Project 5 - Handling SIRDO

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Ecological Sanitation

Dry SIRDO seco tipo "LA ORUGA"

It's installation and operation are extremely simple.


  1. Employing a compass mark on the ground the north-south axis, dig a hole 1.8 m along the axis and 0,80 m wide, go deeper up to 60 cm at the south end and 20 cm deep at the north end.
  2. Give the bottom the right shape so to hold the slope of the sirdo and level the floor until it is horizontal.
Ecological sanitation ?  
take care of the orientation  take care of the orientation
  1. Locate the SIRDO inside the hole ready and fill in and compact the surroundings with earth. Verify the floor is horizontal.
  2. Take a metal support and a boot with the same number, fix the boot. Locate over the SIRDO and fix the 4 legs with cement.
  3. Fix the metal vent pipes to the 45o joint fixed at the SIRDO, and to the boot.
  4. At the deepest, southend of the SIRDO, put 5 cm of lime, 5 cm of fine charcoal or ashes and 5 cm of fine sand.
  5. Cover the whole inside surface with 10 cm of dark, good quality earth with dried leaves.
  6. Spray 100 ml of nutrient and 125 ml of the bacteria mixed with the same amount of clean water.
  7. Use the toilet everday as indicated here.
  8. Make your colonies grow by spraying the same bacteria every week.
natural ventilation  section of a dry SIRDO

Operation: to carbonize

After defecation cover completely the fecal matter with enough saw dust, or ashes, or dried earth, or a mixture. Used toilet paper should be introduced. Sanitary towels, newspapers or magazines shouldn't be introduced.

covering fecal matter 

Clean daily the toilet seat with a wet cloth. Never throw water inside.

daily cleaning of the toilet seat

Maintain always closed the toilet seat and. the solar collector. After 3 months of use, the filling phase should be finished. Open the collector and move the pile formed at the north, towards the south under the collector, to be dried for 3 months. When this maturity process is concluded, spray the dried product with citric bacteriological substance 2 days before extracting the biofertilizer.

Never take out the 'mother earth'.

Never take out the 'mother earth'.

For this biological process to work well it is very important that:

a)  the solar collector receives the sun as many hours as possible.

b)  the bacteria grow many colonies in the 'mother earth'.

When extracting your 1st harvest, after 6 months of use, keep a bag of biofertilizer to use it instead of or together with, saw dust. Afterwards you will harvest every 3 months.

The maintenance cost in minimal given that saw dust, ashes, dried leaves and earth are available in all communities.

It is fundamental to introduce toilet paper and to cover completely the fecal matter with saw dust.

harvesting 'mother earth'  material for covering

Fecal matter is the main pollutant of the environment and essencially of the water we drink, from a bacteriological and parasitical point of view.

For this reason, the Mexico City's authorities and the Xochimilco Delegation have joined efforts with GTA in order to implement an adequate alternative: ecological sanitation units.

instruction board  

Click on small image to enlarge.

SIRDO seco tipo "LA ORUGA"


M.R. 338568 SECOFI



Tel.: 5344-0312      Fax:5343-3748 Mexico City


Composting latrines in
Ciudad Juarez / Chihuahua
  SIRDO in Colonia Nueva Galeana -
Ciudad Juarez / Chihuahua
click on small image to enlarge click on small image to enlarge   click on small image to enlarge click on small image to enlarge

Center for Environmental Resource Management, University of Texas at El Paso
El Paso, Texas, USA
University of Texas at El Paso Center for Environmental Resource Management
Click here for the final presentation of project 5

     More about the composting process in dry toilet systems, sanitary
     aspects and sustainable water management to find within the
     excerpts from project 5's poster presentation.

Wet SIRDO: small wastewater and solid waste treatment plant

The Wet SIRDO is an integral system for decentralised liquid and solid waste recycling.

It operates as a dual hybrid system: processing black waters from conventional WCs by means of an anaerobic phase from which it generates sludge with certain characteristics to be used as inoculant for decomposing solid organic waste by means of an aerobic phase. Grey waters from kitchen, showers, basins, and cloth-washing machine are conducted separately and treated by means of biological filters.

It consists of 3 subsystems: the following table shows detailed information concerning each one.

The International Development Research Centre / GTA report establishes 3 stages of technological development:

Stage 1: There is given the results of data collected during the 80īs which due to be lack of resources is taken in a non-systemathic way, therefore this data is given only as a previous reference. (TEPEPAN I).

Stage 2: Data collected was processed by the Universidad Autónoma Metropolitana (UAM-Ixtapalapa) in a systemathic way to results are statistically significant. Several series of analyses were made during different seasons in order to compare the behaviour of the system during the raining season, and summer- winter time.

Stage 3: The design of the system was improved accordingly to the results of the research and a new SIRDO was build (TEPEPAN III) improving the characteristics of the outputs / effluents.

At the beginning of the IDRC/GTA report it is detailed the methodology employed: the sampling points, the format used, the standards aimed at, etc. There was analysed the characteristics of the water as it flows inside the tank until it reaches the last sampling point and finally the clarified water. In this way one could detect where and why each architectural element was working well or not, therefore the need to improve their performance.

Inputs Outputs Architectural elements of Wet SIRDO Materials employed Main objectives

Black waters (WCs) including toilet paper, liquid and solid fecal matter.

1.Sludge (vivo/alive)

2. Clarified water used for aqua-culture or for irrigation of non-eatable plants in evapo-transpiration impermeable beds.

1. Solid retention unit

2. two valves which are open-closed alternatively every 6 months enabling the entrance of black water to the right or to the left part of the sedimentation tank.

3. Dual aerobic tank for accelerated sedimentation; used for primary and secondary sedimentation in an alternative manner every 6 months.

4. Scams (floating solids) retention

5. Clarifiers (left and right, to de used alternatively every 6 months)

6. Valve to direct sludge to biological chamber.

Reinforced impermeable concrete. Metal. Reinforced plastic with fiber glass. PVC. Tezontle. Antrasita.

Mexican Bacteria.

For small units, plastic reinforced with fiber glass.

1.To generate alive sludge of certain bio-chemical characteristics, maintaining a C/N ratio between 15/1 and 30/1.

2. to remove pathogenic agents in the effluent according to the regulations appropriate to use.1.


1.Sludge alive.

2. Organic solid waste (from kitchens, gardens and basic housing services).

Biofertilizer, very rich in organic carbon (from 45 to 95%) used for all kinds of agricultural products

1. Biological chamber with solar colector.

Reinforced concrete, HD policarbonate, metal, insulating materials.

To remove pathogenic agents, to retain nutrients and organic carbon.

To evaporate liquids.


1. Grey water from showers, basin, kitchen, etc. without detergents made with phosphates, nitrates, etc.

Water for irrigation of all agricultural production.

  1. Solid retention unit.
  2. Grease retention unit
  3. Biological filter with silica gravel and sand.
  4. Cistern for storing treated water.
  5. Pumping system to return treated water to each house to irrigate.
Reinforced concrete, impermeable finishing, fibre glass, PVC, aluminium and other metals. For small units GTA uses rotomolded polyethylene.

To reduce the COD generated mainly by cleaning products.

To clarify water and digest grease.

To reduce BOD to standards.


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