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Santa Cruz Quilehtla is located in Tlaxcala, MX. The town had a population of approximately 6000 people in the Municipal District of Zacatelco. Quilehtla had an existing sewer system but did not have a wastewater treatment system. Quilehtla, located approximately 1 1/2 hours east of Mexico City, has both commercial, residential and agricultural wastewater characterized by a Biological Oxygen Demand (BOD) 4-8 times US standards for municipal wastewater. The wastewater was discharged into a seasonal watercourse without any treatment. The Governor’s office needed a low cost system that would be easy to maintain and operate.
A summary of the design problems include:

1. High strength wastewater, BOD =900-2000 mg/l; flow=85,000 gpd.
2. Limited capital budget
3. Simple to operate and maintain.
4. Minimize operational costs and use of electricity.
5. Provide on-site treatment of sludge.
6. Odor free; no mosquito breeding areas.
7. LIMITED FUNDS - Typical of most projects in Mexico, Quilehtla had a limited capital budget. Imports of equipment and materials would drain money from the State economy. If a wastewater treatment system could be built using local labor and materials, this would keep the money in the State and directly benefit the local economy. Equally important were the long term operating costs. Money paid to replace equipment or pay electricity costs is money lost to pay for local programs such as schools and hospitals.

DESIGN OBJECTIVES - Develop a system that blends with aesthetic site conditions while meeting engineering challenges caused by tight soils, hilly terrain, and limited space. Enhance site features and maximize opportunities to lower all costs to the fullest extent possible.

Meet or exceed the Mexican WQ standards. (Actually meets US secondary standards)

Use local materials and labor. Minimize equipment. Minimize electrical requirements (In fact the treatment process does not use any electricity. A lift station is required for bringing sewage to the treatment site.)