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Team members

Equipo Septico
Team members:

Leslie DellAngelo, Communication Specialist & Drafting Technician

Chris Fehrman, Project Manager

Kimberly Kimmes, Field Engineer & Drafting Technician

Water Quality Testing and Alternative Wastewater Treatment Designs
Santa Cruz, Bolivia

CE 4905 Senior Design Summer 2004
Slide Show Scenes of 2004 Projects

Team Mission
“Provide the Bolivian people with improved living conditions by designing onsite wastewater treatment and providing water testing.”

 

Background

The District Seven public school system which are located on the eastern perimeter of the city of Santa Cruz de la Sur, Bolivia. Four of District Seven’s schools, Escuela Central Obrera Departamental, El Buen Samaritario, the Escuela Fiscal Mato “Guapilo Junin”, and the Unidad Educativa “4 de Febrero” are all located on the perimeter of the city, just outside of the seventh ring. The roads are not paved and entire families live in dilapidated, single room homes. The neighborhoods are serviced by public buses, and the families can not afford personal means of transportation.
The school system provides the facilities and faculty necessary for primary and secondary education. The District Seven schools have struggled with government finances since the day they were established. These public schools are located in low-class neighborhoods. The Bolivian government does not pay for materials or labor for the construction of the school buildings. Nor does the Bolivian government pay for repairs and maintenance of the school buildings. The government is only responsible for the salaries of the teachers and directors and for payment of utilities. The basic utilities at most schools include drinking water and electricity. Many of the faculty salaries are not high enough to support themselves and their families. These teachers must hold other jobs outside of the public school system in order to survive. At times, the schools go for months without electricity because the government fails to pay electric bills.


Field Work
Topographic Surveying Soil Boring Groundwater table Percolation test Flow determination


Water Testing Results

Water Quality Testing

Objective

Verify water quality at schools

Methods and Procedures

  • Collect water samples
  • Inoculate 3M Petrifilm Enterobacteriaceae count plates
  • Inoculate HACH P/A Broth Bottles
  • Incubate at the Saguapac laboratory

Results

  • P/A broth bottles tested negative
  • Petrifilm plates indicate 0 cfu’s

4 de Febrero School
- School is expanding from 5 classrooms to 7.
- Future school population of 515.
- Limited government funds for the facility

Problem
Failing Septic System
Project Objective
Design an improved or replacement and economical wastewater treatment system that will accommodate the future school population of 515.


Design Parameters

Depth to groundwater is 1.8 m
Average percolation rate is 1200 min/in
Design population is 515

 Alternatives
Holding Tank

Advantages
  • No onsite treatment
  • Low maintenance
  • Construction cost: $US 700
Disadvantages  
  • Cost of pumping:$US 50/month
  • Unfamiliar to Bolivian people
Elevated Mound System

Advantages
  • Minimal excavation
  • High quality effluent
Disadvantages
  • High construction costs: $US 5900
  • Large footprint: 26,500 ft2
  • Operational costs
Intermittent Sand Filter

Advantages
  • High quality effluent
  • Low construction costs
  • Subsurface system
  • Soil cover prevents odor
  • Minimal land use: 1430ft2
Disadvantages
  • Regular maintenance
  • Possible clogging of filter
  • Unfamiliar to Bolivian people

Selected Design: Alternative 3 – ISF with Dosing Tank and Siphon

Septic Tank
2 compartments
48-hr detention time
382 ft3 volume
Dosing Tank with Simple Siphon
Dosing Volume
56 gal
2” PVC Siphon

Intermittent Sand Filter Application rate: 1 gal/ft2/day Absorption area: 1430 ft2 24” of Sand Media 8 flush pipes




Buen Samaritano School

Problem: Inadequate bathroom facility
Design Objectives
Effective
Economical

Design Parameters
Soil Type: Fine Sand
Groundwater Depth: 2.75 m
Percolation Rate: 3.63 min/in
Flow: 1030 gal/day

Design Alternatives.
Traditional Bolivian System:
Septic Tank with Seepage Tank
2. Conventional American System:
Septic Tank with Drainage Field

Alternatives
Alternative 1: Traditional Bolivian System

Advantages
  • Familiar to Bolivian people
  • Low construction cost $US 950
Disadvantages
  • Groundwater contamination
  • Treatment
Alternative 2: Conventional American System: Septic Tank with Drainage Field

Advantages
  • Effectively treats domestic wastewater with sandy soils
  • Low construction cost of $US 670.22
Disadvantages
  • Unfamiliar system to the Bolivian people
  • Septic tank requires pumping more frequently due to higher solids removal.
  • Drainage field uses higher amount of the land area than a seepage tank

Recommended Design

Septic Tank
- 2 compartments
- 36 hr detention time
- 5859 L Volume


Distribution Tank - 484 L Volume

 Drainage field
Application rate of 2.70 gal/ft2/day
Absorption area of 382 ft2
3 parallel trenches 56 ft long and 3 ft apart
2 % slope
4” perforated PVC pipe
Conclusion
Although there was no coliform or bacterial contamination found at the sites, drinking water quality remains of concern, especially with the potential for untreated wastewater to contaminate the sources. Equipo Septico recommends more comprehensive water quality testing be completed at the schools to determine if the water meets the World Health Organization’s standards of less than 1 colony forming unit per 100 milliliters of water.
The schools in District Seven of Santa Cruz are also seeking to develop proper wastewater treatment systems. The Buen Samaritano School currently has a hole in the ground for the children to dispose of their sanitary waste. The 4 de Febrero School constructed a traditional Bolivian Septic System three years ago that functioned for only 1 ½ years before failing. After a series of modifications and failures, the school is in need of an alternative design that will work for their site. Equipo Septico completed a conventional US septic system design for Buen Samaritano School and an Intermittent Sand Filter design for 4 de Febrero School. The proposed systems should improve the sanitary conditions for the students and faculty at both schools. The systems will be able to accommodate the increasing enrollment of students at both schools and will further serve to minimize the contaminants that could potentially reach the groundwater at these sites.

 
 

Michigan Technological University
Department of Civil and Environmental Engineering
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Department Phone: 1-906-487-2520
Department Fax: 1-906-487-2943
Department E-mail: cee@mtu.edu


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