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SEWAGE (Domestic Wastewater)



Planta El Vivero,
18.000 Inhabitants. 45 L/s,
Cali, Colombia
BIOTEC has developed a domestic wastewater treatment system with very low investment costs (US$ 30 to 60 per inhabitant) and very low operation and maintenance costs (US$1 to 2 per inhabitant per year) but whose operation requires year round wastewater temperatures of above 15 degrees. It is a typically "tropical" technology and mainly used in Latin America (Colombia, Brazil and Mexico) and in India.
The system comprises a basic treatment in UASB type anaerobic reactors, followed by polishing with trickling filters, activated sludge, SBR, underwater filters or stabilizing and maturation ponds, space permitting.

BIOTEC pioneered the development of UASB reactors in Latin America for the treatment of urban sewage and their application to various climates (highlands, Mediterranean climate). See UASB publication. We now have UASB sewage plants in Colombia, Venezuela, Nicaragua, El Salvador and Guatemala.


Planta San Antonio,
7.000 Inhabitants. 12 L/s,
Sololá, Guatemala

BIOTEC builds UASB plants in countries where it has offices, but also supports third parties such as specialised or local construction companies in order that they can incorporate UASB systems into their own plants to reduce the production of sludge and other operating and maintenance (O&M) costs. BIOTEC also licenses the use of its UASB technology to certain countries or regions.

The standard plant consists of the following:

  • Preliminary treatment (bars, grit and grease removal unit)
  • UASB reactors for the removal of 80% of the COD and BOD
  • Trickling filters and secondary clarifiers for the removal of 50% of the remaining contamination (achieving less than 25 ppm of SS in the final output)

This plant produces clear, odour-free water with 90% of the BOD removed, that contains more than 1 mg of oxygen per liter. It requires an area of only 0.1m2 per inhabitant. The sludge yield is only 0.5 to 1 m3 for every 1,000m3 of wastewater. This sludge is digested and easily dehydrated in drying beds.


Planta San Bartolo,
14.000 Inhabitants. 22 L/s,
Sololá, Guatemala

This type of plant is a real "tropical revolution" and because of its low costs puts decontamination within the reach of Latin American municipalities.

BIOTEC constructs this type of plant in all sizes, from "package" plants for 20 houses to plants for cities with a population of 250,000 inhabitants.

Small plants for up to 250 houses are made from fiberglass or iron.

They are suitable for small housing developments and also for towns where a "condominial" (neighborhood) system rather than the conventional system is designed.

The condominial sewerage system is a block by block system and generally uses small diameter plastic piping.

When the ground-water level is high, as is often the case in coastal regions, it is better to construct condominial systems with treatment plants for each block, or group of blocks. Once the water has been treated, it can drain into the settled sewerage system whose gradient is less steep thus avoiding the need for deep trenches or piping below the ground-water level. See TUMACO.


Planta Jucanyá,
21.000 Inhabitants. 50 L/s,
Panajachel, Guatemala
Plants for more than 1,500 inhabitants are made from concrete but there are standard and modular models that are quick to assemble.

BIOTEC promotes the agricultural use of the sludge (dried or composted) and of the treated water (ferti-irrigation), in addition to the energetic use of the biogas (15m3 per 1,000 inhabitants connected to the sewerage system): production of electricity, domestic connections (for gas cookers) by means of an urban network and/or street lighting (gas lamps).
The use of the by-products from treatment plants benefits the neighbouring population and involves it in the project. In addition, it generates operation revenue for the municipality (or private operator) and promotes local development.

REFERENCES (one per country):
• Colombia: El Vivero, Cali, Colombia, 3.900 m3/day (20,000 inhabitants)
• Guatemala: San Bartolo, Sololá, 1.900 m3/day (10.000 inhabitants)
• El Salvador: Ciudad Corinto, 1.200 m3/day (7,800 inhabitants)
• Nicaragua: Bosques del Capistano, 350 m3/day (2,000 inhabitants)
• Venezuela: Punta Gorda, 520 m3/day (3,000 inhabitants)