, AUSTRALIA. Desalination 106, 311-315.
• Langergraber G (2005). The role of plant uptake on the removal of organic matter and nutrients in subsurface flow constructed wetlands: a simulation study. Conference Information: 9th IWA International Specialised Conference on Wetland Systems for Water Pollution Control, SEP 26-30, 2004 Avignon, FRANCE. Water Science and Technology, 51 (9), 213-223.
• Leal LH, Zeeman G, Temmink H, et al. (2007). Characterisation and biological treatment of greywater. Conference Information: International Conference on Advanced Sanitation, MAR 12-13, 2007 Aachen, GERMANY. Water Science and Technology, 56 (5), 193-200.
• Leal LH, Zeeman G, Temmink H, et al. (2007). Characterisation and biological treatment of greywater. Conference Information: International Conference on Advanced Sanitation, MAR 12-13, 2007 Aachen, GERMANY. Water Science and Technology, 56 (5), 193-200.
• Vymazal J (2008). The use costruced wetlands with horizontal sub-surface flow for various types of wastewater. Ecological Engineering, 35, 1-17.
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