Household systems for wastewater treatment
Ho, G. and Mathew, K. (1998) Household systems for wastewater treatment. In: Proceedings of the Workshop on Adopting, Applying and Operating Environmentally Sound Technologies for Domestic and Industrial Wastewater Treatment for the Wider Caribbean Region: CEP Technical Report No. 43
Isolated dwellings present their own problems of sewage disposal. The septic tank has conventionally been used to treat the sewage. It usually consists of one or two tanks for settling of solids with the overflow disposed via subsurface soil percolation. Depending on soil permeability a soak well is used in very permeable soil, whereas a trench is used where the soil is less permeable allowing for more infiltration area. Settled solids in the tank(s) undergo some anaerobic decomposition, but have to be emptied on a regular basis. Properly designed a septic tank may perform satisfactorily in unobtrusively conveying wastewater away from a dwelling. It can, however, pose health hazards in rocky or tight clay soils resulting in ponding of untreated sewage. More generally septic tanks contaminate groundwater with human pathogens, nutrients (nitrogen and phosphorus) and other pollutants disposed with domestic wastewater. The problems are accentuated where groundwater is close to the surface, or withdrawn for water supply for the isolated dwelling.
There are now a variety of options for wastewater treatment, disposal and reuse for isolated dwellings. Such systems can produce an effluent quality equal to or better than a conventional treatment plant. They may also be more cost effective than reticulated sewerage in rural and semi-rural areas besides isolated dwellings of remote areas, because extensive piping and pumping is avoided. There are also questions from the point of view of a local community particularly in developing countries besides the affordability of the chosen system for them, such as control over technologies that have the potential to influence the dynamics, form and autonomy of the community into which they are introduced. In addition there are now growing environmental and social pressures to consider reusing wastes and to begin introducing systems which are sustainable in the long term.
This section will discus the criteria to be considered in general in the process of selection of a particular technology for isolated dwellings and then describe a few technologies which are approved to be used in Australia to illustrate technologies that can be applied in other parts of the world. Use of local materials, modified design to suit local conditions and preference of a community should be taken into account when determining what is best for a particular case.
|Publication Type:||Conference Paper|
|Murdoch Affiliation:||Environmental Technology Centre|
|Publisher:||UNEP Caribbean Environment Programme|
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