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out a census of every household in the area, as well as collating detailed information on the social, geographical and demographic environment, including such factors as existing sanitation, projected population increases, typical house characteristics and so forth. |
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10.2.3
Evaluation of Potential Solutions |
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Some 60 different systems were assessed for their potential usefulness in the prevailing conditions of the two areas under study. High technology, expensive solutions, such as vacuum, oil-flushed or chemical-based systems, were immediately deemed inappropriate. Other systems were discarded for a variety of reasons, usually because of their high cost, but also because of health risks, social attitudes or complicated technical operation. Following this process of elimination, there remained conventional sewerage or septic tanks with some means of coping with excess liquids and sullage. Although technically adequate, a conventional sewerage system was ruled out on the grounds of cost, especially given the nature of the landscape: in flat areas the need for pumping stations to compensate for low falls increases construction, operation and maintenance costs. Furthermore, conventional sewers require large volumes of water, also adding to the cost to the consumer. It was decided, therefore, to opt for a system based on septic tanks. |
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10.2.4
Preliminary Design of the ASAS System |
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We decided to explore the possibility of combining septic tanks with a non-surface system for the evacuation of liquids. This would have to incorporate some sort of unconventional sewer, able to meet the appropriate efficiency criteria while remaining low cost. |
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A literature search was carried out, but little useful practical information on unconventional sewers was found. Regarding septic tanks, little information was found about internal processes, especially on accumulation, stabilization and compaction of sludge and scum, and its relation to the composition and concentration of solids in house drainage so that a reliable design |
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