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and Col$18300 (US$50) for PVC, while the cost for conventional sewerage was about Col$36000 (US$98). In other words the ASAS system was half the cost of conventional sewerage. |
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In the San Zenon project (1995 prices), the ASAS costs with vitrified clay pipe was Col$262000 (US$325) and for conventional sewerage about Col$800000 (US$1000), that is about three times less expensive. The equivalent costs per person are US$56 for the ASAS system and US$172 for conventional sewerage. |
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The ASAS system does not require additional expense to build house drains if the sanitary unit is built over the intercepting tanks or very close to it. For conventional sewerage the cost per house averages 1518 per cent more for house drains. If wastewater treatment is included in the cost analysis, the difference is even greater because for ASAS it is less costly. |
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Based on results and observations from the ASAS projects that have been carried out to date, the following conclusions can be made. |
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1. A minimum slope of 0.1 per cent appears to be adequate and there seems little reason to increase it. |
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2. A particle size of 0.02 mm has proved an adequate basis for arriving at the minimum cost in all projects. Interceptor tanks which retain that size of particle are sufficiently small (if observed rates of accumulation of sludge and scum are greater than those experienced in the Cartagena project, then the tank dimensions should be enlarged). |
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3. The number of free-flowing fixtures is the most important determinant for the unit load. For projects with a different number and type of fixtures than described here, this must be taken into account. |
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The basic parameters described in this chapter have been used successfully in other ASAS projects where the general conditions were similar or less severe than those experienced in Cartagena. |
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We conclude that ASAS technology is applicable in areas |
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