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Alternative
Wastewater Treatment Design for Escuela Litoral JMP
Engineering |
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Escuela Litoral
is located between the 5th and 6th rings of the city of Santa Cruz,
Bolivia. 1500 students attend classes in two equal shifts throughout
the day. The current septic system is undersized and requires frequent
cleaning & pumping. The government supplies funds for pumping
once a year, so two women frequently clean the tank by hand. To keep
the flow to the system as low as possible, the toilets in the restrooms
are flushed only twice per day. Since the system is frequently at
capacity, excess waste seeps out of the septic tank and dry well and
flows up the soil to the surface. Children play in contaminated soil
at recess and there are many cases of illness. |
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Site
Investigation Drinking water quality Site survey Soil borings Wastewater flow determination Health hazard inquiry |
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Site
Conditions Satisfactory drinking water Limited construction area Clay soils (low permeability) High wastewater flow Biologically contaminated soils |
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Alternatives
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Interim
Design Modified Galeria Filtrante with Low Flow Toilets 1 septic tank 54-hr detention time Dispersal over 7 days Decrease daily flow by 25% Dimensions: 9.7 x 2.7 x 2.25 m 3 modified galeria filtrantes Modified from Bolivian design Filled with sand instead of lined with bricks Less expensive & more treatment Depth: 4 m 2 sizes: 1 – 4 m diameter 2 – 4.5 m diameter Each with three 8 m long trenches Located in low traffic areas with adequate space Estimated construction time: approx. 19 work days |
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Final
Recommendations Current system is failing due to its small size, poor soils, & large flow Design of a new system is constrained by large flow, poor soils, & limited space Interim Design – Modified Galeria Filtrante has an estimated lifetime 10 years Less expensive to keep current system, but extremely hazardous to the health of the children Only permanent solution is a sanitary sewer & wastewater treatment plant for the community |
| Michigan Technological
University Department of Civil and Environmental Engineering 1400 Townsend Drive Houghton, Michigan, 49931 - 1295, USA Department Phone: 1-906-487-2520 Department Fax: 1-906-487-2943 Department E-mail: cee@mtu.edu |