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11
Guidelines for the Design of Simplified Sewers |
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Richard J. Otis, Albert Wright and Alex Bakalian |
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Inadequate sanitation is one of the major environmental problems facing urban areas in developing countries today. The unprecedented population growth in urban centres during the last two decades has severely strained the ability of cities to meet the needs for water supply and wastewater treatment. As local governments have tried to cope with insufficient services, priority has been given generally to high-income areas where full or partial cost recovery is considered feasible. Low-income areas are often left unserved or served by woefully inadequate facilities. |
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The principal reason for this situation is the high cost of conventional sewerage. Treatment alternatives are often considered as a means to reduce total wastewater facility costs, but alternatives to conventional gravity sewers are rarely evaluated, which is suprising as the collection system can represent 6590 per cent of the total construction costs of collection and treatment. Reducing the cost of sewers would have the greatest impact on the affordability of wastewater collection and treatment facilities. Collection alternatives exist which have been proven to be much less costly but, unfortunately, few engineers are familiar with these technologies. |
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Development of less costly wastewater collection alternatives have focused on changing the motive force and/or the characteristics of the wastewater collected. Variable grade, small bore effluent sewers, septic tank effluent pumping pressure sewers (STEP) and grinder-pump pressure sewers and vacuum sewers are examples of new alternatives which have been successful |
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