Latrines and Greywater
Latrines
In the event of an infrastructure failure, dealing with feces—shit—is
an important priority. Feces contain and potentially transmit a variety
of pathogens, including bacteria, viruses, and worms. Exposed feces
also attract flies, who may spread diseases. Latrines are structures
that collect feces in one place, prevent access by insects, keep water
from being contaminated, gives some privacy to the users, and in some
cases, provide useable fertilizer.
Siting Latrines
Due to potential groundwater contamination, latrines should be a
bare minimum of 30 metres (100 feet) from any well, body of water,
or potential drinking water source (though this is less of a problem
with most composting toilets). Medicins Sans Frontieres recommends
a distance of at least 50 metres (164 feet) from water. They should
also be a reasonable distance from dwellings—no less than about
5 metres (16.4 feet) (because of possible smell problems) or more
than about 50 metres (for convenience). Latrines should also be downwind
of dwellings, especially the improvised types.
Choose a site which is not going to flood. When digging a pit, leave
at least 1.5 metres (5 feet) between the bottom of the pit and the
top of the water table.
For hygiene purposes, there should be a source of soap and washwater
near all latrines.
Pit Latrines
The simplest type of latrine is a pit, with some covering. In a wilderness
setting, with few people, feces can simply be buried shallowly in
the soil, at least 30 metres (100 feet) from water. This way the poop
will be broken down by soil organisms easily.
In a setting with a denser population, a larger pit is required.
Sizing the pit is important. The amount of poop that each person produces
per day varies widely based on diet and other variables. A good general
estimate is to assume that one person will give 0.04 m3 (1.4 cubic
feet) of solids per year. (The water content is less important, since
it will drain out or evaporate). So for 25 people, you will need a
pit volume of at least 1 m3 (35 cubic feet) per year of use. (25 x
0.04 m3 = 1.00 m3)
Leave an additional 50 cm of depth from the surface in calculating
the pit volume. You will need this space to put dirt back into, so
make sure to set the dirt aside in a pile to put back in later.
Build a basic structure of some sort on top of the pit with the materials
that you have available. One suggestion is shown in the illustration
on the following page. It is important to have a close-fitting cover
for the pit to reduce odours and keep out flies. Elevated seats are
common in the culture I’m from. However, many people find it
more comfortable to poop from a squatting position. There is some
evidence that this is healthier for you, and it is certainly easier
to make a simple hole in a board. However, this may be less appropriate
for people who have difficulty standing up from a squatting position.
If small children are afraid of falling into the hole, you can make
a “hole cover” with a smaller hole in it, or simply make
a second, appropriately-sized hole in the floor.
If the water table is too high, or the soil too shallow or tough
to dig in, you can dig the pit in an elevated earth mound and/or use
a barrel with a perforated or removed bottom and elevate the structure
above it.
Depending on your soil type, and the shape and depth of the pit,
you may need to line it with rocks or old drums (tops and bottoms
cut off) to prevent it from collapsing. However, the lining should
be porous at the bottom to allow liquids to leave the pit.
After use, when there is only 50 cm left between the surface and
contents of the pit, move the structure on top to a new site, and
fill the full pit in with the dirt.
If smells are a problem, users can put earth, wood ashes, or sawdust
into the pit after each use. Wood ash (hardwood ash especially) is
effective at limiting smell and fly problems.
Trench Latrines
Extend the basic pit latrine out into a line and you have a trench
latrine. It’s pretty self-explanatory.
Trenches can be dug in rows to increase density. Zig-zagging dividers
can be put up for privacy. The trench latrine is generally considered
an emergency measure, suitable for high population densities. Both
it and the pit latrine should be upgraded as soon as possible to a
more hygienic system, such as the Ventilated Improved latrine (VIP).
Ventilated Improved Pit Latrines
The VIP latrine is an enhancement of the basic pit latrine which
addresses smell and fly problems. A ventilation pipe is added (as
shown) which extends at least 50 centimetres (20 inches) above the
top of the shelter roof. As air moves across the top of the pipe,
it draws air up out of the shelter and pit. A mosquito net on top
of the pipe traps flies inside, where they die. The interior of the
shelter should be relatively dim, so that flies are attracted to the
light from the pipe. This latrine does not include a lid for the hole,
since air is constantly drawn through, keeping smells to a minimum,
but you may need to use one anyway in less windy areas.
Other Options
Additional options, such as the pour-flush latrine, exist. The pour-flush
latrine has a U-shaped water seal (the same concept as you might find
underneath many indoor sinks) which reduces smells and flies. The
liquid effluent drains into a leaching pit. For more information on
this and other options, check out the latrine notes.
The pit/trench and VIP latrines can be constructed quickly and easily.
They are relatively safe, provided that they are not close to a food
or water source. Sanitation is aided by the fact that no one has to
handle the feces and urine, the hole is simply refilled.
However, they are likely to introduce pathogens into the groundwater,
even if the pathogens are only near to the latrines. The breakdown
of the feces is mostly an anaerobic (without air) process that produces
a variety of unpleasant gases such as methane and hydrogen sulfide
(which smells like rotten eggs). And the nutrients in the feces and
urine are lost in the pit, which means that gardeners must find alternate
sources of valuable nutrients like nitrogen. On a farm about 80% of
the nitrogen comes from animals. Soils have already been mined of
nutrients, and they need the nutrients in our poop. Besides, for many
people during collapse, the only source of animal manure for gardening
will be their own.
The main alternative to the pit toilet is the composting toilet.
General Latrine Notes
World Health Organization briefs:
www.who.int/docstore/water_sanitation_health/onsitesan/ch04.htm
www.who.int/water_sanitation_health/hygiene/om/en/linkingchap8.pdf
WELL Technical briefs, available at:
www.lboro.ac.uk/orgs/well/resources/technical-briefs/technical-briefs.htm
UNHCR Handbook for Emergencies
UNHCR Water Manual for Refugee Situations
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