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Difference between revisions of "Ecological dry toilets at Pedregal"

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===Creating the Chamber and House===
 
===Creating the Chamber and House===
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#Top of Chamber: <br /> A concrete slab the width and length of the outer walls should be made with a hole for each chamber, these holes will act as the opening to the chamber and the place for the toilet seat.   
 
#Top of Chamber: <br /> A concrete slab the width and length of the outer walls should be made with a hole for each chamber, these holes will act as the opening to the chamber and the place for the toilet seat.   
 
#Hole or Seat: <br /> Whether just using the hole or adding a toilet seat the urine must be separated using a small triangle shaped cup added to the front of the hole/seat. This cup should also have a small hole in the bottom where a tube is attached and this tube leads out to an outside absorption chamber under the ground or to a separate collection chamber.   
 
#Hole or Seat: <br /> Whether just using the hole or adding a toilet seat the urine must be separated using a small triangle shaped cup added to the front of the hole/seat. This cup should also have a small hole in the bottom where a tube is attached and this tube leads out to an outside absorption chamber under the ground or to a separate collection chamber.   
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'''The house:'''
 
'''The house:'''
 
#It is built on top of the slab of the chambers and can have the size, design and materials you want. Just make sure there is good ventilation and that it does not allow the passage of water into the chambers.  Pedregal included a PVC pipe that runs along the outside of the house and encourages decomposing gases to escape to the outside where it will not disturb users.  Pedregals structure was also made of bamboo mats woven together and placed with small openings to allow for ventilation as well as windows above breast height.  <ref> Soil and Water Conservation Committee, State of Alabama.  "Block and Gravel Inlet Protection". http://swcc.alabama.gov/pdf/Handbooks&Guides/2006_sections/12%20Sediment%20Control%20(practices)vol1.pdf </ref>
 
#It is built on top of the slab of the chambers and can have the size, design and materials you want. Just make sure there is good ventilation and that it does not allow the passage of water into the chambers.  Pedregal included a PVC pipe that runs along the outside of the house and encourages decomposing gases to escape to the outside where it will not disturb users.  Pedregals structure was also made of bamboo mats woven together and placed with small openings to allow for ventilation as well as windows above breast height.  <ref> Soil and Water Conservation Committee, State of Alabama.  "Block and Gravel Inlet Protection". http://swcc.alabama.gov/pdf/Handbooks&Guides/2006_sections/12%20Sediment%20Control%20(practices)vol1.pdf </ref>

Revision as of 17:24, 19 September 2010

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Intro

2.5 billion people world wide lack access to basic sanitation. This results in illnesses and deaths including 2 million deaths a year due to diarrhea. [1] They are a cheap and efficient option for sanitation. They save water, produce good quality compost and reduce the incidence of intestinal infections and other diseases.This is one project in a series of soil conservation, groundwater recharge, and farming demonstration projects at Pedregal a Permaculture Demonstration Center in San Andres Huayapam, Mexico.

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Benefits

  • effective at eliminating odor from addition of lime or ash
  • doesn't attract flies
  • reduces human contact with contagious illnesses
  • produces composted fertilizer that is rendered safer for human use as parasites are killed and the bacteria count is reduced
  • prevents contamination of groundwater, since it is closed during composting
  • is great for off grid systems that do not have access to a municipal sewer system
  • it is cheaper then installing a municipal waste treatment system
  • in order to work it does not require the addition of more water, a precious resource better drank then flushed down the toilet in most communities. [2]


How it Functions

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  • Urine is separated from solid excrement
  • There are two chambers, while one is in use, the others contents are being converted into compost


1. Separating the Urine

The special design allows the urine to be separated from the solid waste. The urine is lead to an absorption well dug close to the bathroom or it can be captured into a separate receptacle so that after it has been diluted in water it can be utilized as a fertilizer. Since urine has been found to contain about 88 percent of the N (nitrogen), up to 67 percent of the P (phosphorus) and up to 71 percent of the K (potassium) present in human excreta, it is a great application for fertilizer use. Also since most pathogenic organisms are found in the solid excrement it makes it easier to handle in reapplication. Urine can also make up the bulk of human waste systems, with humans producing half a cubic meter annually, producing enough with enough frequency to maybe become part of a regular fertilizer application program. [3] The solid excrement meanwhile enters the interior of the chamber that is in use.

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2. Drying the Fresh Excrement

After just depositing fresh excrement in the toilet add one cup of mix of either 3 dirt to 1 lime or 3 dirt to 1 ash on the top. This mix helps avoid the presence of flies and eliminates odors. When the toilet is sealed in an environment without light, oxygen, or water this mix also helps chemically burn parasites in the excrement. BE CARFEUL not to add to much lime or ash if using the finished compost for fertilizer, since the mix can make the compost become too basic for use on most plants.

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3. Alternating the Use of the Chambers

  • Chambers are used at alternating times. When one is full, seal the top with a mix of dirt, bolt down the seat cover, and leave to sit, meanwhile using the alternate chamber.

During this time the closed chamber creates an anaerobic environment that gets to high enough temperatures to destroy most pathogens and the action of the lime or ash helps to chemically burn parasites within the waste.

  • A little bit before the second chamber is full, is the time to empty the primary chamber that has been sitting composting and now the waste is ready for use as a high quality fertilizer. After emptying and cleaning out this primary chamber it is ready for reuse and for being resealed.

Process of Decomposition

  1. Aerobic Decomposition:
    Before using each of the cement chambers, deposit 5cm of dry dirt on the floor. While the chamber is in use organisms present in the dirt are introduced to the excrement and help to decompose the waste.
  2. Alkaline Decomposition:
    During the time that the excrement is covered and sealed without the presence of water, light, or air the lime and ash chemically burns the parasites so that after a few months the compost is free of parasites. [4]
  3. Anaerobic Decomposition:
    If urine is not properly separated from the solid excrement the wet conditions and lack of oxygen can allow anaerobic conditions to dominate, where different microbial organisms may help to break down the waste, but much smellier results. Much of the smell from systems that mix urine and solids is that the bacteria in the solid excrement release ammonia from the urea. This ammonia is a form of nitrogen that is very volatile and is one of the forms of nitrogen plants prefer for use in growth and plant processes. [5]

Construction

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Creating the Chamber and House

The double chamber:

  1. Foundation:
    Construct on a foundation of cement 1cm thick to prevent humidity from entering the chamber and to prevent contact between the fresh solid waste and the ground and groundwater. In areas that flood easily it is recommended to raise the foundation with 20cm of rock or more fixed with wire mesh and covered with the 10cm of cement as a top to prevent water from entering.
  2. Walls of Chamber:
    Build the walls of the chambers with dried adobe blocks, rock and mortar, or ferrocement. Pedregal used cement. Each chamber should be separated by a partition wall of similar thickness, which will also act as structural support to the upper part of the bathroom. It is essential that the inside of the chambers has some kind of polished coating, if using something other then cement, in order to counteract the decomposing action of excrement and bacterial organisms on the walls. This coating also helps to prevent moisture from entering the chambers. Each of these chambers should have its own side door to allow for compost removal individually. Doors should be 30cm wide and as tall as the walls.
  3. Top of Chamber:
    A concrete slab the width and length of the outer walls should be made with a hole for each chamber, these holes will act as the opening to the chamber and the place for the toilet seat.
  4. Hole or Seat:
    Whether just using the hole or adding a toilet seat the urine must be separated using a small triangle shaped cup added to the front of the hole/seat. This cup should also have a small hole in the bottom where a tube is attached and this tube leads out to an outside absorption chamber under the ground or to a separate collection chamber.

EcologicalDryToilets3.jpg

The house:

  1. It is built on top of the slab of the chambers and can have the size, design and materials you want. Just make sure there is good ventilation and that it does not allow the passage of water into the chambers. Pedregal included a PVC pipe that runs along the outside of the house and encourages decomposing gases to escape to the outside where it will not disturb users. Pedregals structure was also made of bamboo mats woven together and placed with small openings to allow for ventilation as well as windows above breast height. [6]


Most Common Problems

  • Urine tubes getting disconnected or clogged accounts for around 24% of the composting toilet systems not in perfect condition. [7]
  • Some studies also indicate that the center of the composting toilet piles do not reach high enough temperatures to destroy pathogens through aerobic decomposition. Other studies indicate that alkaline decomposition is better for pathogen removal, though these high PH conditions make it more difficult to break down organic matter and might require an extended storage time of up to 1 year. As one measure of successful decomposition its been found that temperatures greater then 40C are needed to remove all pathogens within a 1 year storage time. [8]
  • Ph levels may remain below the recommended levels needed to destroy pathogens, at a pH 9. In this circumstance increased amounts of lime or ash could be added to the compost. [9]
  • Moisture levels might be above the recommended levels needed for pathogen destruction, at 25% or below. In this circumstance increased additions of sawdust or soil could help as well as insuring that the urine tube was functioning and not clogged or disconnected. [10]

Alternative Human Waste Treatment Systems


References

  1. Mehl, Jessica. Pathogen Destruction and Aerobic Decomposition in Composting Latrines: A Study from Rural Panama. 2008
  2. Soil and Water Conservation Committee, State of Alabama. "Block and Gravel Inlet Protection". http://swcc.alabama.gov/pdf/Handbooks&Guides/2006_sections/12%20Sediment%20Control%20(practices)vol1.pdf
  3. Drangert, JO. Fighting the Urine Blindness to Provide more Sanitation Options. Water SA. Vol 24, No 2. April, 1998. http://www2.gtz.de/Dokumente/oe44/ecosan/en-fighting-urine-blindness-1998.pdf
  4. Soil and Water Conservation Committee, State of Alabama. "Block and Gravel Inlet Protection". http://swcc.alabama.gov/pdf/Handbooks&Guides/2006_sections/12%20Sediment%20Control%20(practices)vol1.pdf
  5. Drangert, JO. Fighting the Urine Blindness to Provide more Sanitation Options. Water SA. Vol 24, No 2. April, 1998. http://www2.gtz.de/Dokumente/oe44/ecosan/en-fighting-urine-blindness-1998.pdf
  6. Soil and Water Conservation Committee, State of Alabama. "Block and Gravel Inlet Protection". http://swcc.alabama.gov/pdf/Handbooks&Guides/2006_sections/12%20Sediment%20Control%20(practices)vol1.pdf
  7. Mehl, Jessica. Pathogen Destruction and Aerobic Decomposition in Composting Latrines: A Study from Rural Panama. 2008
  8. Mehl, Jessica. Pathogen Destruction and Aerobic Decomposition in Composting Latrines: A Study from Rural Panama. 2008
  9. Mehl, Jessica. Pathogen Destruction and Aerobic Decomposition in Composting Latrines: A Study from Rural Panama. 2008
  10. Mehl, Jessica. Pathogen Destruction and Aerobic Decomposition in Composting Latrines: A Study from Rural Panama. 2008