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9
Small Diameter Gravity Sewers: Experience in the United States |
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Water pollution and public health problems from inadequately treated wastewater exist in many small communities throughout the USA. Failures of individual septic tank systems have forced many unsewered communities to consider construction of public collection and treatment facilities. Often, severe financial hardships are created in providing these facilities. It is not uncommon for residents of small communities to pay two to three times as much for sewer services as residents of larger municipalities (Graham, 1982). This higher cost is due primarily to the length of sewer per user which can be more than five times longer than that typical in urban areas. The impact of the higher cost on family budgets can be quite severe because the average annual incomes in rural communities are significantly lower than in more urbanized areas. As a result, plans for construction of needed public facilities are often rejected, allowing public health hazards, nuisances and environmental degradation from failing septic tank systems to continue while economic development is impeded. |
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Traditionally, conventional sewerage is assumed to be necessary without consideration of alternatives. The cost-effectiveness of various treatment alternatives are commonly evaluated, but while the extent of the sewers is sometimes a cost issue, low-cost alternatives for wastewater collection are rarely considered. Yet, conventional sewer construction accounts for 8090 per cent of the total capital costs of the collection and |
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